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Ultrasound scan

Image : “Children´s Day” by Marc Sundstrom. License: CC BY 2.0

Sign and Symptoms of Unilateral Renal Agenesis

The disease course is usually silent and is detected on an ultrasound scan of the patient who presents with repeated urinary tract infections or hypertension. Most patients have no complaints since the existing kidney enlarges to compensate, but 20-30% of patients develop proteinuria and hypertension, associated with glomerular hyperfiltration.

In some cases, unilateral renal agenesis presents with other birth defects and problems with the:

  • Genitals
  • Urinary tract
  • Heart
  • Lungs
  • Stomach and intestines

Female patients are at increased risk of Mullerian duct abnormalities, leading to infertility and blocked menstrual flow. Herlyn-Werner-Wunderlich syndrome refers to unilateral renal agenesis combined with a blind hemivagina and uterus didelphys.

Epidemiology of Unilateral Renal Agenesis

The incidence of unilateral renal agenesis is approximately 1 in 2000. It is slightly more common in males than females, and 56% of URA cases affect the left side.

Etiology of Unilateral Renal Agenesis

Unilateral renal agenesis can be caused by genetic as well as maternal causes. The condition is associated with mutations in RET (10q11.2), BMP4 (14q22-q23), FRAS1 (4q21.21), FREM1 (9p22.3), or UPK3A (22q13.31), PAX2 (10q24.31), HNF1B (17q12), DSTYK (1q32) genes.

Other causative factors associated with unilateral renal agenesis include:

  • Maternal diabetes
  • Maternal obesity
  • Young maternal age
  • Maternal smoking
  • Consumption of large amounts of alcohol during pregnancy

There is a high risk of hypertension, proteinuria, and renal insufficiency associated with unilateral renal agenesis.

Diagnosis of Unilateral Renal Agenesis

Diagnosis is made by ultrasonography showing an empty renal fossa and a solitary kidney that is larger than normal. Vesicoureteral reflux is usually present in patients with unilateral agenesis, and it can be diagnosed with a voiding cystourethrogram. Urinalysis can detect proteinuria and other signs of urinary tract infections and measure GFR, urea, and electrolytes.

MRI can diagnose other non-urinary defects. Genetic tests may detect abnormalities related to an autosomal dominant gene.

Management and Treatment of Unilateral Renal Agenesis

Patients with unilateral renal agenesis require long-term follow up because they are at increased risk of hypertension and proteinuria. The solitary kidney should be monitored with kidney function tests such as urine analysis and glomerular filtration rate.

Prognosis of Unilateral Renal Agenesis

The prognosis is usually good for patients with unilateral renal agenesis. The risk of renal failure is rare and minimal. However, patients are prone to develop hypertension and proteinuria.

Prevention of Unilateral Renal Agenesis

The exact cause of unilateral renal agenesis is unknown, so genetic factors cannot be avoided. However, maternal factors leading to unilateral renal ageneses, like maternal smoking and binge drinking, can be avoided or modified to lower the risk to the fetus.

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