Definition
Renal agenesis is a congenital condition characterized by the absence of one or both kidneys at birth. The kidneys play a crucial role in filtering waste and excess fluids from the blood to form urine. The affected individual is born with either one kidney (unilateral renal agenesis) or no kidneys (bilateral renal agenesis). Unilateral renal agenesis is generally compatible with a normal, healthy life, as the remaining kidney can usually compensate for the absence of the other. However, bilateral renal agenesis is a more severe condition and is often incompatible with life, as it results in a lack of kidney function, leading to the accumulation of toxic waste products in the body.
The exact cause is not always clear, but it is thought to involve a combination of genetic and environmental factors. Prenatal screening and ultrasound examinations during pregnancy can sometimes detect the absence of kidneys in the developing fetus. Treatment options are limited, especially in cases of bilateral renal agenesis, and may involve supportive measures to manage complications. Early detection and intervention are crucial in providing the best possible outcomes for individuals with this condition.
Types of Renal Agenesis
There are two primary types, which are known as unilateral and bilateral.
- Unilateral Renal Agenesis: When just one kidney does not develop normally, this condition is known as unilateral renal agenesis. In certain instances, the afflicted kidney could be partly formed but not functioning, but in others, it might not develop at all.
- Bilateral Renal Agenesis: The condition known as bilateral renal agenesis arises when both kidneys fail to mature correctly over the course of development. This is a far more dangerous problem, and if it is not treated appropriately, it may lead to complications that put the patient’s life in danger.
Prevalence
Unilateral renal agenesis is more common than bilateral renal agenesis. The prevalence of unilateral renal agenesis has been estimated to be around 1 in 500 live births, though this can vary. Bilateral renal agenesis is a much rarer condition and is estimated to occur in approximately 1 in 3,000 to 1 in 5,000 live births.
Pathophysiology
It results when the ureteric bud either fails to develop from the mesonephric (Wolffian) duct or fails to induce the surrounding metanephric mesenchyme to form glomeruli and nephrons. There is a significant familial aggregation of cases.
Symptoms of Renal Agenesis
A child with no working kidneys and underdeveloped lungs (Potter syndrome) will have life-threatening respiratory problems soon after birth.
A child with one working kidney may not have symptoms. When symptoms occur, they include:
- High blood pressure in children.
- High protein levels in urine (proteinuria).
- Vesicoureteral reflux (backflow of urine into the ureters).
Some children with unilateral also have:
- Clubfoot.
- Congenital heart conditions like atrial septal defects (ASD) or ventricular septal defects (VSD).
- Congenital urological anomalies (birth defects that affect the genitals or urinary tract).
- Imperforate anus or anal atresia (a missing anus at the end of the digestive tract).
Causes of Renal Agenesis
The exact cause is unknown, but it is a genetic condition. If you were born with only one kidney or other kidney deformities, your baby is more likely to have the same problem.
It can show up as symptoms of other rare inherited conditions that are present at birth. These include:
- Cat-Eye syndrome, where there’s a fissure in the eye, no anal opening, and renal agenesis
- Rokitansky sequence, where the vagina and uterus don’t form completely
- Fraser syndrome, where your baby is born with sealed eyelids and partially formed sexual organs
- Melnick-Fraser syndrome, which causes hearing loss and kidney deformities
- Mullerian duct, renal, and cervical vertebral defects, or MURCS association, which causes irregular vertebrae and missing vagina and kidneys
Unilateral is common in babies who have poor growth in pregnancy, a condition called intrauterine growth restriction. It is also more common with twins or pregnancies with multiples.
Research suggests certain chemicals and behaviours during pregnancy might increase the risk of renal agenesis. These include:
- Some medications
- Smoking
- Drinking alcohol
- Taking illicit drugs like cocaine
- Obesity
It is rare. The unilateral type happens in 1 of every 1000 to 2000 live births. Bilateral renal agenesis happens in 1 of every 4500 live births. The bilateral type is more common in boys.
What are risk factors of renal agenesis?
Some maternal factors during pregnancy can increase the risk. These include:
- Use of some medications
- Excessive alcohol intake
- Smoking
- Obesity
- Taking illicit drugs such as cocaine
(a) Potter’s facies, distinctive of a fetus subjected to oligohydramnios. (b) Potter’s hand featuring thickened, tapering fingers
What are the complications of Renal Agenesis?
The complications depend on whether it is unilateral (affecting one kidney) or bilateral (affecting both kidneys):
Unilateral Renal Agenesis:
- Asymptomatic Living: Individuals with unilateral renal agenesis often lead normal, asymptomatic lives. The single functioning kidney is usually able to compensate adequately for the absence of the other.
- Increased Risk of Hypertension: Some studies suggest a slightly elevated risk of hypertension (high blood pressure) in individuals with a single kidney. Regular monitoring of blood pressure is recommended.
