What is the major differential diagnosis for polycystic kidney disease?
The various conditions that lead to polycystic kidney disease may be subdivided into nonheritable causes and heritable causes.
Non-heritable/idiopathic causes include the following conditions:
- • Multiple incidental renal cysts : When cysts involve the renal pelvis, they may either be secondary to (1) peripelvic (renal sinus) cysts that arise from the renal hilar lymphatics, which are usually small, multiple, and bilateral; or (2) parapelvic cysts that arise from the renal cortex and extend into the renal sinus fat, which are more commonly solitary and unilateral.
- • Localized cystic renal disease : This is a rare idiopathic benign condition in which a unilateral cluster of tightly spaced variably sized cysts are seen within a kidney. Presence of intervening normally enhancing renal parenchyma and the lack of a surrounding capsule are additional imaging features that are suggestive of this diagnosis.
- • Multicystic dysplastic kidney (MCDK) : This is a nonheritable developmental disorder that is often diagnosed in utero, where one kidney is partially or completely replaced by a cluster of nonfunctioning noncommunicating cysts, sometimes with atrophy of the ipsilateral ureter, renal collecting system, and renal vasculature. Compensatory hypertrophy of the contralateral kidney is often present as well.
- • Acquired cystic renal disease of dialysis (ACKD) : Multiple renal cysts may occur in patients with end-stage renal disease and increase in frequency in proportion to the duration of dialysis. Multiple simple or complex cysts of varying size are typically seen throughout the small shrunken kidneys.
- • Lithium-induced nephrotoxicity : This is secondary to long-term lithium therapy (usually in patients with depression or schizophrenia), where multiple subcentimeter (usually 1 to 2 mm) uniformly distributed cysts are seen throughout the normal-sized kidneys
- • Glomerulocystic kidney disease (GCKD) : This is a rare form of cystic renal disease that is most often seen in neonates and young children, where multiple small cysts are predominantly seen in the subcapsular cortices of the kidneys which may be normal or small in size.
Heritable causes include the following conditions:
- • Autosomal dominant polycystic kidney disease (ADPKD) : This is the most common heritable renal disorder. It typically presents in the third through fourth decades of life, where about 50% of patients develop end-stage renal disease, and is associated with an increased risk of cardiac valve abnormalities and intracranial aneurysms. Multiple cysts are typically seen bilaterally in the kidneys, which may be normal in size but can also be enormously enlarged. The cysts may be simple or minimally complex. Cysts are also commonly seen in the liver and less commonly seen in the pancreas, spleen, ovaries, and testes.
- • Autosomal recessive polycystic kidney disease (ARPKD) : This is a rare heritable renal disorder, which may be diagnosed in utero, in neonates and infants, in children, or in adults but most often presents at the age of 2.5 years. Multiple uniform 1- to 2-mm tubular cysts are typically seen, predominantly in a medullary location, but sometimes larger 1- to 2-cm cysts are also encountered within the kidneys (which are typically large in size). Associated findings of congenital hepatic fibrosis, portal hypertension (including splenomegaly and ascites), and biliary cystic disease are typically present as well.
- • von Hippel Lindau (vHL) syndrome : This is an autosomal dominant condition that is associated with development of renal cysts, RCC, pheochromocytomas, pancreatic cysts, pancreatic neoplasms including serous cystadenoma and neuroendocrine tumors, and central nervous system hemangioblastomas. In vHL syndrome, simple-appearing renal cysts often contain small foci of RCC.
- • Tuberous sclerosis (TS) : This is the second most common phakomatosis (after neurofibromatosis type 1) and is an autosomal dominant condition that leads to hamartoma formation in the various organs of the body. Multiple bilateral renal AMLs are typically seen, which may enlarge and replace the kidneys, often in association with multiple renal cysts. Fat-containing hepatic AMLs and uniformly distributed cystic lung disease are additional suggestive imaging findings that may also be seen.
- • Medullary cystic renal disease : This condition usually occurs in children and young adults. Multiple small 1- to 1.5-cm cysts are seen at the corticomedullary junctions in the kidneys (which are typically small in size).