Inflammatory bowel disease consists of ulcerative colitis and Crohn's disease.
Ulcerative colitis is a diffuse mucosal inflammation limited to the colon while Crohn's disease is a patchy, transmural inflammation that occurs in any part of the gastrointestinal tract.
The ileum and colon are the most frequently affected sites.


  • IBD is confirmed by clinical evaluation and a combination of biochemical, endoscopic, radiologic, histologic and/or nuclear medicine based investigations
  • Specific diagnosis of UC or CD is not determined in about 5% of patients because they have features of both conditions; this is termed as IBD type unclassified (IBDU)


Severity Assessment of Ulcerative Colitis
  • Clinical severity and anatomical extent of an acute attack of UC determines the therapeutic approach
  • Disease severity can be assessed using several disease activity indices (eg Truelove and Witts criteria, Mayo Clinic index, Sutherland index)

Severity Assessment




Bloody stools/day

< 4*

4 or more if

≥ 6 and



< 90 bpm

≤ 90 bpm

> 90 bpm


< 37.5°C

≤ 37.8°C

> 37.8°C

Hemoglobin (Hgb)

> 11.5 g/dL

≥ 10.5 g/dL

< 10.5 g/dL

Erythrocyte Sedimentation Rate (ESR)

< 20 mm/hr

≤ 30 mm/hr

> 30 mm/hr

or C-reactive Protein (CRP)


≤ 30 mg/dL

> 30 mg/dL

Adapted from Dignass A, et al. Second European evidence-based consensus on the diagnosis and management of ulcerative colitis: definitions and diagnosis. 2012.
*Stools may be with or without blood according to the American College of Gastroenterology and the Japanese Society of Gastroenterology 

Severity Assessment of Crohn's Disease
  • CD severity is generally more difficult to determine than UC
  • Crohn’s Disease Activity Index (CDAI) and the Harvey-Bradshaw Index (HBI) are commonly used systems in describing disease severity

Mild-Moderate Disease (Corresponds to CDAI 150-220)

  • Patient is ambulatory
  • Able to tolerate oral alimentation with:
    • No manifestation of dehydration
    • No sign of toxicity (high fever, rigors, prostration)
    • No abdominal tenderness or painful mass
    • No intestinal obstruction
    • <10% weight loss

Moderate-Severe Disease (Corresponds to CDAI 220-450)

  • Fever
  • Significant weight loss (>10%)
  • Abdominal pain or tenderness
  • Intermittent nausea or vomiting (N/V) without obstructive findings
  • Significant anemia
  • May also refer to patients who failed to respond to treatment for mild-moderate disease

Severe-Fulminant Disease (Corresponds to CDAI >450)

  • High fever
  • Persistent vomiting
  • Evidence of intestinal obstruction
  • Rebound tenderness or involuntary guarding
  • Cachexia
  • Evidence of an abscess
  • Also describes patients with persistent symptoms despite outpatient treatment of corticosteroids or biologic agents


  • Complete patient history should include:
    • Recent travel history, intolerances to food, smoking history, sexual history, medication (including use of NSAIDs and antibiotics) and vaccination history, past medical history (eg tuberculosis, intestinal infection), family history
  • Onset and duration of symptoms
  • Stool frequency, consistency, urgency
  • Presence of extraintestinal manifestations (eg arthritis, osteoporosis, fractures, inflammatory ocular symptoms, thromboembolic symptoms, primary sclerosing cholangitis, secondary amyloidosis, erythema nodosum, pyoderma gangrenosum)
  • Presence of mood disorders

Physical Examination

  • General well being, pulse rate, blood pressure, temperature, BMI, hydration/nutritional status, check for anemia
  • Inspection of eyes, mouth, skin and joints for extraintestinal involvement
  • Abdominal tenderness or distension, palpable mass, perianal exam (eg presence of fissures and fistulas)
  • Digital rectal exam for anal strictures, mass

Laboratory Tests

  • CBC, LFT, serum albumin, ferritin, calcium, magnesium, vit B12 level
  • Electrolytes (as indicators of decreased absorption)
  • Erythrocyte sedimentation rate (ESR), C-reactive protein (CRP)
  • Routine stool exam including checking for occult blood or fecal leukocyte and stool culture
  • Stool microbiologic testing for infectious diarrhea including Clostridium difficile toxin, Cytomegalovirus (CMV)
    • Should be considered in severe or refractory colitis
  • Fecal calprotectin to detect intestinal inflammation
  • HIV and TB testing for high-risk population

Serologic Markers

  • Occasionally helpful in identifying patients who are at higher risk for complications and in selected patients in whom no other pathologic or clinical feature differentiates between CD from UC
  • UC: Perinuclear antineutrophil cytoplasmic antibodies
  • CD: Anti-Saccharomyces cerevisiae antibodies, CBir 1 (an anti-flagellin antibody)
  • Not sufficiently sensitive nor specific to be used as screening or diagnostic tool



  • Should attempt to define the type of IBD, mention coexistent diagnosis or complications, and determine presence of dysplasia and its grade
  • UC: Mucosal separation, distortion and atrophy of crypts; acute and chronic inflammatory cells in the lamina propria, preferential homing of neutrophils to the crypt epithelium, increased number of plasma cells near crypt base
  • CD: May be suggested by noncaseating granulomas, transmural inflammation, microscopic focality but absence of these features does not exclude CD



