Influence of ileal pouch anal anastomosis on bone loss in ulcerative colitis patients

Background and aim: Patients with ulcerative colitis (UC) are at an increased risk for low bone mineral density (BMD). It is unclear whether proctocolectomy with ileal pouch-anal anastomosis (IPAA) for UC alters the risk of bone loss. The aim of this study was to compare BMD in UC patients with and without IPAA.

Methods: A total of 267 patients with UC and IPAA (study group) were compared to 119 UC patients without IPAA (control group) in this cross-sectional study. The demographic and clinical variables including dual-energy X-ray absorptiometry scan results were compared. Patients were classified as having normal or low BMD, based on the criteria by the International Society for Clinical Densitometry. Univariate and multivariate analyses were performed to assess risk factors associated with low BMD. Age, gender, race, smoking status, steroid use, alcohol use, body mass index, years of absent estrogen protection, use of calcium, vitamin D supplements and disease duration were selected as covariates.

Results: 83 (31.1%) had low BMD in the study group vs. 18 (15.1%) in the control group (p=0.001). 2/13 (15.4%) had low BMD before surgery. The mean age of patients in the study and control groups were 44.7 ± 14.1 vs. 52.4 ± 17.7 years, respectively (p<0.001). The hip BMD was lower in the study group (0.93 ± 0.17 g/cm2) than that in the control group (0.98 ± 0.17 g/cm2) (p=0.038). Fragility fracture was documented in 23 (8.6%) patients in the study group vs. 3 (2.5%) in the control group (p=0.038) Sixty-four (24.0%) of the study group patients were using corticosteroids after surgery in contrast to 93 (78.2%) in the control group (p<0.001). On multivariable analyses, covariate adjusted factors associated with a low BMD in UC patients were advanced age [odds ratio (OR) 1.51 per 5 years; 95% confidence interval [CI], 1.34-1.71], low body mass index (OR=2.37 per 5 kg/m(2) decrease; 95% CI, 1.68-3.36), and the presence of IPAA (OR=6.02; 95% CI, 2.46-14.70). For the 13 IPAA patients who had information available, BMD before IPAA was low. After a median of 46 (Range 7-84) months after IPAA, BMD improved in 7/13 patients (53.8%), while it continued to be low in 6/13 (46.2%) patients.

Conclusions: Low BMD is common in patients with UC. The risk appears to persist even after colectomy and IPAA surgery suggesting that these patients need to be monitored for bone loss.