Hereditary polycystic kidney diseases in children: changing sonographic patterns through childhood.

OBJECTIVE: To determine which US changes occur with time in children affected by autosomal recessive (ARPKD) and autosomal dominant polycystic kidney disease (ADPKD) and whether any of these changes correlate with the onset of renal failure.

MATERIALS AND METHODS: We reviewed the US features of 29 patients (16 ARPKD, 13 ADPK) imaged by at least two US examinations. We analysed the size and echogenicity of the kidneys, corticomedullary differentiation (CMD), the presence, location and size of cysts and any other anomaly that developed with time. In order to determine whether a relationship could be found between any of the US changes and the onset of the renal failure (based on a glomerular filtration rate < 50 ml/min per 1.73 m2), a Pearson exact chi-square test was calculated.

RESULTS: For ARPKD, renal size was above 4 standard deviations (SD) in 10 of 16 patients, but it remained stable during evolution (10/16). The kidneys appeared hyperechoic (16/16), without CMD in the majority (11/16) of patients. Changes in the appearance of CMD over time were observed in five patients. Small cysts (< 1 cm) were present at the time of diagnosis in seven patients, larger cysts (> 1 cm) in three. A diffuse microcystic pattern was observed in three patients. Diffuse hyperechoic foci developed in 14 patients--13 of whom had developed renal failure at the time of the examination or rapidly thereafter (statistical correlation P=0.0125). For ADPKD, renal size was between 0-2 SD in 7 of 13 patients and above 2 SD in the other 6. Renal echogenicity was normal in five, difficult to assess in five and the kidneys appeared hyperechoic without CMD in three patients. Cysts larger than 1 cm were present in 8 of 12 patients (> 3 cm in 5). In four patients, the cysts measured less than 1 cm. In the last child, the diagnosis had been made antenatally and the first cysts appeared at the age of 6 months. The size of the kidneys (13/13) and of the cysts (11/13) remained stable. No renal failure occurred.

CONCLUSIONS: ARPKD may manifest with various US patterns and there may be evolution in the appearances over time. Our study confirms a significant relationship between the development of diffuse hyperechoic foci and the onset of renal failure. In older children, ARPKD and ADPKD may closely resemble each other. Large (> 3 cm) cysts are the US hallmark for the diagnosis of ADPKD; furthermore, fewer US changes occur with time during childhood in ADPKD.