1985 Volume 76 Issue 8 Pages 1187-1193
Renal dysplasia is defined as arrest of metanephric development, failure of differentiation and persistence of incompletely developed structures. It is ordinarily diagnosed histologically.
The purpose of this report is to classify the renal dysplasia from the histological stand point. Forty kidneys from 40 patients, who were operated on in the past 12 years, were examined under the light microscope.
Histological criteria of the dysplastic kidney was based on the persistence of the primitive duct. Other dysplastic structures, such as primitive tubule, metaplastic cartilage, cysts of various sizes and abnormal glomeruli, were also observed but not uniform in amount or distribution on each specimen. In some kidneys, loose connective tissue was predominant with a few islands of primitive ducts and cortical metanephric structures. In other kidneys, normal nephrons occupied more than 70-80% with a few primitive ducts in the medulla.
According to the quantification of normal metanephric differentiation, renal dysplasia was graded into 4 groups;
Group I: normal cortex and medulla occupied more than half of the cut surface of the kidney
Group II: normal cortex and medulla occupied less than half of the kidney
Group III: dysplastic structures only
Group IV: no differentiation of metanephric blastema
This classification revealed the following features. Among the anomalies of ureteric orifices, the dysplastic grade was higher in ureterocele than ectopic ureter. Multicystic kidney had been considered one of the most severe form of dysplasia, but four fifth of this series showed grade II dysplasia. Moderate-sized kidney and sac-like parenchyma with dilated pelvis appeared low graded dysplasia. There were histological evidences of normal metanephric differentiations in the kidneys which were visualised by renal scintigraphy or enhanced CT. Microscopically, there was some relationship between the dysplastic grade and dysplastic structures, such as primitive tubule or metaplastic cartilage.
