A Fecal Occult Blood Test (FOBT) is a non-invasive screening tool designed to detect hidden blood in your stool sample. A “positive” FOBT result indicates microscopic amounts of blood were found.
Understanding a Positive Result
A positive FOBT result means blood in your stool, but it does not provide a diagnosis of cancer or any other specific medical condition. It functions as a screening test, alerting healthcare providers to bleeding that may originate from various parts of the digestive system. While often used for colorectal cancer screening, a positive outcome signals further diagnostic steps to pinpoint the cause and location.
The test is highly sensitive to hemoglobin, a component of red blood cells, indicating blood has passed through the digestive tract. Approximately one in 14 people who undergo an FOBT will receive a positive result. This warrants additional evaluation.
Common Reasons for Blood
Bleeding detected by an FOBT can stem from various non-cancerous conditions within the digestive system. Hemorrhoids, swollen blood vessels, are a common cause of bleeding. Similarly, anal fissures, small tears in the lining of the anal opening, can also lead to blood in the stool. Both of these conditions are often associated with straining during bowel movements.
Other benign causes include diverticulosis, characterized by small, pouch-like bulges forming in the colon wall. Ulcers, sores in the digestive tract lining, can also lead to occult blood. Non-cancerous polyps, which are growths on the colon or rectal lining, may also bleed. Inflammatory bowel diseases, such as Crohn’s disease and ulcerative colitis, involve chronic inflammation and cause bleeding.
Next Steps After a Positive Test
Following a positive FOBT result, the next recommended step is a colonoscopy. This procedure allows a doctor to visually inspect the entire colon and rectum using a flexible tube with a camera, enabling identification of the bleeding source. A colonoscopy can detect not only colorectal cancer but also precancerous growths, such as polyps, which can be removed during the procedure.
The colonoscopy should ideally be scheduled within 2 to 4 weeks of receiving a positive FOBT result, though timing may vary based on individual risk factors and symptoms. If a colonoscopy is not immediately feasible, other diagnostic tests might be considered, such as a flexible sigmoidoscopy, which examines only the lower part of the colon, or a CT colonography, also known as a “virtual colonoscopy.” However, a colonoscopy remains the primary recommendation for thorough investigation.
Preparing for Further Evaluation
Preparing for a colonoscopy involves specific steps to ensure the colon is clear for examination. Patients are advised to modify their diet in the days leading up to the procedure, often transitioning to low-fiber foods and then to a clear liquid diet the day before. This helps to minimize solid residue in the bowel.
Bowel preparation is a key component, usually involving strong laxatives taken the evening before and sometimes on the morning of the procedure. It is also important to discuss any regular medications with the healthcare provider, as some may need to be adjusted or temporarily stopped. Patients will also need to arrange for transportation home after the procedure, as sedation is commonly used.