Unilateral renal agenesis

Unilateral renal agenesis has a birth prevalence of approximately 1:1000 to 1:2000, but it is often undetected prenatally. Sonographically, one kidney cannot be visualized in either the renal fossa or the pelvis, and the adrenal flattens and fills the renal fossa-the “lying-down” adrenal sign. Color Doppler imaging of the descending aorta reveals just one renal artery. The solitary kidney often develops compensatory hypertrophy. Unilateral renal agenesis is associated with other anomalies, particularly genitourinary abnormalities, and it is a component of several genetic syndromes. Therefore, targeted sonography is indicated, and amniocentesis may be offered. Affected individuals are usually asymptomatic; however, they are at increased risk to develop hypertension and renal insufficiency.