Ulcerative colitis: moving beyond the mucosal dogma.

Area of Science:

• Gastroenterology
• Inflammatory Bowel Disease Research
• Medical Imaging

Background:

• Ulcerative colitis (UC) traditionally viewed as mucosal disease.
• Crohn's disease (CD) characterized by transmural inflammation and fibrosis.
• Emerging evidence suggests UC also involves deeper bowel layers.

Purpose of the Study:

• Summarize evidence of transmural changes in UC.
• Highlight sonographic, macroscopic, and histopathological findings.
• Discuss implications for UC understanding and treatment.

Main Methods:

• Review of existing sonographic, macroscopic, and histopathological data.
• Intestinal ultrasound for in-vivo characterization of bowel wall.
• Analysis of macroscopic and histological findings.

Main Results:

• UC shows transmural alterations: increased bowel wall thickness, submucosal thickening, loss of stratification, haustral loss, mesenteric fibrofatty proliferation.
• Deeper changes like colonic shortening, fibrotic strictures, and muscular remodelling observed.
• Submucosal thickening may persist even in endoscopic remission.

Conclusions:

• UC extends beyond the mucosa, exhibiting transmural changes.
• These changes may contribute to persistent functional bowel symptoms.
• Recognizing UC as a progressive transmural disease may inform future therapeutic targets.