46
CHAPTER
Acute Abdomen
Alessandra Landmann, Morgan Bonds, Russell Postier
OUTLINE
Anatomy and Physiology
History
Physical Examination
Laboratory Studies
Diagnostic Imaging
Diagnostic Laparoscopy
Intraabdominal Pressure Monitoring
Differential Diagnosis
Preparation for Emergency Operation
Special Patient Populations
Pregnancy
Pediatrics
Critical Illness
Immunocompromised
Cardiac Patients
Morbidly Obese
Elderly
Advanced Disease
Summary
The term acute abdomen refers to the signs and symptoms of
abdominal pain and tenderness. This situation often represents
an underlying surgical problem that requires prompt diagnosis
and surgical treatment. While the ready availability of diagnostic
studies such as computed tomography (CT) scans or magnetic
resonance imaging (MRI) has added greatly to our ability to accurately diagnose most of the conditions responsible for the acute
abdomen, the mainstay for diagnosis remains a good history and
physical exam complemented by laboratory and radiologic studies as appropriate. In addition, many conditions that are not surgical or even centered in the abdomen can also cause this presentation.1 A prompt and accurate diagnosis is necessary in order
to select the appropriate therapy, which may be a laparoscopy or
laparotomy.
Age, gender, and a history of prior abdominal surgical procedures are associated with different problems causing the acute
abdomen. Certain diseases like appendicitis and mesenteric adenitis are more common in the young while biliary tract disease,
diverticulitis, and intestinal ischemia are more common in older
populations.2 Chapter 67 deals with abdominal pain in children.
Numerous problems that are not surgical may also present as
an acute abdomen. These include endocrine and metabolic issues,
hematologic problems, and disorders caused by toxins or drugs
(Box 46.1).3,4 Endocrine and metabolic diagnoses include uremia,
diabetic or Addisonian crisis, acute intermittent porphyria, hyperlipoproteinemia, and hereditary Mediterranean fever. Hematologic disorders include sickle cell crisis and acute leukemia. Toxins
and drugs that can cause acute abdominal pain are lead and other
heavy metal intoxications, narcotic withdrawal, and black widow
spider bites. All of these need to be considered when evaluating a
patient with sudden onset abdominal pain.
The need for prompt surgical treatment of those causes of the
acute abdomen that require operation mandates an expeditious
evaluation so that the proper therapy can be carried out (Box
46.2). A focused history and physical examination and indicated
laboratory and imaging studies will then allow for the correct
diagnosis and guide appropriate therapy. While imaging studies
have added greatly to the accuracy of the diagnosis of causes of the
acute abdomen, a thorough history and careful physical examination remain the mainstays of evaluation.
1134
ANATOMY AND PHYSIOLOGY
Abdominal pain is visceral, parietal, or referred. The presentation
for each helps determine the source of the pain. Visceral pain is
vague and localized to the epigastrium, periumbilical region, or
lower abdomen, depending on whether it originates from the foregut, midgut, or hindgut. Visceral pain is usually due to the distention of a hollow viscus. Parietal pain is sharper and better localized
than visceral pain and corresponds to the nerve roots that supply
the peritoneum. Referred pain is perceived at a site distant from
the source of the pain. Common sites of referred pain and their
sources are listed in Box 46.3. Determining whether the pain is
visceral, parietal, or referred can usually be accomplished with a
careful history.
Whenever bacteria or visceral contents from a perforation are
introduced into the peritoneal cavity, an outpouring of fluid from
the peritoneal surface ensues. The peritoneum responds to such
insults by increasing blood flow, increasing permeability, and forming a fibrinous exudate on its surface. A generalized or localized
loss of intestinal motility usually results. Adhesions between loops
or bowel, bowl and omentum, or bowel and abdominal wall then
occur, which help to localize the inflammatory insult. As a result, an
abscess may cause sharp, localized pain but with normal peristalsis
whereas a diffuse process such as a duodenal perforation generally
results in generalized abdominal pain with absent bowel sounds.
CHAPTER 46 Acute Abdomen
BOX 46.1
abdomen.
Nonsurgical causes of the acute
Endocrine and Metabolic Causes
Acute intermittent porphyria
Addisonian crisis
Diabetic crisis
Hereditary Mediterranean fever
Uremia
Hematologic Causes
Acute leukemia
Sickle cell crisis
Toxins and Drugs
Black widow spider poisoning
Lead poisoning
Other heavy metal poisoning
Narcotic withdrawal
Peritonitis is recognized on physical examination by severe tenderness, with or without rebound tenderness, and guarding. It is
due to peritoneal inflammation of any cause. It is usually due to
an inflammatory insult, commonly gram-negative infection with
either an enteric organism or anaerobe.5 It can also be caused by
inflammation that is not due to infection, such as pancreatitis.
Another form of peritonitis that occurs in children and is caused
by Pneumococcus or hemolytic Streptococcal species and occurs in
adults on peritoneal dialysis is called primary peritonitis. The organisms most often seen in the adult, peritoneal dialysis population are Escherichia coli and Klebsiella.
HISTORY
Despite advances in laboratory studies and imaging, a detailed and
focused history is essential to formulating an accurate differential diagnosis in the patient with an acute abdomen. The history
should focus on the onset and nature of the pain, any associated
symptoms such as nausea or anorexia, whether they began before
or after the pain, and the progression of the pain. A history of
inflammatory bowel disease, prior abdominal procedures, either
open or laparoscopic is important in constructing a differential
diagnosis. Often, additional information may be obtained by observing how the patient describes the pain that is experienced. Pain
identified with one finger is more localized and typical of parietal
innervation or peritoneal inflammation as compared to indicating
the area of discomfort with the palm of the hand, which is more
typical of the visceral discomfort of bowel or solid organ disease.
The intensity and severity of the pain are related to the underlying
tissue damage. Sudden onset of excruciating pain suggests conditions such as intestinal perforation or arterial embolization with
ischemia, although other conditions, such as biliary colic, can
present suddenly as well. Pain that develops and worsens over several hours is typical of conditions of progressive inflammation or
infection such as cholecystitis, colitis, or bowel obstruction. The
history of progressive worsening versus intermittent pain can help
differentiate infectious process from the spasmodic colicky pain
associated with bowel obstruction, biliary colic from cystic duct
obstruction, or genitourinary obstruction (Fig. 46.1).
The location, character, and radiation of the pain are important
to elicit. Tissue injury or inflammation can result in visceral and
BOX 46.2
conditions.
1135
Surgical acute abdominal
Hemorrhage
Aortoduodenal fistula after aortic vascular graft
Arteriovenous malformation of the gastrointestinal tract
Bleeding gastrointestinal diverticulum
Hemorrhagic pancreatitis
Intestinal ulceration
Leaking or ruptured arterial aneurysm
Mallory-Weiss syndrome
Ruptured ectopic pregnancy
Solid organ trauma
Spontaneous splenic rupture
Infection
Appendicitis
Cholecystitis
Diverticulitis
Hepatic abscess
Meckel diverticulitis
Psoas abscess
Ischemia
Buerger disease
Ischemic colitis
Mesenteric thrombosis or embolism
Ovarian torsion
Strangulated hernia
Testicular torsion
Obstruction
Cecal volvulus
Gastrointestinal malignancy
Incarcerated hernias
Inflammatory bowel disease
Intussusception
Sigmoid volvulus
Small bowel obstruction
Perforation
Boerhaave syndrome
Perforated diverticulum
Perforated gastrointestinal cancer
Perforated gastrointestinal ulcer
somatic pain. Solid organ visceral pain in the abdomen is generalized in the quadrant of the involved organ, such as liver pain
across the right upper quadrant of the abdomen. Small bowel pain
is perceived as poorly localized periumbilical pain, whereas pain
from a colonic origin is centered between the umbilicus and pubic symphysis. As inflammation expands to involve the peritoneal
surface, parietal nerve fibers from the spine allow for a focal and
intense sensation. This combination of innervation is responsible
for the classic diffuse periumbilical pain of early appendicitis that
later shifts to become an intense focal pain in the right lower abdomen at McBurney point. Further, the pain may also extend well
beyond the diseased site. For example, the liver shares some of its
innervation with the diaphragm. Thus, liver inflammation may
create referred pain to the right shoulder from the C3–C5 nerve
roots. Also, genitourinary pain commonly has a radiating pattern.
