STONE DISEASE

Randomized controlled study of mechanical percussion, diuresis, and inversion therapy to assist passage of lower pole renal calculi after shock wave lithotripsy
Chiong E, Hwee ST, Kay LM, Liang S, Kamaraj R, Esuvaranathan K
Department of Surgery, National University of Singapore, Singapore
Urology. 2005; 65: 1070-4

• Objectives: To determine whether mechanical percussion, diuresis, and inversion (PDI) therapy after shock wave lithotripsy (SWL) improves the clearance rates of lower pole renal stones.
• Methods: In this single-blind study, 108 patients who underwent SWL treatment for lower pole renal stones with a total diameter of 2 cm or less were prospectively randomized into two groups. One group (n = 49) received SWL only and the other group (n = 59) received a median of four sessions of PDI therapy (range 1 to 12), 1 to 2 weeks after each SWL session. PDI therapy was performed as follows. Patients drank 500 mL of water 30 minutes before therapy; they then lay in a prone Trendelenburg position on a 45 degrees -angle couch, and received continuous 10-minute manual mechanical percussion applied over the flank. Stone clearance was documented with plain abdominal radiography, with additional imaging, if indicated, 1 and 3 months after initial SWL therapy.
• Results: The patients from both groups were comparable in terms of total stone diameter, infundibular neck diameter, infundibular length, caliceal height, infundibular-pelvic angles, infundibular-ureteral angles, infundibular-vertebral angles, lower pole cortical thickness, and caliceal number. All patients underwent a maximum of four SWL treatments. For all assessable patients, the radiologically documented complete stone clearance rate at 3 months for the SWL-alone group was 35.4% and for the SWL plus PDI group was 62.5% (chi-square test, P = 0.006).
• Conclusions: PDI therapy is a valuable adjunct in assisting passage of lower pole renal stone fragments after SWL therapy.
  
  
• Editorial Comment
  The dependent location of the lower pole calyces has been shown to constitute an impediment to passage of fragments after SWL. Other anatomic factors, such as the length, width and angle of the lower pole infundibulum also likely contribute to the probability of fragment clearance. Pace and colleagues previously showed in a randomized trial that a regimen of percussion, diuresis and inversion therapy in patients left with residual < 4 mm lower pole calyceal fragments after SWL resulted in an additional 40% of patients clearing fragments from the kidney compared with no further clearance in the observation group (1).
  In the current study, Chiong and associates randomized patients with lower pole stones to undergo 4 formal sessions of percussion, diuresis and inversion therapy starting 1-2 weeks after SWL versus no additional therapy and found a significant improvement in stone free rates in the treated group compared with the control group (63% versus 35%). Although the mean stone size in the 2 groups was 1 cm in the control group and 0.8 cm in the treated group, patients with stones up to 2 cm in size were included, a group that has previously been shown to respond poorly to SWL (2). As such, this regimen offers promise for improving stone free rates in a group of patients who have historically done poorly with SWL. Perhaps combining these mechanical maneuvers with pharmacotherapy using potassium citrate, which has been shown in a randomized trial to improve clearance of residual fragments after SWL of lower pole stones (3), will further improve treatment outcomes in this problematic patient group.

References
1. Pace KT, Tariq N, Dyer SJ, Weir MJ and D’A Honey RJ: Mechanical percussion, inversion and diuresis for residual lower pole fragments after shock wave lithotripsy: a prospective, single blind, randomized controlled trial. J Urol. 2001; 166: 2065-71.
2. Albala DM, Assimos DG, Clayman RV, Denstedt JD, Grasso M, Gutierrez-Aceves J et al.: Lower pole I: a prospective randomized trial of extracorporeal shock wave lithotripsy and percutaneous nephrostolithotomy for lower pole nephrolithiasis-initial results. J Urol. 2001; 166: 2072-80.
3. Soygur T, Akbay A, Kupeli S: Effect of potassium citrate therapy on stone recurrence and residual fragments after shockwave lithotripsy in lower caliceal calcium oxalate urolithiasis: a randomized controlled trial. J Endourol. 2002; 16: 149-52.

Dr. Margaret S. Pearle
Associate Professor of Urology
University of Texas Southwestern Med Ctr
Dallas, Texas, USA