  • May differentiate CD from UC in >85% of patients if used in conjunction with other diagnostic modalities
  • Used to assess disease extent and activity, to monitor response to therapy, and for surveillance of dysplasia or neoplasia
  • Biopsy is an important part of endoscopic exam
    • Differentiates CD from UC and excludes presence of other causes of colitis
    • May help in establishing the extent of inflammation which aids in determining the appropriate therapy and disease prognosis
    • Rectal biopsy for histology is recommended even in the absence of macroscopic changes


  • Should not be done in patients with severe colitis or suspected of toxic megacolon due to increased risk of perforation
  • CD: Findings of segmental or discontinuous colitis or patchiness, rectal sparing, involvement of the terminal ileum and right-sided colon, and anal or perianal disease
    • Presence of ulcers (discrete, aphthous or serpiginous), cobblestoning of mucosa, granulomata
  • UC: Findings of granularity, friability, ulceration of the rectal mucosa and the vascular pattern is lost, diffuse superficial inflammation, erosis, and ulcers
    • These changes, seen endoscopically and histologically, usually involves the distal rectum
  • Colonoscopy with ileoscopy may help distinguish true CD ileitis from backwash ileitis
  • At least 2 biopsies from 5 sites, including distal ileum and rectum, is recommended

Flexible Sigmoidoscopy

  • Performed when colonoscopy is considered high risk (eg fulminant colitis) or where there is higher risk of bowel perforation
  • In patients diagnosed with UC, it helps in assessing disease activity and in evaluating other causes of colitis during disease exacerbations

Capsule Endoscopy

  • A less invasive technique in diagnosing CD when ileoscopy and small bowel follow through are negative or unsuccessful
  • Contraindicated in CD patients with known or suspected high-grade strictures
  • Does not allow tissue sampling
  • Major concern on capsule retention limits its use

Endoscopic Ultrasonography (Rigid Scope or with Flexible Endoscopes)

  • It can accurately assess and characterize Crohn’s perianal fistula
  • Used in assessing disease activity of colitis and transmural disease

Radiologic Studies

  • Complements endoscopic techniques in the diagnosis of IBD

Abdominal Radiography

  • Excludes colonic dilatation, helps assess disease extent in UC or identify proximal constipation
  • In CD, it shows mass in the right iliac fossa or small bowel dilatation, obstruction or perforation

Barium Contrast Examinations

  • Eg small bowel follow-through (SBFT), small bowel enteroclysis (SBE)
  • Typically inferior to colonoscopy
  • Shows luminal narrowing with ulcerations, loop adhesions/separations, and circular fold thickening and alterations
  • SBE is 95% sensitive and 96.5% specific for small bowel diseases especially for early mucosal lesions
  • SBFT is safer and better in detecting gastroduodenal abnormalities as compared to SBE (67-72% accuracy in detecting inflammation)
  • Limitations: extraluminal extensions andbowel wall complications of CD


  • Excludes colonic dilatation, helps assess disease extent in UC and identify proximal constipation
  • A noninvasive, sensitive way of identifying thickened small bowel loops in CD
  • 79% sensitive, 93% specific for stenosis; 71-74% sensitive, 95-96% specific for fistula; 84% sensitive, 93% specific for abscess
  • May also identify abscess and free fluid in peritoneum
  • Also used as an imaging guide during procedures
  • Limitations: limited access to the proximal ileum and jejunum, transverse colon and rectum

Computed Tomography (CT)

  • The gold standard for the detection of extraluminal complications particularly abscess formation
    • UC: May show marked bowel wall thickening, although this finding is nonspecific
  • A better imaging tool against peristalsis and motion because of its rapid pacing
    • 92% sensitive, 100% specific for stenosis; 89% sensitive for inflammation; 70% sensitive, 97% specific for fistula; 85% sensitive, 95% specific for abscess
  • Produces results faster and is readily available as compared to MRI
  • Limitation: may require luminal distention and application of contrast media; carries a potential risk for radiation-induced malignancy

Magnetic Resonance Imaging (MRI)

  • A good imaging tool that limits motion and peristalsis due to its fast sequences
  • 89% sensitive, 94% specific for stenosis; 83% sensitive for inflammation; 76% sensitive, 96% specific for fistula; 86-100% sensitive, 93-100% specific for abscess; 76% sensitive, 96% specific for abscess/fistula/inflammation infiltrates in CD
  • Provides information about disease activity, detects extraluminal findings and wall complications, and helps distinguish between inflammatory and fibrotic stricturing
    • Preferred over CT to minimize cumulative risks of radiation
  • Limitation: Requires administration of contrast media

Nuclear Medicine/Scintigraphy

  • A technique that can identify disease extension and activity
  • Has lower radiation exposure; recommended for children
  • WBC scintigraphy is more sensitive for screening of IBD because of the application of radiolabeled leukocytes
    • There is not enough evidence to support the use of FDG-PET in post-treatment IBD patients

Disease Extent of Ulcerative Colitis

  • Anatomical extent of UC is assessed endoscopically

Distal Colitis (Left-sided Colitis)

  • Limited to below the splenic flexure and therefore may be reached by topical therapy

Extensive Colitis (Pancolitis)

  • Colitis that extends proximal to the splenic flexure and therefore requires systemic therapy
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