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Unilateral Renal Agenesis

Definition and Epidemiology of Unilateral Renal Agenesis

The unilateral renal agenesis is the complete absence of a renal system or parts of it on one side, with a normal kidney on the opposite side. The prognosis is good; in contrast to bilateral renal agenesis, which is rare and invariably fatal, see Potter syndrome.

Epidemiology:

1:1100 to 1:5000. Slightly more common on the left side. Male to female = 2:1.

Causes (Etiology) of Renal Agenesia

Unilateral renal agenesia results from a Developmental disorder of the urogenital ridge, which affects the ureteric bud, the mesonephric duct (Wolff duct), and sometimes also the paramesonephric duct (Müller duct), depending on the time and extent. Concomitant malformations of the internal genital organs are common; see the following section.

Pathology, Signs and Symptoms of Unilateral Renal Agenesia

Malformations of the upper urinary tract:

The ureter is completely missing in 50% of patients. In other cases, rudiments of the ureter are present and may be ectopic. There is an increased risk for pathological findings of the contralateral side like vesicoureteral reflux or ureteropelvic-junction obstruction.

Male genital organs:

The testes and the head of the epididymis are always present; possible malformations in males are the absence of the epididymal body, vas deferens, seminal vesicles, and ejaculatory ducts. Zinner syndrome is unilateral renal agenesis with (sometimes monstrous) seminal vesicle cyst caused by ejaculatory duct obstruction.

Female genital organs:

Uterus unicornis with an absent fallopian tube or rudimentary development on the affected side. Complex uterine malformations with pelvic masses are also possible (hydro- or hematocolpus, OHVIRA syndrome).

Other organ malformations:

Cardiovascular system (15%), gastrointestinal tract (9%), CNS (3%).

Diagnosis of Unilateral Renal agenesia

If the kidney is absent with ultrasound imaging, abdominal MRI or DMSA renal scintigraphy is helpful to confirm the diagnosis. Use MRI for further imaging of pelvic masses.

Therapy:

Surgical therapy of symptomatic and large pelvic masses.

Prognosis of Unilateral Renal Agenesia

Patients with unilateral renal agenesis have an increased risk for proteinuria, arterial hypertension and chronic kidney disease.

References

  Deutsche Version: Unilaterale Nierenagenesie