Blood in the Stool: When to Worry, When to Wait

Seeing blood in the toilet bowl is alarming, and most patients react in one of two ways. Some panic, assume the worst, and arrive in clinic the next morning. Others convince themselves it is 'just piles', try home remedies, and only show up months or years later when something more serious has progressed.

Both reactions miss the point. Blood in the stool is a symptom - sometimes harmless, sometimes the earliest warning of something serious - and a 10-minute outpatient examination is usually all it takes to know which.

This guide explains what different colours and patterns of bleeding usually mean, the warning signs that should never be ignored, and what an evaluation actually involves.

Blood in the stool simply means that somewhere along the digestive tract, a blood vessel is leaking. Where it is leaking from determines what colour you see. Bright red blood usually comes from the anus or lower rectum. Dark red or maroon blood usually comes from higher up in the colon. Black, tarry stool (melaena) usually comes from the stomach or small intestine.

The most common causes - by a wide margin - are benign. Piles and fissures account for the majority of cases. Less common but more serious causes include polyps, colorectal cancer, inflammatory bowel disease, diverticular disease and bleeding ulcers.

The point of evaluation is not to diagnose cancer in everyone - most patients do not have it. The point is to make sure the small percentage who do have something serious are caught early, when treatment is most effective.