Quantification and longitudinal trends of kidney, renal cyst, and renal parenchyma volumes in autosomal dominant polycystic kidney disease

The aims of this study were to assess the accuracy and reproducibility of v olumetric determinations of total kidney, renal cyst, and renal parenchymal volumes, using fast electron-beam computerized tomography scanning, and to determine the rate of change of these volumes. Nine patients with autosoma l dominant polycystic kidney disease (ADPKD) and serum creatinine less than or equal to 1.3 mg/dl and/or an initial iothalamate clearance greater than or equal to to 60 ml/min per 1.73 m(2) were imaged weekly over a 3-wk peri od (total of 3 times). Approximately 8 yr later, they returned for follow-u p studies. The kidney volume estimation technique involved a manual segment ation (perimeter drawing) of the kidneys and a semiautomatic threshold appr oach, using a histogram analysis of the peak densities of renal parenchyma and renal cysts. At entry, total kidney and renal cyst volumes correlated p ositively with age, while renal parenchymal volumes and GFR correlated nega tively with age, The average coefficient of variation values for the three initial consecutive measurements of total kidney, renal cyst tactual and as a percent of total volume), and renal parenchymal volume were 3.4, 7.2, 5. 3, and 5.6%, respectively. During the 8 yr of follow-up, total kidney and r enal cyst volumes increased, while renal parenchymal volumes and GFR declin ed. The rate of increase in total kidney and renal cyst volumes varied mark edly from patient to patient. There was a significant correlation between r ate of increase in renal cyst volume and the rate of decline in GFR. The pa tients with an initial urine protein/osmolality ratio >0.13 mg/L per mosmol per kg had a significantly higher increase in renal volume and decline in GFR than those with a lower ratio. In summary, the results of this pilot st udy suggest that: (1) electron-beam computerized tomography is capable of m easuring total kidney, renal cyst, and renal parenchymal volumes reproducib ly; (2) total kidney and renal cyst volumes increase, while parenchymal vol umes decrease with time; (3) the increase in cyst volume correlates best wi th the decline in renal function; and (4) renal volumes appear to be good s urrogate markers for disease progression in ADPKD.