GROWTH OF THE SOLITARY KIDNEY AFTER NEPHRECTOMY IN CHILDREN WITH UNILATERAL WILMS-TUMOR

Objective. We reviewed the length of the solitary kidney from all ultr asound examinations in 34 children who had undergone unilateral nephre ctomy for Wilms' tumor, in order to determine the frequency of renal h ypertrophy in this population. Standard sonographic criteria for nephr omegaly were used. Materials and methods. We generated a z-score for e ach measurement of the renal length, using an interpolated computer mo del based on published standards for sonographic renal length in relat ion to age. A retrospective age- and gender-matched control population of children with sonographically normal paired kidneys was generated from a departmental computerized pediatric uroradiology data base, and their ipsilateral renal lengths were compared with those of the study patients. Sonographic renal hypertrophy (SRH) was defined by two or m ore consecutive measurements of the renal length exceeding two standar d deviations longer than the mean for the patient's age, with no later normal measurement. Results. Seventeen (50%) of the 34 patients devel oped SRH. The latest measurements of the solitary kidney in the patien ts were significantly longer (mean z = 2.210) than in their controls ( mean z = 0.040), even among the patients who did not develop SRH (pati ents' mean z = 1.000, controls' mean z = -0.210, p < 0.001). Because b oys had slightly longer kidneys than girls (both patients and controls ), SRH was also noted more often in boys. The frequency of SRH was unr elated to age at nephrectomy, side of the solitary kidney, tumor stage , chemotherapy regimen, or treatment with radiation therapy. Conclusio ns. Although renal growth in a solitary kidney is accelerated in most children after unilateral nephrectomy for Wilms' tumor, the sonographi c length of the solitary kidney will be larger than normal in only hal f of the patients.