1136
SECTION X Abdomen
Symptoms are primarily in the flank region, originating from the
splanchnic nerves of T11–L1, but the pain often radiates to the
scrotum or labia via the hypogastric plexus of S2–S4.
Determining what factors, if any, worsen or lessen the pain is
important. Eating will often worsen the pain of bowel obstruction,
biliary colic, pancreatitis, diverticulitis, or bowel perforation. Food
can lessen the pain from peptic ulcer disease or gastritis. Patients
with peritonitis will avoid any activity that stretches or moves the
abdomen. Those patients will describe worsening of the pain with
any sudden body movement and realize that there is less pain if
their knees are flexed. Anything that causes movement of the abdomen, such as the car ride to the hospital, can be agonizing.
Associated symptoms and their timing are important diagnostic clues. Nausea, vomiting, constipation, diarrhea, pruritus,
melena, hematochezia, and hematuria are all helpful symptoms if
present. Vomiting may occur because of severe abdominal pain of
any cause or as a result of either mechanical bowel obstruction or
ileus. Vomiting is more likely to precede the onset of significant
abdominal pain in many nonsurgical conditions, whereas in the
Locations and causes of
referred pain.
BOX 46.3
Left Shoulder
Heart
Left hemidiaphragm
Spleen
Tail of pancreas
Right Shoulder
Gallbladder
Liver
Right hemidiaphragm
Scrotum and Testicles
Ureter
VISCUS
Esophagus,
trachea, bronchi
Heart and
aortic arch
SEGMENTAL
INNERVATIONS
Vagus
T1-T3 or
T4
NERVES
C1
2
3
4
5
6
7
8
T1
Sup. cardiac*
Middle cardiac
Inf. cardiac
Stomach
T5-T7
Biliary tract
T6-T8
Small intestine
T8-T10
2
3
4
5
6
7
8
Kidney
T10-L1
9
10
Maj. splanchnic
Colon
T10-L1
11
Min. splanchnic
Uterine fundus
T10-L1
12
Least splanchnic
Bladder
Rectum
Thoracic cardiac
L1
2
3
4
5
Uterine cervix
S2-S4
S1
2
3
4
5
PLEXUSES
Sacral
Parasympathetic
Bladder
Cervix
Rectum
* No known sensory fibers in sympathetic rami.
FIG. 46.1 Sensory innervation for viscera.
Cardiac
Pulmonary*
Celiac
and
adrenal*
Renal
Spermatic*
Ovarian*
Preaortic
Inf. mesenteric
Sup. hypogastric
Bladder*
Prostate*
Uterus
CHAPTER 46 Acute Abdomen
pain of an acute abdomen with an underlying surgical cause, the
pain will precede the vomiting. Constipation or obstipation can
be the result of mechanical obstruction or decreased peristalsis. It
may either be the primary problem and can be treated with laxatives or prokinetic agents or it may be merely a symptom of an
underlying more serious condition. Knowing whether or not the
patient continues to pass flatus or have bowel movements is thus
important. A complete obstruction, with the absence of flatus or
bowel movements is more likely to be associated with subsequent
bowel ischemia or perforation caused by the significant distention
that can occur. Diarrhea is associated with several conditions that
are not treated with operations. These include infectious enteritis,
inflammatory bowel disease, or parasitic infections. Bloody diarrhea can be seen in these medical conditions as well as in colonic
ischemia.
A careful past history can be exceedingly helpful in making the
correct diagnosis of the patient with acute abdominal pain. Previous illness or diagnoses can greatly increase or decrease the likelihood of certain conditions that may not otherwise be thought of.
For example, patients may report that the current pain is similar
to the pain experienced during the passage of a renal stone several
years previously. A prior history of appendectomy, pelvic inflammatory disease, or cholecystectomy can significantly limit the differential diagnosis. Any abdominal scars present on the abdomen
during the physical exam need to be accounted for in the history
that is obtained.
Certain medications can both create and mask the symptoms
of an acute abdominal condition. High dose narcotics can interfere with bowel motility and lead to obstipation and obstruction.
Narcotics can also contribute to spasm of the sphincter of Oddi
and exacerbate biliary or pancreatic pain. They can also suppress
pain sensations and alter mental status. Both of these impair the
ability of the surgeon to diagnose the condition accurately. Nonsteroidal antiinflammatory drugs are associated with upper gastrointestinal inflammation and perforation. Steroids can block
protective gastric mucous production by chief cells and reduce the
inflammatory reaction to infection, including significant peritonitis. The class of agents that are immunosuppressive increase a
patient’s risk of acquiring various bacterial or viral illnesses and
also blunt the inflammatory response, diminishing the pain that
should be present and limiting the overall physiologic response.
Anticoagulant drugs use is common in our elderly population
and may be the cause of gastrointestinal bleeding, retroperitoneal
hemorrhage, or rectus sheath hematomas. They can also complicate the preoperative preparation of the patient and be the cause
of substantial morbidity if their use goes unrecognized. Finally,
recreational drugs can also be the cause of acute abdominal pain.
Cocaine and methamphetamine use can create an intense vasospasm that can cause life-threatening cardiac or intestinal ischemia
as well as severe hypertension.
The differential diagnosis of the acute abdomen in women includes many more conditions than are found in the male population. In the past, the negative laparotomy or laparoscopy rate in
women with acute abdominal pain was significant and substantially higher than that seen in men. Improvements in, and the
widespread availability of, advanced imaging such as MRI and CT
scans have improved the diagnostic accuracy of the evaluation of
acute abdominal pain in this population. A careful gynecologic
history remains important in the evaluation of abdominal pain
in young women. The likelihood of ectopic pregnancy, pelvic inflammatory disease, mittelschmerz, and severe endometriosis are
all dependent upon the details elicited in the gynecologic history.
1137
PHYSICAL EXAMINATION
The physical examination remains an essential component in the
evaluation of the acute abdomen. You will be able to garner valuable information from this step to better inform the next steps in
the diagnostic pathway. Physical examination will generate a more
precise differential diagnosis, and this will allow for the initiation
of necessary therapy in a timely manner. Despite wider availability
of advanced diagnostic imaging, it cannot replace an organized
and thorough physical examination.
The initial evaluation of all patients should begin with general
inspection. Information regarding the severity of the illness can
quickly be assessed upon walking into the room. Symptoms such
as diaphoresis, pallor, dyspnea, and decreased alertness can be assessed rapidly and will forewarn the examiner that a serious issue
is at hand. For an acute abdomen, the general inspection will be
the first evidence of whether the patient has peritoneal inflammation. These patients tend to be very still as movement aggravates
their abdominal pain. In contrast, patients with abdominal pain
without peritoneal inflammation will fidget in attempts to find a
comfortable position.
Inspection of the abdomen is the next step. Attention is focused on the contour of the abdomen and skin abnormalities.
Abdominal wall distension occurs in several abdominal processes
such as intestinal obstruction, development of ascites, or presence
of a growing mass. Surgical scars should be identified and correlated to the history taken prior to the physical examination. Other
skin findings, such as erythema or blistering, can alert the examiner to the possibility of soft tissue infections that may require
immediate debridement. Ecchymosis can also be an indication of
a fascial necrotizing infection; additionally, it may alert the examiner to accidental or nonaccidental trauma and may warrant
further social investigation.
Historically, the next step in evaluation is auscultation. This
maneuver should be done prior to percussion or palpation as
bowel activity can be affected by manual manipulation. Vascular abnormalities, such as arterial stenosis or arteriovenous fistulas, can be detected by auscultating bruits within the abdomen.
