Understanding Hydronephrosis: Causes, Symptoms, and Treatments

A woman with kidney problems

Hydronephrosis is a rare condition that affects the urinary tract and occurs in 1% of newborn babies and adults in their lifetime.

In infants, hydronephrosis usually resolves before birth, but in adults, it’s typically a symptom of something more serious — like a kidney stone or tumor.

In this article, we’ll discuss the symptoms, treatments, and underlying causes that lead to hydronephrosis.

What is Hydronephrosis?

Hydronephrosis is a condition characterized by the accumulation of urine in one or both kidneys due to a blockage that impedes the normal flow of urine out of the kidneys.

This type of urinary tract obstruction may result from a complete blockage or vesicoureteral reflux (VUR), which is a condition where urine flows backward from the bladder into the ureters and sometimes the kidneys.

Obstructions or blockages that interfere with urine flow can lead to kidney swelling. This swelling can compromise kidney function, risking irreversible damage over time.

Hydronephrosis often signals issues elsewhere in the urinary or pelvic system rather than being a condition on its own. The blockage may occur at any location within the urinary pathway, including the kidneys, ureters, bladder, or urethra.

What are the Causes of Hydronephrosis?

Hydronephrosis arises from various causes, all of which involve an obstruction to the normal flow of urine. The location of this obstruction determines whether one or both kidneys are impacted.

When the obstruction occurs in or below the bladder, hydronephrosis affects both kidneys (bilateral); if the blockage is above the bladder within the urinary system, only one kidney is affected (unilateral).

Some of the causes of hydronephrosis include:

  • Renal calculi (kidney stones)

  • Pelvic cancer or tumors: These may press on structures, blocking the flow of urine from the kidneys, causing, for example, an enlarged prostate, prostate cancer, cervical cancer, or ovarian cysts

  • Pregnancy: As the uterus expands, the developing fetus may block the outflow of urine at various levels in the urinary tract

  • Urethral stricture: This occurs when scarring of the urethra causes it to narrow. It may happen due to previous infections or injuries

  • Bladder tumors or cancer

Hydronephrosis in babies

According to the Boston Children’s Hospital, hydronephrosis affects 1 in 100 babies.

The cause of this condition differs somewhat in children and mainly involves abnormalities present from birth.

Some causes include:

  • Posterior urethral valves: Extra flaps of tissue that block the normal urine flow from the bladder.

  • Ureteropelvic junction obstruction: The ureter is narrowed near its connection with the kidney.

  • Vesicoureteral reflux (VUR): Muscle problems in the bladder cause urine to flow back up the ureter into the kidney.

What are the Signs and Symptoms of Hydronephrosis?

Hydronephrosis symptoms usually indicate an underlying condition. Common signs and symptoms associated with its various causes include:

  • Back, abdomen, or pelvic pain

  • Reduced urine output

  • Presence of blood in urine

  • Weak urine flow

  • The sensation of incomplete bladder emptying or painful urination

  • Split urine stream, where the flow splits or sprays

  • Increased risk of urinary tract infections (UTIs), notably in males (where UTIs are less common, prompting medical consultation)

  • In some instances, no symptoms are observed

How Serious is Hydronephrosis?

Healthcare providers use a specific grading system to assess hydronephrosis, designed to determine the severity of functional tissue loss in kidneys.

Grades range from 0 (normal function) to 4 (severe hydronephrosis with substantial swelling and structural loss).

This evaluation, derived from ultrasound and other imaging scans, helps in determining the condition's severity and tailoring treatment plans.

A condition frequently occurring alongside hydronephrosis is hydroureter which refers to the swelling and dilation of the ureter.

Similar to how urinary blockages can cause hydronephrosis by forcing urine back into the kidneys, these blockages can also lead to ureter dilation.

What Does Hydronephrosis Pain Feel Like?

Hydronephrosis often presents without pain or noticeable symptoms, depending on its cause and development timeline. Typically, any pain experienced is not from hydronephrosis itself but rather from the underlying condition causing it.

Pain caused by swelling

Individuals who experience a rapid onset of hydronephrosis usually feel pain due to the swelling caused by urine accumulation behind the blockage.

The location of this pain varies and is determined by the site of the blockage within the urinary tract, affecting areas such as the urethra, bladder, ureter, or the kidney itself.

The rapid onset of swelling can result from a kidney stone obstructing a part of the urinary tract.

Pain caused by kidney stones

In cases involving kidney stones, the pain experienced is typically acute and fluctuates in intensity, characterized by waves of sharp increase and gradual decrease.

This type of pain, called renal colic, happens because muscles try to push the blockage out, causing the sharp, "spasm-like" pain typical of kidney stones.

