Imaging-Based Diagnosis of Autosomal Dominant Polycystic Kidney Disease

Focal development of an increasing number of renal cysts with age is a hallmark of autosomal dominant polycystic kidney disease (ADPKD), leading to the distortion of normal kidney architecture and, ultimately, ESRD in a majority of patients. Mutations of two genes (i.e., PKD1 and PKD2) account for most of the cases. Clinically, a wide spectrum of cystic disease variability is displayed in ADPKD in part due to strong effects from the gene locus (i.e., PKD1 vs. PKD2) and alleles (i.e., truncating vs. non-truncating PKD1 mutations). Presymptomatic screening of subjects at risk for ADPKD is commonly performed by conventional ultrasonography, which is inexpensive and widely available. Age-dependent ultrasound criteria have been derived for PKD1 and subsequently refined (a.k.a. unified criteria) for evaluation of at-risk subjects with unknown gene type. However, reduced diagnostic sensitivity by conventional ultrasound renders disease exclusion in younger at-risk subjects not possible until 40 years of age. More recently, magnetic resonance imaging (MRI) has been shown to greatly improve imaging-based diagnostic performance in ADPKD. Specifically, “more than a total of 10 renal cysts” can be regarded as sufficient for diagnosis while “less than a total of 5 renal cysts,” sufficient for disease exclusion in at-risk subjects between 16 and 40 years of age. These criteria will greatly facilitate the evaluation of at-risk subjects who wish to be considered as living kidney donors. High-resolution ultrasound can provide excellent diagnostic performance, rivaling that of MRI, but is both center- and operator-dependent. The diagnosis of subjects suspected to have ADPKD without a definitive family history can be challenging and will often require molecular genetic testing.