Renal · Cystic Kidney Diseases
The facts most likely to be tested
ADPKD is an autosomal dominant disorder caused by mutations in the PKD1 (most common, earlier onset) or PKD2 genes.
Patients typically present in the 3rd or 4th decade of life with flank pain, hematuria, palpable abdominal masses, and hypertension.
The most common extrarenal manifestation is hepatic cysts, while the most feared extrarenal complication is a berry aneurysm (saccular aneurysm) in the Circle of Willis.
Diagnosis is primarily established via renal ultrasound, which reveals bilateral enlarged kidneys with numerous fluid-filled cysts.
Patients are at increased risk for mitral valve prolapse and diverticulosis due to systemic connective tissue involvement.
Management focuses on blood pressure control (typically with ACE inhibitors or ARBs) to slow the progression of chronic kidney disease.
Tolvaptan, a vasopressin V2 receptor antagonist, is indicated in select patients to slow the rate of cyst growth and decline in glomerular filtration rate.
Vignette unlocked
A 38-year-old male presents to the clinic for a routine physical. He reports occasional dull flank pain and a family history of 'kidney problems' that required his father to undergo hemodialysis. Physical exam reveals bilateral palpable abdominal masses and a blood pressure of 152/94 mmHg. Urinalysis is positive for microscopic hematuria. A renal ultrasound demonstrates bilateral enlarged kidneys with multiple cortical and medullary cysts.
Which of the following extrarenal complications is this patient at the highest risk for developing?
Intracranial berry aneurysm
The patient's presentation is classic for ADPKD; the most clinically significant extrarenal association that requires screening or high clinical suspicion is a berry aneurysm in the Circle of Willis.
Full handout
High yield triage
Etiology / Epidemiology
Autosomal dominant disorder caused by mutations in PKD1 (85%) or PKD2 (15%). Affects 1 in 400-1,000 individuals.
Clinical Manifestations
Presents with flank pain, hematuria, and palpable abdominal masses. Associated with berry aneurysms.
Diagnosis
Renal ultrasound is the gold standard. Diagnosis requires ≥3 cysts (unilateral or bilateral) in patients 15-39 years old.
Treatment
Management focuses on blood pressure control (ACE inhibitors/ARBs). Avoid NSAIDs to prevent acute kidney injury.
Prognosis
Progresses to End-Stage Renal Disease (ESRD) in 50% of patients by age 60. Monitor for intracranial hemorrhage.
Full handout
Epidemiology & Etiology
ADPKD is the most common hereditary kidney disease, typically manifesting in the 3rd to 4th decade of life. Mutations in the PKD1 gene (chromosome 16) result in a more severe, rapid progression compared to PKD2 (chromosome 4).
Pertinent Anatomy
Cysts arise from the tubular epithelium of the nephron, eventually replacing functional renal parenchyma. Extra-renal manifestations include hepatic cysts and diverticulosis.
Pathophysiology
Defective polycystin proteins disrupt intracellular calcium signaling and ciliary function, leading to epithelial cell hyperproliferation. Fluid secretion into the cyst lumen causes progressive nephromegaly and compression of adjacent healthy tissue.
Clinical Manifestations
Patients often present with hypertension due to activation of the renin-angiotensin-aldosterone system. Flank pain is common due to cyst rupture or infection. Red flags include sudden severe headache, which may indicate a ruptured berry aneurysm (Circle of Willis).
Diagnosis
The Renal ultrasound is the initial test of choice. Diagnostic criteria for patients 15-39 years: ≥3 cysts total. For patients 40-59: ≥2 cysts in each kidney. Genetic testing is reserved for cases where imaging is equivocal or for living donor screening.
Treatment
Strict blood pressure control is the cornerstone of therapy, with ACE inhibitors or ARBs as the preferred agents. Tolvaptan may be used in rapidly progressing disease to slow cyst growth. NSAIDs are contraindicated due to potential for interstitial nephritis and reduced renal perfusion.
Prognosis
The disease is characterized by a slow decline in Glomerular Filtration Rate (GFR). Patients require lifelong monitoring for ESRD and potential need for renal replacement therapy or kidney transplantation.
Differential Diagnosis
Autosomal Recessive PKD: presents in infancy with Potter facies
Medullary Sponge Kidney: associated with nephrolithiasis and UTIs
Acquired Cystic Kidney Disease: occurs in patients with long-term dialysis
Simple Renal Cysts: usually asymptomatic and lack family history
Tuberous Sclerosis: associated with angiomyolipomas and skin findings