Brown JA et al, 2013: Effect of High Shock Number on Acute Complication Development Following Extracorporeal Shock Wave Lithotripsy
Brown JA, Hadj-Moussa M.
University of Iowa, Department of Urology, 200 Hawkins Dr., 3 RCP, Iowa City, Iowa, United States
PURPOSE: We assessed whether high shock number is associated with higher rates of acute complication development following extracorporeal shock wave lithotripsy (SWL).
MATERIALS AND METHODS: A retrospective chart review of 372 patients who underwent 436 SWL procedures at 24 kV using a Medstone STS-T lithotripter (Medstone International Inc., Aliso Viejo, CA). Complications occurred within four weeks of SWL. Treatments were split into three cohorts based on shock number (4,000). Postoperative sequelae of stone-free and residual stone patients were studied separately. Chi-squared tests were used to evaluate the relationship between shock number cohort and postoperative complication development.
RESULTS: SWL treatments recorded for each cohort were 158 (37.4%), 145 (34.4%), and 119 (28.2%), respectively. Short-term complication rate when SWL was successful wasm 8.3% overall. Complication rate for each cohort was 9.5% (11), 7.8% (5), and 7.2% (7), respectively. When SWL was successful, statistical analysis revealed no significant difference between complication rates and shock number cohort (p=0.63). Complications in patients with a residual stone occurred following 41.4% of treatments and trended upward with shock number cohort, but did not reach statistical significance (p=0.84).
CONCLUSIONS: At high voltage, high shock number was not shown to cause higher rates of short-term postoperative complications as experienced by patients when SWL was successful or resulted in a residual stone. Yet complication rates associated with residual stone burden were approximately five times as common. Foregoing higher shock number in the presence of a residual stone may therefore increase the risks of sequelae immediately following SWL.
J Endourol. 2013 Mar 28. [Epub ahead of print]
PMID:23537270 [PubMed - as supplied by publisher]
There are two important questions that need an answer when the total number of shock waves given to a patient is considered: Is a large number of shock waves associated with risks and does a large number of shock waves administered during one session result in a better disintegration or a higher stone free rate? None of these questions was addressed in this article. The authors had their focus on pain, hematuria, urine retention, dysuria, nausea, vomiting and fever. Most of these symptoms (complications) are expected as result of fragment/stone passage or are a reflection of inappropriate attention to the presence of bacteriuria.
The stone-free rates with ≤ 2400 and 2401-4000 shock waves were 75% and 74%, respectively, and in the group treated with > 4000 shock waves the stone-free rate was 45%. The explanation for the inferior result in the last group is most certainly that a large number of shock waves was used to treat patients with a more complicated stone situation, but obviously without expected benefit. There is, unfortunately, no information on the pre-treatment stone burden in patients who became stone-free compared with those who did not.
What I had expected from this study was some information on how the renal tissue and its function were affected by different numbers of shock waves.
Another point to consider is how the stone burden best is expressed. There is absolutely no consensus on this important factor. The authors used the largest diameter or the sum of the largest diameters, when more than one stone was treated. With that method one stone with a size of 15 x 12 mm is comparable with three stones 5x4, 5x4 and 5x4 mm, despite the fact that the stone surface areas for these two cases are approximately 141 mm2 and 47 mm2. An even greater difference will be noticed if the volumes of such stones were estimated. There seems to be need for a consensus on how the stone burden best should be described. In the CT-era the stone volume may be the best choice and when plain films are used: stone surface area.