From the Guidelines
To differentiate between colorectal cancer, Crohn's disease, and chronic pancreatitis, I would order a comprehensive set of laboratory tests and imaging studies, prioritizing colonoscopy with biopsies, abdominal CT scan with contrast, and MRI enterography, as these provide the most accurate and relevant information for diagnosing and distinguishing between these conditions, as supported by recent studies such as 1 and 1.
Laboratory Tests
For laboratory tests, I recommend:
- A complete blood count to check for anemia and inflammation
- Comprehensive metabolic panel to assess liver and kidney function
- Fecal calprotectin to detect intestinal inflammation
- Carcinoembryonic antigen (CEA) as a tumor marker for colorectal cancer
- Fecal occult blood test to detect gastrointestinal bleeding
- Inflammatory markers including C-reactive protein and erythrocyte sedimentation rate to evaluate inflammation in Crohn's disease
- For pancreatic function, serum amylase, lipase, and fecal elastase should be measured
Imaging Studies
Imaging studies should include:
- Colonoscopy with biopsies as the gold standard for diagnosing colorectal cancer and Crohn's disease, allowing direct visualization of the colon and terminal ileum
- Abdominal CT scan with contrast to evaluate bowel wall thickening, masses, and pancreatic changes
- MRI enterography, which is particularly useful for Crohn's disease assessment, as noted in 1 and 1
- MRCP (magnetic resonance cholangiopancreatography) can visualize pancreatic ducts for chronic pancreatitis
- Endoscopic ultrasound may be necessary to evaluate pancreatic parenchyma and obtain tissue samples if needed, as suggested by 1
Rationale
These tests collectively provide the necessary information to distinguish between colorectal cancer, Crohn's disease, and chronic pancreatitis based on their distinct pathological features. The choice of tests is guided by the need to directly visualize the colon and terminal ileum, assess the small bowel for signs of Crohn's disease, and evaluate pancreatic function and structure. Recent studies, such as those published in the Journal of the American College of Radiology 1, support the use of these tests in the diagnosis and management of these conditions.
From the Research
Laboratory Tests
To differentiate between colorectal cancer, Crohn's disease, and chronic pancreatitis, the following laboratory tests can be ordered:
- Complete Blood Count (CBC) to assess for anemia, inflammation, and other abnormalities 2, 3, 4, 5
- Blood chemistry tests, such as liver function tests and pancreatic enzyme tests, to evaluate liver and pancreatic function
- Inflammatory marker tests, such as C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR), to assess for inflammation
- Tumor marker tests, such as carcinoembryonic antigen (CEA), to evaluate for colorectal cancer
Imaging Studies
The following imaging studies can be ordered to help differentiate between colorectal cancer, Crohn's disease, and chronic pancreatitis:
- Computed Tomography (CT) scan of the abdomen and pelvis to evaluate the colon, rectum, and surrounding tissues for tumors or other abnormalities
- Magnetic Resonance Imaging (MRI) of the abdomen and pelvis to evaluate the colon, rectum, and surrounding tissues for tumors or other abnormalities
- Ultrasound of the abdomen to evaluate the liver, pancreas, and surrounding tissues for tumors or other abnormalities
- Colonoscopy to visually examine the colon and rectum for tumors, polyps, or other abnormalities
Other Tests
Other tests that may be ordered to help differentiate between colorectal cancer, Crohn's disease, and chronic pancreatitis include:
- Stool tests, such as stool occult blood test, to evaluate for blood in the stool
- Endoscopy to visually examine the upper gastrointestinal tract for tumors, ulcers, or other abnormalities
- Biopsy to obtain tissue samples for histological examination to confirm the diagnosis of colorectal cancer, Crohn's disease, or chronic pancreatitis 3, 4, 5