Auscultation for bowel activity is controversial. It has been taught
that the quantity and quality of bowel sounds heard correlate with
the motility of the bowel. Ileus is associated with hearing fewer
than one bowel sounds every 15 seconds per quadrant. Conversely, high-pitched tinkling sounds are associated with mechanical
bowel obstruction. Many argue that history of flatus and bowel
movements are more accurate at determining whether the patient
is having a bowel motility issue than auscultation. A recent review
article cited low sensitivity and positive predictive values for auscultating bowel sounds in normal volunteers, patients with bowel
obstruction, and patients with postoperative ileus. They also noted
poor interobserver reliability for bowel auscultation, recording it
at 54%.6 Auscultation can be useful but must be correlated with
history and other exam findings.
Percussion is capable of eliciting a wealth of information. Dull
resonance in the right upper quadrant identifies the liver; measuring the superior-inferior range of this dullness will give the
examiner a rough estimate of liver size. Percussion is useful in determining whether abdominal distension is due to excess air or
fluid. The presence of localized dullness elsewhere in the abdomen should raise concern for an intraabdominal mass. Tympany,
or hyperresonance, is consistent with gas-filled structure deep to
the abdominal wall. If tympany is heard in the right upper quadrant, where the liver is located, this indicates there is air between
1138
SECTION X Abdomen
Right upper quadrant
Liver
Gallbladder
Duodenum
Right kidney
Right ureter
Right lung/pleura
Left upper quadrant
Stomach
Spleen
Pancreas
Left kidney
Left ureter
Left lung/pleura
Right lower quadrant
Appendix
Ileum
Right colon
Right ureter
Bladder
Right ovary or testicle
Left lower quadrant
Sigmoid colon
Rectum
Left ureter
Bladder
Left ovary or testicle
FIG. 46.2 Abdominal structures by palpations quadrants.
the abdominal wall and liver, and intraperitoneal free air should
be suspected. Diffuse dullness to percussion raises suspicion for a
fluid-filled abdomen. A fluid wave can be created by a quick firm
compression of the lateral abdominal wall; a wave should then
travel medially across the abdominal wall.
Percussion can also be useful identifying the presence of peritonitis. A patient with peritonitis will have exquisite tenderness during percussion of the abdomen and may not be able to withstand
the maneuver. Jostling the abdominal viscera by percussing the
flank, iliac crest, or the heel of an extended lower extremity will
illicit the characteristic signs of peritonitis. These maneuvers are
more reliable for detecting inflammation of the peritoneal lining
than the historical technique of deep palpation followed by quick
withdrawal of pressure and asking whether the pressure or release
was most painful. This can be very painful, regardless of the presence of peritonitis, and leaves room for subjective interpretation
by the patient.
The final portion of the abdominal exam is palpation. Generally, this is the most informative portion of the examination.
It provides details that help you localize the source of pain as
well as abnormalities within the abdomen. The examiner should
begin with superficial palpation away from the area with the
most significant pain; superficial palpation allows for assessment of masses or fluid collections anterior to the abdominal
wall and whether the pain is associated with these abnormalities. More pressure should then be applied to perform deep
palpation. Deep palpation allows the examiner to assess pain
from an intraabdominal source as well as the presence of any
intraabdominal masses or organomegaly. Diffuse tenderness to
palpation suggests extensive inflammation or delayed presentation of an ongoing disease process. Identifying the region of
maximum tenderness will give the examiner the likely source of
abdominal pain. By identifying the quadrant causing the pain,
a differential diagnosis can be developed based on the structures
within that quadrant (Fig. 46.2).
Guarding can be encountered while performing abdominal
palpation. It is necessary to differentiate between voluntary and
involuntary guarding. Voluntary guarding occurs when the patient anticipates painful stimuli and tenses their abdominal wall
muscles. To prevent this, have the patient lie supine on the exam
table and bend his or her legs to place the soles of their feet flat
on the bed. Instruct them to take a deep breath while you palpate. These maneuvers result in relaxation of the abdominal wall
as well as distracting the attention of the patient, preventing voluntary guarding. If the abdominal wall tenses despite the above
techniques, the patient has involuntary guarding which is a sign
of peritonitis.
There are several named exam maneuvers associated with different disease processes. These can be seen in Table 46.1. Murphy
sign for acute cholecystitis which involves deeply palpating the
right subcostal region while the patient inspires deeply. If cholecystitis is present, the inspiration will be cut short due to pain
as the gallbladder encounters the anterior abdominal wall. The
obturator and psoas signs can be useful identifying the relative position of an inflamed appendix. Rovsing sign suggests right lower
quadrant peritonitis.
CHAPTER 46 Acute Abdomen
1139
TABLE 46.1 Abdominal examination signs.
History
Danforth sign
Shoulder pain on inspiration
Hemoperitoneum
Inspection
Cruveilhier sign
Cullen sign
Grey Turner sign
Ransohoff sign
Varicose veins at umbilicus
Periumbilical bruising
Local areas of discoloration near umbilicus and flanks
Yellow discoloration of umbilical region
Portal hypertension
Hemoperitoneum
Acute pancreatitis
Ruptured common bile duct
Acute appendicitis
Bassler sign
Blumberg sign
Carnett sign
Chandelier sign
Courvoisier sign
Fothergill sign
Iliopsoas sign
Murphy sign
Obturator sign
Pain or pressure in epigastrium or anterior chest with persistent firm pressure applied to
McBurney point
Sharp pain created by compressing appendix between abdominal wall and iliacus
Transient abdominal wall rebound tenderness
Loss of abdominal tenderness when abdominal wall muscles contracted
Extreme pelvic pain with movement of the cervix
Palpable gallbladder when jaundice is present
Abdominal wall mass that does not cross midline and is palpable when rectus is contracted
Elevation of extended leg against resistance is painful
Pain caused by inspiration while applying pressure to right upper abdomen
Flexion and external rotation of right thigh creates hypogastric pain
Rovsing sign
ten Horn sign
Pain at McBurney point when palpating the left lower quadrant
Pain caused by gentle traction of right testicle
Palpation
Aaron sign
Additional exams often provide useful information. Digital
rectal exam provides information about hollow viscus bleeding
and sources of distal obstruction causing constipation and obstipation. In women, results of pelvic exam will help include or exclude gynecologic sources of lower abdominal pain. A 2014 study
found that of 290 women of reproductive age with right lower
quadrant pain thought to have acute appendicitis 37 (12.8%) had
gynecologic pathology with a normal appendix.7 Pelvic examination may identify this pathology earlier and allow for appropriate
counseling prior to surgery.
LABORATORY STUDIES
Laboratory studies can narrow the differential diagnosis of abdominal pain. Box 46.4 contains a complete list of laboratory tests
that can assist the workup an acute abdomen. A complete blood
count gives several important data points. The white blood cell
count can be elevated or decreased in the setting of an acute abdomen. The best evidence of an acute infection is an elevated absolute number or percentage of band cells, so it is ideal to send for
a complete blood cell count with a white blood cell differential.
Low hemoglobin and hematocrit alert the care team to a source
of bleeding that may be associated with the source of abdominal
pain. If the hemoglobin and hematocrit are higher than normal,
one should evaluate the patient for signs of dehydration.
Patients with abdominal pain should also have a complete
metabolic panel sent. Electrolytes such as sodium, potassium, and
calcium are evaluated as well as renal function tests such as blood
urea nitrogen and creatinine. Alterations in these values will alert
the physician to fluid losses from diarrhea or vomiting as well as
possible endocrine sources of abdominal pain (i.e., hyperparathyroidism). The complete metabolic panel contains “liver function
tests” that, when elevated, should lead to further assessment of
the hepatic and biliary systems. Viral hepatitis panels should be
BOX 46.4
pain.
