Intestinal obstruction
Dr. Tariq al-aubidi
Intestinal obstruction is a common surgical emergency and because of its serious nature it
demand early diagnosis and treatment. It may classified in to two types:
(1)dynamic: here there is peristalsis working against an obstructing agent, which may be
in the lumen such as bolus of incompletely digested material, faeces. Gall stones, in the wall
such as inflammatory or malignant stricture, or out side the
wall as in hernias adhesions, volvulus or intussusceptions.
(2)adynamic: in this condition peristalsis ceases and no true
propulsive wave occur as in paralytic ileus or mesenteric
vascular occlusion.
Dynamic obstruction: is classified clinically in to three types;
(1) acute obstruction: favoring the small gut with central
abdominal pain, early vomiting central abdominal distension
and constipation. (2) chronic obstruction: favoring the large
bowel severe abdominal colic at first and absolute constipation
and distension later. (3) acute-on-chronic: which spread
from the large bowel to involve the small intestine gives early
pain and constipation followed by general distension and
vomiting.
Pathology:
(1) the intestine above the point of
obstruction: have a vigorous peristalsis to over come
obstruction , the peristalsis continue for a period from
48hours to several days. If obstruction is not relived the
peristalsis becomes less and less with increasing distension
finally peristalsis ceases and obstructed intestine becomes
flaccid and paralyzed. (2) the intestine below the point of
obstruction: has normal peristalsis and absorption from it
continue for 203 hours following the obstruction until the residue of its contents has been
passed onwards. Then the empty intestine becomes immobile, contracted and pale and so
it remains until the obstruction has been overcomes or death ensues. (3) distension: this
occurs proximal to obstruction and begins immediately after the obstruction occurs. The
cause of distension is two folds(a) Gas: compose of swallowed air (80%), diffusion from
blood to bowel lumen(22%)and the product of digestion and bacterial activity(10%). When
the oxygen and carbon dioxide has been absorbed in to blood stream the resultant mixture
is made up of nitrogen 90% and hydrogen sulfide.(b)fluid: this made up by various digestive
juices about 8000ml|24hours, above pylorus 4000ml,saliva1500ml,gastric juices2500ml
and below pylorus 4000ml, bile and pancreatic 1000ml,succus entericus 3000ml. the
absorption of gut is retarded and excretion of water and electrolyte in he lumen persist and
even be increased and the loss usually by vomiting ,defective of absorption and
sequestrations in lumen of the bowel. Toxins appears in the peritoneal cavity only when the
viability of the bowel wall is affected by cutting its blood supply(strangulation). These are
endotoxins of gram negative bacilli leads to septic shock and death if not relieved.
Strangulation: of the bowel occurs when it trapped by a hernia or a band or involved in a
volvulus or intussusceptions in such way that its blood supply is progressively interfered
with. It is a very dangerous condition and demands early treatment before gangrene of the
bowel arise. Mesenteric vascular occlusion alone give rise to gangrene with out mechanical
obstruction. The onset of gangrene first compression of the veins cause the strangulated
bowel. When venous return is completely occluded the color change from the purple to
black. As time passed ,increased edema at the point of obstruction the arterial supply is in
danger , the peritoneal coat loses its glistening appearance, the mucous membrane
becomes ulcerated and moist gangrene is imminent.
Clinical features of acute intestinal obstruction:
there are four important
symptoms and signs ,pain, vomiting distension and constipation.(1) abdominal pain is the
1st symptom it commences suddenly and often without warning it becomes increasingly
severe then passes off gradually only to returns to interval of a few minutes. These attacks
of intestinal colic which last from 3-5 minutes, spread all over the abdomen but are
localized mainly at umbilicus. In between attacks the patient is often quite free from the
pain. Recurring attacks of severe abdominal pain are a leading feature of all varsities of
acute intestinal obstruction with the exception of paralytic ileus. (2)vomiting: when the
jejunum is a mechanically obstructed ,vomiting occurs with 1st and each succeeding attack
of pain. In the much more common obstruction of the ileum the patient may vomit once ,
following which there is an interval of several hours during which time the attacks of pain
occur with out vomiting. Ultimately copious, forcible, repeated vomiting sets in. as acute
intestinal obstruction progress the character of the vomitus alters. Initially it contains partly
digested food, next it consists entirely of yellow or green from regurgitation of bile finally it
is faeculent. (3) distention: in early cases of obstruction of the small intestine ,abdominal
distension often slight or even absent. Centrally placed distension is present in fully
established cases of obstruction of ileum. Visible peristalsis may be present , borborygmi
are sometime loud enough to be heard by unaided ear, more often auscultation is
necessary. The sound of turbulent peristalsis coinciding with an attack of colic is valuable
evidence of intestinal obstruction. In all cases of suspected intestinal obstruction it is
essential to examine the common hernia sites. Irreducible external hernia may be present
although the patient is entirely unaware of it. (4)constipation: in complete intestinal
obstruction after the contents of the bowel below the obstruction has been evacuated
there is constipation and usually neither faeces nor flatus is passed, that is absolute
constipation appeared.(5)dehydration: repeated vomiting and also loss of the absorptive
power by the distended intestine leads to dehydration and when the patient is 1st examined
obvious signs of dehydration, a dry skin and dry tongue and sunken eye may be present.
The out put of the urine is small ,it is concentrated and contain a little chloride. The level
urea might be raised.
