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Unilateral Renal Agenesis - Causes, Symptoms, Diagnosis, and Treatment

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Unilateral renal agenesis is the absence of a kidney on one side, which increases the size of the kidney on the opposite side due to over-function.

Medically reviewed byDr. Yash Kathuria

Published At May 2, 2023
Reviewed AtNovember 10, 2025

Introduction:

Unilateral renal agenesis (URA) is a congenital disorder characterized by the absence of a kidney on one side. The lack of renal tissues results from a failure in kidney formation during the embryonic growth period.

What Is the Embryology of Unilateral Renal Agenesis?

Kidney formation in human beings is initiated in the fifth week of intrauterine life. It is characterized by a highly synchronous sequence of events that involves interactions between the metanephric mesenchyme and the growing bud of the mesonephric duct. As a consequence of this interaction, the ureteric bud will not form the ureter, collecting ducts, renal pelvis, and the renal mesenchyme. As a result, the nephrons are not formed, eventually leading to failure in the formation of a kidney on the corresponding side.

What Are the Causes of Unilateral Renal Agenesis?

The most common cause of unilateral renal agenesis is gene mutations. Several studies and research suggest mutations in a minimum of seven linked genes identified. The gene mutations are responsible for a defective mechanism in kidney formation in intrauterine life.

The less common causes are

What Is the Prevalence of Unilateral Renal Agenesis?

Several studies show that unilateral renal agenesis most frequently occurs in males on the left side. However, the side of occurrence was reported to be random in many cases (50 % left and 50 % right). The incidence is approximately one in 2000 to 3000 live births.

Who Are at the Risk of Unilateral Renal Agenesis?

It is an autosomal dominant disorder. If a child inherits a single copy of a mutated gene from one parent, it will develop the disease. Most frequently, children of parents affected with unilateral renal agenesis develop the disease. A parent with a gene mutation has a 50 percent probability of transferring it to their children.

How Is the Diagnosis of Unilateral Renal Agenesis Made?

  • Unilateral renal agenesis is often confused with incomplete or atypical renal development, leading to a non-functioning kidney, as seen in renal aplasia or multicystic dysplastic kidney (MCDK).

  • An apparent diagnosis of unilateral renal agenesis can be made by routine fetal ultrasound sonography imaging (USG) in the gestation period.

  • Post-natal ultrasound imaging like renal scintigraphy and MRI (magnetic resonance imaging) can help differentiate between multicystic dysplastic kidney, renal ectopia (cross-fused kidney or pelvic kidney), or renal aplasia. However, it is essential to note that unilateral renal agenesis can be diagnosed from the involution of the multicystic dysplastic kidney.

What Are the Congenital Disorders Associated With Unilateral Renal Agenesis?

Unilateral renal agenesis is frequently associated with congenital disorders of the contralateral kidney and urinary tract, often referred to as congenital anomalies of the kidney and urinary tract (CAKUT). The anomalies are

Apart from the congenital renal anomalies, patients with unilateral renal agenesis are often associated with extrarenal developmental malformations involving the cardiac, gastrointestinal, and genital systems. However, the prevalence of the associated anomalies still needs to be well established.

What Is the Importance of Assessing the Contralateral Kidney in Unilateral Renal Agenesis?

  • Evaluation of the associated congenital malformations in unilateral renal agenesis will help the physician determine the renal and general prognosis. According to some earlier studies, genetic conditions are considered more or less harmless. At the same time, recent studies suggest that 40 to 50 percent of patients with unilateral renal agenesis had a need for dialysis by the age of 30. It mainly occurs due to impairment of the solitary functioning kidney.

  • The impaired functioning can be explained by the hyperfiltration hypothesis described three decades back by Brenner et al. based on animal studies. The hypothesis states that the lack of one kidney will result in a considerable reduction in renal mass, leaving a solitary kidney for performing the whole filtration functions. The reduced renal mass will lead to a chain of events causing glomerular hyperfiltration as a compensatory mechanism. However, in the long run, the hyperfiltration will lead to renal injury, causing.

