Metabolic evaluation in first-time renal stone formers in north India: A single center study

The risk of stone recurrence in first-time stone formers (FTSF) varies from 26% to 53%. There is no consensus regarding metabolic evaluation in these individuals. We evaluated the metabolic abnormalities in first-time renal stone forming patients in North India. Thirty-nine patients, (29 males and 10 females with mean age 39.3 ± 12.9 years) who presented with nephrolithiasis for the first time were evaluated. We evaluated the calcium homeostasis [serum corrected total calcium, phosphorous, creatinine, alkaline phosphatase, albumin, parathormone (iPTH), 25-hydroxy cholecalciferol (25(OH)D 3 ), 1-25 di-hydroxy cholecalciferol (1,25(OH) 2 D 3 )] and performed the calcium load test also. Two 24-h urine collections were taken for citrate, oxalate, calcium and uric acid. Ammonium chloride loading test for diagnosis of distal renal tubular acidosis was performed in all patients. For each of the diagnostic categories, descriptive statistics were computed for all biochemical variables. A two-tailed P-value <0.05 was regarded as significant. Metabolic abnormalities were detected in 92.3% of the patients (n = 39) studied. Of them, almost 60% had two or more metabolic abnormalities. The most common metabolic abnormality was hypo-citraturia (82%), followed by hyper-oxaluria (56%) and hyper-calciuria (41%). Five percent of the patients had incomplete renal tubular acidosis, signifying the importance of the ammonium chloride loading test in patients with renal stones. None of the study patients were detected to have primary hyperparathyroidism. In three patients, the etiology could not be detected. Our findings suggest that an underlying disorder is present in majority of first-time renal stone formers. Intervention with appropriate treatment can prevent recurrences. Hence, comprehensive metabolic evaluation is recommended in all FTSF.