Nem’s Notes…
Phase 2 Year 2
GASTROENTEROLOGY 6 (page 1 of 5)
Diarrhoea & GI Tract Infections
True Diarrhoea Increase in stool weight > 300g/24hrs usually accompanied by increased frequency
Patients and doctors often define diarrhoea in different ways. Other frequent uses of
the word are for loose stools or increased frequency.
Pathophysiology
(a) Osmotic Diarrhoea
The gut mucosa acts as a semipermeable membrane allowing fluid to enter
the gut if there are large quantities of hypertonic substances in the lumen
The diarrhoea usually stops after stopping eating.
(i) Ingestion of unabsorbable purgative or substance
(ii) Malabsorption
(iii) Specific absorptive defect
(b) Secretory Diarrhoea
This mechanism is due to seretion of electrolytes and fluid into the gut as
well as decreased absorption. The diarrhoea does not stop when the patient
stops eating.
(i) Enterotoxin (cholera, E. coli)
(ii) Hormones (vasoactive intestinal peptide)
(iii) Bile acids/fatty acids in colon after ileal resection
(iv) Some laxatives
(c) Inflammatory Diarrhoea (Mucosal Destruction)
Damage to intestinal mucosal cells leads to loss of fluid and blood into the
lumen. In addition there is defective absorption of fluid and electrolytes.
(i) Infection (dysentery due to shigella)
(ii) Inflammatory bowel disease (ulcerative colitis)
(d) Abnormal Motility
Not a true diarrhoea since it is usually due to increased frequency rather than
volume or weight. It is due to abnormal upper gut motility.
(i) Diabetes
(ii) Post-vagotomy
(iii) Hyperthyroid
Causes
Chronic
(a) Inflammatory Bowel Disease
(b) Parasitic/fungal infection
(c) Malabsorption
(d) Gut resection
(e) Drugs
(f) Colonic neoplasia
(g) Endocrine
Panreatic tumour
Medullary carcinoma
Thyrotoxicosis
Diabetic neuropathy
Acute
(a) Dietary Indiscretion
(b) Infective
Food poisoning
Viral gastroenteritis
(c) Traveller’s Diarrhoea
E. coli
Giardia
Shigella
Entamoeba histolytica
(h) Faecal impaction in elderly
Investigations
Investigation is only required if the diarrhoea has lasted for more than 1 week. In
chronic diarrhoea investigation is always required. The basic repertoire of tests
include: (a) Stool culture and exam (cysts, parasites)
(b) Sigmoidoscopy
(c) Rectal biopsy
(d) Small bowel follow through (SBFT)
(e) VIP
(f) ERCP
more online at http://homepage.virgin.net/nemonique.sam/noteindx.htm page 1 of 5
Nem’s Notes…
Phase 2 Year 2
GASTROENTEROLOGY 6 (page 2 of 5)
Diarrhoea & GI Tract Infections
Malabsorption
Malabsorption is the decreased absorption of food from the gut leading to clinical
symptoms and can be caused by the following mechanisms:
(a) Intraluminal maldigestion due to deficiency of bile or pancreatic
enzymes leading to inadequate solubilisation and hydrolysis.
(b) Mucosal malabsorption due to small bowel resection or small intestine
epithelial damage causing decreased surface area for absorption.
(c) Postmucosal Lymphatic Obstruction which prevents uptake and
transport of absorbed lipids into the lymphatic vessels. The increased
pressure causes leakage back into the intestinal lumen.
