Is an 8mm right lower calyceal non-obstructing renal stone with mild pelvocaliceal dilatation an indication for Extracorporeal Shock Wave Lithotripsy (ESWL)?

From the Guidelines

An 8 mm right lower calyceal non-obstructing renal stone with mild pelvocaliceal dilatation is generally indicated for ESWL (Extracorporeal Shock Wave Lithotripsy).

Key Considerations

• The size of the stone (8 mm) falls within the range typically considered suitable for ESWL, which is usually effective for stones between 5-20 mm, with optimal results for those under 10 mm.
• The location of the stone in the lower calyceal area may affect the success rate of ESWL due to issues with gravity-dependent drainage, but it does not preclude its use as a first-line treatment.
• The presence of mild pelvocaliceal dilatation indicates some obstruction to urinary drainage, supporting the decision for intervention rather than watchful waiting.

Pre-Procedure Evaluations

Before proceeding with ESWL, it is essential to conduct:

• A complete metabolic evaluation to understand the underlying causes of the stone formation.
• A urine culture to rule out any infection that could be exacerbated by the procedure or indicate a need for alternative treatment.
• An assessment of stone composition if possible, as this can influence the choice of treatment and predict the likelihood of success with ESWL.

Expected Outcomes and Post-Procedure Care

• Patients should be informed that the success rates for ESWL in treating lower pole stones range from 50-70%, and there is a possibility that multiple sessions may be required or alternative treatments like ureteroscopy might be needed if ESWL is not successful.
• Post-procedure, patients typically require analgesics for pain management and should be advised to increase fluid intake to facilitate the passage of stone fragments, as noted in guidelines such as those discussed in 1.

Decision Making

The decision to proceed with ESWL for an 8 mm right lower calyceal non-obstructing renal stone with mild pelvocaliceal dilatation is supported by the stone's size and the patient's condition, considering the potential benefits and risks, and the availability of alternative treatments if needed, as per the principles outlined in studies like 1.

From the Research

Indications for ESWL

• The patient has an 8 mm right lower calyceal non-obstructing renal stone with mild pelvocaliceal dilatation, which may be indicated for Extracorporeal Shock Wave Lithotripsy (ESWL) 2.
• ESWL is a treatment option for renal stones between 10 and 20 mm in size, excluding lower polar stones 2.
• However, for lower polar stones between 10 and 20 mm in size, ESWL can be considered if the anatomy is favorable 2.

Factors Influencing ESWL Success

• Stone size and location are significant factors that correlate with treatment outcomes regarding the need for further treatment and stone fragmentation 3.
• The mean attenuation value (MAV) is a better predictor of treatment success compared to stone size 3.
• Skin-to-stone distance (SSD) and MAV can be useful in decision-making for more dubious scenarios, but their inclusion does not provide substantial advantages when compared to relying solely on KUB 3.

Alternative Treatment Options

• Flexible ureteroscopy can be an option for lower pole stones between 1.5 and 2 cm in size, especially in cases of difficult lower polar anatomy and ESWL-resistant stones 2.
• Percutaneous nephrolithotomy (PCNL) is indicated for stones larger than 20 mm2, staghorn and partial staghorn calculi, and stones in patients with chronic kidney disease 2.
• Active monitoring has a limited role and can be employed in post-intervention residual stones, as well as asymptomatic patients with no evidence of infection and fragments less than 4 mm 2.