Role of CT Scan in Prognosticating the Outcome of Medical Expulsive Therapy for Distal Ureteric Stone.

Background: This study aimed to evaluate the correlation of Hounsfield unit (HU) to the success rate of medical expulsive therapy (MET) for distal ureteric calculus of size 4-10 mm.

Methods: All recruited patients were divided into two groups: Group A, who successfully passed the stone, and group B, who failed to expel the stone. All patients were prescribed with silodosin for a maximum period of 4 weeks. The stone expulsion rate, mean stone area, mean HU, stone expulsion time, number of pain episodes, grades of hydronephrosis (HDN) and laterality of stone were studied.

Results: Out of 87 patients, eight patients were excluded from the study: Four patients had adverse drug reactions, and other four patients were lost to follow up. Hence, 79 patients were finalised for the study. Group A comprised 57 patients, and group B comprised 22 patients. No statistical difference was found between the two groups in terms of mean age, gender, stone density (HU) and side or grade of HDN ( > 0.05). The mean stone area ( = 0.001) and number of pain episodes per day ( = 0.0004) were significantly less in patients who successfully passed stone. The HU was lower in the MET success group (816.04) than in the failure group (900.86), but the difference was not statistically significant ( = 0.123). Receiver operating characteristic analysis showed that the cut off values for stone area and stone density were ≤38 mm and ≤992 HU, respectively.

Conclusions: MET is undoubtedly a treatment modality for lower ureteric stones of size 10 mm. On computed tomography (CT) scan, stone area can be used as an effective parameter, but stone density (HU) cannot determine MET success. Further studies that include more patients and an evaluation of stone composition are required.