Predictors of Success of Extracorporeal Shock Wave Lithotripsy Based On the Hounsfield Units of Calculi Measured By Non-Contrast Computed Tomography

Agha Zohaib, Habibullah Akbar Mohammad, Wajahat Fareed, Salman el Khalid, Asad Abdullah

Abstract

Objective

To predict the success of extracorporeal shock wave lithotripsy (ESWL) for renal calculi based upon the Hounsfield units (HU) obtained from non-contrast computed tomography scans, along with patient related variables.

Study design

Retrospective analytic study.

Place & Duration of study

Lithotripsy Department, The Kidney Centre Postgraduate Training Institute Karachi, from January 2021 to June 2021

Methodology

Patients with renal calculi of < 2-cm were divided into two groups: Group-A (HU < 1000) and Group-B (HU = 1000). All patients underwent ESWL. The energy levels varied from 60 to 90 shocks per minutes, while the frequency ranged between 0.5 to 2 Hertz. A total of 4000 shockwaves per session were administered based on the size and hardness of the calculus. The success of the ESWL was defined as complete clearance of the calculi or clinically insignificant residual fragments that were less than 4-mm in size noted either on plain x-ray abdomen or ultrasound scan, and did not cause any symptom for three months following the procedure.

Results

The records of 142 participants (Group A: n=90 - 63.4% and Group B: n=52 - 36.6%) were analysed. The mean age of the patients was 40.2±14.6 years. There was male preponderance (n=74 - 52.1%). Renal pelvis was the commonest location (n=58 - 40.8%) of the calculi. The predictors of the success of ESWL were male gender, BMI of <30 kg/m2 kg/m2, absence of comorbid conditions, and HU of <1000 (p < 0.05). BMI was the only statistically significant predictor for the success of ESWL when adjusted with other variables.

Conclusions

BMI was a strong predictor of ESWL success rate. With higher HU and BMI, a decreased rate of clearance of calculi was found.

Key words

Extracorporeal shock wave lithotripsy, ESWL, Non-contrast computed tomography, Hounsfield unit, Body mass index.