Comparison of fracture risk between patients with ileal pouch-anal anastomosis for ulcerative colitis and the general population.

Background: Restorative proctocolectomy with ileal pouch-anal anastomosis (IPAA) is the preferred surgical treatment for ulcerative colitis (UC). Little is known of how the operation affects bone metabolism and fracture risk. The aim of this retrospective cohort study was to investigate fracture risk and serum markers of bone metabolism following IPAA in a national cohort of Danish UC patients.

Methods: Diagnostic codes for 1757 patients and 8785 controls were obtained from the National Patient Register while blood results were collected from a regional database. Postoperative fracture free survival was evaluated on a Kaplan-Meier plot. Fracture hazard ratios (HR) after IPAA were calculated from Cox proportional hazards regression analysis.

Results: Fracture risk after IPAA was significantly reduced (adjusted HR = 0.49, 95% CI: 0.43; 0.55, p<0.001). Prior fractures and alcoholism independently increased fracture risk significantly. Osteoporotic fracture risk after IPAA was reduced, significantly for wrist fractures (aHR = 0.39, 95% CI: 0.22; 0.71, p = 0.002), and borderline insignificantly for spine fractures (aHR = 0.51, 95% CI: 0.26; 1.01, p = 0.054). Vitamin D and calcium levels were significantly higher in the patient group (61.2 nmol/L vs. 58.9 nmol/L, p = 0.04 and 1.24 mmol/L vs. 1.21 mmol/L, p<0.01, respectively), while parathyroid hormone and phosphate levels were significantly lower (4.9 pmol/L vs. 6.2 pmol/L, p<0.01 and 1.08 mmol/L vs. 1.12 mmol/L, p<0.01, respectively).

Conclusion: Fracture risk after IPAA is significantly reduced compared to the general population. Prospective studies are needed to verify the biochemical results.