Obstructive nephropathy: kidney damage from a urinary blockage

Each kidney makes urine, which drains down a narrow tube called a ureter into the bladder and then leaves the body through the urethra. Obstructive nephropathy is the term used for kidney damage that follows when something interrupts that route. Urine that cannot leave builds up behind the blockage and the pressure is passed back to the kidney.

The NHS uses the name hydronephrosis for the swelling of one or both kidneys that results from a build-up of pee. In practice the two terms describe two sides of the same problem: hydronephrosis is the swelling that doctors see on a scan, and obstructive nephropathy is the effect on how well the kidney works. The blockage can sit anywhere along the route, from the kidney itself to the end of the urethra, and it can be partial or complete, sudden or slowly progressive.

Because the problem is mechanical, it is often one of the more treatable causes of kidney trouble. Relieving the blockage early usually gives the kidney the best chance of recovering, which is why the condition is taken seriously even when the first symptoms seem mild.

Symptoms depend on how quickly the blockage develops and how complete it is. The NHS lists the following symptoms of hydronephrosis. Some people have very few, particularly if the blockage comes on slowly, which is one reason it is sometimes found during tests for something else.

• Pain in the lower back, side or tummy (abdomen).

• Needing to pee more often than usual.

• Difficulty peeing.

• Pee that looks cloudy, or blood in your pee.

• A high temperature, or feeling hot, cold or shivery.

The NHS says to ask for an urgent GP appointment or get help from NHS 111 if you have symptoms of hydronephrosis, because it is important to find out what is causing them as soon as possible. For men with an enlarged prostate, the NHS also lists being unable to pee at all, blood in the pee and pain when peeing as reasons to seek urgent help.

A blocked kidney that becomes infected can be serious. The NHS says a kidney infection can cause sepsis if it is not treated, and that you should call 999 or go to A&E if you are confused, drowsy or have difficulty speaking. A very high temperature, shivering, pain under the ribs or in the lower tummy, blood in the pee or not having peed all day are listed as reasons to seek urgent advice from a GP or NHS 111 if you think you may have a kidney infection.

The NHS lists several things that can block the flow of urine. Which one applies depends heavily on age, sex and general health.

A GP will ask about your symptoms and any past kidney stones, prostate problems or operations. The NHS says tests may include blood or pee tests to check for infection, a rectal examination to check for an enlarged prostate, and an X-ray, CT scan or other imaging to look for a blockage around the kidneys, bladder and ureters.

If kidney function is affected, a blood test for creatinine is how acute kidney injury is diagnosed, according to the NHS. NICE Clinical Knowledge Summaries add that assessment of someone with acute kidney injury should include checking for signs of urological obstruction, and that people with a history of urological obstruction are at increased risk of acute kidney injury.

Some blockages are found before birth. The NHS notes that hydronephrosis in an unborn baby is usually found at the 20-week scan, and that it is often caused by the baby producing more urine in later pregnancy and usually goes away on its own.

The NHS says treatment depends on what is causing the blockage and how severe it is. In adults the first step is usually to drain the pee to relieve pain and prevent damage to the kidneys. This is done by passing a thin tube (catheter) into the bladder, either through the urethra or through a small cut in the tummy.

Once the urine is draining, the cause can be dealt with. The NHS gives the examples of medicine to treat an infection or surgery to remove a blockage. Kidney stones may be passed with medicines for pain and sickness, or broken up or removed in hospital; for an enlarged prostate the NHS describes medicines first and then surgery such as transurethral resection of the prostate if symptoms are severe or medicines have not helped.

If the kidneys have been injured, treatment follows the pattern for acute kidney injury. The NHS lists stopping or changing any medicine that could be causing damage, fluids through a drip, a catheter to drain urine, surgery to remove a blockage and, if severe, dialysis that is usually needed for only a few days or weeks until the kidneys recover.

Outlook depends on how long the blockage was present and how well the kidney was working beforehand. The NHS says that when hydronephrosis is treated promptly it does not usually cause any long-term problems and most people recover quickly. If it is not treated or is severe, it can damage the kidneys and may eventually lead to kidney failure, and then dialysis or a transplant may be needed.

Some people are left with permanent loss of kidney function. NICE Clinical Knowledge Summaries list obstructive uropathy among the possible causes and risk factors for chronic kidney disease, and the NHS lists blockages in the flow of urine, such as kidney stones that keep coming back or an enlarged prostate, among the causes of chronic kidney disease. After an episode of acute kidney injury, regular blood tests and check-ups are advised to make sure the kidneys are working as expected.

Preventing a return of the blockage matters as much as the first treatment. That might mean preventing kidney stones, treating an enlarged prostate, or reviewing medicines that affect the bladder or kidneys with a doctor.

A suspected blocked kidney is normally assessed urgently through the NHS, starting with a GP, NHS 111 or A&E, followed by imaging and, where needed, a urologist or kidney specialist. Emergency drainage and treatment of a blocked, infected kidney are NHS emergency services.

Some people also see a private urologist, usually for faster access to scans or for planned procedures such as stone treatment or prostate surgery. The investigations and operations are broadly the same in both settings; the differences are mainly in waiting time and choice of surgeon and hospital. Whichever route you use, ask who is responsible for follow-up kidney blood tests afterwards.