From the Guidelines
A stool test for melena, such as the fecal occult blood test (FOBT), is the most appropriate initial diagnostic step to detect digested blood in the stool, as recommended by recent guidelines 1. When performing a stool test for melena, it is essential to collect a small stool sample in a clean container and submit it to a laboratory for analysis. The most common tests used are guaiac-based tests like Hemoccult or immunochemical tests (FIT), which can detect even small amounts of blood not visible to the naked eye.
- To ensure accurate results, patients should avoid consuming red meat, certain vegetables (turnips, horseradish), and medications like aspirin or NSAIDs for 72 hours before testing, as these can cause false positives.
- Additionally, vitamin C supplements should be avoided, as they may cause false negatives. Melena indicates upper gastrointestinal bleeding, typically from the esophagus, stomach, or small intestine, as blood becomes black after being digested by intestinal enzymes.
- If melena is detected, further investigation with endoscopy is usually necessary to identify the bleeding source, which could be peptic ulcers, gastritis, esophageal varices, or other conditions requiring prompt medical attention, as highlighted in the 2024 update of the ACR Appropriateness Criteria for nonvariceal upper gastrointestinal bleeding 1.
From the Research
Stool Test for Melena
- A stool test for melena typically involves a fecal occult blood test (FOBT) to detect hidden blood in the stool 2, 3.
- The FOBT can be used to diagnose occult gastrointestinal bleeding, which may present as melena, hematemesis, or hematochezia 3.
- A positive FOBT result may indicate the presence of blood in the stool, which can be further evaluated using colonoscopy or esophagogastroduodenoscopy 2.
- In patients with melena, a negative upper endoscopy may prompt a colonoscopy to investigate the source of bleeding 4.
- Imaging tests such as computed tomography (CT) angiography, nuclear medicine scintigraphy, and conventional catheter angiography may also be used to localize and treat lower gastrointestinal bleeds, including those presenting as melena 5.
Diagnostic Approach
- The diagnostic approach to gastrointestinal bleeding, including melena, involves a combination of clinical evaluation, laboratory tests, and imaging studies 3.
- Accurate clinical diagnosis is crucial in guiding definitive investigations and interventions 3.
- The choice of diagnostic test depends on the severity and duration of bleeding, as well as the patient's symptoms and medical history 2, 5.
Treatment and Management
- Treatment of gastrointestinal bleeding, including melena, often involves endoscopic ablation of the bleeding site with thermal energy, if the site is accessible 2.
- Angiographic embolization may be used to treat lesions that cannot be reached endoscopically 2.
- Medical treatment, usually with combined hormone therapy, has limited utility in managing diffuse vascular lesions, which are not uncommon in patients with gastrointestinal bleeding 2.