ENDOUROLOGY & LAPAROSCOPY

Is lower pole caliceal anatomy predictive of extracorporeal shock wave lithotripsy success for primary lower pole kidney stones?
Sorensen CM, Chandhoke PS
From the Departments of Surgery (Urology) and Medicine (Renal Diseases), University of Colorado Health Sciences Center, Denver, Colorado
J Urol. 2002; 168:2377-82

• Purpose: The management of lower pole kidney stones is controversial. We examined whether lower pole caliceal anatomy could predict the success of extracorporeal shock wave lithotripsy of primary lower pole kidney stones 20 mm. or less.
• Materials and Methods: From December 1997 to June 2001, 246 adults with a single, 20 mm. or less radiopaque lower pole renal stone were treated with the Doli 50 lithotriptor (Dornier Medical Systems, Marietta, Georgia) while under general anesthesia. Of the 246 patients 190 (77%) had excretory urography available for review. Lower pole infundibular length and width, lower pole infundibulopelvic angle and caliceal-pelvic height were measurable on 161 (85%), 129 (68%), 128 (67%) and 163 (86%) excretory urograms, respectively. Extracorporeal shock wave lithotripsy was considered a failure if residual stone fragments remained after 1 month, or an auxiliary procedure or re-treatment was required.
• Results: The overall stone-free rate was 78% (32 of 41) for stones 5 mm. or less, 73% (98 of 135) for stones 6 to 10 mm., 43% (22 of 51) for stones 11 to 15 mm. and 30% (7 of 19) for stones 16 to 20 mm. in maximum linear dimension. The stone-free rates grouped according to stone surface area were 76% (48 of 63 stones) for stone surface area 25 mm.2 or less, 69% (97 of 141) for 26 to 100 mm.2 and 33% (14 of 42) for 101 to 400 mm.2. Caliceal anatomy was not predictive of success even with stones grouped as 10 or less or 11 to 20 mm. Grouping patients with favorable (lower pole infundibulopelvic angle 70 degrees or greater, lower pole infundibular length 30 mm. or less and lower pole infundibular width greater than 5 mm.) versus unfavorable (70 degrees or less, greater than 30 mm. and 5 mm. or less, respectively) anatomy was also not predictive of success.
• Conclusions: On the Doli 50 machine stone size rather than caliceal anatomy is predictive of treatment outcome. Initial treatment failures with this machine should be managed by alternative endoscopic procedures if necessary rather than by repeat shock wave lithotripsy.
  
  
• Editorial Comment
  The concept of lower pole anatomy impacting the results of shock wave lithotripsy for lower pole renal calculi is hotly debated. Initially proposed only on theoretical anatomical basis by Dr. Sampaio in 1992 (J Urol. 1992; 147:322-324), several initial clinical series suggested that indeed a tighter infundibulopelvic angle of the lower pole (i.e., more dependent lower pole) is associated with poorer results. Subsequently, however, there have been several articles (including this one) that have challenged this association. It is notable that in the refuting articles the percentage of patients with a lower pole infundibulopelvic angle greater than 70–100 degrees, which is the range of upper limit of “favorable” angles proposed by various authors, has usually been far less than in the articles that did report an association of infundibulopelvic angle and shock wave lithotripsy success. This distinction, which may be due to differences in patient population, or of the measurement techniques, likely accounts for much of the discrepancy. That lower pole anatomy impacts the results of shock wave lithotripsy makes intuitive sense, but there is no agreement on how to measure the angle and whether or not other factors, such as infundibular length, infundibular width, or calyceal-pelvic height, are important. Until there is a clearer consensus in the literature, the exact impact of lower pole anatomy will not be defined. While we are waiting for this, I for one will continue to use a gross visual assessment of the caliceal anatomy, without specific measurements, when advising patients about treatment options for lower pole renal calculi.

Dr. J. Stuart Wolf Jr.
Associate Professor of Urology
University of Michigan
Ann Arbor, Michigan, USA