Hydronephrosis

Overview

Hydronephrosis (say: high-droh-nef-ROH-sis) means a kidney has become stretched and swollen because urine is not draining out of it properly. Your kidneys filter blood and make urine, which then flows down a thin tube called the ureter into your bladder. If something slows or blocks that flow — or if urine flows backwards — it builds up and presses on the kidney, a bit like a balloon slowly filling with water. Hydronephrosis is not a disease on its own. It is a sign that something is affecting how urine drains, so doctors will look for the underlying cause. It can be mild and harmless, or more serious if it is left unchecked.

Yes, it is quite common. It is one of the most frequent findings on ultrasound scans in unborn babies, and doctors often spot mild hydronephrosis by chance in adults having a scan for something else. Many of these people never have any symptoms and need no treatment beyond a check-up.

Anyone can get hydronephrosis, at any age. It is more often seen in older men whose prostate gland has grown and is pressing on the bladder outlet, in people with kidney stones, in pregnant women (the growing womb can press on the ureters), in unborn babies and young children with a narrowed urine tube or reflux, and in people with nerve or spinal problems that affect the bladder.

Symptoms

Common symptoms

• Many people have no symptoms at all — it is only picked up on a scan
• A dull ache or pain in the back or side, just below the ribs
• Pain that comes in waves and may spread to the tummy or groin
• Blood in the urine, which may look pink, red or cola-coloured
• Burning or stinging when passing urine, or needing to go more often
• Feeling sick or being sick
• A swollen or tender tummy, or a lump you can feel
• Passing less urine than usual, or feeling that your bladder is not emptying
• Feeling very tired, and sometimes a higher blood pressure reading than usual

Symptoms in children

• Often found before birth on a routine pregnancy ultrasound scan
• A baby who is fussy, feeds poorly or is not gaining weight as expected
• A fever with no obvious cause, or repeated urine infections
• A soft lump or swelling in the tummy
• Wetting the bed again in a child who had been dry
• Pain in the side or tummy, which a young child may struggle to describe

Symptoms in older adults

• Symptoms can be quiet or put down to 'just getting older'
• Passing urine more often at night, or a weak urine stream
• Repeated urine infections
• Feeling more confused or sleepy than usual, especially with an infection
• Poor appetite, feeling sick or losing weight without trying
• Swelling in the tummy or ankle swelling

Causes

Main causes

• Kidney stones stuck in the ureter, blocking the flow of urine
• An enlarged prostate gland pressing on the bladder outlet in men
• Pregnancy — the growing womb can press on the ureters, and pregnancy hormones slow the flow
• A narrowed or kinked join where the kidney meets the ureter (doctors call this a pelvi-ureteric junction obstruction)
• Reflux, where urine flows backwards from the bladder up towards the kidney (common in children)
• Scar tissue or a growth in the urinary tract, which can narrow the tubes
• Nerve or spinal problems that stop the bladder emptying properly
• A blocked urinary catheter, or a blood clot or fungal ball in the urine
• In women, a large fibroid or ovarian swelling pressing on a ureter

Risk factors

• Having had kidney stones before
• Being a man over 60 with prostate enlargement
• Being pregnant
• Frequent urine infections
• A family history of problems with the urinary tract
• Previous surgery, radiotherapy or injury in the pelvis or tummy
• A spinal cord injury or a nerve condition such as MS
• Not drinking enough fluids, which makes stones more likely
• Some medicines can affect urine flow — ask your pharmacist or doctor if you are unsure about yours

When to see a doctor

See a doctor urgently if:

• Fever, shivering and pain in your back or side
• Blood in your urine
• Severe or worsening pain in your back, side or tummy
• You are vomiting and cannot keep drinks down
• You are passing very little or no urine
• You have hydronephrosis and feel suddenly much more unwell

Book a routine appointment if:

• A scan has shown hydronephrosis and you have been told to have it checked
• An ache in your back or side that keeps coming back
• Repeated or unexplained urine infections
• Changes in how you pass urine that last more than a few days
• A family member has had kidney or urinary tract problems, and you are worried

Diagnosis

Hydronephrosis is most often found on an ultrasound scan. The scan shows a kidney that looks stretched, and the doctor then works out why by asking about your symptoms, examining you and arranging a few tests. Sometimes it is spotted before birth on a routine pregnancy scan. Your doctor will also want to know how well your kidneys are working and whether there is an infection or a blockage.

Tests that may be done

• Ultrasound scan of the kidneys and bladder — painless, uses sound waves, no needles
• Blood test to check how well your kidneys are filtering
• Urine test to look for infection, blood or crystals
• A CT or MRI scan for a clearer picture of any blockage, stone or growth
• A special scan that shows how well each kidney drains (using a safe, short-lived tracer)
• A bladder X-ray test in children to check for reflux
• A camera test into the bladder, or pressure tests on the bladder, in some cases
• Repeat ultrasound scans over months to see whether things are improving

What to expect at your appointment

Most tests are quick and painless, though some scans need you to drink water beforehand or to empty your bladder at a certain time. You may be given a tracer injection for a drainage scan, which feels like a small scratch. Results usually come back within days to a few weeks. If your case is mild, your doctor may simply suggest repeating the scan in a few months to check the swelling has settled.

