Genitourinary Radiology > Embryology > Maturation of the Urinary Tract > Renal Agenesis

Renal Agenesis

When the ureteric bud fails to reach the metanephric blastema, there is no induction of nephron development, and the result is renal agenesis. Associated ipsilateral abnormalities are almost always present, and include absence of ureter, hemitrigone, or vas deferens, seminal vesicle cyst, or Muellerian anomalies such as unicornate uterus. Absence of the ipsilateral adrenal gland is seen in 10% of these patients. Incidence of renal agenesis is one per 1000 live births, 75% of which are male. Bilateral renal agenesis, a fatal anomaly, occurs in one per 3000 live births, and due to oligohydramnios, these newborns present with Potter’s syndrome—low-set ears, broad flat nose, prominent skin folds below the lower eyelids, pulmonary hypoplasia and pneumothorax.

Left renal agenesis can be diagnosed on plain abdominal radiograph, showing a medially dislocated and looped splenic flexure, seen medial to the lesser curvature of the stomach. Ultrasound, CT, and radionuclide scan provide definitive diagnosis. As long as the contralateral kidney remains functional, unilateral renal agenesis is asymptomatic. The contralateral kidney usually becomes hypertrophic and enlarged to compensate.

Contrast enhanced CT shows no left kidney in the renal fossa. The splenic flexure of the colon (SF) has moved into the left renal fossa. Evidence that this is renal agenesis includes unusually flattened appearance to the left adrenal gland (arrow) known as the "lying down adrenal". In the absense of the left kidney, this adrenal gland does not have the typical splayed limbs.

3D coronal reconstruction of CT IVP in the excretory phase shows normal left kidney but no right kidney in renal fossa or anywhere along the path of ascent of the kidney from the right pelvis through the right paravertebral regions consistent with right renal agenesis.

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