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P194. Lithogenic factors in inflammatory bowel disease

P. Figueiredo1, C. Outerelo2, T. Meira1, F. Teixeira-Costa2, A. Vieira1, J. Freitas1, 1Hospital Garcia de Orta, Gastroenterology, Almada, Portugal, 2Hospital Garcia de Orta, Nephrology, Almada, Portugal

Background

Nephrolithiasis is not rare in patients with inflammatory bowel disease (IDB). Among known lithogenic factors (LF), the most relevant are uric acid, oxalate, calcium, citrate and magnesium. Our aim was to assess the prevalence of LF and of predisposing clinical settings in IBD patients, namely disease severity.

Methods

This was an observational transversal study of IBD clinic patients in our institution. All patients were in clinical remission. Clinical and laboratory data were collected, including measurements on a 24-hour urinary specimen. Disease severity was defined by presence of 3 surrogate markers: history of hospital admissions, bowel resection surgery and/or prescription of immunomodulators.

Results

Ninety-eight patients were included in the study (59 females, 39 males; mean age 46.8±16.7 years), 58.2% with Crohn's disease (CD) and 41.8% with Ulcerative colitis (UC). Among DC patients, 63.2% had ileal involvement and 36.8% had had small bowel surgery. No UC patient underwent surgery. Overall, 45.9% had previous hospital admissions, 35.7% were under azathioprine and 24.5% under infliximab or adalimumab.

LF were a common finding: hyperuricusuria in 10.3%, hyperoxaluria in 29.6%, hypercalciuria in 10.3%, hypocitraturia in 16.5% and hypomagnesiuria in 55.7%.

Comparing LF in CD Vs UC patients, there was significantly less magnesiuria (62.07±36.88 Vs 83.27±34.91 mmol/24h, p = 0.005) and a trend for increased oxaluria (0.36±0.16 Vs 0.31±0.10 mmol/24h, p = 0.09) in CD. Within CD patients, ileal involvement was only associated with hypomagnesiuria (53.50±26.88 Vs 75.94±36.94 mmol/24h, p = 0.03).

As for disease severity, hypomagnesiuria (0.30±0.10 Vs 0.36±0.16 mmol/24h; p = 0.031) and hyperoxaluria (80.4±39.4 Vs 65.0±35.0 mmol/24h; p = 0.047) were significantly associated with presence of one or more Vs absent surrogate markers. However, patients with more than one surrogate marker were not shown to have a further increase in LF.

Analysis of disease severity markers found significant hypomagnesiuria in patients who underwent surgery (53.2±39.4 Vs 76.3±38.2 mmol/24h; p = 0.01). Yet, hyperoxaluria was not significantly associated with any marker.

Conclusion

This study found a high prevalence of hypomagnesiuria and hyperoxaluria in IBD patients, mostly in CD. These LF were associated with disease severity. Of note, there was a strong association of hypomagnesiuria with small bowel resection surgery.