Other renal cysts: medullary, dysplastic, acquired
- Lesion
Not every cystic kidney is polycystic: some cysts sit in the medulla, some reflect faulty development and some come with age or dialysis.
What it is
Several smaller disorders complete the list of renal cysts. Medullary sponge kidney has dilated medullary collecting ducts and causes stones in adults. Nephronophthisis, a recessive ciliopathy, gives small kidneys with corticomedullary cysts and kidney failure in children and teenagers. Autosomal dominant tubulointerstitial kidney disease (ADTKD; once called medullary cystic kidney disease) causes slow interstitial fibrosis in adults, from variants such as UMOD (uromodulin, with gout) and MUC1. Multicystic dysplasia is a developmental error with immature tissue. Acquired cysts follow long dialysis; simple cysts come with age.
Structure
- Medullary sponge: small cysts in the papillae, often with stones, kidneys of normal size.
- Nephronophthisis: small kidneys, cysts at the corticomedullary junction, tubular atrophy with thickened, laminated tubular basement membranes.
- Dysplasia: cysts of varied size among undifferentiated mesenchyme, smooth muscle and islands of cartilage.
- Acquired cysts: lined by hyperplastic or atypical epithelium; some contain papillary tumours.
Clinical notes
- In a teenager with polyuria, anemia and small kidneys but bland urine, think of nephronophthisis.
- Dialysis patients are screened for tumours in acquired cysts.
Test yourself
Think of the answer, then tap the question to see it.
What complication is typical of medullary sponge kidney?
Calcium stones in the dilated medullary collecting ducts, with hematuria and infection.
What distinguishes nephronophthisis from polycystic kidney disease?
Kidneys are small, cysts sit at the corticomedullary junction, and kidney failure occurs in childhood or adolescence.
Which gene of ADTKD is associated with early gout?
UMOD, which encodes uromodulin.
Elsewhere in DurgiPedia
Connections
Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.
Sources: Polycystic kidney disease: MedlinePlus Genetics (MedlinePlus, US National Library of Medicine, 2025).
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Representative model, for educational purposes only.