Chronic obstruction: this is commonly due to carcinoma or diverticulitis of the colon.
here constipation appears first may last for days ,weeks and finally becomes absolute when
the passage of flatus ceases. Abdominal distension then occurs, especially in the flanks. As
the obstruction occurs in the large bowel , the caecum becomes ballooned and might be
perforated and makes general peritonitis. Pain accompanies the distension and there are
regular bouts of colic usually in the hypogastrium. It is not uncommon for vomiting to be
delayed for 2-3days and dehydration is very late. On palpation a neoplasm occasionally can
be felt in line of colon , a rectal examination will enable a carcinoma of rectum or mass of
impacted faeces to be felt and it may be possible to feel a neoplasm in then pelvic colon.
Acute-on-chronic obstruction: this starts with all the features of chronic obstruction
but after a few days ,the pain vomiting and central distension , then ileocaecal valve is
opened and faeculent fluid has passed up via the ileum in to stomach from which is rapidly
vomited.
Strangulation: it is of the highest importance to distinguish strangulating from non
strangulating intestinal obstruction , because if the former is not relieved by urgent
operation ,gangrene follows quickly. The picture is usually that of an obstruction together
with a degree of shock which is sometimes severe. In strangulation, the pain so severe and
never completely absent and the symptoms usually commences very suddenly and spasms
of intestinal colic recurs 3-4 times in a minute. Generalized tenderness and rigidity are
indicative of early laparatomy to be performed. Rebound tenderness is very severe over
strangulated coil and if hernia is present usually the lump is tense, tender, irreducible and
no cough impulse and has recently increase in size, these points ar3e most voluble in
diagnosis. Also the vital signs is indicative as increase in pulse rate and decrease in blood
pressure, sign of shock is usually present in strangulation.
Investigations:
plain abdominal x-rays taking in standing and lying down position,
multiple air-fluid level in side the coils of intestine usually centrally located in case of small
intestine and peripheral location in large intestine. The small bowel distinguish by valvulae
conniventes while the large bowel by haustration. In infants under 2years age a few fluid
levels in small intestine are normal occurrence. In adults two inconstant fluid levels must be
regarded physiological, one on duodenal cap and the other which is more infrequent is with
in terminal ileum. In intestinal obstruction fluid levels appeared later than gas shadows. The
number of fluid levels is proportionate to the degree of obstruction and to the site of small
intestine. In large bowel obstruction a plain film show a large amount of gas in the caecum
and Ba-enema is contraindicated during attack of intestinal obstruction. Multiple gas filled
loops above fluid levels in both small and large bowel are also seen in paralytic ileus.
Treatment: we start by conservative treatment and this can be relief the obstruction or
it may be preparation of doing operation. It consist of (1) gastro-duodenal or gastrointestinal suction drainage by nasogastric tube to prevent vomiting and to examine the
color of fluid and calculate the amount of the fluid.(2) replacement of the fluid as normal
saline or ringer solution .(3) relief of obstruction by operation.(4) antibiotics in form of 3 rd
generation cephalosporin and metronidazole to prevent complications from sepsis and
peritonitis. (5) calculate of vital signs of pulse rate, blood pressure ,urine output by making
a chart and putting a folly's catheter.(6) prepare a blood for transfusion, if needed.
The main indication for early operation after conservative treatment (1) obst8cted or
strangulated external hernia.(2) internal intestinal strangulation. (3) acute or acute on
chronic obstruction and the most urgent is intestinal strangulation. Relief of obstruction by
operation through repair of obstructed hernia or lysis of peritoneal adhesions. If the bowel
is hugely distended should be evacuated by aspiration and suction and then relief the
obstruction. If there is strangulation and gangrene seen , a loop of gangrenous bowel
should be resected and anastomosis done. Viable bowel should be distinguish from non
viable by:
intestine
circulation
peritoneum
Intestinal musculature
viable
Dark color becomes lighter,
mesentry bleed if pricked
shiny
Firm, pressure rings may or
may
not
disappear,
peristalsis may be observed.
Non-viable
Dark color remains, no
bleeding if mesentry pricked.
Dull and lusterless
Flabby, thin, and friable,
pressure rings persist, no
peristalsis.
Paralytic ileus: this has already been defined as a state in which the intestine fails to
transmit peristaltic waves and is due to failure of neuromuscular mechanism. This result in
collection of fluid and gas in the intestine with resulting distention, vomiting, absent bowel
sound and failure to pass flatus.
Causes: (1)postoperative: some degree of ileus either local or general may follow any
abdominal operation. The intestinal mobility and absorption commonly returns to normal
in about sixteen hours. (2)infective: peristalsis ceases as normal response to prevent
dissemination but afterwards bacterial toxins prevent normal activity of nerve plexus. (3)
reflex: in case of spine, ribs fractures, retroperitoneal hemorrhage or application of plaster
jacket.(4) uremia (5) hypokalaemia.
Clinical features(1) there has been no passage of flatus. (2) there is no returns of bowel
sound on auscultation. (3) abdominal distension more marked.
Management: (1) primary cause must be removed as hypokalaemia, uremia. (2) normal
bowel activity will be returned if distension is relieved by nasogastric tube as
decompression. (3) morphine or pethedine in small doses are well proved. (4) close
attention to and electrolyte balance by giving parenteral fluid and potassium. (5) peristaltic
stimulants have no place in treatment. The object is to rest the bowel not to stimulate it.