Polycystic Kidney Disease – Top USMLE Diseases

The kidneys are a pair of bean-shaped organs located retroperitoneally against the posterior wall of the abdomen on either side of the spine. As part of the urinary tract, the kidneys are responsible for blood filtration and excretion of water-soluble waste in the urine. The kidneys also play a major role in homeostatic processes, including electrolyte concentration, blood pressure, and acid–base regulation. Grossly, they consist of an outer cortex and inner medulla. Microscopic functional units known as nephrons filter the blood through a structure called the glomerulus, and this filtrate is then modified and concentrated as it moves through a complex tubular system. The renal arteries supply the kidneys via a central opening, known as the renal hilum, on its medial side; large renal veins empty directly into the vena cava.

Congenital renal abnormalities arise from embryologic/genetic defects and cause a variety of isolated or syndromic renal disorders, including renal agenesis, dysgenesis, and ectopia. Congenital renal abnormalities are generally identified prenatally and represent approximately ⅓ of all prenatal anomalies. Because of the fetal kidney’s role in the production of amniotic fluid, oligohydramnios detected on prenatal ultrasounds often prompts the workup that identifies congenital renal anomalies. Unilateral renal involvement in the presence of a functioning contralateral kidney may only be an incidental finding later in life. In many cases, treatment is supportive.

Polycystic kidney disease (PKD) is an inherited genetic disorder leading to the development of numerous fluid-filled cysts in the kidneys. The 2 main types of PKD are autosomal recessive polycystic kidney disease (ARPKD), which is often diagnosed antenatally or shortly after birth, and autosomal dominant polycystic kidney disease (ADPKD), which is often diagnosed in adulthood. Autosomal recessive polycystic kidney disease is primarily characterized by cystic dilatations of the renal collecting ducts and intrahepatic bile duct dilatation with hepatic fibrosis. Diagnosis is through physical exam and ultrasonography. Management requires a multidisciplinary approach to slow the progression of renal disease by controlling hypertension, proteinuria, and symptoms. The prognosis of ARPKD depends on the age at presentation, along with the degree of hepatic and renal involvement. Patients progressing to end-stage renal disease (ESRD) will need renal replacement therapy.

Polycystic kidney disease (PKD) is an inherited genetic disorder leading to the development of numerous fluid-filled cysts in the kidneys. The 2 main types of PKD are autosomal dominant polycystic kidney disease (ADPKD), which is often diagnosed in adulthood, and autosomal recessive polycystic kidney disease (ARPKD), which is often diagnosed antenatally or shortly after birth. ADPKD patients commonly present with hypertension, hematuria, and flank pain. Extrarenal manifestations include intracerebral aneurysm, hepatic and pancreatic cysts, and cardiac valvular abnormalities. Diagnosis is by history, physical exam, and ultrasonography. Management requires a multidisciplinary approach and many patients require renal replacement therapy. The end goal is to slow the progression of renal disease by controlling hypertension, proteinuria, and symptoms. ADPKD prognosis is dependent on a variety of factors. A cerebral aneurysm is a complication associated with a particularly poor prognosis.