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Clinical Scenarios in Chronic Kidney Disease: Kidneys' Structural Changes in End-Stage Renal Disease.

Acquired cystic kidney disease (ACKD) and renal cell carcinoma (RCC) are the most important manifestations of end-stage kidneys' structural changes. ACKD is caused by kidney damage or scarring and it is characterized by the presence of small, multiple cortical and medullary cysts filled with a fluid similar to preurine. ACKD prevalence varies according to predialysis and dialysis age and its pathogenesis is unknown, although it is stated that progressive destruction of renal tissue induces hypertrophy/compensatory hyperplasia of residual nephrons and may trigger the degenerative process. ACKD is almost asymptomatic, but it can lead to several complications (bleeding, rupture, infections, RCC). Ultrasound (US) is the first level imaging technique in ACKD, because of its sensitivity and reliability. The most serious complication of ACKD is RCC, which is stimulated by the same growth factors and proto-oncogenes that lead to the genesis of cysts. Two different histological types of RCC have been identified: (1) RCC associated with ACKD and (2) papillary renal clear cell carcinoma. Tumors in end-stage kidneys are mainly small, multifocal and bilateral, with a papillary structure and a low degree of malignancy. At US, RCC appears as a small inhomogeneous nodule (<3 cm), clearly outlined from the renal profile and hypoechoic if compared with sclerotic parenchyma. In some cases, tumor appears as a homogeneous and hyperechoic multifocal mass. The most specific US sign of a small tumor in end-stage kidney is the important arterial vascularization, in contrast with renal parenchymal vascular sclerosis.