[New concepts in the natural history of multicystic dysplastic kidney]

Retroperitoneoscopy has shown that US involution is not synonymous with complete regression of the dysplastic renal parenchyma in US-involuted multicystic dysplastic kidney (MCDK). The objective is to analyze the meaning of this results.

16 patients (nine girls and seven boys) with unilateral MCDK that showed complete involution on ultrasonography, underwent prospectively a retroperitoneoscopic approach. US showed complete cysts involution at the mean age of 10 months (ranging from five to 22 months). All patients underwent a retroperitoneoscopic approach after US involution of the MCDK. The mean age of retroperitoneoscopy was 36 months (ranging from eight to 56 months).

The retroperitoneoscopic approach revealed persistence of dysplastic renal tissue in 100% of the patients. The mean lenght of the renal renmant was 2 cm (ranging from 1 and 3.5 cm). All patients had a mean length of stay of less than 24 hours. Anatomo-pathological study of the samples showed a wide spectrum of dysplastic renal tissue and the absence of preneoplastic cells.

Ultrasonography is our method of choice to follow up MCDK until cyst involution takes place. The presence of a dysplastic renal remnant which is not visible on US, requires an appropriate long-term follow up to screen for the growth of tumors. In our experience, retroperitoneoscopy allows the diagnosis and treatment of the displastic renal renmant in the same minimally invasive ambulatory procedure, avoiding long-term development of tumors. Overall, it is our responsibility to sufficiently inform to the family about the persistence of dysplastic renal remnant to facilitate their decision about the best treatment for their child.