Hydronephrosis: Causes, Symptoms & Treatment in Canada

Hydronephrosis is a condition where urine builds up inside one or both kidneys, causing them to swell and potentially leading to serious damage if left untreated. It develops when something blocks the normal flow of urine out of the kidney, putting increasing pressure on delicate kidney tissue. For Canadians experiencing unexplained flank pain or urinary changes, understanding this condition is an important first step toward getting the right care.

How Hydronephrosis Affects Your Kidney Health

Recognizing swollen kidney causes early can make a significant difference in treatment outcomes. Whether the blockage stems from kidney stones, an enlarged prostate, or another underlying issue, timely diagnosis through your family doctor, a walk-in clinic, or a Canadian emergency department can help prevent permanent kidney damage. This article covers the causes, symptoms, diagnosis, and treatment options available across Canada.

What Is Hydronephrosis?

Hydronephrosis Treatment Options: Benefits and Considerations

Treatment Option	How It Works	Benefits	Considerations
Watchful Waiting	Regular monitoring with ultrasound and urine tests; no immediate intervention	Non-invasive; appropriate for mild hydronephrosis or prenatal cases that may resolve on their own	Requires consistent follow-up appointments; not suitable if infection or significant obstruction is present
Ureteral Stent Placement	A thin, flexible tube is inserted into the ureter to keep it open and allow urine to drain	Rapid relief of obstruction; minimally invasive; can be done under local or general anaesthesia	May cause discomfort or urinary urgency; typically a temporary measure; requires removal or replacement
Percutaneous Nephrostomy	A drainage tube is inserted directly into the kidney through the back to bypass the blockage	Provides immediate drainage when other methods are not feasible; effective in emergency situations	Carries a small risk of infection or bleeding; external drainage bag required; limits daily activities
Pyeloplasty (Surgical Repair)	Reconstructive surgery to remove the narrowed or obstructed segment of the ureter and reconnect it	Long-term solution with high success rates; often curative for ureteropelvic junction (UPJ) obstruction	Requires general anaesthesia and recovery time; laparoscopic or robotic options available at major Canadian centres
Antibiotics	Prescribed when hydronephrosis is caused or complicated by a urinary tract or kidney infection	Treats underlying infection; prevents progression to serious kidney damage or sepsis	Must be combined with addressing the underlying obstruction; antibiotic selection guided by urine culture results

Your kidneys filter waste from your blood and produce urine. That urine travels through a tube called the ureter and into the bladder. When something blocks that path, urine backs up and puts pressure on the kidney.

This backup causes the inner part of the kidney — called the renal pelvis — to swell. The small collecting tubes inside the kidney, called calyces, also widen under that pressure. In more advanced cases, the kidney tissue itself can thin out and stop working properly.

Hydronephrosis can affect one kidney or both. When the blockage happens at or below the bladder, both kidneys are usually affected. According to Mayo Clinic, this condition can develop quickly or slowly depending on the cause.

Common Causes of Hydronephrosis

Many different things can block urine flow and lead to hydronephrosis. Some causes are present from birth, while others develop over time.

The most common causes include:

• Kidney stones: Hard mineral deposits that form in the kidney and can get stuck in the ureter
• Congenital blockages: Narrowing at the spot where the renal pelvis meets the ureter, present from birth
• Tumours: Growths pressing on the ureter or bladder from outside
• Enlarged prostate: In men, a large prostate can block urine from leaving the bladder
• Ureter kinking: A bend or twist in the ureter that stops urine from flowing freely
• Infections: Tuberculosis or other infections that cause scarring inside the urinary tract
• Bladder outlet obstruction: A blockage at the base of the bladder that affects both ureters

Kidney stones are the leading cause of hydronephrosis in Canada. Even a small stone can cause significant damage depending on where it lodges and how long it stays there.

How Kidney Stones Cause a Blockage

A kidney stone can be complete or partial in the way it blocks urine flow. A complete blockage stops urine entirely, while a partial blockage still allows some urine to pass. Both types raise pressure inside the urinary tract above the stone.

This raised pressure is what drives the swelling and eventual damage to the kidney. The longer the blockage stays in place, the greater the risk of permanent kidney injury.

How Hydronephrosis Affects the Kidney

When urine cannot drain properly, pressure builds up in the renal pelvis and calyces. Over time, this pressure damages the tiny filtering units inside the kidney called nephrons.

As nephrons are destroyed, the kidney loses its ability to filter waste from the blood. The kidney tissue becomes thin and may scar. In severe or long-standing cases, the kidney can lose most of its function.

Furthermore, the high pressure can cause urine to leak into the tissue surrounding the kidney. This can trigger inflammation around the kidney and ureter, leading to scarring that may affect urinary function even after the blockage is removed.