Effects of
Malabsorption
(a) General
Lethargy
Depression
Anaemia (Fe, folate, B12 deficiency)
Poor wound healing (vitamin C, protein, zinc deficiency)
Purpura/Bruising (vitamin C, K deficiency)
(b) Mouth
Angular stomatitis (Fe, folate, B12 deficiency)
(c) Limbs
Peripheral neuropathy (B12 deficiency)
Peripheral oedema (hypoalbuminaemia)
Paraesthesia, tetany (Ca, Mg deficiency)
(d) Bone
Osteomalacia, rickets (vitamin D, Ca deficiency)
(e) Muscle
Wasting (protein deficiency)
Proximal myopathy (vitamin D)
Investigation
(a) Haematology Microcytic anaemia (Iron deficiency)
Macrocytic anaemia (Folate, B12 deficiency)
Increased Prothrombin Time (vitamin K deficiency)
(b) Biochemistry Hypoalbuminaemia
Hypocalcaemia, vitamin D deficiency
Hypomagnesaemia
Phosphate, zinc deficiency
(c) 14C-trolein breath test (increased fat)
(d) Duodenal biopsy, aspirate
(e) Barium studies
(f) Pancreatic function tests
(g) Imaging (CT/MRI)
Small Bowel
Bacterial
Overgrowth
Normal upper intestine organisms never exceed 10 3/ml. In bacterial overgrowth the
normal mechanisms controlling organisms in the mouth fail and there may be
108-1010/ml. Caused by: (a) decreased acid
(b) decreased motility
(c) structural abnormalities
(d) decreased immunity
Symptoms include:
(a) Watery diarrhoea +/- steatorrhoea
(b) B12 deficiency anaemia
(c) Symptoms of underlying GI problems
Investigations include:
(a) FBC
(b) Barium follow through
(c) Endoscopic duodenal biopsy
Management
(a) Treat underlying cause
(b) Tetracycline/Metronizadole/Ciprofloxacin
(c) B12 supplements IM in chronic cases
more online at http://homepage.virgin.net/nemonique.sam/noteindx.htm page 2 of 5
Nem’s Notes…
Phase 2 Year 2
GASTROENTEROLOGY 6 (page 3 of 5)
Diarrhoea & GI Tract Infections
Escherichia
Coli
E. Coli is one of the organisms which can cause Traveller’s Diarrhoea. Clinical
features include: (a) Diarrhoea
(b) Vomiting
(c) Abdominal cramps/pain
(d) Fever
Enterotoxigenic E. Coli (ETEC) produces toxins and acts on cAMP to secrete water
and electrolytes into the lumen.
Management:
(a) Oral fluids and electrolytes
(b) Ciprofloxacin in severe cases
Prophylaxis to ETEC is with trimethoprim and doxycycline alongside good hygiene
and well cooked food.
Salmonella
Salmonella can cause:
(a) Gastroenteritis (S. enteritidis, S. typhimurium)
Diarrhoea
Malaise
Nausea
Headache
(b) Typhoid fever (S. typhi)
Insiduous onset of headache
Increasing fever
Cough, sore throat
Initial constipation leading to diarrhoea
Investigations:
(a) FBC/Blood culture (leucopenia, positive culture)
(b) Widal test (serum agglutins to O and H antigens)
Management:
(a) Ciprofloxacin/Chloramphenocol/Cotrimoxazole/Amoxycillin
Prophylaxis:
(a) Good food hygiene
(b) Annual vaccination
Shigella
Gram negative bacteria usually causing disease in children under 5 yrs.
Symptoms:
(a) Acute fever
(b) Malaise
symptoms increasing in severity
(c) Abdominal pain
(d) Watery diarrhoea
Investigation:
(a) Sigmoidoscopy (inflamed mucosa and ulcers)
(b) Stool culture is diagnostic
Treatment:
(a) Symptomatic treatment
(b) Antibiotics in severe cases
Campylobacter Gram negative bacteria causing the following symptoms:
(a) Acute diarrhoea +/- blood
(b) Asymptomatic carriers in children
(c) Fever
(d) Headache
(e) Severe cramping abdominal pain
Investigation:
(a) Sigmoidoscopy (shows acute colitis)
(b) Stool microscopy is diagnostic
(c) Blood/stool culture
Management:
(a) Usually self-limiting in 5-7 days
(b) Antibiotics if severe
more online at http://homepage.virgin.net/nemonique.sam/noteindx.htm page 3 of 5
Nem’s Notes…
Phase 2 Year 2
GASTROENTEROLOGY 6 (page 4 of 5)
Diarrhoea & GI Tract Infections
Yersinia
Enterocolitica
Causes enterocolitis which presents with the following symptoms:
(a) Fever
(b) Diarrhoea
(c) Severe abdominal pain
(d) Arthritis
Usually self-limiting and no treatment is needed unless severe.
