Multicystic renal dysplasia

**Definition:** Multicystic renal dysplasia, or multicystic dysplastic kidney (MCDK), is a congenital condition where a kidney fails to develop properly in the womb, becoming a non-functional collection of fluid-filled cysts instead of normal kidney tissue. It most often affects a single kidney, allowing the other healthy kidney to compensate for its function, and is usually discovered via prenatal ultrasound. Bilateral MCDK, affecting both kidneys, is a very serious condition with a high risk of kidney failure and is often incompatible with long-term survival.