Chronic appendicitis
Peritoneal inflammation
Intraabdominal source of abdominal pain
Pelvic inflammatory disease
Periampullary mass
Rectus muscle hematoma
Retrocecal acute appendicitis
Acute cholecystitis
Pelvic abscess or inflammatory mass
(appendicitis)
Acute appendicitis
Acute appendicitis
Laboratory tests for abdominal
• White blood cell count with differential
• Hemoglobin
• Platelets
• Electrolytes
• Creatinine and blood urea nitrogen
• Amylase and lipase
• Total and fractionated serum bilirubin
• Serum lactate levels
• Viral hepatitis panel
• Urinalysis
• Urine human chorionic gonadotropin
• Clostridium difficile culture and toxin assay
sent when a source for elevated liver enzymes cannot be identified.
Amylase and lipase are indicated when pancreatitis is a suspected
source of abdominal pain.
Arterial blood gas with serum lactate measurements are valuable tests when evaluating any severely ill patient. In the setting
of the acute abdomen, lactic acidemia is a sign of hypoperfusion
and depending on the circumstances raises the concern for mesenteric ischemia. Mesenteric ischemia is a serious condition with
significant mortality despite improvements in critical care and can
be tricky to diagnose in some patients. Attempts to identify additional markers specific to mesenteric ischemia are underway but
not yet available for clinical use.8
Urine studies should be a standard laboratory test sent in a
patient with abdominal pain. A urinalysis can give several points
of information. The presence of bacteria, white blood cells, and
leukocyte esterase in the sample raises concern for a urinary tract
1140
SECTION X Abdomen
infection and possibly pyelonephritis; this would account for suprapubic pain or flank pain, respectively. Nephrolithiasis and nephritic syndromes can be detected by noting red blood cells in
urine. Casts within the urine should also raise concern for a renal
source of abdominal pain. Finally, in women of childbearing age,
a urine human chorionic gonadotropin level should be sent as her
symptoms may be due to complications of pregnancy.
Additional tests should be sent in select cases. Patients with
diarrhea should have stool samples sent for culture and ova assessment. Importantly, Clostridium difficile culture and toxin
measurements should be performed as the incidence of this infection is increasing within the community.9 Women in the third
trimester of pregnancy with right upper quadrant pain, elevated
liver enzymes, and low platelets should be assessed for HELLP
syndrome; expedient diagnosis is necessary to get the patient lifesaving plasma exchange therapy.10
DIAGNOSTIC IMAGING
Diagnostic imaging should be the final step in the work up of
a patient with an acute abdomen. It is imperative that, prior to
ordering any diagnostic imaging, a working differential diagnosis
has been formulated so that the appropriate modality is chosen.
There is a wide range of options. Many are expensive and can expose patients to ionizing radiation, so it is important to choose the
most useful modality for the patient being worked up.
Ultrasound is a relatively cheap and expedient imaging modality that can be very useful in evaluating the acute abdomen. It remains the best modality for evaluating right upper quadrant pain,
especially pain that is suspected to emanate from the gallbladder.
Ultrasound sensitivity and specificity are high for detecting pericholecystic fluid, gallbladder wall thickening, and gallstones.11 It is
also a useful modality for diagnosing appendicitis in patients where
avoiding ionizing radiation is desired, such as the pediatric population and early pregnancy.12,13 When ruling out gynecologic sources
of acute abdominal pain, transvaginal ultrasound should be utilized
as it is more accurate than transabdominal ultrasound. Ultrasonography can have limitations with visualization due to abdominal
wall thickness, bowel gas contents and operator experience.
Plain films of the abdomen can provide useful information
in certain patients. When concerned for hollow viscus perforation, an upright plain film taken at the level of the diaphragm
will reveal free air under the diaphragm which is diagnostic and
should prompt surgical exploration (Fig. 46.3). It has been shown
that time to surgical consultation and time to the operating room
is shorter if diagnosis can be made with plain film as opposed
to CT. However, CT can provide more information regarding
location of perforation and specific cause.14 Historically, upright
and supine radiographs of the abdomen have been used to diagnosis bowel obstructions. Small bowel obstruction is suspected
on plain film when air-fluid levels are seen in the upright position and paucity of gas in the distal colon with distended bowel
loops in the supine position. Haustral markings from the teniae
coli will help differentiate small bowel gas from colonic gas (Fig.
46.4). However, the diagnostic accuracy of plain films to diagnose mechanical bowel obstruction or paralytic ileus in a patient
with abdominal pain is low.15 Colonic volvulus can be diagnosed
on plain films as well. Cecal volvulus typically appears as a comma shape loop of bowel with the concavity facing inferiorly and
to the right. Sigmoid volvulus presents as the “bent inner tube”
or “coffee bean” sign, where the apex of the dilated colon points
into the right upper quadrant (Fig. 46.5).
FIG. 46.3 Upright plain abdominal film demonstrating pneumoperitoneum, a finding consistent with perforated hollow viscus.
FIG. 46.4 An abdominal film of a patient with large bowel obstruction.
The dilated loop of bowel can be identified as transverse colon by the
haustral markings.
CT has become the primary diagnostic tool in patients with
abdominal pain over the past decades. It is readily available, provides detailed information about the entire abdomen and pelvis,
and can be performed relatively quickly. The quality of the CT
images is less dependent on operator skill than ultrasound and
provides more detail than plain films. A differential diagnosis will
guide the CT technique needed. For example, if nephrolithiasis is
suspected the imaging will be done without contrast but if a small
bowel obstruction is suspected the CT should be ordered with
CHAPTER 46 Acute Abdomen
1141
Diagnostic Laparoscopy
Diagnostic laparoscopy can be used as a final diagnostic adjunct
should other tests prove equivocal; the advantage is that it may
also prove therapeutic. A study of patients over 70 years old compared laparoscopic versus open exploration and intervention for
the acute abdomen. The laparoscopic group showed no difference
in morbidity or mortality.20 Laparoscopy can be safely used in patients with sepsis if measures to reduce the negative hemodynamic
effects of pneumoperitoneum are employed; these include keeping
the intraabdominal pressure under 12 mm Hg and making sure
appropriate antibiotics have been given prior to insufflation. Diagnostic laparoscopy should not be used when irreversible sepsis is
present or if the operator is uncomfortable with laparoscopy. An
emergency situation is not the appropriate time to learn new skills.
A relative contraindication to diagnostic laparoscopy is extremely
dilated bowel as visualization can limit complete exploration, but
this would depend on the surgeon’s comfort with laparoscopy.21
While it should not be used routinely, diagnostic laparoscopy can
assist determining the cause of the acute abdomen in select cases.
INTRAABDOMINAL PRESSURE MONITORING
FIG. 46.5 Abdominal plain film showing sigmoid volvulus. Note the
distended sigmoid colon in the right upper quadrant; this is the classic
“coffee bean” or “bent inner tube” sign.
oral and intravenous contrast. These considerations are essential
to provide the most diagnostic images.
Many studies have shown the improved diagnostic accuracy of
CT over other imaging modalities. It has been shown that using
CT as part of an imaging pathway will result in earlier diagnosis,
though it will not decrease hospital stay or morbidity.16 This is
particularly true for appendicitis (Fig. 46.6). A recent evidencebased review reported that the sensitivity and specificity of CT
for identifying appendicitis were 98.5% and 98%, respectively.
Several studies included in this review showed a decrease in the
negative appendectomy rate with the use of CT.17 A retrospective
study sought to determine the effect of CT imaging on diagnosis
and disposition in patients over age 80. They found that their
diagnosis changed in 43% of patients after obtaining a CT; this
difficulty with diagnosis was particularly prominent in the presence of small bowel obstruction, colonic obstruction, and diverticulitis. Clinically, the findings on CT resulted in a statistically
significant change in disposition.18 These findings demonstrate
the usefulness of CT.
