Chronic diarrhoea is a common and debilitating complication in patients with advanced HIV/AIDS, particularly in regions with poor access to clean water. It is a significant cause of morbidity and wasting syndrome in this population.
📌 Key Point: Chronic diarrhoea is often multifactorial and may stem from infectious, inflammatory, neoplastic, or idiopathic causes. Immune suppression increases susceptibility to opportunistic gastrointestinal (GI) infections.
Pathophysiology and Clinical Impact
- In patients with CD4 counts <200 cells/mm³, the GI tract becomes a target for opportunistic infections.
- Chronic diarrhoea contributes to malabsorption, nutrient loss, dehydration, and cachexia (wasting syndrome).
- It can be classified by site of involvement:
- Large bowel (colonic) diarrhoea
- Small bowel (enteric) diarrhoea
Differential Diagnosis Based on Site of Involvement
Large Bowel (Colonic) Diarrhoea
1. Bacterial Enteric Pathogens
- More frequent and severe in HIV-positive individuals than the general population.
- Key pathogens:
- Shigella spp.
- Salmonella spp.
- Campylobacter jejuni
🧪 Stool cultures are essential for pathogen identification.
2. Clostridioides difficile (C. difficile) Colitis
- Consider if patient has received antibiotics recently.
- Presents with watery diarrhoea, abdominal pain, and fever.
- Diagnosis:
- Stool toxin assay or PCR for C. difficile.
- Colonoscopy may reveal pseudomembranous colitis.
3. Cytomegalovirus (CMV) Colitis
- Seen in CD4 <100 cells/mm³.
- Symptoms: Chronic diarrhoea, fever, weight loss.
- Colonoscopy: Ulcers (often on left colon).
- Biopsy: "Owl’s eye" inclusion bodies (classic histological finding).
🎯 CMV diagnosis requires biopsy confirmation due to nonspecific imaging.
🌊 Small Bowel (Enteric) Diarrhoea
1. HIV Enteropathy
- Diagnosis of exclusion.
- Characterized by:
- Watery diarrhoea
- Absence of fever
- Profound weight loss
🔍 Pathophysiology involves direct HIV infection of enterocytes and gut-associated lymphoid tissue (GALT).
2. Parasitic Infections (Protozoa)
| Pathogen | Features | Diagnostic Method |
|---|---|---|
| Cryptosporidium | Chronic watery diarrhoea, especially in CD4 <100 | Modified acid-fast stain or PCR |
| Microsporidia | Chronic diarrhoea, malabsorption, wasting | Electron microscopy or PCR |
| Isospora belli | Watery diarrhoea, may cause eosinophilia | Acid-fast stain; oocysts in stool |
🧫 All are obligate intracellular protozoa that infect enterocytes, impairing absorption.
Clinical Approach
📋 History and Symptoms
- Onset: Acute vs. chronic
- Character of stool: Watery, bloody, fatty
- Associated symptoms: Fever, weight loss, abdominal pain
- Recent antibiotic use
- Travel history and water source
- CD4 count and ART history
🩺 Physical Examination
- Hydration status
- Signs of malnutrition
- Abdominal tenderness or distention
- Oral candidiasis (often concurrent with GI infections)
🧪 Diagnostic Workup
- Stool analysis: O&P, culture, C. difficile toxin, AFB stain
- CD4 count and viral load
- Sigmoidoscopy or colonoscopy with biopsy for persistent or bloody diarrhoea
- Serology or PCR for pathogens like CMV or microsporidia
Treatment Principles
- Rehydration and electrolyte correction
- Nutritional support with calorie-dense diets and micronutrient supplementation
- Targeted antimicrobial therapy based on pathogen
- Initiate or optimize ART to restore immune function
- Antidiarrheal agents (e.g., loperamide) may be used cautiously if no invasive infection is suspected
Prevention
- Safe drinking water
- Proper food handling and sanitation
- Avoiding raw foods in immunocompromised individuals
- Prophylactic therapy (e.g., TMP-SMX) in patients with low CD4 counts
Summary Table
| Category | Example | CD4 Threshold | Diagnostic Feature |
|---|---|---|---|
| Bacteria | Shigella, Salmonella | Any | Stool culture |
| C. difficile | Antibiotic-related | Any | Toxin assay / Colonoscopy |
| CMV colitis | Opportunistic virus | <100 cells/mm³ | Colon ulcers, Owl's eye inclusion |
| HIV enteropathy | Idiopathic | <100–200 cells/mm³ | Exclusion diagnosis |
| Protozoa (Cryptosporidia) | Parasitic, small bowel | <200 cells/mm³ | AFB stain / PCR |
