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

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.

Inclusion criteria

• Age 18-65 years
• BMI 18-30 kg/m²
• Single radio-opaque renal stone 1-2 cm
• Suitable for ESWL per clinical assessment

Exclusion criteria

• Multiple renal stones
• Solitary kidney
• Impaired renal function
• Congenital renal anomalies
• Ureteric obstruction
• Systemic comorbidities
• Pregnancy