Pain caused by kidney infections

Sometimes, pain occurs in the “costovertebral” or "kidney angle," which is the area on your back just below the ribs. With kidney infections, touching this area can cause severe pain.

This type of pain often comes from kidney infections that result from hydronephrosis.

Pain caused by tumors

Pain in hydronephrosis can also come from tumors in the pelvic or urinary tract area pressing on nearby structures.

Early-stage tumors may not hurt, but when they do, the pain can either feel dull and hard to locate, or sharp and easy to identify, depending on where the tumor is.

This pain isn't directly from hydronephrosis but from the tumors that cause it.

How Is Hydronephrosis Diagnosed?

Healthcare providers use various diagnostic tests to identify hydronephrosis and its causes. These tools help evaluate kidney health, detect obstructions, and inform treatment strategies.

Below are the essential tests for hydronephrosis assessment:


Your healthcare provider may conduct an ultrasound to examine the size and structure of the kidneys, aiding in the diagnosis of hydronephrosis.

A more specific kidney, ureter, and bladder scan (KUB ultrasound) might also be performed to identify potential causes of hydronephrosis.


This type of urine testing involves using test strips and lab tests to check the health status of the kidneys. Urinalysis is instrumental in identifying complications related to hydronephrosis, including a urinary tract infection.

Blood tests

Certain blood tests can determine your degree of kidney function. Generally, these tests may need to be repeated to check whether your kidney function is improving over time.

Voiding cystourethrogram (VCUG)

During this procedure, a dye visible on X-rays is introduced into the bladder through a catheter (a tube inserted into the urethra).

Subsequent X-rays track the dye's movement during urination, helping to identify urinary system abnormalities.

VCUG is usually only done on children to further investigate the cause of hydronephrosis once it's been diagnosed.

Computerized tomography (CT) scan

This imaging test can not only assist in diagnosing hydronephrosis but also in identifying its cause. This is especially useful if the cause is external, i.e., outside of the urinary tract, such as cancerous or benign tumors.

Key Point: What Should You Avoid If You Have Hydronephrosis?

If you have poor kidney function due to hydronephrosis, your doctor may recommend limiting phosphate-rich foods such as meat, chicken, nuts, beans, and dairy.

Normally, phosphate is removed from the body by healthy kidneys but it may accumulate when kidney function is impaired. Excess phosphate is dangerous as it weakens your bones by drawing out calcium and making them brittle.

What are the Treatments for Hydronephrosis?

The treatment for hydronephrosis varies based on its underlying cause.

Initially, the priority is to relieve the buildup of urine, which can be achieved by inserting a catheter either through the urethra or directly into the bladder via the skin in a process called suprapubic catheterization.


  • Antibiotics: These are essential for treating UTIs that may occur as a complication of hydronephrosis.

  • Pain medications: Drugs that relieve pain are vital for managing the severe discomfort caused by conditions like kidney stones and cancer.

  • Specific treatments: Certain medications that treat the cause of hydronephrosis can also be prescribed. This includes prostate medications that improve the flow of urine through an enlarged prostate.

Surgical interventions

  • Nephrostomy: This involves inserting a tube into the ureter or kidney to drain urine that’s backed up, especially when regular catheters are ineffective.

  • Corrective surgery: When birth defects do not naturally improve, surgical correction may be required. The decision to operate is only made if other interventions are not expected to work.

  • Tumor excision: Cancers and tumors can be surgically removed to resolve urine buildup in the kidneys.

Can Hydronephrosis Go Away on its Own?

The potential for hydronephrosis to resolve without intervention depends on its cause:

  • Kidney stones: Following your consultation, your doctor may decide that waiting for kidney stones to pass spontaneously is the best course of action. This may, however, not be viable if your kidney stones are causing you significant pain.

  • Infant cases: Some cases of hydronephrosis in babies may resolve without intervention, but a healthcare provider’s guidance is essential. Never wait and see whether your child’s condition improves on its own.

  • Pregnancy-related: When hydronephrosis occurs during pregnancy, it usually resolves after childbirth.

Where Can You Learn More About Hydronephrosis?

Are you noticing changes in your urine output or are you struggling with a urinary tract infection that's causing discomfort? These could be signs of hydronephrosis.

While the severity of hydronephrosis may vary from case to case, it's important to seek medical attention immediately to prevent further complications.

Be sure to consult a healthcare provider who can help diagnose and treat your condition to prevent long-term complications.

If you have any other concerns about your urinary health, schedule a virtual appointment with LifeMD.

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This article is intended for informational purposes only and should not be considered medical advice. Consult a healthcare professional or call a doctor in the case of a medical emergency.

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