From the Guidelines
The workup for diarrhea with blood in stool should begin with a thorough history and physical examination, followed by laboratory and stool studies, including complete blood count, comprehensive metabolic panel, C-reactive protein, and stool studies including culture, ova and parasite examination, Clostridioides difficile testing, and fecal calprotectin, as recommended by the most recent guidelines 1.
Initial Evaluation
The initial evaluation of a patient with diarrhea and blood in stool should include a thorough history and physical examination to identify potential causes and risk factors. This should be followed by laboratory tests, including:
- Complete blood count to assess for anemia or infection
- Comprehensive metabolic panel to evaluate electrolyte imbalance and kidney function
- C-reactive protein to assess for inflammation
- Stool studies, including culture, ova and parasite examination, Clostridioides difficile testing, and fecal calprotectin to identify infectious or inflammatory causes
Further Testing
Depending on the patient's age and risk factors, further testing may be necessary, including:
- Colonoscopy to visualize the colon directly and obtain biopsies, particularly for patients over 40 or with concerning symptoms like weight loss or family history of colorectal cancer
- Imaging studies, such as CT scan of the abdomen and pelvis, if there is concern for inflammatory bowel disease, diverticulitis, or other structural abnormalities
Common Causes
Common causes of bloody diarrhea include:
- Infectious colitis (from pathogens like Shigella, Salmonella, Campylobacter, or E. coli)
- Inflammatory bowel disease (ulcerative colitis or Crohn's disease)
- Ischemic colitis
- Diverticular bleeding
- Colorectal cancer
Urgency of Workup
The urgency of the workup depends on the severity of symptoms, with severe bleeding, significant abdominal pain, or signs of sepsis warranting immediate hospitalization and expedited evaluation. While awaiting diagnostic results, supportive care with hydration and electrolyte replacement is essential, as recommended by the Infectious Diseases Society of America guidelines 1.
From the Research
Diarrhea with Blood in Stool Workup
- The workup for diarrhea with blood in stool may involve stool tests, including bacterial culture, ova and parasites, and Clostridium difficile toxin assays 2.
- However, studies have shown that stool cultures and ova and parasite examinations are often low-yield and may not be necessary for patients with nosocomial diarrhea 3, 4, 5.
- The presence of blood in stool may indicate an inflammatory cause, and additional diagnostic evaluation and management may be warranted 6.
- Molecular studies are preferred over traditional stool cultures, unless an outbreak is suspected 6.
- Targeted antibiotic therapy may be appropriate following microbiologic stool assessment, but empiric antibiotics are rarely warranted except in cases of sepsis or inflammatory diarrhea 6.
- A thorough history and physical examination, including evaluation for signs of dehydration, sepsis, or potential surgical processes, are essential in the workup of diarrhea with blood in stool 6.