Can Campylobacter (a type of bacteria) cause melena (black, tarry stools)?

Can Campylobacter Cause Melena?

Yes, Campylobacter can cause melena, though it more commonly presents with bloody diarrhea rather than black tarry stools. Melena represents upper gastrointestinal bleeding or slow colonic bleeding with prolonged transit time, which is an atypical but documented presentation of Campylobacter enterocolitis.

Clinical Presentation Spectrum

Campylobacter infection typically causes proctocolitis with bloody diarrhea rather than melena 1. The pathogen causes inflammation of the colonic mucosa extending up to 12 cm above the anus, which usually manifests as:

• Bloody diarrhea (most common presentation) 1
• Abdominal cramping and pain 1
• Fever 2, 3
• Fecal leukocytes on stool examination 1

However, melena can occur as documented in case reports where Campylobacter enterocolitis presented with melena as the primary complaint, confirmed by colonoscopy showing spotty redness with dark-red coagulation from the splenic flexure to the rectum 4. This presentation is unusual because it suggests either upper GI involvement or slower colonic bleeding with sufficient transit time for blood degradation.

Diagnostic Approach When Melena is Present

When a patient presents with melena and suspected infectious colitis:

1. Perform stool culture and microscopy immediately to identify Campylobacter and other pathogens 4
2. Consider colonoscopy or sigmoidoscopy if the diagnosis is unclear or the patient has severe symptoms, as endoscopy can reveal characteristic mucosal changes (spotty redness, coagulated blood) 4, 1
3. Rule out upper GI bleeding with endoscopy if melena persists without diarrhea 4
4. Check for fecal leukocytes on stool examination 1

When to Suspect Campylobacter Despite Atypical Presentation

Consider Campylobacter even with melena if the patient has:

• Recent consumption of undercooked poultry 3
• Recent travel history 3
• Contact with livestock or contaminated water 3
• Immunocompromised status (higher risk for severe disease and bacteremia) 2, 5, 6

Treatment Recommendations

Initiate azithromycin immediately if Campylobacter is suspected, especially within 72 hours of symptom onset 2, 5:

• Azithromycin 1000 mg single dose OR 500 mg daily for 3 days 5
• Clinical cure rate of 96% 2, 5
• Reduces symptom duration from 50-93 hours to 16-30 hours when started early 2, 5

Avoid fluoroquinolones due to resistance rates exceeding 90% in many regions, with 33% clinical failure rates when the isolate is resistant 2, 5

Critical Complications to Monitor

Campylobacter can cause severe complications beyond typical gastroenteritis:

• Toxic megacolon (requires urgent imaging with abdominal X-ray or ultrasound) 6, 7
• Intestinal perforation (identified by plain abdominal X-ray) 6
• Bacteremia (particularly in immunocompromised patients and pregnant women) 6
• Guillain-Barré syndrome (develops 1-3 weeks post-infection in approximately 30% of GBS cases worldwide) 6
• Reactive arthritis (occurs in approximately 2% of cases) 6

Common Pitfalls

Do not dismiss infectious colitis based solely on melena presentation - while atypical, Campylobacter can present this way and requires the same aggressive treatment approach 4. Always obtain stool cultures even when melena is the primary symptom, as bacteriological examination combined with endoscopy is essential for diagnosis 4. Treat immunocompromised patients immediately even with mild symptoms due to high risk of bacteremia and systemic spread 2, 5, 6.