The presence of visible blood in stool, known as rectal bleeding or hematochezia, is a symptom of gastrointestinal bleeding. Bleeding can originate anywhere from the esophagus down to the anus. Determining the source and speed of the blood loss is the primary goal of medical evaluation.
When Blood in Stool is a Medical Emergency
Immediate medical assistance is required when blood loss is rapid and significant, leading to hypovolemic shock. Symptoms of shock include sudden dizziness, fainting, confusion, a rapid heart rate, or low blood pressure. Passing a large volume of blood in a single bowel movement or continuous, heavy bleeding indicates a severe hemorrhage.
The color of the blood helps physicians narrow the location of the bleed. Bright red blood (hematochezia) typically signals a bleed in the lower gastrointestinal tract, such as the colon or rectum. Conversely, black, tarry, and foul-smelling stool (melena) results from blood digested as it passed through the upper GI tract. Melena suggests a slower, more serious bleed higher up, though rapid upper GI bleeding can sometimes present as hematochezia.
Common Causes of Minor Bleeding
The most frequent causes of blood in the stool are non-life-threatening and originate from the anal region. Hemorrhoids, swollen veins in the rectum or anus, are the most common source of visible blood. This bleeding is typically bright red, appearing on the toilet paper, dripping into the bowl, or coating the surface of the stool. Straining during a bowel movement, often due to constipation, is a common trigger.
Another common minor cause is an anal fissure, a small tear in the lining of the anal canal. Fissures typically cause sharp pain during or immediately after a bowel movement, accompanied by a small amount of bright red blood. Both hemorrhoids and fissures often respond well to conservative treatments like increased fiber intake and stool softeners. Mild inflammation of the rectum, or proctitis, can also cause minor spotting of blood and mucus.
Serious Underlying Conditions
Bleeding that is persistent or recurrent, even if not a sudden emergency, requires prompt investigation. Peptic ulcers in the stomach or duodenum erode the protective lining, frequently causing upper GI bleeding that presents as melena. These ulcers are commonly linked to Helicobacter pylori infection or the long-term use of nonsteroidal anti-inflammatory drugs (NSAIDs).
Inflammatory Bowel Disease (IBD), including Crohn’s disease and Ulcerative Colitis, causes chronic inflammation and ulceration of the intestinal lining. Bleeding in IBD is often accompanied by abdominal pain, weight loss, and persistent diarrhea. Diverticular disease involves small, bulging pouches (diverticula) in the colon wall; a diverticulum can rupture a blood vessel, leading to significant, painless bleeding.
Colorectal polyps are growths on the colon lining that may bleed intermittently, sometimes microscopically (occult). Certain polyps are precancerous, and colorectal cancer, particularly in its early stages, can also cause slow, visible bleeding. Angiodysplasia, which involves abnormal, fragile blood vessels in the GI tract, may also be the source of chronic blood loss.
Diagnostic Tests and Medical Procedures
The initial medical evaluation begins with a physical examination, including a digital rectal examination (DRE), to check for external sources. Blood tests, such as a complete blood count (CBC), assess for anemia resulting from chronic, slow blood loss. A fecal occult blood test (FOBT) or fecal immunochemical test (FIT) detects microscopic amounts of blood not visible to the eye.
If the bleeding source is unknown, endoscopic procedures are employed to visualize the gastrointestinal tract directly. An upper endoscopy examines the esophagus, stomach, and the beginning of the small intestine, primarily to look for causes of melena. For lower GI bleeding, a colonoscopy is the standard method, allowing the physician to view the entire large intestine and remove polyps or cauterize bleeding sites. A flexible sigmoidoscopy is a similar procedure that examines only the lower part of the colon and the rectum.