Pyelectasis And Kidney Health

Pyelectasis is a foetal condition which commonly occurs during the second trimester, where an unborn baby has a buildup of urine inside the central part of one or both of their forming kidneys (known as the renal pelvis). In a normally-developing foetus, waste products circulating their body will filter out of the bloodstream and collect in the kidneys as urine. The urine then travels from the kidney to the bladder, through a tube called the ureter that connects the two organs. Once in the bladder, the urine is expelled into the amniotic sac. In a baby who develops pyelectasis, however, the urine builds up in the renal pelvis of their kidney(s) and does not leave, resulting in larger-than-normal kidneys. When the condition only affects one kidney, this is known as unilateral pyelectasis, whereas when the condition affects both kidneys, this is known as bilateral pyelectasis.¹  

Although this sounds alarming, fortunately roughly 90% of all pyelectasis cases are mild and can resolve themselves over the course of the pregnancy.¹ However, in 10% of cases, the significant and persistent swelling of the kidneys can lead to severe pyelectasis, known as antenatal hydronephrosis. These more severe cases do require medical attention as if left untreated, the condition could affect kidney health.² It is very important to maintain kidney health as these organs help keep your body functioning properly - by removing waste products from the blood, by producing hormones, by controlling your blood pressure, and by maintaining healthy amounts of water, salts and minerals.

This article will detail the causes of pyelectasis, how severe pyelectasis can affect a foetus’ kidney health, and the diagnosis and treatment methods used to resolve the condition.   

Causes and risk factors of pyelectasis

There are two main causes of pyelectasis:

• Ureteropelvic junction obstruction - One reason why pyelectasis occurs is when a blockage forms in the foetus’ ureter, preventing the urine from leaving the kidney and travelling to the bladder. This is called ureteropelvic junction obstruction. This blockage might form due to a narrowing of the ureter.³ 
• Vesicoureteral reflux - Another reason why pyelectasis occurs is when, instead of the urine travelling from the kidney down the ureter to the bladder, the opposite occurs. This flow back from the bladder to the kidneys happens when the ureterovesical junction (which is where the ureter meets the bladder) does not close properly, allowing for the urine to travel back up the tube.⁴ 

Alongside these two main causes of pyelectasis, some genetic disorders are associated with an increased risk of developing the condition. The main example is Down’s syndrome - although most cases of pyelectasis are not associated with genetics if your foetus has Down syndrome, they are more likely to develop pyelectasis during the second trimester.⁵  

Is it possible to prevent pyelectasis from happening?

It is not possible to prevent pyelectasis from developing in a foetus, as it is a condition which usually occurs due to a random variation in the development of the baby.¹ 

The impact of pyelectasis on kidney health 

In 90% of all foetal pyelectasis cases, the enlargement of the renal pelvis is between 4 to 9 millimetres in diameter. These cases are referred to as mild pyelectasis and typically do not cause any noticeable symptoms in the foetus or the mother. This means mild pyelectasis has no significant impact on the foetus’ short-term or long-term health of its kidney. It is common in such cases for the build-up of urine in their kidneys to resolve itself by the third trimester.¹  

In the other 10% of cases, the enlargement of the renal pelvis is greater than 10 millimetres, resulting in a balloon-shaped kidney which can persist throughout the entire pregnancy to after birth. This more severe type of pyelectasis is known as antenatal hydronephrosis. Unlike mild pyelectasis, antenatal hydronephrosis can affect kidney health if left untreated.⁵ Examples of how antenatal hydronephrosis can damage the foetus’ kidneys include the following:

• A common complication of antenatal hydronephrosis is the development of a urinary tract infection (UTI), as the urine insider the renal pelvis makes them more susceptible to developing an infection. This UTI could in turn lead to pyelonephritis (infection of the kidney itself). If such kidney infection spreads to the rest of the baby’s organs via the bloodstream, then it can cause the serious issue of sepsis.
• Antenatal hydronephrosis can lead to high blood pressure.
• Antenatal hydronephrosis can result in scarring of kidney tissue due to the extreme enlargement of the renal pelvis.⁵

All the potential damage that can occur to the kidneys when a baby has antenatal hydronephrosis (listed above) can result in a significant decrease in healthy kidney function, which in turn can lead to kidney disease and sometimes even failure.⁵  

Hence, in order to prevent any damage to one’s kidney health, it is important to properly diagnose and treat severe pyelectasis. 

