What is the diagnostic approach and treatment for inflammatory bowel disease?

Diagnostic Approach for Inflammatory Bowel Disease

The diagnosis of IBD requires clinical evaluation combined with biochemical markers, endoscopic visualization with histology, and exclusion of infectious causes—colonoscopy with biopsies from multiple segments is the cornerstone of diagnosis. 1

Initial Clinical Assessment

History

Obtain specific details about: 1

• Stool characteristics: frequency, consistency, urgency, presence of blood
• Abdominal pain: location, character, timing
• Systemic symptoms: fever, malaise, weight loss, anorexia (more common in Crohn's disease)
• Extraintestinal manifestations: joint pain, skin lesions, eye symptoms
• Recent travel and medication use (especially NSAIDs, antibiotics)
• Smoking history (protective in UC, risk factor in CD)
• Family history of IBD

Physical Examination

Document: 1

• Vital signs (pulse, blood pressure, temperature)
• Signs of anemia, dehydration, weight loss
• Abdominal tenderness, distension, or palpable masses
• Perianal examination (critical for detecting fistulae/abscesses in Crohn's disease)

Laboratory Investigations

Initial Blood Tests

Order the following panel: 1

• Complete blood count (assess for anemia, leukocytosis)
• Erythrocyte sedimentation rate (ESR) or C-reactive protein (CRP)
• Electrolytes and renal function
• Liver function tests
• Albumin (marker of nutritional status and disease severity)

Stool Studies

Mandatory to exclude infectious causes: 1

• Comprehensive stool culture for bacterial pathogens
• Clostridium difficile toxin
• Ova and parasites (especially if travel history)
• Fecal calprotectin (excellent sensitivity for IBD, though poor specificity) 1, 2

Additional Screening

Before initiating immunosuppression: 1

• Tuberculosis screening (chest X-ray, tuberculin skin test or interferon-gamma release assay)
• Hepatitis B and C serologies
• Varicella zoster virus serology (if no reliable vaccination history)
• HIV serology (after counseling)
• Epstein-Barr virus serology

Imaging Studies

Plain Abdominal Radiography

Essential in suspected severe IBD to: 1

• Exclude colonic dilatation (transverse colon >5.5 cm)
• Assess disease extent in UC
• Identify small bowel dilatation or masses in CD

Cross-Sectional Imaging

For Crohn's disease evaluation: 1

• MR enterography (MRE) is preferred over CT to limit radiation exposure (97% sensitivity for small bowel disease)
• Intestinal ultrasound is highly accurate (92% sensitivity) and superior for colonic disease in newly diagnosed patients (67% vs 47% for MRE)
• CT reserved for acute presentations only

Endoscopic Evaluation

Ulcerative Colitis Diagnosis

For patients with diarrhea, perform sigmoidoscopy initially: 1

• Rigid or flexible sigmoidoscopy should be performed
• Look for: loss of vascular pattern, granularity, friability, ulceration
• Obtain rectal biopsy even if mucosa appears normal

For mild-to-moderate disease, colonoscopy is preferable to assess full disease extent: 1

• In moderate-to-severe disease, defer colonoscopy due to perforation risk—use flexible sigmoidoscopy instead
• Obtain at least 2 biopsies from each colonic segment (rectum, sigmoid, descending, transverse, ascending, cecum) plus terminal ileum 1
• Store biopsies in separate vials to map disease distribution 1

Diagnostic criteria for UC: 1

• Clinical suspicion
• Appropriate macroscopic findings on endoscopy
• Typical histological findings (diffuse, continuous inflammation; basal plasmacytosis; crypt distortion)
• Negative stool examinations for infectious agents

Crohn's Disease Diagnosis

Ileocolonoscopy is standard: 1

• Obtain biopsies from terminal ileum and multiple colonic segments
• Look for: focal, asymmetric inflammation; skip lesions; cobblestoning; aphthous ulcers
• Diagnosis depends on demonstrating focal, asymmetric, often granulomatous inflammation 1

Additional endoscopy may be needed: 3

• Esophagogastroduodenoscopy if upper GI symptoms present
• Standard in pediatric patients

Histological Requirements

Optimal biopsy protocol: 1

• Minimum of 2 biopsies from ileum and each colon segment (rectum, sigmoid, descending, transverse, ascending, cecum)
• Separate collection in individual vials for accurate mapping
• Multiple tissue levels examined (2-6 sections per biopsy recommended)

Key histological features: 1

• UC: Diffuse mucosal inflammation, basal plasmacytosis, crypt distortion/branching/atrophy, cryptitis, crypt abscesses
• CD: Focal/patchy inflammation, transmural inflammation, non-caseating granulomas (when present), focal crypt irregularities

Diagnostic Algorithm

Step 1: Clinical Suspicion

Patient presents with chronic diarrhea (>4 weeks), abdominal pain, rectal bleeding, or weight loss 1

Step 2: Initial Workup

• Blood tests (CBC, CRP/ESR, albumin, liver function)
• Stool studies (culture, C. difficile, fecal calprotectin)
• Plain abdominal X-ray if severe symptoms 1

Step 3: Endoscopic Evaluation

• If suspected UC: Flexible sigmoidoscopy with biopsies; proceed to colonoscopy if mild-moderate disease 1
• If suspected CD: Ileocolonoscopy with biopsies from multiple segments 1
• Acute severe colitis: Unprepared flexible sigmoidoscopy only; defer full colonoscopy 1

Step 4: Confirm Diagnosis

• Correlate clinical, endoscopic, and histological findings
• Ensure infectious causes excluded 1
• Classify disease extent using Montreal classification (adults) or Paris classification (children) 1

Step 5: Additional Imaging (if Crohn's Disease)

• MR enterography or intestinal ultrasound to assess small bowel involvement 1

Common Pitfalls to Avoid

• Do not delay corticosteroid treatment while awaiting stool microbiology in severe colitis 1
• Do not perform colonoscopy in moderate-to-severe disease due to perforation risk—use flexible sigmoidoscopy 1
• Do not rely on single-segment biopsies—multiple segments are essential for accurate diagnosis and classification 1
• Do not assume normal-appearing mucosa excludes IBD—obtain biopsies regardless 1
• Do not forget perianal examination in suspected Crohn's disease 1

Disease Classification

Once diagnosed, classify using Montreal classification (adults): 1

• UC: Extent (proctitis, left-sided, extensive/pancolitis)
• CD: Age at diagnosis, location (ileal, colonic, ileocolonic, upper GI), behavior (inflammatory, stricturing, penetrating), perianal disease modifier

This classification guides prognosis: extensive colitis carries 19% 10-year colectomy rate versus 5% for proctitis 1