[Comparison between Valdivia position and prone position in percutaneous nephrolithotomy].

Introduction: Although the supine position created by Dr. Valdivia two decades ago to perform the procedure known as percutaneous nephrolitectomy (PNL) presents advantages against the prone position in some aspects concerning anesthesia and surgical ergonomy, its use has failed to spread widely among the urology community due to certain technical difficulties, a lower rate of calculi clearing and a higher rate of complications, in spite of the fact that the scarce comparative studies do not show enough data to support this opinion. The present study compares both positions considering the technical difficulties encountered, their effectiveness and their results and complications.
Material and Methods: A series of 50 patients that underwent PCNL by prone position is compared retrospectively with another series of 54 patients that underwent consecutively PCNL by prone position. All procedures were performed under general anesthesia, the inferior calyx approach was the one used the most over the supracostal approach, and the sole tract over the multi-tract approach was predominant. Dilatation of the nephrostomy tract was done, in most of the cases, with a high-pressure balloon catheter. The stone surface treated was 399.93+/-58.2 mm2 for the supine group, and 416.36+/-46.54 mm2 for the prone one (p=0.456). The management of the stones was carried out by ultrasonic or ballistic fragmentation, and a small group of patients underwent direct stone removal.
Results: As far as demographic parameters and operative variables such as number of tracts performed, calyx election, type of tract dilatation and kind of energy used for fragmentation, both groups were homogeneous. In 3 cases of each group there was a failure to access the kidney. The rate of failure was 6%, and 5.56%, for the supine and prone groups, respectively (p=0.716). Average operating time was 74.55+/-25.54 and 91.82+/-24.82 minutes, respectively, p=0.123. A postoperative x-ray showed a stone-free rate of 76% for the supine group and 74% for the prone group, p=0.308. ESWL was the supplementary treatment for 12% of the patients in the supine group, and for 12.96% of the patients in the prone group p= 0.478, and a second procedure was performed on 4 (8%) patients in the supine group and on 3 (5.56%) in the prone one, p=0.697. Hospital stay was the same for both groups (5.89+/-4.7 for the supine group, and 5.5+/-4.09 for the prone one, p=0.694). As far as analgesia required, 6.89+/-4.87 was administered for the supine against 6.18+/-4.09 for the prone, p=0.580. The complications rate was very low for both groups and also very similar; one of the patients in the supine group suffered a lesion to the colon.
Conclusion: Valdivia position is as feasible as the prone position for PCNL. Success rates, as far as stone clearing, and complications are similar for both positions.