What is the comprehensive approach to investigating and managing inflammatory bowel disease (IBD)?

Comprehensive Approach to Investigating Inflammatory Bowel Disease

Initial Clinical Evaluation

The diagnosis of IBD requires a systematic combination of clinical assessment, laboratory testing, endoscopic evaluation with histology, and radiological imaging to establish the diagnosis and differentiate between Crohn's disease and ulcerative colitis. 1

History and Physical Examination

• Document stool frequency, consistency, urgency, rectal bleeding, and nocturnal symptoms to assess disease severity 1
• Record systemic symptoms including fever, malaise, anorexia, weight loss, and abdominal pain (more common in Crohn's disease) 1
• Assess for extraintestinal manifestations affecting joints, skin, and eyes 1, 2
• Obtain recent travel history, antibiotic exposure, medication use (especially NSAIDs), and smoking status 1, 3, 2
• Document family history of IBD or colorectal cancer, as first-degree relatives have a 4-fold increased risk 2
• Perform general examination checking for anemia, fluid depletion, weight loss, abdominal tenderness or masses, and conduct perianal examination 1

Laboratory Investigations

Initial blood work must include complete blood count, comprehensive metabolic panel, liver function tests, and inflammatory markers (ESR or CRP), as CRP is more sensitive than ESR for detecting active inflammation. 1, 4

• Obtain microbiological stool testing for bacterial pathogens, Clostridium difficile toxin, and ova/parasites to exclude infectious causes 1, 3
• Measure fecal calprotectin, with values <100 μg/g associated with lower relapse probability, 100-200 μg/g warranting repeat testing, and >200 μg/g triggering endoscopic evaluation 1
• Additional testing may be needed for patients with travel history 1

Radiological Assessment

• Obtain abdominal radiography in suspected severe IBD to exclude colonic dilatation, assess disease extent in UC, or identify small bowel dilatation or masses in CD 1
• CT abdomen/pelvis with IV contrast serves as the gold standard for evaluating complications, achieving 95% sensitivity/specificity for identifying serious pathology including abscesses, strictures, or fistulae 4
• Small bowel imaging via follow-through or enterography remains the standard for defining extent and location of Crohn's disease 1

Endoscopic Evaluation

For all patients with suspected IBD, rigid or flexible sigmoidoscopy should be performed initially, with colonoscopy to the terminal ileum preferred in mild-to-moderate disease to assess full extent and obtain biopsies. 1, 3

Sigmoidoscopy

• Perform rigid sigmoidoscopy unless flexible sigmoidoscopy is immediately planned 1
• Obtain rectal biopsy even if mucosa appears macroscopically normal, as microscopic changes may be present 1, 3
• Macroscopic features of UC include loss of vascular pattern, granularity, friability, and ulceration 1

Colonoscopy

• In mild-to-moderate disease, colonoscopy with terminal ileal intubation is preferred over flexible sigmoidoscopy to assess disease extent and obtain terminal ileal biopsy for Crohn's disease evaluation 1, 3
• In moderate-to-severe disease, defer colonoscopy until clinical improvement due to perforation risk; flexible sigmoidoscopy is safer 1
• Terminal ileal biopsy documents examination extent and may reveal microscopic evidence of CD even when macroscopically normal 1
• Approximately 10-20% of UC patients show backwash ileitis extending into terminal ileum 1

Histopathological Assessment

Multiple biopsies from different colonic segments and terminal ileum should be obtained and stored in separate containers to map inflammation distribution, as diagnostic accuracy increases from 66% to 92% with segmental biopsies versus random sampling. 1

• Fix biopsies immediately in buffered formalin prior to transport 1
• Examine multiple sections from each sample, with 2-3 tissue levels consisting of five or more sections recommended 1
• Serial sectioning is superior to step sectioning for detecting focal lesions 1
• Rectal biopsies are necessary to confirm or reject rectal involvement and differentiate IBD from other inflammatory conditions 1
• Routine hematoxylin and eosin staining is appropriate for diagnosis 1

Diagnostic Criteria

Ulcerative Colitis

• Diagnosis requires clinical suspicion supported by appropriate macroscopic findings on sigmoidoscopy/colonoscopy, typical histological findings on biopsy, and negative stool examinations for infectious agents 1

Crohn's Disease

• Diagnosis depends on demonstrating focal, asymmetric, and often granulomatous inflammation 1
• Investigation selection varies according to presenting manifestations, physical findings, and complications 1
• At least 50% require surgery within 10 years, and 70-80% within their lifetime 1

Monitoring Disease Activity

A multimodal approach combining clinical indices (partial Mayo or Simple Clinical Colitis Activity Index), hemoglobin, CRP, fecal calprotectin, and endoscopy with histology should be used to monitor remission. 1

• Fecal calprotectin correlates well with clinical, endoscopic, and histological disease activity 1
• Values <250 μg/g are associated with endoscopic and histological remission and protection against hospitalization or colectomy 1
• Intestinal ultrasound represents an emerging non-invasive monitoring tool where available 1, 5

Critical Pitfalls to Avoid

• Do not rely on clinical symptoms alone, as they correlate poorly with active inflammation; objective measures are essential 1, 5
• Always exclude infectious causes (especially C. difficile and Cytomegalovirus) during flares, as these can mimic or exacerbate IBD 2
• Do not defer colonoscopy indefinitely based on normal inflammatory markers alone, as clinical examination is only 40-65% accurate 4
• Avoid performing colonoscopy in moderate-to-severe disease due to perforation risk; stabilize patient first 1
• Double contrast barium enema is inferior to colonoscopy as it prevents mucosal biopsy and may underestimate disease extent 1

Standardized Reporting

Interdisciplinary care requires standardized reporting across endoscopy, surgery, and histopathology, with each report including a core set of items covering disease activity, extent, complications, and surveillance recommendations. 1