Factors predicting outcomes of micropercutaneous nephrolithotomy: results from a large single-centre experience.

OBJECTIVES

To present our single-centre experience of the micropercutaneous nephrolithotomy (microperc) technique and define its role in the management of renal calculi as well as to analyse the factors predicting outcome.

PATIENTS AND METHODS

We retrospectively analysed data from 139 patients who underwent microperc for renal calculi between June 2010 and November 2014 at our institution. The factors analysed were demographic variables, which included age, sex, stone volume, stone density (Hounsfield units [HU]) and stone location, and intra- and peri-operative variables, such as operating time, drop in haemoglobin level, stone clearance and complications.

RESULTS

The mean ± sd (range) patient age was 38.99 ± 17 years (9 months to 73 years), stone volume was 1 095 ± 1 035 (105-6 650) mm(3) and stone density was 1 298 ± 263 HU. The mean ± sd (range) operation duration was 50.15 ± 9.8 (35-85) min, hospital stay was 2.36 ± 0.85 (2-5) days and drop in haemoglobin level was 0.63 ± 0.84 (0-3.7) mg/dl. Eight patients had renal colic that was managed by antispasmodic medication, four patients had renal colic severe enough to warrant JJ stenting and three patients had urinary tract infections which were managed with appropriate antibiotics. We were able to complete microperc in 130 patients, with 119 (91.53%) patients being rendered completely stone-free, while in 11 patients (8.46%) there were some residual fragments seen on imaging. On multivariate analysis, stone number, volume and density were found to be significant predictors of clearance. Conversion to mini- or standard percutaneous nephrolithotomy was required in nine patients (6.47%), with intra-operative complications and stone number being the significant factors warranting conversion on a multivariate basis.

CONCLUSION

The outcomes in the present study suggest that microperc is a promising treatment method for solitary renal stones with volumes <1 000 mm(3) and stones with low density (HU), regardless of stone location. In the present series we achieved a high success rate with low morbidity; however larger, prospective and comparative studies from multiple centres are required to further establish the role of microperc in the management of renal calculi.