Renal agenesis, unilateral

This code signifies the congenital absence of one kidney. It is a developmental anomaly where one kidney fails to form during fetal development, leading to a solitary kidney. The remaining kidney is typically hypertrophied to compensate for the missing organ.

Apply this code when documentation clearly indicates the congenital absence of a single kidney, confirmed by imaging studies such as ultrasound, CT, or MRI. It is appropriate for both asymptomatic individuals and those presenting with complications related to the solitary kidney.

• Ensure documentation specifies "unilateral" agenesis; bilateral agenesis is coded differently.
• Do not confuse with renal hypoplasia (underdevelopment) or atrophy (shrinkage) of a kidney that was once present.
• Code any associated congenital anomalies of the genitourinary system separately.