Using a three-dimensional computer assisted stone volume estimates to evaluate extracorporeal shockwave lithotripsy treatment of kidney stones.

Abstract

This study describes and evaluates the use of non-contrast enhanced computerized tomography (NCCT) before and after extracorporeal shockwave lithotripsy (SWL). Computer measured stone volume was used as an exact measurement for treatment response. 81 patients received SWL of kidney stones at Herlev Hospital between April 2013 and January 2014 and follow-up was possible in 77 (95%) patients. NCCT was used before and after treatment. Treatment response was expressed as a reduction of the stone volume. Stone characteristics as the stone volumes, HU, SSD and localization were measured by radiologist using a vendor non-specific computer program. Complications, patient characteristics and additional treatment were registered. On average, 5858 shocks were given each patient. The follow-up NCCT was performed 24days after treatment. It was possible to calculate the stone volume in 88% of the patients-the remaining 12% it was not possible due to stone disintegration. The stone free rate was 22%. The average relative reduction in stone burden was 62%. Only 8% of the patients were radiological non-responders. Steinstrasse was observed in 13 (17%) and 28 (36%) patients had additional treatment performed. Irradiation dose per NCCT was 2.6mSv. Stone volume could be calculated in most patients. The relative reduction in stone burden after treatment was 62%. The stone volume was redundant when evaluating stone free patients, but in cases of partial response it gave an exact quantification, to be used in the further management and follow-up of the patients.