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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:

In men, ipsilateral malformations of the Wolffian duct system may be present, for example aplasia or hypoplasia of parts of the epididymis, vas deferens, seminal vesicle, or ejaculatory duct. If the seminal vesicle is present but obstructed, Zinner syndrome may develop: renal agenesis with an ipsilateral seminal vesicle cyst.

Female genital organs:

In women, associated Müllerian duct anomalies should be actively investigated, such as a unicornuate uterus with an absent fallopian tube or complex malformations with vaginal septa, an obstructed hemivagina, and hematocolpos (OHVIRA syndrome).

Other organ malformations:

In addition to urogenital malformations, extrarenal anomalies may also occur, particularly cardiovascular, gastrointestinal, musculoskeletal, or central nervous system malformations. Consider syndromic associations in patients with renal agenesia.

Diagnosis of Unilateral Renal agenesia

If a kidney is not visualized on ultrasound, abdominal MRI is useful to confirm the diagnosis and to detect possible pelvic masses.

Therapy:

Long-term follow-up of the congenital solitary kidney is essential and should include ultrasound, blood pressure monitoring, urine testing for proteinuria, and serial assessments of kidney function. Surgical treatment is required for 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

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