    1. Hypertension.

    2. Micro-albuminuria.

    3. Chronic kidney diseases.

  • Apart from the renal damage from hyperfunction, the congenital anomalies of the kidney and urinary tract have a high prevalence of occurrence in solitary functioning kidneys. Therefore constant evaluation of the contralateral kidney is necessary for patients with unilateral renal agenesis.

What Are the Symptoms of Unilateral Renal Agenesis?

The typical clinical presentation of children with unilateral renal agenesis are

  • An increase in blood pressure in children.

  • Proteinuria: Increased excretion of protein through the urine.

  • Vesicoureteral Reflux: Reversible flow of urine into the ureters.

  • Clubfoot: Shapeless or twisted foot.

  • Congenital heart defects like ventricular septal defects and atrial septal defects.

  • Congenital Urological Anomalies: Congenital defects of the urinary and genital tract.

  • Anal Atresia or Imperforate Anus: Absence of anus.

How to Manage Patients With Unilateral Renal Agenesis?

  • Patients with unilateral agenesis are given medications to lower their blood pressure. A regular visit to the nephrologist should be made in frequent intervals for physical examination, imaging, urine analysis, kidney function tests, and urine protein tests.

  • The patients should be advised to a kidney-friendly diet that involves reducing the sodium and sugar intake and increasing potassium and fiber.

  • Avoid the use of non-steroidal anti-inflammatory drugs and painkillers.

  • Actively maintain health and body weight.

  • Regular examination of blood pressure.

  • Avoiding physical activities like football and martial arts that have a high risk of trauma to the solitary kidney.

Can Unilateral Renal Agenesis Be Prevented?

Genetic counseling can significantly help minimize the risk of passing defective mutated genes to children in parents with gene mutations related to renal agenesis. Preimplantation genetic diagnosis helps identify embryos that do not have a mutated gene. Thereafter, invitro fertilization can be used to implant safe embryos into the female reproductive system.

Conclusion:

From the above article, it is clear that unilateral renal agenesis is a common congenital anomaly. In addition, every one in three patients have other associated genetic disorders of the kidney and urinary tract. In addition to the renal abnormalities, several patients show extrarenal malformations too. The extrarenal malformations include cardiac, gastrointestinal, and musculoskeletal defects. A definitive treatment strategy does not exist for unilateral renal agenesis. Treatment is based mainly on the presenting symptoms and an approach to safeguard the solitary functioning kidney.

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Frequently Asked Questions

Yes, it is possible to live with renal agenesis, but it presents a unique set of challenges. Renal agenesis refers to the absence of one or both kidneys from birth. In cases of unilateral renal agenesis (absence of one kidney), many individuals can lead relatively normal lives, with the remaining kidney compensating for the lost function. However, management and monitoring by healthcare professionals are essential to address potential complications.

Yes, one-sided renal agenesis may not always be present, and the person might not show any noticeable symptoms. In the majority of cases, the uninvolved kidney will handle the duties at its disposal in the absence of its partner, thus working normally. There are often no apparent symptoms of which patients may be unaware, and accidental detection may take place during routine medical checks or for some other issues.

The time of ablation has its own influence on these. In the occurrence of unilateral renal agenesis lacking one kidney, individuals may hardly notice any problems and can live a normal life while being entirely healthy. Nonetheless, these adverse reactions, such as increasing blood vessel pressure, can cause proteinuria or other kidney problems. The constant evaluation of the disease course by health specialists is necessary for ensuring that any unanticipated problems are detected and dealt with promptly.

Even though there is no specific one-size-fits-all diet for an individual with renal agenesis, it is crucial to follow near-perfect healthy nutrition. Among the things involved are water adequacy, a balanced diet with limited salt intake, and continuous monitoring of protein consumption. People who are interested in learning more about a specific diet should have a talk with healthcare professionals or dietitians. They will provide advice that will be adapted to the health condition and kidney function of the person.