Management and treatment of pyelectasis

Diagnosis of pyelectasis

Due to the fact that most cases of pyelectasis lead to no observable symptoms in the foetus or the mother, the condition is typically found and diagnosed during routine ultrasound checkups during the second trimester of pregnancy (which is when the kidneys should be developed). Medical professionals will diagnose pyelectasis if they notice the enlargement of one or both of the kidneys during these ultrasound scans.⁶ 

Monitoring of pyelectasis

Once a foetus is diagnosed with pyelectasis, medical professionals will monitor the condition throughout the remainder of the pregnancy via additional ultrasound scans, to assess whether the enlargement of the kidney worsens, stays the same, or resolves itself. With mild pyelectasis cases, by the third trimester, the kidneys have returned to their healthy size.⁶ 

With more severe pyelectasis cases (antenatal hydronephrosis), alongside the additional ultrasound monitoring throughout the pregnancy, the baby will likely go through further tests during the few weeks after birth, to check if there are continuing problems. These include the following: 

• Blood tests, blood pressure tests and urine tests to assess kidney function and investigate whether the kidney is infected or damaged. 
• Ultrasound scans to visualise the baby’s kidney, to see whether the ballooning of the kidney has decreased.
• A micturating cystourethrogram (MCUG) is a test where a clear special liquid called contrast is passed through a thin tube placed into the baby’s bladder, and then a series of X-ray pictures are taken. This allows visualisation of the urinary system, to see if urine is flowing properly into the bladder. 
• A dimercaptosuccinic acid (DMSA) scan or MAG3 Renogram scan are test where special substances called isotopes are injected into the baby’s veins and are then absorbed into the kidneys. These isotopes will show up on devices called gamma cameras, which are used to take pictures of the baby’s kidneys. Using these scans will help medical professionals to investigate the structure and function of the kidneys.

Treatments for severe pyelectasis (antenatal hydronephrosis) 

In most babies with antenatal hydronephrosis, the condition will get better as they get older. If their post-birth scans do show continuing problems with their kidneys, then the main type of treatment given is antibiotics. By giving these babies antibiotics, it will reduce their risk of developing a UTI and damaging their kidney health. 

In very rare cases where the antenatal hydronephrosis is exceptionally severe and is caused by a ureteropelvic junction obstruction, then surgery can be done. The most common type of surgery which is performed is a pyeloplasty. This surgery effectively corrects the blockage found in the ureter, as the surgeon cuts out this blockage, allowing urine to then freely flow from the kidneys to the bladder.⁷  

Summary

Pyelectasis is the foetal condition that concerns the build-up of urine in the kidneys of the baby, leading to the swelling of the organ. It usually occurs during the second trimester of pregnancy, when the kidneys have developed. The most common causes of pyelectasis include a blockage in the ureter connecting the kidneys to the bladder, or vesicoureteral reflux (when urine backflows into the kidneys from the bladder). Although pyelectasis sounds serious, over 90% of cases resolve themselves spontaneously by the time the baby is born. However, in 10% of cases, this swelling of the kidneys due to urine build-up can persist, and this is called antenatal hydronephrosis. If such type of severe pyelectasis is left untreated, it can damage kidney health by increasing the baby’s blood pressure, scarring kidney tissue, and leading to infection. In order to prevent this, once diagnosed through a routine ultrasound scan during the second trimester of pregnancy, pyelectasis is monitored through additional scans throughout the rest of the pregnancy and the weeks after birth. If problems do persist after birth, babies can be given antibiotics to prevent any damage to their kidneys. In very rare cases, the surgery pyeloplasty can be done to correct any blockage found in the ureter to allow normal flow of urine and to protect kidney health.