Due to the radiation exposure associated with CT, studies have
sought whether low-dose imaging retains diagnostic accuracy. In
one recent study, two radiologists compared high-dose and lowdose CT images in patients with nontraumatic abdominal pain.
They reported high confidence in their interpretation for both radiation doses despite there being slightly more image noise in the
low-dose images. Diagnostic accuracy was not statistically significant between radiation doses; the low-dose CT had a sensitivity
and specificity of 93.7% and 88.2%, respectively, while the highdose CT had a sensitivity and specificity of 95.8% and 94.1%,
respectively.19 Low-dose CT should be considered in children and
patients who undergo frequent imaging.
The acute abdomen can either cause or be due to increased intraabdominal pressure. If the intraabdominal pressure is sustained
above 20 mm Hg it is defined as abdominal compartment syndrome (ACS). This is a life-threatening condition as the elevated
pressure results in decreased venous return and tidal volumes from
elevated inspiratory pressures. It can also lead to visceral ischemia
due to poor perfusion.
Normal intraabdominal pressure should be between 5 to 7
mm Hg. Abdominal obesity, accessory muscle respiration, and
upright positioning will all artificially increase intraabdominal
pressure. Bladder catheter pressure monitoring is used to measure
intraabdominal pressures. The World Society of the Abdominal
Compartment Syndrome (WSACS) recommends measuring bladder pressures after instilling 25 mL of room temperature saline
into the bladder. The patient should be supine with the transducer
at zeroed at the midaxillary line. Pressure measurements should be
taken at the end of expiration or with the patient paralyzed with
the ventilator paused if unable to participate in exam.22 Grades of
intraabdominal hypertension can be seen in Table 46.2.
Treatment of intraabdominal hypertension and ACS depends
on the cause and severity. Primary ACS is due to a disease process within the abdomen that is best treated with decompressive
laparotomy and correction of the inciting disease process. Abdominal closure may not be possible without causing recurrent
ACS which should prompt use of a temporary abdominal closure
maneuvers. Secondary ACS is a condition that arises from a condition not located in the abdomen or pelvis. Initial management
of secondary ACS without evidence of end organ damage should
be treated medically. Medical management includes correcting a
positive fluid balance, evacuating intraluminal contents via a nasogastric tube, Foley and enemas, relaxing the abdominal wall with
adequate sedation and pain control, and drainage of peritoneal
fluid.22 A low threshold should be held for decompressive laparotomy to limit morbidity and mortality from this condition.
DIFFERENTIAL DIAGNOSIS
Formulation of the differential diagnosis for an acute abdomen
should be a continuous process throughout every step of evaluation. The list developed after history and physical examination
1142
SECTION X Abdomen
A
A
B
FIG. 46.6 (A) Computed tomography demonstrating a dilated retrocecal appendix (arrow) with periappendiceal stranding. (B) This image represents a pelvic abscess (A) caused by perforated appendicitis. The arrow
shows the inflammatory process extending into subcutaneous tissues.
TABLE 46.2 Abdominal hypertension and treatment by grade.
INTRAABDOMINAL PRESSURE
Normal pressure
Grade 1 hypertension
Grade 2 hypertension
Grade 3 hypertension
Grade 4 hypertension
5–7 mm Hg
12–15 mm Hg
16–20 mm Hg
21–25 mm Hg
>25 mm Hg
should guide the laboratory and imaging tests you order. By the
end of the evaluation, the list of potential diagnoses should be
narrowed to one or two processes. The art of refining differential
diagnoses requires extensive knowledge of the medical and surgical causes of acute abdominal pain. This knowledge must then be
integrated with the demographics of the patient being evaluated.
It is imperative to determine early whether the disease process
causing acute abdominal pain requires urgent surgical intervention. Many present with sepsis which must be managed expediently, even without a specific diagnosis. Box 46.5 presents examination, laboratory, and imaging findings associated with surgical
disease. However, in real world situations, the patient may not be
stable enough to be transported to another department for some
of these tests. One option is to consider a test that can be performed at bedside such as ultrasonography or abdominal plain
films. Another option is diagnostic peritoneal lavage. Using local
anesthetic, a small incision is made in the midline near the umbilicus. A catheter is placed into the peritoneal cavity to infuse 1 L
of normal saline, which is then siphoned out of the abdomen. The
siphoned fluid is sent for cellular and biochemical analysis. Diagnostic peritoneal lavage can be used to detect hemoperitoneum
and/or hollow viscous perforation.
Delays in surgical intervention should be avoided. Once you
have diagnosed a patient with a surgical abdomen, there is no
advantage to waiting for further diagnostic tests. Morbidity and
mortality increase with unwarranted delays. Fluid resuscitation
and stabilization of vital signs can continue in the operating room
through multidisciplinary approach with anesthesia and nursing.
Laparoscopy can assist in guiding placement of the laparotomy
incision if forced to proceed to the operating room without a definitive diagnosis.
TREATMENT
None
Maintain euvolemia
Nonsurgical decompression (diuresis, etc.)
Surgical decompression via laparotomy
Surgical decompression; explore for cause
Findings that suggest need for
surgical intervention.
BOX 46.5
Physical Exam Findings
Abdominal compartment pressure >25 mm Hg
Involuntary guarding
Rebound tenderness
Pain out of proportion to exam
Unexplained systemic sepsis
Transabdominal penetrating trauma
Laboratory Findings
Anemia from gastrointestinal hemorrhage requiring >4 units of blood transfusion
Evidence of hypoperfusion (acidosis, rising creatinine, rising liver function
tests)
Diagnostic Imaging Findings
Pneumoperitoneum
Progressive dilatation of stationary loop of intestine (sentinel loop)
Evidence of bowel perforation (air or contrast near loop of bowel)
Fat stranding or thickened bowel wall with systemic sepsis
Bowel wall pneumatosis
Diagnostic Peritoneal Lavage Findings
Presence of feculent or particulate matter
>250 white blood cells per milliliter
>300,000 red blood cells per milliliter
Peritoneal bilirubin > serum bilirubin (bile leak)
Peritoneal creatinine > serum creatinine (urine leak)
CHAPTER 46 Acute Abdomen
Some patients are diagnosed with a medical cause of acute
abdominal pain. This does not mean that a surgical process will
not develop. These patients need close, careful observation in a
monitored setting. Serial examinations and laboratories should be
scheduled to ensure the patient is improving with medical therapy. Ideally, examinations are performed by the same examiner
to avoid missing significant changes in the patient’s condition or
development of complications.
PREPARATION FOR EMERGENCY OPERATION
Patients with an acute abdomen vary greatly in their overall state
of health at the time the decision to operate is made. Regardless of
the patient’s severity of illness, all patients require some degree of
preoperative preparation. Intravenous access should be obtained,
and any fluid or electrolyte abnormalities corrected. Nearly all patients will require antibiotic infusions. The bacteria common in
acute abdominal emergencies are gram-negative enteric organisms
and anaerobes. Infusions of antibiotics to cover these organisms
should be begun once a presumptive diagnosis is made. Patients
with generalized paralytic ileus or vomiting benefit from nasogastric tube placement to decrease the likelihood of vomiting and
aspiration. Foley catheter bladder drainage to assess urine output,
a measure of adequacy of fluid resuscitation, is indicated in most
patients. Acidosis due to intestinal ischemia or infarction may be
refractory to preoperative therapy. Significant anemia is uncommon, and preoperative blood transfusions are usually unnecessary, however cross-matched blood should be available at operation. The need for preoperative stabilization of patients must be
weighed against the increased morbidity and mortality associated
with a delay in the treatment. The underlying nature of the disease
process, such as infarcted bowel, may require surgical correction
before stabilization of the patient’s vital signs and restoration of
acid-base balance can occur. Resuscitation should be viewed as
an ongoing process and continued after the surgery is completed.
Deciding when the maximum benefit of preoperative therapy in
these patients has been achieved requires good surgical judgment.