Clostridium
Difficile
Gram positive bacteria which causes pseudomembranous colitis. It is usually hospitalacquired and becomes established when colonic bacterial flora are disrupted by
antibiotic treatment. It produces endotoxins and causes mucosal inflammation and
ulceration and, if severe, an adherent ‘pseudomembrane’ (fibrin, debris, polymorphs).
Symptoms:
(a) Insidious onset of lower abdominal pain
(b) Profuse watery diarrhoea
Management:
(a) Stop antibiotics
(b) Vancomycin/Metronizadole
Clostridium
Perfringens
Causes food poisoning due to spores in food which survive boiling.
Symptoms:
(a) Watery diarrhoea
(b) Cramping abdominal pain
Investigation:
Stool/food culture is diagnostic
Mycobacterium Droplet infection of M. tuberculosis causes TB and tuberculous peritonitis. Symptoms
Tuberculosis
include:
(a) Insidious onset of fever
(b) Anorexia
(c) Weight loss
(d) Abdominal pain
(e) Ascites
Investigation:
(a) Peritoneal fluid exam/culture
(b) Tubercle biopsy (laparoscopically)
Management:
(a) Chemotherapy for 18 months – 2 years
Giardiasis
Usually ingested in contaminated water in tropical regions. Incubation of 1-3 weeks.
Symptoms:
(a) Diarrhoea/Steathorrhoea
(b) Abdominal pain
(c) Weakness
(d) Anorexia
(e) Nausea/Vomiting
Investigation:
(a) Malabsorption of xylose, B12
(b) Lactose intolerance
(c) Sigmoidoscopy (partial villous atrophy)
(d) Stool exam for cysts
Management:
(a) Tinidazole/Metronizadole
Amoebiasis
Commonly caused by entamoeba histolytica which is ingested in food contaminated
with human faeces. The organism causes amoebic ulceration. Symptoms are chronic
including:
(a) Abdominal pain
(b) Alternating diarrhoea/constipation
(c) Mucous in stool
Investigation:
(a) Naked eye stool exam for organisms
(b) Sigmoidoscopy shows ulcers and scraping examined
Management:
(a) Metronizadole/Tinidazole
more online at http://homepage.virgin.net/nemonique.sam/noteindx.htm page 4 of 5
Nem’s Notes…
Phase 2 Year 2
GASTROENTEROLOGY 6 (page 5 of 5)
Diarrhoea & GI Tract Infections
Cryptosporidiosis
Usually caused by cryptosporidium parvum, a protozoan with a 7-10 day
incubation causing:
(a) Watery diarrhoea
(b) Abdominal cramp
Investigation:
(a) Faecal microscopy for cysts
Management:
(a) Not necessary unless immuno-compromised
Strongyloides
This is a nematode parasite found in the tropics, sub-tropics and Far East. The worm
burrows into the skin causing initial dermatalogical symptoms and then into the gut
mucosa inducing inflammation and malabsorption.
Symptoms:
(a) Abdominal pain
(b) Diarrhoea
(c) Steatorrhoea
(d) Weight loss
Investigation:
(a) Faecal microscopy will show motile larvae
Management:
(a) Ivermectin/Albendazole
AIDS & GIT
Problems
Weight loss and diarrhoea are extremely common in HIV infection. Wasting is usually
due to systemic effects causing anorexia. ‘HIV enteropathy’ is a syndrome of
diarrhoea, malabsorption and weight loss where there is no other pathology. This is
probably due to infection of white cells in the gut mucosa by the HIV virus.
more online at http://homepage.virgin.net/nemonique.sam/noteindx.htm page 5 of 5