Characteristics of Kidney Stones that Lead to High Stone-Free Rates in Supine Ultra-Mini Percutaneous Nephrolithotomy.

BACKGROUND

The increasing frequency of health checkups has led to an increasing diagnosis of renal stones. There exist various treatments for renal stones, but the less invasive ultra-mini percutaneous nephrolithotomy (UMP) treatment is gaining wide attention. The present study aimed to confirm the characteristics of renal stones that help achieve a high stone-free rate through UMP regardless of the complications.

METHODS

A retrospective study was conducted on 100 consecutive patients from May 2016 to February 2021. The study used a 7.5 Fr nephroscope and an irrigation pump. Renal stones were pulverised into as small particles as possible using a holmium laser discharged through an 11/12 Fr operating sheath. Kidneys, ureters, and bladder (KUB) and stone computed tomography (CT) scans were performed four weeks after surgery to confirm the stone-free state in patients.

RESULTS

The present study enrolled 72 men and 28 women who underwent UMP. The mean age of the patients was 61.5 years. The average size of the stones was 2.7 ± 1.1 cm. The average operation time was 74.7 ± 38.5 minutes. Three collecting system injuries occurred; However, no damage to other organs or bleeding was observed. At the one-month follow-up, the overall stone-free rate of UMP was 66%, lower than the target stone-free rate of 87%. The multivariate logistic regression analysis revealed that a high surgical success rate could be predicted in the cases of a single calcium oxalate or uric acid stone with a stone size <3 cm.

CONCLUSIONS

UMP can be considered the first treatment option for single renal calcium oxalate or uric acid stones with a size <3 cm.