Etymology:

• Named after Burrill Crohn, who first described the disease in 1932.

AKA:

• Regional enteritis
• Ileitis
• Granulomatous colitis

What is it?

• Crohn’s disease is a
  •  chronic
  • relapsing inflammatory bowel disease (IBD) characterized by
    • transmural inflammation that can affect any part of the gastrointestinal (GI) tract,
    • from mouth to anus, with a
    • predilection for the terminal ileum and colon (1).

Caused by:

• Multifactorial etiology, including:
  • Genetic predisposition (e.g., NOD2 gene mutation) (2).
  • Environmental factors, such as smoking and diet.
  • Dysregulated immune response to intestinal microbiota.

Resulting in:

• Chronic inflammation with potential complications, including:
  • Strictures, (skip lesions
  • fistulas, and
  • abscesses.
  • presents with ileal, ileocolonic, or colonic disease in roughly one-third of patients each.(4)
  • Malabsorption and nutritional deficiencies.
  • Increased risk of colorectal cancer (4).

Structural changes:

• Cobblestone mucosa.
• Bowel wall thickening and strictures.
• Skip lesions with normal segments of bowel between inflamed areas.
• Creeping fat sign (8).

Pathophysiology:

• Transmural inflammation leads to ulceration, fibrosis, and granuloma formation.
• Creeping fat is associated with mesenteric inflammation and fibrosis (9).

Pathology:

• Histologic findings include
  • non-caseating granulomas,
  • transmural inflammation, and
  • focal ulcerations (3).

Diagnosis:

• Combination of
  • clinical presentation,
  • imaging, and
  • endoscopic findings.
• Definitive diagnosis requires:
  • Endoscopy with biopsy.
  • Imaging studies such as
    • CT enterography and
    • MR enterography (7).

Clinical:

• Symptoms:
  • Abdominal pain, diarrhea (often bloody), weight loss, and fatigue.
  • Extraintestinal manifestations, including
    • arthritis, uveitis, and erythema nodosum (1).
• Complications:
  • Perianal disease (e.g., abscesses and fistulas).
  • Small bowel obstruction (SBO) due to strictures.

Radiology:

• Imaging modalities, including CT and MR enterography, provide critical insights into disease extent, activity, and complications (7, 11).

Labs:

• Elevated inflammatory markers (CRP, ESR).
• Anemia and hypoalbuminemia in severe disease.
• Fecal calprotectin as a non-invasive marker for disease activity (2).

Management:

• Medical therapy:
  • Anti-inflammatory drugs (e.g., 5-aminosalicylates).
  • Immunosuppressants (e.g., azathioprine).
  • Biologics targeting TNF-α or integrins (4).
• Surgical intervention:
  • Reserved for complications like strictures, fistulas, or small bowel obstruction.
  • Not curative but necessary in many cases (5).

Radiology Detail: X-Ray:

• Findings:
  • May show non-specific signs such as bowel dilation or perforation.
• Associated Findings:
  • Limited role in initial diagnosis (6).

Barium Studies:

• Characteristic Signs and Findings
  • Aphtoid Ulcers
    • Bulls Eye
    • Target Lesions
  • Ulcers
  • Strictures
  • Thickened Folds
  • Cobblestone
  • Pseudodiverticula
  • Fistula
    • The most common barium imaging finding in patients with Crohn’s disease is aphthoid ulcers
    • produce a “bulls-eye” or “target” lesion consisting of a small central collection of barium surrounded by a radiolucent halo due to granulomatous inflammation.
    • enlarge and coalesce to form stellate or linear areas of ulceration
    • Effective in showing cobblestone pattern due to alternating deep longitudinal and transverse ulcerations with intervening edematous mucosa.
    • Excellent at identifying strictures, fistulae, and small bowel obstruction.
    • Can demonstrate skip lesions clearly (16, 17).

Stricture in Ileum Chronic

CT:

• The most common imaging finding  is mural thickening. This finding is frequently observed on both CT enterography (CTE) and MR enterography (MRE) and is indicative of active inflammation. Mural thickening is often accompanied by mural hyperenhancement, which is another sensitive indicator of active disease.[1-3]
• Parts:
  • Involves ileum, colon, and perianal region.
• Size:
  • Variable bowel wall thickening.
• Shape:
  • Cobblestone mucosa (16).
    • can be visible  particularly when using
    • CT enterography (CTE).
      • enhances visualization
      • by using large volumes of ingested
      • neutral enteric contrast material,
• Position:
  • Patchy distribution, skipping normal segments.
• Character:
  • Hyperenhancement of active inflammation.
  • Creeping fat: Demonstrates increased density of mesenteric fat encroaching around inflamed bowel loops, which is pathognomonic for Crohn’s disease (8, 9).
• Time:
  • Chronic disease with acute flares.
• Associated Findings:
  • Abscesses, fistulas, strictures, or lymphadenopathy (17).

MRI:

• Preferred modality for soft tissue contrast and activity assessment.
• Gadolinium-enhanced studies highlight mucosal hyperenhancement and edema (18).

Recommendations:

• MRI enterography is the first-line imaging modality for diagnosis and monitoring.
• Barium studies are useful in assessing structural abnormalities like strictures, fistulae, and small bowel obstruction.
• Fecal calprotectin should be used for non-invasive monitoring (11).

 

• Other Studies 
  • Ultrasound:
    • Limited role but can detect thickened bowel walls and complications (7).

Key Points and Pearls:

• Imaging plays a pivotal role in diagnosing and managing Crohn’s disease.
• Differentiation from ulcerative colitis is critical.
• Cobblestone mucosa, skip lesions, creeping fat, fistulae, and small bowel obstruction are hallmark findings (8, 9).

Chronic Crohn’s Disease

 

References