Renal Cyst

Excerpt

A renal cyst is the most common lesion of the kidney. Renal cysts are so ubiquitous that they are present in approximately 40% of the patients undergoing imaging. Cystic renal disease can be focal, multifocal, unilateral, or bilateral. Renal cysts can be acquired or the result of a congenital disease process. The acquired form is the most common.

Renal cysts can range from benign to malignant or indeterminate. A categorization system for adult renal cysts was introduced in the late 1980s, known as the Bosniak classification. It was introduced in attempts to standardize the characterization and management of renal cysts.

The terminology of congenital renal cysts has changed throughout the years, with the current characterization known as the Potter classification. The Potter classification has four categories: Type I is infantile polycystic kidney disease, Type II is multicystic dysplastic kidney disease, Type III is adult polycystic kidney disease, and Type IV is obstructive renal dysplasia.

Infantile polycystic kidney disease is also known as autosomal recessive polycystic kidney disease. ARPKD demonstrates no gender predilection with a ratio of 1:1. The age range of diagnosis is neonate to childhood, depending on the severity of the disease.

Multicystic dysplastic kidney disease is a non-inherited kidney disease that develops in utero. It is most commonly unilateral, with a higher incidence on the left side. The diagnosis is often made while still in utero or very early in a neonate.

Adult polycystic kidney disease is also known as autosomal dominant polycystic kidney disease. A patient with ADPKD has a normal appearance of the kidneys at birth and begins to develop multiple cysts bilaterally in their 20s to 30s. It is the most common inherited cause of end-stage renal failure, with more than 50% of patients requiring dialysis by the age of 60 years.

Obstructive cystic renal dysplasia results from an obstruction during development that causes scattered cysts throughout the affected kidney.