The lack of proper therapy can only either reduce the symptoms or console the patient’s mental state. Therapeutic management for renal agenesis may involve the support of quality of life by limiting the number of possible complications and the overall function of the kidney. Routine medical checkups, blood pressure monitoring, and handling of any issues that arise at the right time are included in the treatment plan. When urgent situations occur, or complications are detected, healthcare professionals devise interventions that are meant for the specific individual.

The type of congenital disorder that renal agenesis belongs to is largely the function of the evaluation or testing being conducted during prenatal ultrasound examinations. Through the use of this imaging procedure, the obstetric team is able to see the fetus while it is in the process of development and identify deformities, such as the absence of the left or right kidneys. Early detection, most likely in some cases in the first trimester, enables the medical teams to monitor and manage the pregnancy appropriately and plan for any potential interventions or securities.

The genetic identity of renal agenesis is painful because it includes genetic as well as environmental factors. The appearance of FPI may be triggered by people carrying specific genetic mutations, and sometimes, it has no clear genetic cause and may appear randomly. While researchers have focused a lot on the most intricate genetic predispositions and environmental influences that may lead to this birth defect, this area remains unexplored to date.

Unilateral agenesis, which is the unilateral absence of the kidney, is a relatively less common occurrence rather than being rare. The precise rate depends on a variety of factors, but it is calculated as about 1 in 500 births in expanded demographics. It should be emphasized that numerous people with unilateral renal agenesis develop perfectly normal lives whose health depends only on the healthy one and the ability of this one to replace the missed kidney.

Yes, nephrons, or filtering units of a kidney, can be beneficial to babies with just one healthy kidney. The most common genetic condition is unilateral renal agenesis, but it generally does not affect a potentially healthy life. The rest of the kidney, on the other hand, acquires the required ability by adapting, which makes all kidneys required for maintaining the overall health of the kidney. It is better to get a medical check-up at least once or twice a year to make sure the kidneys are working well and quickly to correct any problems.

A single kidney (uni-renal agenesis) is a condition in which one kidney is absent. Discriminatory features shall consist in the tendency to have usual lifespans as well as healthy people for those with these genetic changes. The unilateral compensatory hypertrophy (the doubling in size of the single left kidney) enables optimal left kidney function. The complications that should be considered in this regard are linked to kidney diseases such as hypertension and proteinuria; this makes medical monitoring and care a priority throughout the whole process.

Estimates of the birth rate among those with one kidney born, which is unilateral renal agenesis, are about 1 in 500. It is a relatively rare condition and not a common one. Many people with a single kidney can lead normal lives because they are found out early and with proper medical monitoring.

Kidney transplants are safe, as people with one kidney can live normal lives, but there are some considerations after the surgery. It is, however, a good idea to keep yourself hydrated and manually maintain a balanced diet low in salt and protein concentrate, while NSAIDs are not the only good option. Maintaining kidney health is paramount, and regular medical examinations are summoned to define the extent of kidney function and respond to unexpected complications immediately.

A man with only one kidney is not said to have a disability. Individuals with just one kidney frequently enjoy good lives and may lead very active lifestyles with only minor restrictions. Nonetheless, exclusive conditions and health states must be taken into account, and there would be an assessment of interpersonal ability that would be based on the overall mental and physical performance of an individual.

Early warning signs of kidney disease include: Early warning signs of kidney disease include:


- The urological symptoms include more frequent and less controlled urinating or, in other words, bladder issues.


- For prolonged edemas, swelling in the legs tends to be more typical than swelling in the ankles or feet.


- For example, tiredness, weakness, or other conditions could mean that a person has renal function problems.


- Understanding these symptoms and addressing them early is an imperative step toward timely medical intervention and follow-up.

For kidney health, it is advisable to limit the intake of:


- Excessive sodium food consumption is considered to be the main reason behind the development of hypertension and water retention.


- Phosphorus and potassium are essential nutrients that are found in many types of foods; however, when such foods are consumed by people with kidney problems, they can lead to kidney failure.


- Sugary or processed foods lead to weight gain and metabolic issues.

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