3D-CT vs Ellipsoid for JJ Stent Prediction Before ESWL

Overview

This prospective single-center study compares 3D-CT volumetry versus traditional ellipsoid formula to determine critical stone burden predicting JJ stent necessity before ESWL for 1-2 cm renal stones. Fifty-six patients with single radio-opaque renal stones will receive up to two ESWL sessions using Dornier lithotripter without initial stenting. Stone characteristics will be assessed via NCCT: linear dimensions (ellipsoid formula), 3D volume (voxel-based segmentation), Hounsfield units, and skin-to-stone distance. Patients will be stratified by ESWL outcomes to compare volume measurements between clearance success and stent-requiring groups..

This prospective single-center study at Ain Shams University evaluates 3D-CT volumetry versus traditional ellipsoid formula for predicting critical stone burden requiring preoperative JJ stent placement in patients undergoing ESWL for 1-2 cm renal stones. Eligible patients (target n=56) with single radio-opaque renal stones will receive two ESWL sessions using Dornier lithotripter without initial stenting. Stone characteristics will be assessed via non-contrast CT (NCCT): linear dimensions (ellipsoid formula: length×width×height×0.52), 3D volume (automated voxel-based segmentation), Hounsfield units, and skin-to-stone distance. Patients will be stratified by ESWL outcomes: stone clearance without stenting versus those requiring JJ stent due to complications (infection, incomplete fragmentation, obstruction/Stein Strasse). Volume measurements will be compared between groups using appropriate statistical tests (t-test, ROC analysis). The study aims to establish a 3D-CT volume threshold for stent prediction and validate its superiority over ellipsoid formula, particularly for irregular stone morphology.