Pale Stools / Dark Tarry Stools

A significant change in stool color is a critical clinical sign. Dark, tarry, foul-smelling stools, known as melena, are the hallmark of an upper gastrointestinal bleed, where hemoglobin is altered by stomach acid and intestinal bacteria. Common causes include peptic ulcers and esophageal varices. Conversely, pale or clay-colored stools, known as acholic stools, indicate a lack of bile reaching the intestine. This is a sign of biliary obstruction, often caused by a gallstone in the common bile duct or a tumor of the pancreas or bile ducts. Both melena and acholic stools are medically urgent symptoms that require immediate evaluation to identify and treat the serious underlying pathology.