SPECIAL PATIENT POPULATIONS
Pregnancy
The workup and treatment of acute abdominal pain in the pregnant patient creates several unique diagnostic challenges. Providers often rely on imaging to differentiate between an urgent
surgical problem from a nonsurgical or obstetric cause.23 However, the greatest threat facing the pregnant patient with acute
abdominal pain is the potential for delayed diagnosis and which
have been proven to be far more morbid than the operations
themselves.24,25 Delays occur for several reasons: symptoms of
abdominal pain, nausea, and vomiting are often attributed to the
underlying pregnancy, pregnancy can alter the presentation of
some disease processes and make the physical examination more
challenging because of the enlarging uterus, and fear of exposure
of a fetus to radiation or unnecessary procedures.26 Laboratory
studies such as white blood cell counts and other chemistries are
also altered in pregnancy, making recognition of disease processes
more difficult. These differences cause extra emphasis to be placed
on other modalities, such as vital signs and laboratory studies,
which can confuse or underestimate the extent of intraabdominal
disease. Finally, physicians naturally tend to be more conservative
in treating pregnant patients, especially in regard to imaging and
surgical intervention.
1143
Ultrasound is the initial imaging study of choice in the pregnant patient.26,27 In addition to diagnosing the most common abdominal pathologies, appendicitis and cholelithiasis, this modality also adds the benefit of assessment of the fetus and evaluating
for obstetrical pathology.27 Radiation exposure should be avoided
whenever possible, especially during the first trimester during organogenesis, and the next study of choice should be MRI.26,27 If
CT is the only imaging study available, risks and benefits should
be weighed as a delay in diagnosis is often more morbid than a
single imaging study. Studies have shown that up to 50 mGy of
ionizing radiation, the equivalent of five abdominal plains films
or one abdominal CT scan, results in no significant increase in
teratogenic effects of radiation.27 Whenever possible, such as during imaging of the brain, cervical spine, or chest x-ray, the fetus
should be shielded with lead.
It is important to remember that pregnancy is a highly controlled process that involves almost every organ system in a selfregulated environment that is extremely sensitive to maternal volume loss and catecholamine response.26 Maternal hemorrhage is
often compensated by decreased uterine flow, and marked fetal
distress is often the first manifestation of an acute surgical pathology, even before maternal hypotension or tachycardia is identified.26 The presence of peritoneal signs is not a normal finding
in pregnancy, and the development of peritonitis can often be
delayed by abdominal laxity and an enlarged uterus. Its presence
should prompt an immediate search for its cause to avoid additional morbidity and mortality.28
The differential diagnosis of acute abdomen in pregnancy can
be broad; however, the presentation does not differ much from
that of the adult patient if one pays special attention to patient
symptomatology and history. The most common pathologies and
the recommended screening imaging studies are listed in Table
46.3. In addition to gastrointestinal pathology, it is important to
include gynecologic and obstetrical causes of acute abdomen in
the patient’s workup, including uterine rupture, ectopic pregnancy, ruptured corpus luteum cyst, adnexal torsion, placenta percreta, among others.27 Ovarian torsion can often be distinguished
from other abdominal pathology with its characteristic presentation of waxing and waning abdominal pain.28
Acute appendicitis is the most common nonobstetric abdominal emergency requiring surgery with an overall incidence of 101
cases per 100,000 pregnancies.23 Diagnostic findings on ultrasound are a dilated, blind-ending, thickened, tubular, and noncompressible structure 6 mm or larger in size.29 Ultrasound can
have its limitations and should be followed by advanced imaging
if the diagnosis is in question. MRI and CT findings are similar to ultrasound and also include periappendiceal inflammation,
presence of an appendicolith, or the presence of an established
abscess.29 Twenty percent of patients will have peritonitis or established intraabdominal abscess at presentation, with an associated
higher risk of complications including a 20% to 35% rate of fetal
loss for perforated appendicitis.23 The added difficulties in evaluating the pregnant patient with right lower quadrant abdominal
pain have resulted in significantly higher negative appendectomy
rate compared with nonpregnant patients in the past. Although
this diagnostic error rate would be unacceptable in a typically
young healthy woman, it is widely accepted because of the fetal
mortality risk when appendicitis progresses to perforation before
surgery.
General anesthesia is considered safe in all stages of pregnancy
and patients should be considered a high aspiration risk for induction. Pregnant women should be treated as though they have
1144
SECTION X Abdomen
TABLE 46.3 Differential diagnosis of abdominal pain in pregnancy and recommended imaging
studies.
SITE
PREFERRED IMAGING MODALITY FOR DIAGNOSIS
Gallbladder disease
Hepatitis
Pancreatitis
Bowel obstruction
Perforated ulcer
Appendicitis
Nephrolithiasis
Inflammatory bowel disease
Gynecologic causes
Diverticulitis
Trauma
US > MRI
US > MRI
US > MRI > CT
US > MRI > CT
Plain films > CT
US > MRI > CT
US > MRI > CT
MRI > CT
US > MRI
MRI > CT
US > CT> MRI
Adapted from Baheti AD, Nicola R, Bennett GL, et al. Magnetic resonance imaging of abdominal and pelvic pain in the pregnant patient. Magn
Reson Imaging Clin N Am. 2016;24:403–417.
CT, Computed tomography; MRI, magnetic resonance imaging; US, ultrasound.
a full stomach whenever intubation is planned.28 Intraoperative
care during pregnancy is focused on optimal care of the mother. If
the fetus is previable, fetal heart tones should be measured before
and after the surgery. If the fetus is viable, fetal heart tones should
be measured throughout the surgery with a provider capable of
performing an intervention available. The safety of laparoscopic
surgery in pregnancy has been extensively studied and established.
Laparoscopy allows for decreased manipulation of the uterus, and
as a result, less uterine irritability with lower risk of contractions,
spontaneous abortions, preterm labor, and premature delivery.30
In order to safely enter the abdomen, the open Hassen technique
is considered standard, with care to avoid injury to the enlarging
uterus.31
Additional causes of acute abdomen include biliary disease,
bowel obstruction, and pancreatitis, among others. Biliary disease
is common, as sex steroids interfere with gallbladder emptying resulting in bile stasis.28 Ultrasound is the diagnostic test of choice.
Treatment is recommended in the second trimester to avoid complications of biliary disease as the pregnancy progresses. Gallstone
pancreatitis and acute cholecystitis should be managed more carefully. Gallstone pancreatitis has been associated with a fetal loss as
high as 60%. If a woman does not respond quickly to conservative
treatment with hydration, bowel rest, analgesia, and judicious use
of antibiotics, further evaluation should be performed as surgical
intervention may be indicated. Endoscopic retrograde cholangiopancreatography is considered safe and low radiation risk to the
fetus, should the patient present with cholangitis or choledocholithiasis.
Small bowel obstruction is often confused with the normal
nausea and vomiting associated with pregnancy. It is important
to remember that peritoneal signs in the presence of nausea and
vomiting is never considered normal and should prompt further
workup.28 Abdominal distention with colic should key the clinician to the diagnosis.
Pediatrics
Evaluating a child with an acute abdomen can be difficult for the
clinician not accustomed to performing an abdominal exam in
children. In contrast to performing an examination on an adult
who is able to communicate with the clinician and give feedback
when abdominal pain is elicited, much of the examination on a
child occurs through observation. Children can be poor historians
because of their age, being afraid of the situation, and being unable to verbalize their symptoms. Clues to the extent of peritoneal
irritation include a child’s willingness or unwillingness to stand
or move about the hospital bed freely. Children with peritonitis will demonstrate abdominal pain with standing, jumping, or
coughing.3 The abdominal exam should be performed thoughtfully and only to the extent to identify the presence of abdominal
wall spasm in response to intraabdominal pathology.
