What is the pathophysiology of autosomal dominant polycystic kidney disease (ADPKD)?

Updated: Mar 24, 2020
  • Author: Roser Torra, MD, PhD; Chief Editor: Vecihi Batuman, MD, FASN  more...
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Answer

The main feature of ADPKD is a bilateral progressive increase in the number of cysts, which may lead to ESRD. Hepatic cysts, cerebral aneurysms, and cardiac valvular abnormalities also may occur. [10, 11]

Although ADPKD is a systemic disease, it shows a focal expression because less than 1% of nephrons become cystic. In ADPKD, each epithelial cell within a renal tubule harbors a germ-line mutation, yet only a tiny fraction of the tubules develop renal cysts.

It is currently held that the cells are protected by the allele inherited from the parent without ADPKD. When this allele is inactivated by a somatic event (mutation or otherwise) within a solitary renal tubule cell, the cell divides repeatedly until a cyst develops, with an aberrant growth program causing endless expansion. The severity of ADPKD is thought to be a direct consequence of the number of times and the frequency with which this cystogenic process occurs within the kidneys over the life of the patient. However this hypothesis is hard to understand in neonatal cases.

The hyperplastic cells cause an out-pocketing of the tubule wall, with the formation of a saccular cyst that fills with fluid derived from glomerular filtrate that enters from the afferent tubule segment. Progressive expansion eventually causes most of the emerging cysts to separate from the parent tubule, leaving an isolated sac that fills with fluid by transepithelial secretion. This isolated cyst expands relentlessly as a result of continued proliferation of the mural epithelium together with the transepithelial secretion of sodium chloride and water into the lumen.

The expanding fluid-filled tumor masses elicit secondary and tertiary changes within the renal interstitium evinced by thickening and lamination of the tubule basement membranes, infiltration of macrophages, and neovascularization. Fibrosis within the interstitium begins early in the course of the disease.

Cellular proliferation and fluid secretion may be accelerated by cyclic adenosine monophosphate (cAMP) and growth factors, such as epidermal growth factor (EGF). In summary, cysts function as autonomous structures and are responsible for progressive kidney enlargement in ADPKD.


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