Efficacy and Safety of Narrow Focus (F1) Versus Wide Focus (F3) of Shock Wave Lithotripsy (SWL) for Renal Calculi

Which is Better: Narrow vs. Wide Focus for Shock Wave Lithotripsy of Renal Stones

This study aims to compare the narrow focus (F1) versus the wide focus (F3) in terms of the efficacy of Shock Wave Lithotripsy (SWL) in the management of renal calculi 1-2 cm and their injurious effect on the kidney.

Recently, some Shock Wave Lithotripsy (SWL) devices have been announced in the market with a different focus points. One early experimental study found that stone disintegration is better with small focusing points than larger focusing points. Nevertheless, these findings, in terms of the efficacy of stone disintegration, need to be validated in-vivo. Furthermore, the effect of focal size on renal injury during SWL need to be studied as well. Therefore, the objectives of this study are to compare the effect of using the narrow focus of 2mm (F1) versus the wide focus of 8 mm (F3) on the Stone Free Rate (SFR) following SWL for renal stones 1-2cm and estimating renal injury effect of F1 vs. F3 by urinary renal injury markers such as neutrophil gelatinase-associated lipocalin (NGAL) for assessment of proximal and distal renal tubules injury & Kidney Injury Molecule-1 (KIM-1) for assessment of proximal renal tubules injury).

The SWL device:

Lithotripter type: Piezo Lith3000 plus ( from Richard Wolf, Germany.

Inclusion Criteria:

1. Adult patients (>18years old) with 1-2 cm single renal stone.
2. Normal functioning kidney.

Exclusion Criteria:

1. Pregnancy.
2. Bleeding diatheses.
3. Radiolucent stones.
4. Radio-opaque stones with Hounsfield Unit (HU) > 1200
5. Patients with a pacemaker.
6. Active Urinary Tract Infection (UTI).
7. Severe skeletal malformations.
8. Morbid obesity with Body Mass Index (BMI) ≥40 kg/m2.
9. Renal artery aneurysm at the same site of the stone.
10. Anatomical obstruction distal to the stone.
11. Patients with renal impairment with serum creatinine > 1.2 mg/dL.