Growth of renoprivals following uninephrectomy for Wilms' tumour: application and suitability of a method of assessment

Growth of the solitary kidney after nephrectomy in children with unilateral Wilms' tumor

OBJECTIVE

We reviewed the length of the solitary kidney from all ultrasound examinations in 34 children who had undergone unilateral nephrectomy for Wilms' tumor, in order to determine the frequency of renal hypertrophy in this population. Standard sonographic criteria for nephromegaly were used.

MATERIALS AND METHODS

We generated a z-score for each measurement of the renal length, using an interpolated computer model based on published standards for sonographic renal length in relation 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 more consecutive measurements of the renal length exceeding two standard deviations longer than the mean for the patient's age, with no later normal measurement.

RESULTS

Seventeen (50 %) of the 34 patients developed SRH. The latest measurements of the solitary kidney in the patients were significantly longer (mean z = 2.210) than in their controls (mean z = 0.040), even among the patients who did not develop SRH (patients' mean z = 1.000, controls' mean z = -0. 210, p < 0.001). Because boys had slightly longer kidneys than girls (both patients and controls), SRH was also noted more often in boys. The frequency of SRH was unrelated to age at nephrectomy, side of the solitary kidney, tumor stage, chemotherapy regimen, or treatment with radiation therapy.

CONCLUSIONS

Although renal growth in a solitary kidney is accelerated in most children after unilateral nephrectomy for Wilms' tumor, the sonographic length of the solitary kidney will be larger than normal in only half of the patients.

Renal growth in patients nephrectomized for Wilms tumour as compared to renal agenesis

Compensatory growth in 27 undiseased congenital solitary kidneys and in 31 solitary kidneys in patients with Wilms tumour was monitored in long-term follow-up studies by ultrasound volume biometry. In congenital solitary kidneys hypertrophy was not detectable at the time of birth. Parenchymal mass increase achieved 188% of the volume of a healthy kidney within at least 4 years of life and afterwards paralleled the physiological growth documented in healthy kidney pairs. Disease-free kidneys in Wilms tumour patients all developed a similar 180% volume augmentation within 2-4 years after nephrectomy, irrespective of the chosen mode of radiation and single or triple chemotherapy. The age of the patient at onset of surgical and concomitant conservative therapy determined slight differences in kinetics but not in degree of compensatory growth.

Renoprival growth following treatment of unilateral Wilms' tumour

The renal growth pattern following uninephrectomy for Wilms' tumour was analysed in 18 boys and 18 girls by means of a comparison between renal parenchymal and body surface area. No straightforward correlation was noted between age at nephrectomy, chemo- and radiation therapy applied, and subsequent renoprival dimensions. Five years on average after operation, a mean renal size corresponding to approximately 125 per cent of the normal for one of two healthy kidneys was recorded. However, wide variations in size were observed, but only 10 patients had a compensatory growth of the remaining kidney equivalent to that seen in patients nephrectomized for unilateral, non-malignant renal disease.