Polycystic Kidney Disease for PA
Polycystic Kidney Disease for the Physician Assistant Licensing Exam
- Definition:
- Polycystic kidney disease (PKD) is a genetic disorder characterized by the development of numerous cysts in the kidneys, leading to progressive kidney dysfunction. The two primary forms are autosomal dominant polycystic kidney disease (ADPKD) and autosomal recessive polycystic kidney disease (ARPKD).
- Etiology:
- Autosomal Dominant Polycystic Kidney Disease (ADPKD):
- Caused by mutations in the PKD1 or PKD2 genes, with PKD1 mutations causing more severe disease. ADPKD typically presents in adulthood and is the most common form of PKD.
- Autosomal Recessive Polycystic Kidney Disease (ARPKD):
- Caused by mutations in the PKHD1 gene, ARPKD presents in infancy or early childhood with both renal and hepatic involvement.
- Clinical Features:
- ADPKD:
- Hypertension: One of the earliest signs, due to cyst expansion and activation of the renin-angiotensin-aldosterone system (RAAS).
- Flank Pain: Caused by cyst expansion, hemorrhage, or infection.
- Hematuria: May occur with cyst rupture.
- Recurrent Urinary Tract Infections (UTIs): Infected cysts cause fever, flank pain, and bacteriuria.
- Nephrolithiasis: Kidney stones are common, often composed of calcium oxalate or uric acid.
- Progressive Renal Failure: ADPKD leads to chronic kidney disease (CKD) and eventually end-stage renal disease (ESRD).
- Extrarenal Manifestations: Include hepatic cysts, intracranial aneurysms, and mitral valve prolapse (MVP).
- ARPKD:
- Presents in infancy with enlarged, echogenic kidneys. Respiratory distress from pulmonary hypoplasia is common in neonates.
- Liver Disease: Congenital hepatic fibrosis leading to portal hypertension and hepatosplenomegaly.
- Diagnosis:
- Ultrasound: The first-line diagnostic tool for detecting renal cysts. Diagnostic criteria depend on the number of cysts and the patient's age.
- Genetic Testing: May confirm PKD1, PKD2, or PKHD1 mutations in uncertain cases.
- Management:
- Blood Pressure Control:
- ACE inhibitors or ARBs are the first-line treatment for hypertension in ADPKD.
- Pain Management:
- Cyst-related pain can be managed with analgesics or cyst drainage in refractory cases.
- Infection Treatment:
- Cyst infections are treated with antibiotics that penetrate cysts, such as fluoroquinolones or trimethoprim-sulfamethoxazole.
- Renal Replacement Therapy (RRT):
- ESRD is managed with dialysis or kidney transplantation.
Key Points
- Polycystic kidney disease is a genetic disorder causing multiple renal cysts, leading to progressive renal failure.
- ADPKD presents in adulthood with hypertension, hematuria, recurrent UTIs, and nephrolithiasis, while ARPKD presents in infancy with severe renal and hepatic complications.
- Diagnosis is primarily based on ultrasound imaging, with genetic testing for confirmation in ambiguous cases.
- Treatment focuses on controlling blood pressure, managing cyst-related complications, and providing renal replacement therapy for ESRD.