What Is Bilateral Renal Agenesis?

Introduction

Bilateral renal agenesis is an uncommon medical condition characterized by the absence of both kidneys during fetal development.

Typically, humans are born with a pair of kidneys, one situated on the left and the other on the right side. These vital organs play a crucial role in the urinary system, filtering waste and excess fluids from the bloodstream, which are then expelled from the body as urine. Additionally, kidneys produce hormones that contribute to bone strength, blood pressure regulation, and the production of red blood cells.

Kidneys start forming in the early stages of a developing fetus. By approximately the 12th week of pregnancy, they begin generating urine, which is essential for maintaining the amniotic fluid, the protective fluid surrounding the baby in the womb. Adequate amniotic fluid is crucial for fetal lung development.

In the case of bilateral renal agenesis, infants are born without any kidneys. Consequently, there is a severe deficiency or complete absence of amniotic fluid by the time of the 20-week prenatal scan. The absence or minimal presence of amniotic fluid signifies that the baby's lungs cannot develop properly. Tragically, this condition is fatal for these infants, and there is currently no known way to prevent or cure it.

Causes

Genetic Factors

Bilateral renal agenesis in humans occurs when the ureteric bud and the metanephric mesenchyme fail to develop properly during the fetal stage.

Mutations in various genes can lead to unilateral renal agenesis, where only one kidney forms. Additionally, maternal diabetes mellitus has been implicated.

Environmental Factors

The use of certain medications during pregnancy can also contribute to the occurrence of renal agenesis.

Prevalence

According to Angie Jelin, MD, in the American Journal Of Obstetrics And Gynecology, unilateral kidney absence occurs in about 1 in every 1,000 live births, whereas the rarer condition known as bilateral renal agenesis is found in approximately 1 in every 3,000 to 4,000 pregnancies. 

When it comes to unilateral renal agenesis, things generally look quite optimistic for the affected individuals. On the other hand, bilateral renal agenesis presents a more challenging scenario with a higher risk of perinatal health problems and even fatalities.

This heightened risk is primarily due to the absence of the protective amniotic fluid, which can lead to underdeveloped lungs and serious breathing issues in the unborn baby, known as lethal pulmonary hypoplasia.¹

Symptoms

• Lack of both kidneys is a fatal condition.
• 40% of infants with this condition are stillborn.
• Surviving infants typically live for only a few hours.

Unique physical characteristics include

• Dry, loose skin
• Widely spaced eyes
• Prominent folds at the inner corner of the eyes
• Sharp nose
• Large, low-set ears with absent ear cartilage

Commonly associated issues:

• Underdeveloped lungs
• Absent urinary bladder
• Anal atresia
• Esophageal atresia
• Unusual genitals
• The absence of amniotic fluid contributes to problems like undeveloped lungs, a sharp nose, and clubbed feet.
• Developmental issues arise due to the simultaneous formation of kidneys and affected structures during fetal life.²

Diagnosis

Prenatal Diagnosis

Identification of bilateral renal agenesis or hypoplasia can be made during prenatal screening through ultrasound.

However, prenatal findings should always be confirmed with postnatal assessments.³

Postnatal Diagnosis

Bilateral renal agenesis or hypoplasia is definitively confirmed after birth through various diagnostic methods, including abdominal ultrasound, CT scans, MRI scans, surgery, or autopsy.

In infants showing features of the Potter sequence, bilateral renal agenesis should be strongly considered.

The recognition of bilateral renal hypoplasia postnatally depends on the severity and residual kidney function.

Unilateral renal agenesis or hypoplasia might not present clinical symptoms at birth if the opposite kidney is functional, potentially leading to a delayed diagnosis occurring months or even years after birth.³

Differential Diagnosis

Unilateral Renal Agenesis: In this condition, only one kidney is absent, while the other is present. It can be a differential diagnosis for bilateral renal agenesis.

Multicystic Renal Dysplasia: This is a congenital kidney condition characterized by the presence of non-functioning cysts in one or both kidneys. It can sometimes be mistaken for bilateral renal agenesis.

Polycystic Kidney Disease (PKD): PKD is a genetic disorder that causes cysts to form in the kidneys. Although it typically affects both kidneys, in some cases, it might be considered in the differential diagnosis.

Posterior Urethral Valves (PUV): PUV is a congenital obstructive anomaly of the urinary tract, and it can sometimes cause severe kidney damage, which might mimic bilateral renal agenesis.

Ectopic or Pelvic Kidneys: When renal agenesis is suspected, the presence of other normal or abnormal ectopic or pelvic kidneys should be excluded.⁴

Complication

Approximately 40% of fetuses with bilateral renal agenesis either experience stillbirth or premature birth before the 37th week of pregnancy.

The absence of kidneys leads to underdeveloped lungs due to a lack of amniotic fluid, resulting in respiratory failure and death in most newborns shortly after birth.⁵

Treatment Options

New experimental treatments provide hope for newborns with bilateral renal agenesis.

• One such treatment involves injecting saline solution into the uterus during pregnancy to restore amniotic fluid levels, allowing proper lung development.
• After birth, babies with this condition receive dialysis until they can undergo a kidney transplant, but this treatment is still in the experimental stage and not widely available.⁵

Summary

Bilateral renal agenesis is a rare medical condition characterized by the absence of both kidneys during fetal development. Kidneys play a crucial role in the urinary system, and their absence leads to a severe deficiency or complete absence of amniotic fluid, affecting fetal lung development and resulting in a fatal condition for affected infants. The causes of bilateral renal agenesis can be genetic or related to environmental factors, such as maternal diabetes or medication use during pregnancy.

The prevalence of bilateral renal agenesis is about 1 in every 3,000 to 4,000 pregnancies, with a higher risk of perinatal health problems and fatalities due to the lack of amniotic fluid. Symptoms include unique physical characteristics and various associated issues. Diagnosis can be made prenatally through ultrasound but needs confirmation through postnatal assessments. Complications often lead to stillbirth or premature birth, and most affected infants do not survive long after birth.

Experimental treatments, such as injecting saline solution into the uterus during pregnancy to restore amniotic fluid levels and subsequent dialysis and kidney transplant after birth, offer hope for newborns with bilateral renal agenesis, though these treatments are still in the experimental stage and not widely available.