Time to stone passage for observed ureteral calculi: A guide for patient education

Purpose: We analyze the natural history of stone passage in patients with u reterolithiasis, and define factors predictive of spontaneous passage. Materials and Methods: A total of 75 patients with ureteral calculi were pr ospectively followed for stone passage. Clinical data included patient gend er and age, stone size and location, pain medication requirements and inter val to stone passage. Of the 75 patients 13 (17%) required intervention and 62 (83%) were followed until spontaneous stone passage. Stones requiring i ntervention were not included in the time to passage analysis. Results: Of the 75 patients 41 (55%) had ureteral stones 2 mm. or smaller w ith an average time to stone passage of 8.2 days and only 2 (4.8%) required intervention, 18 (24%) had stones between 2 and 4 mm. with an average time to stone passage of 12.2 days and 3 (17%) required intervention, and 16 ha d stones 4 mm. or greater with an average time to stone passage of 22.1 day s and 8 required intervention. For 95% of stones to pass it took 31 days fo r those 2 mm. or less, 40 days for those 2 to 4 mm. and 39 days for those 4 to 6 mm. Multivariate analysis revealed that size, location and side were statistically related to stone passage interval (p = 0.012). Stones that we re smaller, more distal and on the right side were more likely to pass spon taneously and required fewer interventions. Conclusions: Interval to stone passage is highly variable and dependent on stone size, location and side. Degree of pain, and patient gender and age h ad no bearing on the time to stone passage. Of ureteral stones 95% 2 to 4 m m. pass spontaneously but passage may take as long as 40 days. Intervention may be required in 50% of ureteral calculi greater than 5 mm.