Increased risk of nephrolithiasis in patients with steatorrhea

Patients with ileal disease have increased absorption of dietary oxalate, hyperoxaluria, and an increased incidence of nephrolithiasis. Patients with steatorrhea of varying etiologies also have hyperoxaluria. To determine whether steatorrhea per se is associated with nephrolithiasis, we reviewed the charts of all adult patients who had a 72-hr fecal fat analysis from 1968 to 1978. The 159 patients with steatorrhea were compared to 162 patients without steatorrhea. The two groups were comparable in age, sex, urine specific gravity, and serum uric acid and phosphorus; serum calcium was slightly less in the steatorrhea group (8.7 +/- 0.1 vs 9.0 +/- 0.1, P less than 0.02). Although 19 patients with steatorrhea had nephrolithiasis compared to 7 control patients (P = 0.01), 15 of these 19 patients had ileal disease and only 4 of the 118 patients with steatorrhea but without ileal disease had stones. Categorical data analysis revealed that steatorrhea, diarrhea (stool weight greater than 225 g/day), male sex, and ileal disease were significantly associated with nephrolithiasis with a relative risk of 3.0, 2.7, 3.1, and 8.0, respectively. When patients without ileal disease were analyzed separately, however, steatorrhea, diarrhea, and sex were no longer risk factors. In contrast, in patients with ileal disease the incidence of nephrolithiasis increased with the severity of steatorrhea. The relative risk of nephrolithiasis in male patients with ileal disease and fecal fat greater than 20 g/day was 26.3 (P less than 0.01). Thus, the presence of both ileal disease and steatorrhea greatly increases the risk of nephrolithiasis; however, neither steatorrhea alone nor ileal disease alone are risk factors for nephrolithiasis.