Serial followup of the contralateral renal size in children with multicystic dysplastic kidney.

PURPOSE: Multicystic dysplastic kidneys have negligible renal function and the contralateral kidney (solitary kidney) frequently exhibits abnormalities that may affect growth. We previously showed that nomograms related to renal size constructed from digitalized ultrasonographic measurements of renal parenchymal area are a sensitive measure of renal growth and correlate with functional mass. We assess the age-dependent characteristics of compensatory renal growth in infants and children with multicystic dysplastic kidneys by construction of a growth curve for the contralateral kidney, assess these characteristics in comparison to normal renal growth of right and left kidneys, analyze the extent of compensatory renal growth and evaluate abnormal growth in solitary kidneys in infants and children.
MATERIALS AND METHODS: From 1988 to 2000 we reviewed 152 serial sonograms from 48 patients with a diagnosis of multicystic dysplastic kidneys. We also reviewed 209 renal sonograms in patients whose studies, done for other purposes, showed normal bilateral kidneys. Using computer planimetry, parenchymal area and pelvicaliceal area were determined after digitalization of ultrasound images. Parenchymal area was calculated by parenchymal area minus pelvicaliceal area and expressed as a mean of 3 measurements. A parenchymal area growth curve was generated for the contralateral kidney in the multicystic dysplastic kidney group from birth to 216 months, and for right and left normal kidneys from birth to 338 months. Data were plotted as mean parenchymal area +/- 2 SD on a nomogram generated by linear regression. Differences in parenchymal area between normal right and left kidneys, between normal kidneys and the contralateral to multicystic dysplastic kidney were analyzed by unpaired Student t test.
RESULTS: Of the 48 patients with multicystic dysplastic kidneys 36 had contralateral normal kidneys and 12 (25%) had a contralateral abnormality. Of the 12 cases 4 and an additional 5 without an identified abnormality (9 of 48) or 18.7% had solitary kidneys 2 SD below the normal growth curve for total parenchymal area, indicating a smaller than expected increase in compensatory renal growth. Conversely, 8 of 12 including 1 with grade V reflux into a solitary kidney exhibited normative compensatory renal growth. Left normal kidneys demonstrated a small but statistically significantly larger parenchymal area throughout growth. Solitary kidneys did not demonstrate growth differences associated with side. Solitary kidneys showed accelerated growth from 0 to 22 months while normal kidneys showed accelerated growth from 0 to 15 months.
CONCLUSIONS: Nomograms constructed from ultrasonographic measurements of renal parenchymal area may be useful for assessing abnormal renal growth in solitary kidneys. Patients with solitary kidneys identified by conventional ultrasonographic measurement as normal may not exhibit expected growth. Clinical decision making may be improved by identification of solitary kidneys at risk for poor growth.