What is the initial workup for a patient suspected of having Inflammatory Bowel Disease (IBD)?

Initial Workup for Suspected Inflammatory Bowel Disease

For patients aged 16-40 with chronic lower gastrointestinal symptoms lasting >4 weeks, begin with faecal calprotectin testing alongside basic laboratory investigations, followed by urgent gastroenterology referral and ileocolonoscopy if calprotectin is >250 μg/g. 1

Primary Care Assessment and Initial Testing

History Taking

Obtain a detailed history focusing on:

• Stool characteristics: frequency, consistency, urgency, and presence of rectal bleeding 1
• Systemic symptoms: abdominal pain, malaise, fever, and weight loss (document objective weight loss) 1
• Red flag features: rectal bleeding plus any combination of abdominal pain, change in bowel habit, weight loss, or iron deficiency anemia 1
• Recent travel and medication use (particularly NSAIDs, which can elevate calprotectin) 1
• Smoking status and family history of IBD or gastrointestinal cancer 1
• Extraintestinal manifestations: joint symptoms, skin changes, and eye problems 1

Physical Examination

Perform a focused examination documenting:

• Vital signs: pulse rate, blood pressure, temperature, and weight 1
• Signs of anemia: pallor suggesting chronic blood loss 1
• Fluid depletion: assess skin turgor and mucous membranes 1
• Abdominal examination: tenderness, distension, or palpable masses 1
• Perianal examination: essential for detecting Crohn's disease-related fistulae or abscesses 1

Mandatory Laboratory Investigations

Order the following tests in primary care:

• Complete blood count to detect anemia, leukocytosis, or thrombocytosis 1, 2
• Urea and electrolytes to assess for dehydration and electrolyte imbalances 1
• C-reactive protein (CRP) as a marker of systemic inflammation 1, 2
• Coeliac serology to exclude celiac disease as a differential diagnosis 1
• Stool culture to exclude infectious causes including Clostridium difficile toxin 1

Faecal Calprotectin Testing Strategy

Faecal calprotectin is the single most important screening test, with 93-95% sensitivity and 91-96% specificity for differentiating IBD from non-IBD diagnoses. 1

Interpret results as follows:

• <100 μg/g: IBS likely, treat as IBS in primary care 1
• 100-250 μg/g: Consider repeat testing off NSAIDs or routine gastroenterology referral 1
• >250 μg/g: Refer urgently to gastroenterology after excluding infection 1

Critical caveat: Do not perform calprotectin testing if NSAIDs have been used in the past 6 weeks, as this causes false elevation. 1

Secondary Care Diagnostic Workup

Endoscopic Evaluation

Ileocolonoscopy with terminal ileal intubation and multiple biopsies is the reference standard for IBD diagnosis. 1, 3

For ulcerative colitis diagnosis:

• Perform colonoscopy or flexible sigmoidoscopy to assess disease extent 1
• Look for loss of vascular pattern, granularity, friability, and ulceration 1
• Take biopsies from affected and normal-appearing areas, including the rectum even if macroscopically normal 1, 3
• In moderate to severe disease, flexible sigmoidoscopy is safer than full colonoscopy due to perforation risk 1

For Crohn's disease diagnosis:

• Perform colonoscopy to the terminal ileum to document focal, asymmetric inflammation 1
• Take terminal ileal biopsies even if macroscopically normal to detect microscopic disease 1
• Obtain biopsies from multiple segments to document skip lesions 1, 3
• Consider upper endoscopy if upper GI symptoms are present, particularly in pediatric patients 1

Cross-Sectional Imaging

All patients with confirmed or strongly suspected IBD require cross-sectional imaging at diagnosis to assess small bowel involvement and detect complications. 1, 3

• MR enterography is preferred over CT enterography to avoid radiation exposure in this young patient population 1, 3
• Imaging is essential for Crohn's disease to define extent and site of disease, particularly small bowel involvement beyond colonoscopic reach 1
• Plain abdominal radiography is essential in suspected severe IBD to exclude colonic dilatation and assess disease extent 1

Additional Investigations for Specific Scenarios

• Small bowel capsule endoscopy: Consider if ileocolonoscopy is inconclusive but clinical suspicion remains high 1
• Balloon-assisted enteroscopy: Reserve for diagnostic evaluation when other modalities are inconclusive or when therapeutic intervention is needed 1
• Upper GI endoscopy with biopsies: Particularly useful in pediatric patients and adults with upper GI symptoms 1

Common Pitfalls to Avoid

Do not rely on CRP alone: Approximately 15-20% of patients with active IBD have normal CRP levels, particularly in ulcerative colitis. 2, 3 CRP correlates better with endoscopic activity in Crohn's disease than ulcerative colitis. 2

Do not defer colonoscopy based on intermediate calprotectin values (100-250 μg/g) if clinical suspicion is high based on symptoms or family history. 1

Do not perform colonoscopy in severe colitis without experienced endoscopist involvement: There is higher perforation risk in moderate to severe disease; flexible sigmoidoscopy is safer. 1

Do not forget to exclude infection: Always test for C. difficile toxin and other infectious causes before confirming IBD diagnosis. 1, 2

Admit patients urgently if systemically unwell or suspected acute severe colitis rather than pursuing outpatient workup. 1