1987 Volume 78 Issue 6 Pages 1051-1059
It is not infrequent that a kidney smaller than normal is visualized on the excretory urogram (IVP) in patients with vesicoureteral reflux (VUR). The renal ratio (renal length/length between L1 to L4) was calculated on 731 children with VUR whom we treated in the past 12 years. We analysed the clinical features of 124 children who had one or two kidneys that were at least-2SD smaller than normal for age.
1) The prevalence of small kidney was 15.6% in primary VUR (97/623 children) and 25.0% in secondary VUR (27/108 children). The percentage of the patients with small kidney was about the same in each age group.
2) VUR was graded according to the international classification. About 80% of the kidneys associated with moderate (grade-IV) to severe (grade-V) reflux.
3) Types of pyelonephritic changes were graded and designated as pyelonephritis grade (PG): PG-O, no changes; PG-I, calyceal deformities; PG-II, not more than two scarred areas; PG-III, more generalized scarring, but some areas of normal tissues; PG-IV, generalized scarring; and PG-V; end-stage shrunken kidney. Pyelonephritic scarring (PG-II or more) was apparent in 80 to 90% of the kidneys.
4) According to the radiological features such as renal outline, parenchymal thickness, evidence of calyceal deformities and the number of calyces, the small kidneys were subdivided into three types: congenital hypoplasia, scarred atrophy, and the combination of the two. About half of the kidneys in primary VUR were diagnosed as scarred atrophy, and 40% as congenital hypoplasia.
5) The renal ratio of the contralateral kidney was calculated in 87 children with unilateral small kidney. Hypertrophy of the contralateral kidney, which is+2SD larger than normal for age, was apparent in about half of the children.
6) The renal growth was evaluated by the changes of the renal ratio in 79 small kidneys which were followed for more than lyear; the mean follow-up period was 3 years. Twenty kidneys, that had been in the normal range at the first examination, became small during the course. Accelerated growth was only exceptional.
To know the renal growth after the antireflux surgery, 53 kidneys which were followed for more than 1year after operation (mean follow-up period was 2 years and 9 month) were analysed. While about 3/4 remained small during the pre-and post-operative periods, 1/4 showed a retarded growth after the operation.
It is concluded that the origin of the small kidney associated with VUR is not restricted to post-pyelonephritic shrinkage. We discussed the possible role of congenital hypoplasia in cases with primary VUR. The renal growth was independent of the hypertrophy in the contralateral kidney, and most of the small kidneys showed gradual increase in renal length parallel to the expected growth curve. It is suggested that surgery is needed even in cases with small kidney to get rid of the influence of VUR.
