Torricelli FCM. et al, 2019: Renal Stone Features Are More Important Than Renal Anatomy to Predict Shock Wave Lithotripsy Outcomes: Results from a Prospective Study with CT Follow-Up
Introduction: Lower pole kidney stones have been associated with poor shock wave lithotripsy (SWL) outcomes because of its location. However, the real impact of collecting system anatomy on stone clearance after SWL is uncertain. There is a lack of prospective well-controlled studies to determine whether lower pole kidney stones have inferior outcomes than nonlower pole kidney stones when treated with SWL. Methods: We prospectively evaluated patients with a single kidney stone of 5-15 mm undergoing SWL from June 12 through January 19. All patients were subjected to computed tomography before and 3 months after the procedure. Demographic data (age, gender, and body mass index), stone features (stone size, stone area, stone density, and stone-skin distance-SSD), and collecting system anatomy (infundibular length and width, and infundibulopelvic angle) were recorded. Outcomes (fragmentation and stone clearance rates) were compared between lower pole and nonlower pole cases. Then, a multivariate analysis including all variables was performed to determinate which parameters significantly impact on SWL outcomes. Results: One hundred and twenty patients were included in the study. Mean stone size was 8.3 mm and mean stone density was 805 Hounsfield units. Overall stone fragmentation, success, and stone-free rates were 84.1%, 64.1%, and 34.1%, respectively. There were no significant differences in stone fragmentation (76.0% vs 71.4%; p = 0.624), success rate (57.6% vs 53.3%; p = 0.435), and stone-free rate (40.2% vs 35.7%; p = 0.422) in the lower vs nonlower pole groups, respectively. On multivariate analysis, only stone density (p < 0.001) and SSD (p = 0.006) significantly influenced fragmentation. Stone size (p = 0.029), stone density (p = 0.002), and SSD (p = 0.049) significantly influenced kidney stone clearance. Conclusions: Stone size, stone density, and SSD impact on SWL outcomes. Lower pole kidney stones have similar fragmentation and stone clearance compared with nonlower pole kidney stones.
J Endourol. 2020 Jan;34(1):63-67. doi: 10.1089/end.2019.0545. Epub 2019 Nov 21.
Good study with a result against common believe.
The authors classified two different positive results:
Stone-free: absence of residual fragments
Success: presence of fragments t computed scan - NCCT to assess … anatomic features of the renal collecting system.” The classical anatomic parameters - infundibular length, infundibular, width and the infundibulopelvic angle - were measured on coronal views. I think it is very difficult to determine these parameters on coronal views which are by definition parallel planes while the pyelocaliceal anatomy is not orientated in planes but, more or less stochastically orientated. The task should be nearly impossible in non-dilated systems not opacifyed by contrast material.
The authors are aware of the problem and state: “Our study has limitations. First, renal collecting system anatomy was evaluated by CT scan without contrast, which is not the gold standard exam for this purpose. However, there are studies showing its feasibility and equivalence to intravenous urography (1).” But in that study intravenous iodinated contrast medium was used in the CT examinations. The present study used non-contrast CTs.
1 Rachid Filho D, Favorito LA, Costa WS, Sampaio FJ. Kidney lower pole pelvicaliceal anatomy: comparative analysis between intravenous urogram and three dimensional helical computed tomography. Journal of endourology 2009;23(12):2035 2040.