Bilateral Renal Agenesis:
- Incompatible with Life: Bilateral renal agenesis is a more severe condition and is typically incompatible with life. In the absence of both kidneys, there is a complete lack of renal function, leading to an inability to filter waste products from the blood and regulate fluid and electrolyte balance.
- Oligohydramnios and Pulmonary Hypoplasia: In cases of bilateral renal agenesis, the lack of amniotic fluid (oligohydramnios) during pregnancy can lead to underdevelopment of the fetal lungs (pulmonary hypoplasia), which poses a significant risk to the newborn’s survival.
- Potter Syndrome: Bilateral renal agenesis is a major component of Potter syndrome, a constellation of physical features and complications that result from the lack of amniotic fluid and abnormal fetal development. Potter syndrome may include facial anomalies, limb deformities, and other structural abnormalities.
It’s important to note that the severity of complications in unilateral renal agenesis is generally much milder than in bilateral cases.
Significant phases in the development of the Potter sequence
Diagnosis and tests
The diagnosis of renal agenesis is typically made through various prenatal and postnatal diagnostic methods. Here are some common approaches:
Prenatal Ultrasound
- Routine Screening: Unilateral or bilateral renal agenesis can often be detected during routine prenatal ultrasounds, which are a standard part of prenatal care. Ultrasound imaging can visualize the developing fetus and identify the absence of kidneys or abnormalities in kidney structure.
- Fetal Anomaly Scan: A detailed ultrasound, known as a fetal anomaly scan, is usually performed around 18-20 weeks of gestation. This scan assesses the overall fetal anatomy, including the kidneys.
Amniocentesis
In certain cases where there is a suspected genetic or chromosomal abnormality, amniocentesis may be performed. This involves the extraction of a small amount of amniotic fluid for genetic testing. Amniocentesis can provide information about the presence of chromosomal abnormalities but may not specifically diagnose renal agenesis.
Magnetic Resonance Imaging (MRI)
In some situations, especially when a detailed assessment is needed, an MRI may be used to provide more detailed images of the fetal anatomy, including the kidneys.
Postnatal Imaging
After birth, if it is suspected based on prenatal findings or clinical signs, imaging studies such as ultrasound or other radiological scans can be performed to confirm the absence of one or both kidneys.
Genetic Testing
In cases where there is a family history of renal anomalies or when there are additional concerns about genetic factors, genetic testing may be recommended. This can include chromosomal analysis or testing for specific genetic mutations associated with renal agenesis.
The specific diagnostic approach may vary based on individual circumstances, clinical presentation, and the healthcare provider’s judgment.
Treatment of Renal Agenesis
Treatment typically involves:
Supportive Care
Patients may require specialized nutrition and hydration support to help maintain their health.
Dialysis
Dialysis is a medical procedure used to filter and purify the blood when kidney function is impaired. It can help remove waste products from the body that would otherwise accumulate due to poor kidney function.
Renal transplant
The primary surgical treatment is a renal transplant.
Pyeloplasty
In some cases, a procedure called pyeloplasty may be used to create an artificial connection between the bladder and the ureter. This procedure is usually only performed if the patient has no other option, as it carries risks and can be difficult to perform.
Lifestyle changes
lifestyle changes such as avoiding certain foods that can worsen symptoms, exercising regularly, maintaining a healthy weight, reducing stress levels, and avoiding exposure to toxins.
Supplements
Omega-3 fatty acids, for example, may help lower inflammation linked with renal disease.
Cognitive behavioral therapy (CBT)
Supportive therapies such as cognitive behavioral therapy (CBT) can help manage emotions related to living with a chronic condition like renal agenesis.
Prevention
Preventing involves understanding its potential causes and risk factors. However, it’s important to note that in many cases, the condition is not preventable because it is often related to genetic or developmental factors that are not easily influenced. Here are some general considerations:
Prenatal Care: Early and comprehensive prenatal care is crucial. Regular check-ups and ultrasounds during pregnancy can help detect abnormalities, including renal agenesis, early on.
Genetic Counselling: If there is a family history of renal anomalies or if previous pregnancies were affected, seeking genetic counselling can provide information about the risk of recurrence and potential genetic factors.
Avoiding Teratogens: Teratogens are substances that can cause birth defects. Avoiding exposure to known teratogens during pregnancy is important. This includes certain medications, chemicals, and infections. Consult with healthcare providers to ensure that any medications or substances being used are safe during pregnancy.
Maintaining a Healthy Lifestyle: Maintaining overall maternal health is essential. This includes a balanced diet, regular exercise, and avoiding harmful habits such as smoking and excessive alcohol consumption.
Management of Chronic Conditions: Proper management of chronic medical conditions, such as diabetes or hypertension, before and during pregnancy is important, as these conditions can impact fetal development.
Early Detection through Screening: Utilizing advanced prenatal screening methods, such as ultrasound and other diagnostic tests, can help identify potential abnormalities early in pregnancy. Early detection allows for informed decision-making and appropriate medical management.