Implications of sonographic identification of duplex kidney in adults

Duplication of the renal pelvis and ureter constitutes the most common anomalies of the upper urinary tract. Most patients are asymptomatic and don't need treatment. However, the associated anomaly and acquired renal disease may cause morbidity and mortality. The aim of this study was to investigate the prevalence of duplex kidney in sonographic examinations and the predictive capability of this method. An analysis of patients with urography-confirmed duplication anomaly was also performed.

During a period of 9 year (from 1988 to 1996), sonographic examination records of 19,287 patients were reviewed. Patients with a diagnosis of duplex kidney were enrolled. Their clinical characteristics and radiological images were recorded and evaluated.

One hundred and sixty-three patients were found by sonography to have duplex kidney, for an prevalence of 0.85%. Urography studies were done on 64 (39.2%) patients, and 42 patients were proven to have duplex kidney. The positive predictive rate of sonography was 65.6%. Eighty percent of patients with duplex kidney had associated ureteral duplication. No associated anomalies were found. Four patients had urolithiasis, and 3 patients had recurrent urinary tract infection. One patient had coexisting uroepithelial malignancy, and 1 patient had refractory gross hematuria.

Duplex kidney is an uncommon finding during adult sonographic examinations. The sensitivity and specificity of sonography in identifying this anomaly are controversial. An experienced hand with good knowledge of the anomaly and its sonographic signs is helpful in more accurately diagnosing this anomaly.