Stool is the waste product expelled through rectum after the absorption of nutrients from food particles. Normal color of the stool is varying shades of brown or dark yellow. The color of the stool is due to the presence of bilirubin in blood. Black stool in adults can be indicative of bleeding of intestinal tract. Sometimes the food we eat can change the normal color of the stool. Any abnormality in the quality, quantity and color of the stool can be due to intestinal problems.
How stool is formed?
As the food passes through the stomach various enzymes are released from the pancreas to break down the food particles. The liquid content of the food would then pass through the intestine wherein nutrients are fully absorbed and the waste products are passed on to the colon which further absorbs the water molecules sending the stool into the rectum. Any change in bilirubin content and concentration can cause changes in stool color.
You need not always worry if the stool color is different. It can be due to the food you ate last night or the iron pills you took yesterday. Common anti-inflammatory drugs like Ibuprofen and Aspirin can affect the normal stool color. Hence changes in stool color are not due to any disease all the time.
Certain medical conditions can affect the color of the stool. Stomach ulcer can produce black stool. Changes in intestinal tract can cause black stool. Bleeding of gastrointestinal tract, formation of tumor in the bile ducts can cause black stool. A person undergoing radiation therapy can get black stool.
Any bleeding in the esophagus, stomach or intestine can produce black stool. Blood swallowed accidentally during dental procedures can cause black stool. Medications like bismuth, iron, and beets can change the stool color. Pregnant women may get black stool due to daily intake of iron and vitamin tablets. Diarrhea can cause changes in normal stool color and texture.
Occasional changes in stool color are quite common due to ingested food. But if there is persistent black stool you need to check with your doctor and never ignore if you pass black stools with other symptoms. But if you have additional symptoms like abdominal pain, swelling of abdomen, diarrhea, flatulence, nausea or vomiting, and loss of appetite it can be indicative of intestinal problem. Foul smelling stool can be due to bacterial infection. For some people, it can cause flu like symptoms along with black stool.
In rare cases, black stool can be serious requiring immediate medical help if accompanied by symptoms like confusion, dizziness, high fever, palpitations, fast beating of heart, shortness of breath, severe pain in the abdomen and severe diarrhea etc. Getting black stool recurrently can be due to very serious causes like internal blood leakage, spreading of cancer and due to shock.
Your doctor cannot diagnose the cause of the problem based on black stool alone. He would complete physical exam and collect your medical history. He would ask about dietary changes which can change the stool color. Stool sample would be tested in the lab for the presence of infectious bacteria, fat or blood (FOBT test). Blood test would be done to check anemic condition or underlying problems in the gallbladder or liver. He may collect the enzymes from your pancreas to rule out any infection or disease in pancreas.
Screening is done to detect any cancer or tumor formation in the colon. Presence of hemoglobin in the stool can be detected using multiple tests indicating hemorrhage or bleeding in the intestine. In addition, your doctor may order for endoscopy of the intestine or colonoscopy test to get clear picture of the internal parts. If needed, CT or MRI scanning is done to find out celiac disease or cancer or any problems in the bile duct.
Your doctor can proceed to give treatment after knowing the actual cause of black stool. Depending on the result of the diagnosis, suitable medications and treatments are given. No treatment is needed if you are getting black stool once or twice. It can be due to intake of medications. Depending on the health condition of the patient and symptoms treatment is started.
Drugs are available to control peptic ulcer and gastrointestinal bleeding. To arrest abnormal bleeding from the intestine, medications are injected using endoscopic procedure. In some cases, radiologists would inject chemicals directly on the bleeding arteries to stop further bleeding. If conservative methods are not working, surgery is to be done to fix the problem.