RENAL PELVIS HISTOPATHOLOGY CORRELATES WITH RADIOLOGIC OUTCOME FOLLOWING PYELOPLASTY IN CHILDREN WITH UPJ OBSTRUCTION

Background: The clinical management of children post-pyeloplasty with persistent hydronephrosis (HN) by ultrasonography(US) or prolonged t 1/2 drainage by Well Tempered Renography (WTR) is not well structured. Reasons for unresolved hydronephrosis include irreversible pathologic changes in the proximal collecting system, transient obstruction due to edema at the site of repair, and persistent obstruction due to failed pyeloplasty. To help in the differentiation of these possibilities, this study correlated various histopathologic features of the excised renal pelvic specimen to radiologic outcome following pyeloplasty. Methods: Of 220 children that underwent pyeloplasty between 1988-1996 for isolated ureteropelvic junction (UPJ) obstruction, 41 children (42 kidneys) on retrospective review had adequate postoperative radiographic studies (US and/or WTR), and histologic specimens. Prenatal hydronephrosis was the diagnosis in 36/41 patients. The median age at time of pyeloplasty was 3.3 months. Median follow-up was 19.7 months (range 3 months to 7 yrs) with intervals at 3, 6, 9, 12 months and 2 years. Radiologic improvement in HN was defined as a decrease in [is greater than or equal to] 1 grade (Society for Fetal Urology grading system). Improvement in a WTR was defined as a decrease in drainage time (t 1/2 [is greater than] 5 min or 20%) or non-obstructed curve. Histologic features of the muscularis propria (MP) in the renal pelvic specimen ([micro]m thickness, % surface area collagen and elastin content / distribution) were correlated with the radiographic time line. Results: Post Pyeloplasty Radiologic Improvement follow-up based on US based on WTR 3 months 8/26 (31%) 9/15 (60%) 6 months 17/30 (57%) 14/18 (78%) 9 months 22/26 (80%) 22/26 (85%) 12 months 26/27 (96%) 25/28 (89%) 2 years 29/30 (97%) 25/27 (93%) Radiologic Improvement via MP Thickness follow-up 250 um p value 3 months 9/9 (100%) 6/21 (29%) Of the various histologic measures, only MP thickness significantly correlated with radiologic improvement (n=39). At 3 months, 15/30 (50%) patients with radiologic improvement had a mean MP thickness of 240[micro]m [+ or -] 33.0 (mean [+ or -] S.E.M.) while the remaining 15 patients without improve had a mean MP thickness of 377[micro]m [+ or -] 16.3 (p [is less than] .001). At 6 months, 22/34 (64.7%) patients with radiologic improvement had a mean MP thickness of 255[micro]m [+ or -] 25.7 while the remaining 12 patients without improve had a mean MP thickness of 376[micro]m [+ or -] 18.7 (p [is less than] .001). Two patients that did not have radiologic improvement and underwent reoperation at 9 months and 20 months (MP thickness were 397 [micro]m and 416 [micro]m respectively). Average MP thickness of the age matched control was 97 [micro]m (n=9). Both % collagen and elastin did not correlate with improvement of hydronephrosis and/or drainage time at any study time point. Conclusions: MP thickness of the renal pelvis was found to correlate significantly with the radiographic improvement during clinical follow-up i.e. specimens with MP thickness [is less than] 250 [micro]m show faster improvement in US and/or WTR than thicker specimens. Additionally, we have shown a time line to expect radiologic improvement in post-pyeloplasty children. These findings can be clinically used post-pyeloplasty to guide pediatric urologists to differentiate children with non improved radiologic studies with ultimate good outcome from those requiring intervention for persistent obstructive hydronephrosis. Peter D. Furness III, MD; Sang Won Han, MD; Max Maizels, MD FAAP; Pauline M. Chou, MD; Sandra K. Fernbach MD; and Earl Y. Cheng, MD. Department of Urology, Yonsei University College of Medicine, Seoul, Korea; Departments of Pathology, Radiology and Urology, Children's Memorial Hospital, Chicago, IL.3
Peter D. Furness III, MD; Sang Won Han, MD; Max Maizels, MD FAAP; Pauline M. Chou, MD; Sandra K. Fernbach MD; and Earl Y. Cheng, MD. Department of Urology, Yonsei [...]