Can H. pylori Cause Dark Stools?
Yes, H. pylori infection can cause dark stools, but only indirectly through its complications—specifically peptic ulcer disease with bleeding or gastric cancer. Dark stools (melena) indicate upper gastrointestinal bleeding, which is a complication of H. pylori-related pathology rather than a direct effect of the infection itself.
Mechanism of Dark Stools in H. pylori Infection
H. pylori does not directly cause dark stools; rather, it causes conditions that lead to gastrointestinal bleeding:
- Peptic ulcer disease is a primary manifestation of H. pylori infection that can bleed, producing melena 1, 2, 3
- Gastric cancer, which H. pylori strongly predisposes to, can also present with bleeding and dark stools 1, 2, 4
- The chronic gastritis caused by H. pylori itself typically does not produce bleeding severe enough to cause melena 2, 5
Clinical Significance of Dark Stools in H. pylori Context
When a patient presents with dark stools, H. pylori should be considered as an underlying cause if peptic ulcer disease is suspected:
- Dark stools represent a serious complication requiring urgent evaluation, as they indicate active upper GI bleeding 6
- H. pylori testing and eradication is specifically recommended in patients with active or past history of peptic ulcer disease 3, 6
- The presence of melena warrants endoscopic evaluation to identify the bleeding source and obtain biopsies for H. pylori testing 7
Important Clinical Distinctions
H. pylori's primary manifestations do not include dark stools as a direct symptom:
- The main clinical manifestations are chronic gastritis, peptic ulcer disease, gastric MALT lymphoma, and gastric cancer 2, 3
- H. pylori is not associated with diarrhea as a primary manifestation, distinguishing it from acute gastroenteritis 2
- Dark stools signal a complication (bleeding ulcer) rather than uncomplicated H. pylori gastritis 1, 2
Extragastric Manifestations to Consider
The Maastricht IV/Florence Consensus recognizes iron-deficiency anemia as an established extragastric manifestation of H. pylori:
- Iron-deficiency anemia has Grade A evidence for H. pylori testing and eradication 7
- This can occur through chronic occult blood loss from gastritis or ulcers, which may not always produce visible dark stools 7
- Vitamin B12 deficiency and idiopathic thrombocytopenic purpura are also recognized extragastric manifestations 7, 2
Common Pitfall
Do not attribute dark stools solely to H. pylori infection without investigating for bleeding complications:
- The presence of melena indicates active bleeding requiring urgent evaluation regardless of H. pylori status 6
- Failing to perform endoscopy in patients with melena can miss serious pathology like bleeding ulcers or gastric cancer 1
- H. pylori eradication alone will not stop active bleeding; the bleeding source must be identified and treated 3, 6