In an adult with inflammatory bowel disease, how do Crohn’s disease and ulcerative colitis differ in their risks of developing uveitis, ileal intussusception, and inflammatory low‑back pain?

Comparison of Crohn's Disease and Ulcerative Colitis: Uveitis, Ileal Intussusception, and Inflammatory Low Back Pain

Crohn's disease carries a significantly higher risk of uveitis compared to ulcerative colitis, while ileal intussusception is essentially exclusive to Crohn's disease due to its ability to cause transmural ileal inflammation; inflammatory low back pain from sacroiliitis occurs with similar frequency in both conditions.

Risk of Developing Uveitis

Crohn's disease patients have approximately twice the risk of developing uveitis compared to ulcerative colitis patients. 1

• The prevalence of uveitis in Crohn's disease is 3.27% versus 1.60% in ulcerative colitis, representing a 1.76-fold increased risk in Crohn's disease 1
• Uveitis is more common in women with inflammatory bowel disease, and importantly, it runs independent of intestinal disease activity 2
• The anterior uveitis pattern is the predominant ocular manifestation in both conditions 3
• Extra-intestinal manifestations overall are more common in Crohn's disease than ulcerative colitis, particularly when colonic involvement is present 2

Risk of Developing Small Bowel Intussusception in the Ileum

Ileal intussusception is essentially a Crohn's disease-specific complication and does not occur in ulcerative colitis under normal circumstances.

• Ulcerative colitis is limited to the colon and does not primarily involve the ileum 4, 5
• The terminal ileum is the most commonly affected site in Crohn's disease, which demonstrates transmural inflammation extending through all intestinal wall layers 4
• Approximately 20% of patients with extensive ulcerative colitis or pancolitis may develop "backwash ileitis," but this represents secondary inflammation from severe colonic disease extending into the most distal ileum, not primary ileal pathology that would cause intussusception 5
• Crohn's disease causes transmural inflammation with potential for stricturing and penetrating complications in the ileum, creating the anatomical substrate for intussusception 4, 6

Risk of Developing Inflammatory Low Back Pain

Both Crohn's disease and ulcerative colitis carry similar risks for developing inflammatory low back pain from sacroiliitis, affecting 20-50% of patients radiologically, though progressive ankylosing spondylitis occurs in only 1-10%.

• Radiological evidence of sacroiliitis occurs in 20-50% of patients with both ulcerative colitis and Crohn's disease 2
• Progressive ankylosing spondylitis with syndesmophytes develops in only 1-10% of inflammatory bowel disease patients, regardless of subtype 2
• Ankylosing spondylitis is more common in males, while other extra-intestinal manifestations like uveitis are more common in females 2
• Critically, axial spondyloarthropathy and inflammatory low back pain run independent of intestinal disease activity, unlike most other extra-intestinal manifestations 2
• MRI using T1-weighted spin-echo, short tau inversion recovery, and fat-saturated T2-weighted sequences should be performed in patients under 40 years with inflammatory back pain lasting more than 3 months to identify non-radiographic sacroiliitis 2

Important Clinical Caveats

• HLA-B27 is found in 25-75% of inflammatory bowel disease patients with ankylosing spondylitis but only 7-15% with isolated sacroiliitis, making it unreliable as a standalone diagnostic test 2
• The probability of developing any extra-intestinal manifestation increases with disease duration and in patients who already have one extra-intestinal manifestation 2
• Management of complex extra-intestinal manifestations should involve multidisciplinary team discussion including rheumatology and ophthalmology 2