The most common cause of acute surgical abdomen in the
pediatric population remains acute appendicitis and occurs most
commonly in older children and adolescents with a presentation
of anorexia, low-grade fever, and right-lower quadrant pain similar to adult patients.32 Younger children may present differently
and pose a challenge to the clinician with reports from parents of
a vague onset of symptoms. Their inability to characterize their
pain, nonspecific signs, and difficulty in eliciting a physical exam
results in imaging playing a crucial role in diagnosis. Almost all
children, 99% in some reports, with appendicitis will have preoperative imaging before surgical intervention.32–34 Ultrasound
often demonstrates pathologic concordance when performed in
the hands of an experience ultrasonographer, especially those performed at a free-standing children’s hospital.34 Children presenting to a nonchildren’s hospital are more likely to have a CT scan
diagnosis of appendicitis, despite the recommendations from multiple pediatric societies on the risks of radiation.34
Additional causes of acute abdomen are broken down by age
and listed in Table 46.4. Intussusception should be considered in
the differential of abdominal pain in children less than 3 years
old. Gastroenteritis, Meckel diverticulitis, and C. difficile colitis are among other causes of abdominal pain, and presentation
is similar to adult patients. Inconsolable crying and lethargy in
small infants can be ominous. Any history of emesis in a newborn
should prompt careful questioning regarding the character and
timing of emesis episodes; bilious emesis is a surgical emergency
and prompts urgent evaluation for midgut volvulus. A history of
fever, passage of currant jelly stools, and lower gastrointestinal
track bleeding should prompt further workup.35
Critical Illness
Establishing a diagnosis of an acute abdomen in the critically ill
can be challenging. The clinician must navigate an environment
of deep-sedation, multiple etiologies of sepsis, multiorgan failure,
CHAPTER 46 Acute Abdomen
1145
TABLE 46.4 Differential diagnosis of abdominal pain in children by age.
< 2-YEARS OLD
2- TO 5-YEARS OLD
5- TO 12-YEARS OLD
>12-YEARS OLD
Intussusception
Gastroenteritis
Constipation
Infantile colic
Malrotation with midgut volvulus
Incarcerated inguinal hernia
Obstruction due to Hirschsprung
disease
UTI
Meckel diverticulum
Intussusception
Appendicitis
Gastroenteritis
Constipation
Mesenteric adenitis
Malrotation with midgut volvulus
Sickle cell crisis
Appendicitis
Gastroenteritis
Constipation
Mesenteric adenitis
Functional abdominal pain
Pneumonia
Sickle cell crisis
Appendicitis
Gastroenteritis
Constipation
Ovarian/testicular torsion
Dysmenorrhea
Pelvic inflammatory disease
Ectopic pregnancy
Henoch-Schonlein purpura
UTI
Trauma
Meckel diverticulum
Henoch-Schonlein purpura
UTI
Trauma
Adapted from Yang WC, Chen CY, Wu HP. Etiology of non-traumatic acute abdomen in pediatric emergency departments. World J Clin Cases.
2013;1:276–284.
UTI, Urinary tract infection.
TABLE 46.5 Differential diagnosis of acute abdomen in transplant patients.
LIVER37
LUNG38
HEMATOPOIETIC STEM CELL39
Biliary complications of transplant
Vascular complications of transplant
Small bowel obstruction
Acute appendicitis
Urinary tract infection
Acute diverticulitis
Acute pancreatitis
Gastroesophageal reflux
Infectious enterocolitis
Peptic ulcer disease
Gastroparesis
Diverticulitis
Pancreatitis
Gastrointestinal bleed
Acute graft versus host disease
Cholangitis
Neutropenic enterocolitis
Infectious enterocolitis
Pneumatosis
and absent or subtle clinical exam findings. Unrecognized abdominal pathology can cause patients to persist in their critical state
or even progress to their demise. Critically ill patients may not be
able to demonstrate the typical signs and symptoms of acute abdomen due to narcotic analgesia, blunting of the inflammatory response due to antibiotics or immunosuppression, and nutritional
deficiency.
Imaging is often necessary to establish a diagnosis as multiple
causes for abdominal distention, sepsis, or organ failure may be at
play in the intensive care unit (ICU) patient.36 Some patients, will
be unstable for transport and the clinician will be challenged with
the risks and benefits of obtaining advancing imaging, such as CT,
versus operative exploration with the potential of a nontherapeutic laparotomy. Determining which patients are stable enough to
survive an operation, potentially a nontherapeutic intervention,
can be unpredictable.37 A small cohort of clinicians advocate for
diagnostic laparoscopy in the ICU as a mode of both diagnosis
and treatment of the acute abdomen in the critically ill patient.
However, this is coupled with the difficulties of performing bedside laparoscopic surgery, the invasive nature of procedure, and
the costs of the equipment and anesthesia.37 As technology continues to advance, this is an area where change is likely to occur.
Immunocompromised
Transplant patients often present to the emergency room with
abdominal complaints. In one study, researchers found that
33% to 60% of transplant patients sought care in the emergency
room after their procedure.38 Inflammation is necessary in the
pathophysiology of abdominal pain and peritonitis, and this may
be blunted in the transplant patient. This can result in unreliable
leukocytosis, delayed development of fever, and subjectively decreased abdominal symptoms. They may also present in a delayed
fashion, which may be very quickly followed by overwhelming
systemic collapse. As a result, although the abdominal pathology
is similar to that seen in healthy adult patients, the immunosuppressed may have atypical presentations with very minimal symptoms.
In one study of over 70,000 transplant patients, the incidence
of emergency surgery was found to be 2.5%. The indications for
surgical intervention were biliary disease (80%), gastrointestinal
perforation (9%), complicated diverticulitis (6%), small bowel
obstruction (2%), and appendicitis (2%). Overall mortality in
this patient cohort was 5.5%.38 A differential diagnosis of abdominal pathology is listed in Table 46.5 broken down by type
of transplant.
Routine blood work should be performed in addition to checking serum levels of immunosuppressive drugs. These medications
can cause many side effects that may cloud the presentation of
acute abdomen, including loss of gastrointestinal mucosal integrity and regeneration, alterations in gastric acidity, and impaired
immune response to illness. This often presents as diarrhea, abdominal pain, nausea, vomiting, and weight loss.38 Transplant
patients may not mount an inflammatory response to illness, and
serum markers may not be elevated despite ongoing abdominal
pathology.
Pseudomembranous colitis has increasingly been seen in the
immunocompromised patient, independent of a recent association with broad-spectrum antibiotics. Typical presentations
1146
SECTION X Abdomen
include diarrhea, abdominal pain, fever, and leukocytosis; however, this may not be seen in this patient cohort. A high index
of suspicion, reliance on CT imaging and stool assays should be
considered early.
Cytomegalovirus infection is another important pathogen to
consider in the transplant patient. The presentation can vary, including diarrhea, dysphagia, nausea, vomiting, abdominal pain,
gastrointestinal bleeding, and intestinal perforation. Cytomegalovirus is diagnosed by biopsy demonstrating virus in the gastric or
intestinal mucosa and is treated with antivirals.
Atypical infections, including peritoneal tuberculosis, fungal
infections, and endemic mycoses, can also be seen in this group.
Due to the decreased inflammatory response, an abdominal infection may not present with a typically walled off abscess and CT
scan imaging may not demonstrate classic findings.39 Immunosuppressed patients with suspicious abdominal pathology should
have inpatient monitoring with a low threshold for operative intervention if an atypical infection that is not improving despite
adequate therapy.
Cardiac Patients
Risk factors for the
development of gastrointestinal
complications after cardiothoracic surgery.
