What investigations are recommended for a 67-year-old patient presenting with bloody diarrhea for a month?

From the Guidelines

For a 67-year-old patient with bloody diarrhea for a month, I strongly recommend a comprehensive workup including complete blood count, comprehensive metabolic panel, stool studies (including culture, ova and parasites, Clostridioides difficile toxin), and fecal calprotectin. Colonoscopy with biopsies is essential and should be performed promptly to directly visualize the colon and obtain tissue samples, as suggested by the guidelines for the investigation of chronic diarrhoea, 2nd edition 1. Additional investigations should include abdominal imaging (CT scan or ultrasound) to evaluate for masses or inflammatory changes, and inflammatory markers such as C-reactive protein and erythrocyte sedimentation rate. These investigations are crucial because bloody diarrhea persisting for a month in an older adult raises significant concerns for colorectal cancer, inflammatory bowel disease, ischemic colitis, or infectious colitis, as highlighted in the 2017 infectious diseases society of america clinical practice guidelines for the diagnosis and management of infectious diarrhea 1. The patient's age (67) places them at higher risk for malignancy, and the duration of symptoms (one month) suggests a non-self-limiting process. Anemia assessment is also important as ongoing blood loss may have led to iron deficiency. If the patient is taking anticoagulants or NSAIDs, medication review is warranted as these can contribute to gastrointestinal bleeding. Prompt investigation is essential as prolonged bloody diarrhea can lead to dehydration, electrolyte imbalances, and significant anemia requiring urgent intervention. Some key points to consider in the investigation of this patient include:

• The importance of stool testing for various pathogens, including Salmonella, Shigella, Campylobacter, Yersinia, C. difficile, and STEC, as recommended by the 2017 IDSA guidelines 1.
• The need for blood cultures in certain situations, such as in infants <3 months of age, people with signs of septicemia, or those with systemic manifestations of infection 1.
• The consideration of a broader set of bacterial, viral, and parasitic agents in the context of a possible outbreak of diarrheal illness, as suggested by the 2017 IDSA guidelines 1.

From the Research

Investigations for Bloody Diarrhea

For a 67-year-old patient presenting with bloody diarrhea for a month, the following investigations are recommended:

• A patient history and physical examination to evaluate for pathologies such as celiac disease or inflammatory bowel disease 2
• Laboratory tests including:
  • Complete blood count
  • C-reactive protein
  • Anti-tissue transglutaminase immunoglobulin A (IgA)
  • Total IgA
  • Basic metabolic panel 2
• Stool studies to categorize diarrhea as watery, fatty, or inflammatory 2
• Tests for Clostridioides difficile infection, such as:
  • Toxigenic culture
  • Glutamate dehydrogenase (GDH)
  • Nucleic acid amplification test (NAAT)
  • Toxins A/B enzyme immunoassay (EIA) 3, 4
• A multistep approach to CDI diagnosis, such as either GDH or NAAT followed by toxins A/B EIA, in conjunction with laboratory stewardship 4

Differential Diagnosis

The differential diagnosis for bloody diarrhea is broad and includes:

• Inflammatory bowel disease
• Clostridioides difficile infection
• Colitis
• Colorectal cancer 2, 5, 3, 4, 6
• Other disorders that can cause inflammatory diarrhea, such as microscopic colitis and endocrine disorders 2