Predictors for spontaneous stone passage in patients with renal colic secondary to ureteral calculi.

Objectives: To determine the clinical, laboratory, and imaging variables that can predict spontaneous stone passage in patients with renal colic secondary to ureteral calculi.

Methods: We prospectively analyzed the medical records of 114 patients who admitted to the emergency department for renal colic from June until November of 2010. Forty-six of them were excluded. The presence of ureteral calculi was confirmed by either a kidney-ureter-bladder plain film or an ultrasound or a computer tomography. In all patients, a second visit after 1 month was planned and the stone status was checked by the same imaging techniques.

Results: From the 68 patients, 16 had a calculus in the upper ureter, 10 in the mid ureter, and 42 in lower part. Stone size was ranged from 2.3 to 15 mm, 52.9% of them were located in the left ureter and 51.5% were radiopaque. Stones passed spontaneously in 36 patients. In multivariate analysis, serum white blood cell count found to be the most significant predictor (P = 0.028) for spontaneous passage followed by stone size (P = 0.037). In analysis of patients with stone size <10 mm, left side (P = 0.017) and serum white blood cell count (P= 0.032) found to be significant predictors.

Conclusions: Serum white blood cell count is an easy to assay variable in everyday practice. This study showed that its value, at the acute phase of a renal colic, is a significant predictor for stone spontaneous passage and should be considered. Stone size remains a valuable predictor. Stones <10 mm on the left ureter have a higher likelihood to pass spontaneously.