Is pelvicaliceal anatomy a risk factor for stone formation in patients with solitary upper caliceal stone?

To investigate the effect of pelvicaliceal anatomy on stone formation in patients with solitary upper caliceal stones. The records of patients with solitary upper caliceal stones between 1996 and 2004 were reviewed. After the exclusion of patients with hydronephrosis, major anatomic abnormalities, noncalcium stones, metabolic abnormalities, history of recurrent stone disease, multiple stones, and previous renal surgery, 42 patients (24 male, 18 female) and 42 healthy subjects (22 male, 20 female) with normal results on intravenous pyelography (IVP) were enrolled into the study. With a previously described formula, upper pole infundibulopelvic angle (IPA), infundibular length (IL) and width (IW), and pelvicaliceal volume of the stone-bearing and contralateral normal kidney of patients and bilateral normal kidneys of healthy subjects were measured from IVP. Forty-two stone-bearing and 126 normal kidneys (42 contralateral, 84 healthy) were assessed. The mean stone size was 153.47 mm 2 (range, 20 to 896 mm 2). There were no statistically significant differences in terms of upper caliceal specifications between stone-bearing and normal kidneys. The mean (± standard deviation) pelvicaliceal volume of 42 stone-bearing and 126 normal kidneys was 2455.2 ± 1380.2 mm 3 and 1845.7 ± 1454.8 mm 3, respectively ( P = 0.019). These values were 2114 ± 2081.5 mm 3 ( P = 0.34) and 1709.5 ± 989.1 mm 3 ( P = 0.001) for contralateral normal kidneys (n = 42) and normal kidneys of healthy subjects (n = 84), respectively. Explanation of the etiology of the upper caliceal stone by the anatomic features is very difficult, and these caliceal anatomic variables (IPA, IL, IW) seem not to be a significant risk factor for stone formation in the upper calyx.