Evidence of Extraordinary Growth in the Progressive Enlargement of Renal Cysts

Background and objectives: In autosomal dominant polycystic kidney disease, cysts derived from tubules are detected at birth by ultrasound (threshold for detection >7.0 mm); thus, fetal cyst growth rates must exceed 2300%/yr. In adults, the combined renal cyst component enlarges at approximately 12%/yr by growth of individual cysts. To explore this discrepancy, the growth rates of individual cysts were determined in adult polycystic kidneys. Design, setting, participants, & measurements: Diameter, volume, and growth rates of individual cysts were measured by magnetic resonance in 30 individual cysts in three adult patients over a span of 3 years. Results were confirmed in 22 cysts measured in five patients by computed tomography over a span of 11 years. Results: Mean cyst diameters were 20.4 ± 9.9 mm (range 7.1 to 40.5 mm) at baseline and 25.8 ± 15.6 mm (range 7.8 to 49.6 mm) after 3 years. Mean cyst volumes, determined by manual segmentation and summation of magnetic resonance cross sections, were 8.7 ± 12.9 cm3 (0.3 to 43.3 cm3) and 24.2 ± 66.3 cm3 (0.3 to 364.8 cm3) after 3 years. Mean cyst growth rates ranged from 6.9 to 23.9%/yr; the maximum growth rate was 71.1%/yr, far less than required to develop a 7-mm diameter cyst in utero. Results were similar in 22 cysts examined by computed tomography. Conclusions: It was concluded that renal cysts detected by ultrasound in newborns must have grown at exuberant rates in utero; thereafter, expansion appears to proceed at much slower rates.