Can colitis cause rectal bleeding?
Yes, colitis can cause rectal bleeding, which may appear as blood in the stool (hematochezia) or as streaks of bright red blood on toilet paper or the surface of the stool. The likelihood and severity of bleeding depend on the underlying cause and extent of inflammation in the colon.
Inflammatory bowel diseases—such as ulcerative colitis and Crohn’s disease—are common causes of colitis-associated bleeding. In ulcerative colitis, inflammation is typically continuous and confined to the mucosa and submucosa of the colon and rectum; this often leads to friable, ulcerated tissue that bleeds readily during bowel movements. Crohn’s colitis may also cause bleeding, though it tends to be less consistent due to its patchy, transmural involvement.
Other causes of colitis—including infectious colitis (e.g., from *Campylobacter*, *Shigella*, *Salmonella*, or *Clostridioides difficile*), ischemic colitis, and microscopic colitis—vary in their propensity to cause overt bleeding. For example, infectious and ischemic colitis frequently present with hematochezia, especially in moderate-to-severe cases, whereas microscopic colitis (lymphocytic or collagenous) rarely causes visible blood loss—diarrhea is the predominant symptom.
It is important to note that any new-onset rectal bleeding warrants prompt medical evaluation. While colitis is a plausible explanation, other serious conditions—including colorectal cancer, diverticular disease, angiodysplasia, or hemorrhoidal bleeding—must be ruled out through clinical assessment, laboratory testing, stool studies, and often endoscopic evaluation (e.g., colonoscopy with biopsy).