Gastrointestinal

Question 1

What conditions can lead to infarction of bowel? What are the clinical features of ischaemic bowel? What parts of the bowel are most susceptible to ischaemic injury and why? Describe the intestinal response to an acute ischaemic insult. What are the factors that predispose to ischaemic bowel disease? Regarding acute transmural infarction caused by arterial obstruction, describe the pathological course. What are the outcomes of chronic bowel infarction?

Answer 1

1. Causes of ischaemic bowel
   - Acute arterial obstruction: Embolism, thrombus, atherosclerotic plaque, hypercoagulable states, aneurysm, dissection
   - Intestinal hypoperfusion: Shock, dehydration, cardiac failure
   - Others: Volvulus, vasculitis, radiation
2. Clinical features of ischaemic bowel
   - Severe abdominal pain
   - Peritonitic abdomen
   - N+V
   - No bowel output or PR bleeding
   - Shock
3. Bowel susceptible to ischaemic injury
   - Watershed areas: Splenic flexure, sigmoid colon, rectum -> At the end of the arterial supply
   - Surface epithelium of gut: Villi more susceptible than crypts -> Intestinal capillaries run from crypts to villi surface
4. Acute ischaemic insult causes
   - Initial tissue hypoxia injury
   - Secondary reperfusion injury -> Major injury sustained during this phase -> Due to release of reactive oxygen species, inflammatory mediators, neutrophils
   - Magnitude of injury determined by -> Vessels involved, areas supplied
5. Risk factors for acute ischaemic bowel
   - Acute arterial occlusion
   + Arterial thrombosis: Atherosclerosis, aortic dissection, vasculitis, hypercoagulable state, OCP use
   + Arterial embolism: SBE, AF
   + Venous thrombosis: Malignancy, liver cirrhosis, OCP use
   - Intestinal hypoperfusion: Shock, cardiac failure
6. Pathological course of acute transmural infarction
   - Occlusion -> Congestion and stasis -> Edema, inflammation, hemorrhage -> bloody fluid -> Mucosal necrosis -> Gangrene -> Metabolic and cardiovascular derangement -> Perforation -> Death
7. Outcomes of chronic bowel infarction
   - Strictures
   - Patchy mucosal degeneration

Question 2

List common pathogens involved in infectious gastroenteritis. What is pseudomembranous colitis? What are the risk factors for development of pseudomembranous colitis? What are the clinical features of pseudomembranous colitis?

Answer 2

1. Pathogens involved in AGE
   - Bacterial: Staph aureus, shigella, salmonella, campylobacter
   - Viral: Novovirus, adenovirus, rotavirus
   - Parasites: Giardia lamblia, entamoeba
2. Pseudomembranous colitis
   - Colitis due to clostridium difficile
   - Due to antibiotics use
   - Pseudomembranous layer is formed made up of inflammatory cells and debris
3. Risk factors for pseudomembranous colitis
   - Elderly
   - Antibiotic use
   - Prolonged hospital stay
4. Clinical features of pseudomembranous colitis
   - Fever
   - Abdominal pain
   - Cramping
   - Profuse watery diarrhoea
   - +ve toxins detected in feces
   - Treated with PO Metronidazole or Vancomycin