Influence of the renal lower pole anatomy and mid-renal-zone classification in successful approach to the calices during flexible ureteroscopy.

Abstract

The aim of this paper is to analyze if the anatomy type of the collector system (CS) limits the accessibility of flexible ureteroscopy (FUR) in the lower pole. We analyzed the pyelographies of 51 patients submitted to FUR and divided the CS into four groups: A1-kidney midzone (KM) drained by minor calices (Mc) that are dependent on the superior or on the inferior caliceal groups; A2-KM drained by crossed calices; B1-KM drained by a major caliceal group independent both of the superior and inferior groups, and B2-KM drained by Mc entering directly into the renal pelvis. We studied the number of calices, the angle between the lower infundibulum and renal pelvis, and the angle between the lower infundibulum and the inferior Mc. With the use of a flexible ureteroscope, the access attempt was made to all of lower pole calices. Averages were statistically compared using the ANOVA and Unpaired T test (p < 0.05). We found 14 kidneys of A1 (27.45 %); 4 of A2 (7.84 %); 17 of B1 (33.33 %); and 16 of B2 (31.37 %). The LIP was >90° in 31 kidneys (60.78 %) and between 61° and 90° in 20 kidneys (39.22 %). We did not find angles smaller than 60°. The group A1 presented 48 Mc and the UF was able to access 42 (87.5 %); the group A2 had 11 Mc and the UF was able to access 7 (63.64 %); the group B1 had 48 Mc and the UF was able to access 41 (85.42 %) and in group B2 we observed 41 Mc and the UF could access 35 (85.36 %). There was no statistical difference in the accessibility between the groups (p = 0.2610). Collecting system with kidney midzone drained by crossed calices presented the lower accessibility rate during FUR.