Background: Previous studies investigating urinary stone risk after colonsurgery have demonstrated significant reductions in urinary pH, volume,citrate, and magnesium that correspond to an increased incidence of kidneystones. These studies, however, have consistently included patients withinflammatory bowel disease (IBD) which may bias their findings due toknown urinary abnormalities present prior to surgery and differences inlength of bowel removed compared to other types of colon surgery. Thisstudy aims to evaluate urinary stone risk after colon surgery in patientswith and without IBD.Methods: Retrospectively, baseline 24-hour urine samples of 21 kidneystone patients with a history of colon resections were evaluated from adata set of over 800 patients. Urinary chemistries of those who requiredcolon surgery for IBD (9 patients) and non-IBD reasons (12 patients) werecompared to each other and a control of 52 first-time stone formers withoutbowel disease.Results: The IBD colectomy group had a significantly lower urinary pH(5.55 vs. 6.08, p=0.003), magnesium (41.8 mg/d vs. 103.7 mg/d, p=0.0002),citrate (109.8 mg/d vs. 230.4 mg/d, p=0.0001), sodium (95.2 mmol/d vs.7.9 mmol/d, p=0.013), and calcium (109.8 mg/d vs. 230 mg/d, p=0.01) thanthe control. The non-IBD colectomy group had lower pH (5.69 vs. 6.09,p=0.015) and higher supersaturation of uric acid (1.62 vs. 0.87, p=0.015)compared to the control. The IBD colectomy group revealed a lower magnesium(p=0.04), citrate (p=0.007), and sodium (p=0.045) than the non-IBDcolectomy group. 66% of the colectomies in the IBD group were total while100% of the colectomies in the non-IBD group were partial.Conclusions: The urinary stone risk of colectomy patients with IBD issignificantly different from colectomy patients without IBD and is morereflective of abnormalities present in IBD patients prior to surgery such aslow citrate, magnesium, and urinary pH. It is likely the IBD patients biasedthe findings of previous studies investigating the urinary stone risk aftercolon surgery. Patients who underwent colon surgery for non-IBD reasons,however, have few urinary abnormalities and a urinary risk more similar tofirst-time stone formers. The difference in urinary risk of colectomy patientswith and without IBD may be explained by the intrinsic stone risk presentin IBD and the differences in length of bowel removed.
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