What diagnostic tests are indicated for a patient presenting with rectal bleeding characterized by dark chocolate-colored stools, a positive fecal occult blood test, leukocytosis, elevated Red Cell Distribution Width-Standard Deviation (RDW-SD), neutrophilia, impaired renal function, and coagulopathy?

From the Guidelines

For a patient presenting with rectal bleeding characterized by dark chocolate-colored stools, a positive fecal occult blood test, leukocytosis, elevated Red Cell Distribution Width-Standard Deviation (RDW-SD), neutrophilia, impaired renal function, and coagulopathy, I strongly recommend ordering a comprehensive diagnostic workup including a complete blood count (CBC), comprehensive metabolic panel (CMP), coagulation studies, and imaging studies such as abdominal/pelvic CT scan with contrast and colonoscopy, as these tests are crucial in identifying the source and severity of the bleeding, and guiding further management 1.

Diagnostic Approach

The patient's presentation suggests a lower gastrointestinal bleed, and the diagnostic approach should focus on identifying the source of the bleeding.

• A CBC will help assess for anemia and infection, while the CMP evaluates kidney function and electrolyte balance.
• Coagulation studies (PT/INR, PTT) are important to rule out bleeding disorders.
• Type and cross for potential blood transfusion should be ordered given the active bleeding.
• The patient's current labs show leukocytosis, elevated neutrophils, and elevated BUN with high BUN/creatinine ratio, suggesting possible dehydration or upper GI bleeding.
• The elevated RDW-SD indicates variation in red blood cell size, often seen with chronic blood loss.

Imaging and Endoscopy

• Colonoscopy is the gold standard for evaluating lower GI bleeding, as it allows for direct visualization of the colon and identification of the bleeding source 1.
• CT angiography can help identify active bleeding sites and guide further management, such as transcatheter embolization.
• If bleeding is severe or the patient is hemodynamically unstable, immediate surgical consultation and possible emergent endoscopy should be considered.

Management of Coagulopathy

• Coagulopathy is a well-known risk factor for recurrent bleeding, and correction of coagulopathy is the first step for stable patients 1.
• In unstable patients, transcatheter embolization using liquid embolic agents such as N-Butyl cyanoacrylate (NBCA) may provide effective hemostasis.
• Alternative agents such as ethylene-vinyl alcohol copolymer can be used in patients with underlying coagulopathy or low platelet count.

From the Research

Diagnostic Tests for Rectal Bleeding

The patient's presentation of dark chocolate-colored stools, a positive fecal occult blood test, leukocytosis, elevated Red Cell Distribution Width-Standard Deviation (RDW-SD), neutrophilia, impaired renal function, and coagulopathy suggests a possible lower gastrointestinal bleed. The following diagnostic tests are indicated:

• Computed tomography (CT) angiography to localize the source of bleeding 2
• Nuclear medicine scintigraphy to detect active bleeding 2
• Conventional catheter angiography to deliver treatment if a source of bleeding is identified 2
• Colonoscopy to directly visualize the colon and identify potential sources of bleeding 3, 4, 5
• CT enterography to evaluate the small intestine for potential sources of bleeding 2
• Nuclear medicine Meckel scan to evaluate for a Meckel's diverticulum, a possible source of bleeding 2

Rationale for Diagnostic Tests

The patient's positive fecal occult blood test and iron deficiency anemia suggest occult gastrointestinal bleeding, which can be caused by various lesions in the gastrointestinal tract 3, 4. The presence of leukocytosis, elevated RDW-SD, neutrophilia, impaired renal function, and coagulopathy may indicate a more severe bleed or an underlying condition that requires further evaluation. The diagnostic tests listed above can help identify the source of bleeding and guide management.

Considerations for Diagnostic Evaluation

The diagnostic evaluation of patients with rectal bleeding may be suboptimal due to inadequate risk factor assessment and prioritization of other concurrent medical problems 5. A thorough evaluation, including a complete medical history, physical examination, and laboratory tests, is essential to identify the underlying cause of rectal bleeding. The use of fecal occult blood tests, such as the Guaiac test or immunochemical test, can help detect occult blood in the stool, but their validity may vary depending on the test used and the population being screened 6.