Diagnostics

• Evaluate patients with hematochezia and fecal urgency for ulcerative colitis.

• Rule out infectious gastroenteritis.

• Consult gastroenterology for ileocolonoscopy with histological examination

• Consider CT or MRI abdomen if direct endoscopy is contraindicated.

Stool testing for causes of gastroenteritis is indicated in all patients. Blood tests are not routinely required for diagnosis but help assess disease activity and severity.

• Blood tests

  • CBC: anemia, leukocytosis, thrombocytosis [4]

  • ESR, CRP: Elevated levels may indicate active ulcerative colitis and often correlates with disease severity.

  • Hypoalbuminemia

  • ALP, GGT: elevated in patients with concurrent PSC

  • Perinuclear ANCA (pANCA) [2]

    • Not routinely recommended

    • Elevated in up to 70% of patients with ulcerative colitis

• Stool diagnostic studies

  • Stool test for Clostridioides difficile infection

  • PCR panel for other enteric infections: depending on the patient's symptoms and risk factors for diarrhea

  • Stool culture and microscopy: to assess for bacteria and ova and parasites if a stool PCR panel is not available

  • Fecal calprotectin: can help assess for mucosal inflammation

• Recommended method for diagnosis and disease monitoring

• Severe disease is a relative contraindication.

• Sigmoidoscopy

  • Indications

    • Initially used as an alternative to colonoscopy, e.g., in ASUC

  • Findings are similar to colonoscopy findings.

• EGD: recommended for patients with upper gastrointestinal symptoms to rule out Crohn disease

Patients with severe ulcerative colitis have a high risk for colonic perforation; therefore, caution should be used when performing biopsies.

Imaging studies are not routinely recommended for diagnosing ulcerative colitis but may be used as an adjunct to endoscopy, particularly for the detection of complications, or if endoscopy is not possible.

• Indication: initial and serial evaluation of suspected ASUC

• Findings

  • Typically normal in mild-to-moderate disease

  • Loss of colonic haustra (lead pipe appearance) may be seen in severe cases

  • May show signs of complications, e.g.:

    • Toxic megacolon: massive distention

    • Ulceration: segmental dilation with irregular edges outlined by gas [17]

    • Perforation: pneumoperitoneum

• Indications

  • Patients with abdominal symptoms that cannot be explained by the disease activity seen on endoscopy

  • To evaluate for:

    • Proximal disease involvement if endoscopy is not possible

    • Complications, e.g., bowel perforation

    • Differential diagnoses, e.g., Crohn disease

• Findings

  • Loss of haustra

  • Increased bowel wall thickness

  • Mural hyperenhancement

  • Signs of complications (similar to abdominal x-ray findings)

The role of barium enema is limited, as it is less sensitive than other imaging modalities and is contraindicated in patients with obstruction or perforation.

• Indication: can be considered for assessment of the proximal colon if colonoscopy is contraindicated

• Findings

  • Granular appearance of the mucosa

  • Deep ulcerations

  • Loss of haustra

  • Pseudopolyps that appear as filling defects

• Indication: monitoring disease activity and treatment response

• Findings: increased bowel wall thickness

• Early stages

  • Granulocyte (neutrophil) infiltration: limited to mucosa and submucosa

  • Crypt abscesses: an infiltration of neutrophils into the lumen of intestinal crypts due to a breakdown of the crypt epithelium

• Chronic disease

  • Lymphocyte infiltration

  • Mucosal atrophy

  • Altered crypt architecture

    • Branching of crypts

    • Irregularities in size and shape

  • Epithelial dysplasia

In ulcerative colitis, the extent of intestinal inflammation is limited to the mucosa and submucosa. In contrast, Crohn disease shows a transmural pattern of intestinal involvement.

Noncaseating granulomas are seen in Crohn disease but are not a feature of ulcerative colitis!

• Crohn disease (see “Differential diagnostic considerations: Crohn disease and ulcerative colitis”)

• Exudative-inflammatory diarrhea

• Diverticular disease

• Appendicitis

• Ischemic colitis

• Infectious colitis

  • C. difficile colitis

  • Shigella dysenteriae

  • Salmonella enterocolitis

  • Escherichia coli colitis

  • Campylobacter enterocolitis

  • Yersiniosis

  • Tuberculosis

  • CMV colitis

• Radiation colitis

• Celiac disease

• Inflammatory diarrhea

• Definition: an idiopathic, inflammatory form of colitis that is characterized by a normal macroscopic appearance of bowel on colonoscopy and collagenous or lymphocytic infiltrates on microscopy

• Forms: collagenous colitis and lymphocytic colitis

• Epidemiology

  • Peak incidence: ∼ 60 years of age

  • ♀ > ♂

• Etiology: unknown

• Clinical features

  • Chronic, nonbloody, watery diarrhea for > 4 weeks

  • Weight loss

  • Abdominal pain

• Pathology

  • Gross pathology: normal appearance

  • Histology

    • Collagenous colitis: proliferation of collagenous connective tissue that forms a thick, subepithelial collagen band

    • Lymphocytic colitis: mainly lymphocytic infiltrates with little/no proliferation of connective tissue

• Treatment

  • Cease nonsteroidal anti‑inflammatory drugs (NSAIDs may be a trigger for disease)

  • Symptomatic therapy (e.g., loperamide for mild diarrhea)

  • Corticosteroids