Enteritis

Enteritis in the immunocompromised host

• Seen in AIDS patients or transplant patients
• Aetiology
  • Protozoa
    • Cryptosporidium, isospora and microsporidium are the most frequent agents causing diarrhoea in AIDS patients
    • Diagnose based on acid-fast staining of stool or duodenal secretions, or specific antigen-based tests
    • Immunochromatography cards are available with >90% sens/spec
    • Symptoms mostly diarrhoea
    • Treatment is prophylactic cotrimoxazole and a highly active antiretroviral therapy
  • Bacteria
    • Salmonella and Shigella easily established by stool cultures
    • Campylobacter often gives negative stool cultures, but can be tested on PCR
    • Typically give high fever, abdominal pain and diarrhoea that may be bloody
    • Imipenems or ciprofloxacin are effective
    • C. diff is also more common in patients with AIDS, treat as normal
  • Mycobacteria
    • Most commonly secondary to mycobacterium tuberculosis or Mycobacterium avium complex (MAC)
    • Usual route of infection by swallowed organisms that directly penetrate mucosa
    • Mycobacterium tuberculosis is most frequently found in TI and caecum (90% of cases), with a gross appearance of ulcerative and hypertrophic disease. Acute inflammation will be seen along with strictures and even fistula formation. The serosal surface is covered with multiple tubercles and mesenteric lymph nodes are frequently enlarged and thickened, with caseous necrosis. Distinguishing lesion is a granuloma, with caseating granulomas found in the lymph nodes. Patients get non-specific chronic abdominal pain, weight loss, fever and diarrhoea. Treat the same as for non-immunocompromised patients.
    • MAC infection typically causes massive thickening of the proximal small intestine
    • Diagnosis by acid-fast stain, culture of the excised tissue, or PCR assay
    • Indications for surgery
      • Obstruction (may resolve with medical treatment)
      • Fistula formation (mostly responsive to medical treatment)
      • Free perforation
      • Perforation with abscess
      • Massive haemorrhage
    • Treatment is usually resection with primary anastomosis
  • Virus
    • Most commonly CMV, but also reported with other more typical viruses
    • Mucosal ischaemic ulcerations - high rate of perforation
    • Patients can therefore present with abdominal pain, peritonitis or haematochaezia
    • Diagnosis
      • Histopathology - viral inclusions. Most characteristically, intranuclear inclusion surrounded by a halo, producing an owl's-eye appearance.
      • Cultures for CMV are usually positive when inclusion bodies are present, but still non-sensitive
    • Treatment - usually ganciclovir - usually effective
  • Fungal
    • GIT histoplasmosis - often a/w pulmonary or hepatic disease. Diagnose with fungal smear and culture of tissue or blood. Treated with amphotericin B
    • Coccidioidomycosis of GIT is rare - occurs in the context of systemic infection
• Presentation
  • Diarrhoea, abdominal pain, acute abdomen, or GIT bleeding in the immunocompromised patient

Typhoid enteritis

• Acute systemic infection caused primarily by Salmonella typhi
• Epidemiology
  • Suspect with recent travel to developing countries
• Pathophysiology
  • Initiated by ingestion of typhoid bacillus
  • Organisms penetrate small bowel mucosa, passing through lymphatics then entering systemic circulation
  • Associated with hyperplasia of the reticuloendothelial system, including lymph nodes, liver and spleen
  • Peyer patches in the small bowel become hyperplastic and may subsequently ulcerate, complicated by haemorrhage or perforation
• Investigation
  • Blood culture - positive in 90% of patients during first week, and confirms diagnosis
  • Bone marrow culture
  • Stool culture
  • Widal test (high titres of agglutinins against O and H antigens) is no longer necessary as it is non-specific
  • PCR for S. typhi are inaccurate
• Management
  • Antibiotics
    • Immediate broad-spectrum antibiotics if suspected
    • Fluoroquinolones or third-generation cephalosporins
• Complications
  • Haemorrhage
    • Usually managed with transfusion as necessary
    • Laparotomy for uncontrollable life-threatening haemorrhage
  • Perforation
    • Occurs through an ulcerated Peyer patch in 2% of cases
    • Typically single perforation in TI - can be closed primarily
    • Multiple perforations require resection with primary anastomosis or loop ileostomy