What is hydronephrosis, commonly referred to as kidney enlargement?

It is the enlargement of the anatomical structure called the pelvis, which allows urine to flow from the kidneys to the ureter. This condition usually develops due to blockages in this area and, if left untreated, can result in loss of kidney function.

On the other hand, there is also a condition called hydroureteronephrosis, which refers to the dilation of both the pelvis and the ureters. This condition indicates that the obstruction blocking urine flow is located further down the urinary tract.

Approximately 20% of congenital anomalies are urinary system (kidney and urinary tract) anomalies. These anomalies can be grouped into four categories: size anomalies, kidney tissue (parenchyma) anomalies, cyst presence, and antenatal hydronephrosis (pre-birth enlargement of the baby's urinary tract).

The most common urinary system anomaly found in ultrasounds during pregnancy is hydronephrosis, with a prevalence of 1-5%. Most of these are temporary conditions caused by the slow development of the urinary system and usually resolve on their own in the womb or within one year after birth, meaning they have no clinical significance.

Despite this, unfortunately, many of these patients undergo unnecessary and invasive tests by physicians who lack knowledge about the subject or are overly cautious. As the degree of hydronephrosis increases or if it is diagnosed very early in utero, the risk of ureteropelvic junction obstruction increases in these patients. For example, while the rate is around 10% in mild hydronephrosis, it rises to 60-65% in severe hydronephrosis.

What is the prevalence of hydronephrosis?

It is detected in 1-5% of pregnancies and is twice as common in male babies than in female babies.

How is hydronephrosis diagnosed?

Recently, with the increase in prenatal monitoring and the accumulation of knowledge and experience in this field, as well as advances in ultrasound technology, the diagnosis of hydronephrosis, like all congenital anomalies, is generally made prenatally, i.e., in the womb.

If prenatal diagnosis is not made, it is diagnosed after birth during examinations conducted for reasons such as recurrent urinary tract infections, developmental delay, inability to feed, abdominal pain, or other reasons.

What Are the Causes of Hydronephrosis?

The causes of hydronephrosis can be examined under two headings. It can be divided into two categories: temporary, which resolves on its own and accounts for 50-70% of cases, and permanent. It can also be divided into two categories: obstructive and non-obstructive hydronephrosis.

Although there are many non-obstructive causes, the most common cause is vesicoureteral reflux (backflow of urine from the bladder to the kidney), which accounts for 10-40% of cases.

The main causes of obstruction are: UPD (ureteropelvic junction obstruction, narrowing at the exit of the kidney), which accounts for 10-30% of cases, and UVD (ureterovesical junction obstruction, narrowing at the entrance to the bladder), which accounts for 5-15% of cases. Posterior urethral valve (narrowing of the urinary tract in male children) accounts for 1-5%, and ureterocele (cyst formation within the bladder) accounts for 1-3%.

Figure: Most Common Causes of Hydronephrosis; Ureteropelvic Stenosis, Vesicoureteral Reflux, and Ureterovesical Stenosis

What Are the Symptoms of Hydronephrosis?

It can be detected while the baby is still in the womb. In newborns, symptoms of hydronephrosis may include lethargy, restlessness, high fever, refusal to feed, vomiting, and failure to gain weight. In older children, abdominal and flank pain, fever, and burning during urination may occur.

What Problems Does Late Diagnosis of Hydronephrosis Cause?

Delayed diagnosis and chronic infection can lead to kidney inflammation, kidney damage, hypertension, and chronic renal failure.

What Findings Are Important When Diagnosing Hydronephrosis in the Womb?

Some important considerations when diagnosing hydronephrosis in the womb include:

• The month of pregnancy in which hydronephrosis appeared, as early onset may indicate a more serious condition and require more careful monitoring.
• Whether hydronephrosis affects one kidney or both kidneys.
• The degree of enlargement.
• Whether there are any changes in the parenchyma (the part of the kidney that produces urine) of the baby's kidney.
• Whether there is a decrease in amniotic fluid (the fluid in which the baby is immersed during pregnancy).

Is intervention required in utero for babies with hydronephrosis?

This may be necessary in rare, selected cases. The decision should be made jointly by a pediatric surgeon, pediatric nephrologist, obstetrician, and the family. The procedure should be evaluated in terms of the baby's and mother's lives, and it should be beneficial for the baby.

Should Babies with Hydronephrosis Be Delivered Early?

If there is no condition that requires early delivery for the baby and mother, it is not necessary. The baby can be delivered at the normal time and through normal delivery. In fact, normal delivery may be more beneficial for the baby's lungs.

What Should Be Done After Delivery in Babies with Hydronephrosis?

If the enlargement is not severe and urgent surgical intervention is not considered, there is no need to rush into postnatal examinations. In particular, there is no need to rush into an ultrasound scan. This is because after birth, the baby will urinate less for a certain period of time and then urinate more for a certain period of time. This situation may cause the hydronephrosis to appear less or more severe on the ultrasound scan. Therefore, an ultrasound of the urinary system (kidneys) and a urine test should be performed at the end of the first week. Follow-up and treatment are decided and planned based on the results obtained from these tests.

What Tests Should Be Performed When a Prenatal Diagnosis Is Made or When a Diagnosis Is Made Later?

First and foremost, a thorough and systematic physical examination is required. In particular, the patient is examined for other anomalies. Subsequently, the following tests specific to the patient may be performed: urine and blood tests, ultrasound, voiding cystography (also known as micturition cystography), scintigraphy, MR urography, and cystoscopy. However, it should be noted that not all of these tests are necessary for every patient. Which tests are performed on which patient depends on the patient's age, gender, history of urinary tract infections, other clinical findings, and the underlying cause of the hydronephrosis. The treatment option is determined based on the results of these tests.

How Should Postnatal Follow-up of Infants with Hydronephrosis Be Performed?

Similarly, the treatment option is determined based on the patient's age, gender, history of urinary tract infection, other clinical findings, kidney condition, and the cause of the pathology leading to hydronephrosis. It can be monitored only, and follow-up can be performed with clinical evaluation and ultrasonography. It can be monitored with antibiotic prophylaxis. A JJ catheter can be inserted, or surgery can be performed, which can be open or closed.

Is Circumcision Necessary in Male Infants with Hydronephrosis?

Yes, it should be performed to reduce the risk of urinary tract infection.

What Diseases Should Be Considered in Babies with Prenatal (In Utero) Hydronephrosis?

Keeping in mind that this may be a temporary and physiological condition, the following diseases may be considered.

• Vesicoureteral Reflux
• Ureteropelvic Stenosis
• Ureterovesical Stenosis.
• Ureterocele
• Posterior Urethral Valve
• Neurogenic Bladder

*** The information provided here is intended to inform visitors to the website. None of the information should be considered as advice by visitors and should not lead to any decisions or actions. Families should have their child examined by a pediatric surgeon, consult with them, and make decisions based on their individual advice.