BOX 46.6
• Age >70
• Low cardiac output
• Peripheral vascular disease
• Need for reoperation due to hemorrhage
• Acute/chronic renal failure
• Cardiopulmonary bypass time >150 minutes
• Intraaortic balloon pump
• Preoperative inotropic support
• Active smoker
• Chronic obstructive pulmonary disease
• Prolonged ventilation
• Valve surgery
• Sepsis/sternal wound infections
• Liver failure
• Myocardial infarction
Abdominal emergencies in the cardiac patient can be easily
masked by their postoperative recovery, ongoing management of
their cardiac dysfunction, mechanical ventilation, arrhythmias,
hemodynamic instability, and sedation.40 Risk factors are associated with the procedure performed, such as length of cardiopulmonary bypass, interventions on valvular heart disease, and need
for intraaortic balloon pump. In addition, the patient’s preoperative physiology also has some effect, such as arrhythmias, hypertension, hypercholesterolemia, diabetes, renal disease, and need
for preoperative inotropic support.41 Patients undergoing an open
abdominal aortic aneurysm repair have the highest incidence, especially those repaired through a transabdominal approach. The
highest mortality is seen in patients with intestinal ischemia and
in those patients who required a valve repair.40
The pathophysiology of gastrointestinal complications is
thought to be associated with disturbances in the superior mesenteric artery blood flow during cardiopulmonary bypass.42 The
most common gastrointestinal diagnoses are ileus, pancreatitis,
mesenteric ischemia, bowel obstruction, acute cholecystitis, and
perforation.41 Risk factors for development of an abdominal complication after cardiothoracic surgery are listed in Box 46.6.
From Buczacki SJA, Davies J. The acute abdomen in cardiac intensive
care unit. In: Valchanov K, Jones N, Hogue CW, eds. Core topics in
cardiothoracic critical care. 2nd ed. Cambridge: Cambridge University
Press; 2018:294–300.
Morbidly Obese
may require multiple films to image the entire abdomen. CT may
be limited due to weight restrictions on the examination table,
although this is increasingly becoming less of an issue due to the
increasing numbers of morbidly obese patients. Early laparoscopy,
especially in the postoperative bariatric patient, is often used for
both diagnosis and treatment. Examples of concerning CT imaging findings are listed in Box 46.7.
The classic presentation of an acute abdomen is not a reliable indicator of intraabdominal pathology in the morbidly obese. The
presentation is often subtle, leading to rapid progression to sepsis,
organ failure, and death.42 In contrast to normal weight patients,
the morbidly obese can mask the signs of peritonitis, even in the
setting of abdominal catastrophes, such as anastomotic leaks, until
very late in the disease process, leading to a high incidence of complications and increased mortality.42 Physical examination findings
are difficult to interpret. Abdominal sepsis may only be associated
with malaise, shoulder pain, hiccups, and shortness of breath.43
Severe abdominal pain is uncommon. Appreciation of abdominal
distention or a mass is difficult because of their increased abdominal girth. The presence of anorexia is also highly unpredictable,
and their reported symptoms or abdominal complaints can be
exceedingly vague. With an unreliable physical exam, clinicians
must rely on laboratory exams, tachycardia, x-ray imaging findings, and subtle clinical symptoms to make the diagnosis of an
abdominal problem.42 Abdominal x-rays have reduced clarity and
Concerning CT imaging findings
in the postbariatric surgery patient.
BOX 46.7
• Dilated alimentary limb
• Dilated excluded stomach
• Dilated biliopancreatic limb
• Transition between dilated and nondilated bowel
• Mesenteric swirl sign
• Cluster of small bowel loops
• Horizontal position of the superior mesenteric artery
From Karila-Cohen P, Cuccioli F, Tammaro P, et al. Contribution
of computed tomographic imaging to the management of acute
abdominal pain after gastric bypass: correlation between radiological
and surgical findings. Obes Surg. 2017;27:1961–1972.
CT, Computed tomography.
Elderly
The diagnosis of an acute abdomen in the elderly patient is no
different from that of the adult patient. This patient population,
however, is unique in that they often suffer from delay in surgical treatment as a result of their age due to biases regarding the
morbidity of the proposed intervention. This often occurs despite
data to suggest that increased age does not independently affect
mortality, morbidity, or length of hospital stay.44 With an aging population, surgeons and clinicians are now challenged with
how to care for this patient cohort, and they must let go of their
strong-held beliefs that patients can be “too old,” “too high risk,”
CHAPTER 46 Acute Abdomen
BOX 46.8
Differential diagnosis of acute
abdomen in the elderly patient.
BOX 46.9
• Peptic ulcer disease
• Gastrointestinal bleed
• Biliary disease
• Pancreatitis
• Bowel obstruction (large and small)
• Volvulus
• Diverticulitis
• Appendicitis
• Abdominal aortic aneurysm
• Mesenteric ischemia
• Tumor infiltration
• Gastrointestinal bleed
• Bowel obstruction
• Biliary disease
• Appendicitis
• Neutropenic enterocolitis
• Invasive aspergillosis
• Digestive tract graft versus host disease
• Mesenteric ischemia
• Diverticulitis
From Rubinfeld I, Thomas C, Berry S, et al. Octogenarian abdominal
surgical emergencies: not so grim a problem with the acute care
surgery model? J Trauma. 2009;67:983–989; and Magidson PD,
Martinez JP. Abdominal pain in the geriatric patient. Emerg Med Clin
North Am. 2016;34:559–574.
or “nonsurvivable.”45 Approaching these patients with a “damagecontrol” mentality of aggressive resuscitation and careful attention
to hypothermia, coagulopathy, acidosis, or hypotension and returning after adequate resuscitation are suggested to improve outcomes.45 Box 46.8 lists the most common indications for surgical
intervention in the elderly patient population.
Advanced Disease
Surgery in patients with advanced or disseminated cancer can
be fraught with complications with little chance of prolonging
their survival. Emergency procedures, such as for perforation or
obstruction, are performed in this patient population with grave
risks, as their disseminated disease has little chance of cure. One
study demonstrated that those that undergo an operation for perforation have an approximate 1 in 3 chance of mortality; this is
only slightly improved to 1 in 6 for those undergoing an operation
for obstruction.46 These complications may occur as a side effect
of cancer treatment or it may represent disease progression. Regardless the cause, frank discussion with patients and their families are fundamental, and decisions regarding the patient’s goals of
care, overall survival, and prolonged institutionalization should be
discussed with respect to the patient’s wishes.46 Emergency surgery in patients with advanced disease often heralds an inflection
point in their care and these patients are unlikely to obtain their
goal of discharge home.46 Box 46.9 lists the differential diagnosis
of acute abdomen in the oncologic patient.
SUMMARY
Despite improvements in laboratory examinations and imaging,
the evaluation and management of the patient with acute abdominal pain remains a challenging part of a surgeon’s practice.
However, a careful history and thorough physical examination
continue to remain the most important part of the evaluation of
the patient with acute abdominal pain. The surgeon continues
to be required to make the decision to perform laparoscopy or
laparotomy with some degree of uncertainty as to the expected
findings. The increased morbidity and mortality associated with
a delay in the treatment of many of the surgical causes of the
acute abdomen argue for an aggressive and expeditious surgical
approach.
1147
Differential diagnosis of acute
abdomen in the oncology patient.
From Mokart D, Penalver M, Chow-Chine L, et al. Surgical treatment
of acute abdominal complications in hematology patients: outcomes
and prognostic factors. Leuk Lymphoma. 2017;58:2395–2402; and
Cauley CE, Panizales MT, Reznor G, et al. Outcomes after emergency
abdominal surgery in patients with advanced cancer: Opportunities to
reduce complications and improve palliative care. J Trauma Acute Care
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This paper reviews the presentations of abdominal emergencies in pregnant patients as well as the best way to approach
these conditions.
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An excellent resource for systematic evaluation and diagnosis
in a patient with an acute abdomen.
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A consensus statement that defines abdominal compartment
syndrome and provides evidence-based algorithm on its diagnosis and treatment.
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This paper highlights the usefulness of minimally invasive surgery in approaching the acute abdomen.
Steinheber FU. Medical conditions mimicking the acute surgical
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This classic article nicely reviews the various medical conditions that can manifest as an acute abdomen. It is well
written and remains pertinent to the evaluation of these
patients.