Treatment

Treatment depends on the cause, how severe the swelling is, and how well your kidneys are working. If the swelling is mild and your kidney function is normal, the usual plan is to watch and wait with a repeat scan. If something is blocking the flow, the aim is to relieve it — either by treating the cause or by draining the urine another way. Your doctor will explain the options and why one is being suggested for you.

Self-care at home

• Drink fluids regularly through the day unless your doctor has told you to limit them
• Go to the toilet when you need to rather than holding on
• Avoid getting constipated, as a full bowel can put pressure on the bladder and kidneys
• Keep your follow-up scans and appointments, even if you feel completely well
• Know what is normal for you — how often you pass urine and what it looks like
• Take any prescribed medicines as directed and ask your pharmacist if you are unsure
• Note down new symptoms such as fever, pain or blood in the urine and mention them early

Medical treatments

Doctors treat the cause rather than the swelling itself. If there is an infection, medicines to treat infection will be prescribed. Some people are given medicines that relax the muscles of the urinary tract or shrink an enlarged prostate. Pain relief may be suggested while tests are underway. If urine needs to be drained urgently, a thin tube (catheter) may be placed in the bladder, or a small soft tube called a stent may be put inside the ureter to hold it open — this is usually done by a urology team. Kidney stones may be allowed to pass, or broken up and removed. Very rarely, a small tube is placed through the skin of the back to drain the kidney directly. Your medical team will explain any treatment carefully and answer your questions.

When is surgery considered?

Surgery may be suggested if a blockage does not clear on its own, if kidney function is dropping, if there are repeated infections or stones, if a narrow join between the kidney and ureter needs reshaping, or if a child has significant reflux that is not settling. These operations aim to restore normal drainage and protect the kidney — most are done with keyhole or camera-guided techniques. The decision is always made together with you, weighing up the benefits and the risks.

Living with this condition

For many people, living with hydronephrosis means a few check-up scans and staying alert to symptoms. Keep a simple note of any pain, fever or change in your urine, and bring it to your appointments. If you have a stent or catheter, ask your team how to care for it and what to do if it becomes blocked or uncomfortable.

Lifestyle tips

• Stay well hydrated, especially in hot weather or when exercising
• Cut back on very salty foods, which can encourage stones
• Empty your bladder fully and regularly
• Treat constipation early with fibre, fluids and movement
• Keep blood pressure in a healthy range, as it protects the kidneys
• Stop smoking if you smoke — it helps your whole urinary system
• Keep a list of your medicines and share it at every appointment

Diet and exercise

A balanced diet with plenty of vegetables, fruit and fibre is good for your kidneys. Eating less salt and drinking enough water helps prevent stones. Regular movement — walking, swimming, cycling — supports digestion and healthy blood pressure. If you have had stones, your doctor may suggest specific changes, such as eating fewer oxalate-rich foods like spinach and nuts, but always ask before cutting out whole food groups. Your individual plan is best agreed with your healthcare team.

Mental health and emotional wellbeing

It is very normal to feel anxious when a scan shows something wrong with a kidney, and parents of babies with hydronephrosis often feel especially worried. Waiting for results can be stressful. Try to write down your questions before appointments and bring someone with you if that helps. If worry is affecting your sleep, mood or daily life, tell your doctor — support is available, and talking about it helps. If you ever feel overwhelmed or hopeless, contact your local crisis or mental health support service straight away.

Prevention

Not all hydronephrosis can be prevented — some babies are born with a narrow tube or reflux, and some causes are simply out of our control. But you can lower your risk from some of the common causes. Staying well hydrated, eating less salt, treating urine infections promptly, and getting prostate symptoms checked early all help. If you have had kidney stones, following your doctor's advice on diet and fluids reduces the chance of another one.

Screening programmes

There is no routine screening programme for hydronephrosis. In unborn babies it is usually picked up on the routine pregnancy ultrasound scan, and children with a mild finding are often re-scanned after birth. Adults are usually tested only if they have symptoms or a scan shows something.

Complications

If left untreated

• Scarring and reduced kidney function if the pressure goes on for a long time
• A kidney infection, which can make you very unwell and needs prompt treatment
• A collection of pus around the kidney (an abscess) in serious infections
• Kidney stones forming more easily when urine sits still
• Higher blood pressure, which itself puts strain on the kidneys
• Long-term kidney disease, and in rare cases kidney failure, if a blockage is left untreated for a long time
• In children, slower growth or repeated infections if reflux or blockage is not managed

Long-term outlook

The outlook is generally good. Most mild cases, especially in babies, settle by themselves with simple monitoring. When a blockage needs treating, clearing it usually protects the kidney well, and many people go on to have normal kidney function. The key is to have the cause checked and to keep your follow-up appointments. If you are worried at any point, speak to your doctor — asking early is always the right move.

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