For more on how kidneys work and what affects them, visit Health Canada’s kidney health resources.

Signs and Symptoms of Hydronephrosis

The symptoms of hydronephrosis depend on how quickly the blockage develops, how complete it is, and whether an infection is also present. Some people have very noticeable symptoms, while others may have none at all.

Pain

Pain is one of the most common signs of hydronephrosis. When a kidney stone causes a sudden, complete blockage, the result is a renal colic — a sharp, cramping pain in the side or back that can be severe. The pain often comes in waves and may spread to the groin or lower abdomen.

However, when a blockage develops slowly and only partially blocks urine flow, the pain may be a dull ache rather than sharp cramping. This duller pain is called nephralgia and is typical with stones lodged in the calyces.

Other Common Symptoms

Beyond pain, hydronephrosis can also cause:

• Nausea and vomiting
• Frequent urge to urinate
• Burning sensation when urinating
• Cloudy or foul-smelling urine (a sign of infection)
• Fever and chills (if infection is present)
• Swelling or a lump in the abdomen in severe cases
• Decreased urine output

In newborns and infants, hydronephrosis is sometimes found on a prenatal ultrasound before any symptoms appear. In these cases, the condition is monitored closely after birth.

When Symptoms Are Silent

Some forms of hydronephrosis cause little to no pain, especially when the blockage develops slowly. As a result, the condition may go unnoticed until a routine test or imaging scan picks it up. This is why regular check-ups with your family doctor matter, especially if you have a history of kidney stones.

How Is Hydronephrosis Diagnosed?

Your doctor will start with a physical exam and ask about your symptoms and medical history. From there, they will order tests to confirm the diagnosis and find the cause of the blockage.

Common diagnostic tests include:

• Ultrasound: The first test used in most cases. It shows swelling in the kidney without any radiation.
• CT scan: Provides detailed images of the kidney, ureter, and bladder. Very effective at spotting kidney stones.
• MRI: Used when more detail is needed or when avoiding radiation is a priority.
• Urine tests: Check for infection, blood, or signs of kidney stress.
• Blood tests: Measure how well the kidneys are filtering waste (creatinine and eGFR levels).

In Canada, these tests are typically covered under provincial health plans. Your family doctor can refer you for imaging and lab work, or you can visit a walk-in clinic if your symptoms come on suddenly.

Treatment Options for Hydronephrosis

Treatment depends on the cause, how severe the blockage is, and whether the kidney is already damaged. The main goal is to relieve the obstruction and protect kidney function.

Treating the Underlying Cause

If a kidney stone is causing the blockage, treatment may include drinking extra fluids, pain medication, or procedures to remove or break up the stone. Smaller stones often pass on their own. Larger stones may need shock wave therapy, a scope procedure, or surgery.

If a tumour or enlarged prostate is pressing on the ureter, treatment will focus on addressing that condition directly. Your family doctor will refer you to the appropriate specialist, such as a urologist or oncologist.

Surgical Options

In some cases, surgery is needed to fix the problem permanently. A procedure called pyeloplasty reshapes the junction between the renal pelvis and the ureter to restore normal urine flow. This procedure prevents further kidney damage from ongoing pressure.

In emergency situations where the kidney is severely blocked, a temporary drain called a nephrostomy tube or a ureteral stent may be placed to relieve pressure right away while a longer-term plan is developed.

For a detailed overview of urinary tract conditions, Healthline’s urology section offers helpful, evidence-based information.

When to See a Doctor

You should contact your family doctor if you notice any persistent back or side pain, blood in your urine, or changes in how often you urinate. These can all be early signs of hydronephrosis or another urinary tract problem.

Go to a walk-in clinic or emergency department right away if you experience:

• Severe, sudden pain in your side or back
• High fever with chills and pain when urinating
• Significantly reduced urine output
• Nausea and vomiting alongside back or flank pain

If hydronephrosis is caught early, treatment is usually very effective. However, delays in care can lead to permanent kidney damage. Do not wait to seek help if something feels wrong.

As always, speak with your doctor or a qualified healthcare provider before making any decisions about your health. This article is for general information only and does not replace professional medical advice.

Key Takeaways

• Hydronephrosis means the kidney is swollen due to a blocked urine flow.
• Kidney stones are the most common cause in Canada.
• Symptoms include flank pain, changes in urination, fever, and nausea — but some cases cause no symptoms at all.
• Left untreated, hydronephrosis can permanently damage kidney function.
• Diagnosis usually involves ultrasound, CT scan, and blood or urine tests — all covered under most provincial health plans.
• Treatment depends on the cause and may include stone removal, medication, or surgery such as pyeloplasty.
• See your family doctor promptly if you have ongoing back or side pain, or visit a walk-in clinic if symptoms are sudden or severe.