Autosomal dominant polycystic kidney disease - type 2. Ultrasound, geneticand clinical correlations

Background. Ultrasound, genetic and clinical correlations are available for ADPKD-1, but lacking for ADPKD-2. The present study was carried out to add ress: (i) the age-related diagnostic usefulness of ultrasound compared with genetic linkage studies; (ii) the age-related incidence and prevalence of relevant symptoms and complications; and (iii) the age and causes of death in patients with ADPKD-2. Methods. Two hundred and eleven alive subjects, from three ADPKD-2 families at 50% risk, were evaluated by physical examination, consultation of hospi tal records, biochemical parameters, ultrasound and with genetic linkage an d DNA mutation analyses. Nineteen deceased and affected family members were ;also included in the study. Results. Of the 211 alive members, DNA linkage studies and direct mutation analyses showed that 106 were affected and 105 were not. Ultrasound indicat ed 94 affected, 108 not affected and nine equivocal results in nine childre n under the age of 15. For all ages, the false-positive diagnostic rate for ultrasound was 7.5% and the false-negative rate was 12.9%. The difference between ultrasound and DNA findings was most evident in children aged 5-14 years where the ultrasound was correct in only 50% and wrong or inconclusiv e in the remaining 50%. The mean age of the 106 alive, ADPKD-2 genetically affected patients was 37.9 years (range: 6-66 years). Among them, 23.5% had experienced episodes of renal pain, 22.6% were treated for hypertension, 2 2.6% had experienced at least one urinary tract infection, 19.8% had nephro lithiasis, 11.3% had at least one episode of haematuria, 9.4% had asymptoma tic liver cysts, 7.5% had developed chronic renal failure and 0.9% had reac hed end-stage renal failure. Of the 19 deceased members, nine died before r eaching end-stage renal failure at a mean age of 58.7 years (range: 40-68 y ears), mainly due to vascular complications,while the remaining 10 died on haemodialysis at a mean age of 71.4 years (range: 66-82 years). Conclusions. DNA analysis is the gold standard for the diagnosis of ADPKD-2 , especially in young people. Ultrasound diagnosis is highly dependent on a ge. Under the age of 14, ultrasound is not recommended as a routine diagnos tic procedure, but ultrasound becomes 100% reliable in excluding ADPKD-2 in family members at 50% risk, over the age of 30. ADPKD-2 represents a mild variant of polycystic kidney disease with a low prevalence of symptoms and a late onset of end-stage renal failure.