Left kidney pain is usually felt as a dull ache or a sharp pain in the left side of your back, just below the ribs. The two kidneys work independently, so a stone, an infection or a blockage often affects only one of them. Most causes are treatable, but kidney pain that comes with fever, blood in the urine or vomiting needs medical attention the same day.
Where is the left kidney, and what does kidney pain feel like?
Your kidneys sit towards the back of your body, one on each side of the spine, just under the lower ribs. Kidney pain is usually felt on one side, in the back or the side of the tummy, and it can spread down to the lower tummy or groin. It often arrives with other symptoms, such as fever, pain when you urinate, cloudy or bloody urine, or nausea.
Pain in this area often has nothing to do with the kidneys. An ache from the back muscles tends to change when you move, bend or press on the spot, and it does not come with urinary symptoms or fever. If you are not sure which it is, a simple urine test at your doctor’s rooms is a good place to start.
What causes left kidney pain?
Kidney stones
Stones form when minerals in the urine clump together. A small stone can pass without you noticing. A larger one causes pain that usually starts in the side of the tummy or lower back and can travel to the groin. It can be severe and may come and go. You may also feel sick, need to urinate more often, or notice cloudy urine.
Most small stones pass on their own with plenty of water and pain relief. Larger stones may need hospital treatment, either shock wave therapy to break the stone up or a small operation to remove it.
Kidney infection
A kidney infection usually starts as a bladder infection that travels upwards. It causes a high temperature, pain in the lower back or side, a burning feeling when you urinate and cloudy urine. It is treated with antibiotic tablets, usually for 7 to 14 days, and most people recover within two to three weeks.
Do not leave it. An untreated kidney infection can become serious and may lead to sepsis. Pregnant women with these symptoms should be seen urgently. Our article on cramps during pregnancy explains the other warning signs to watch for.
A blocked, swollen kidney (hydronephrosis)
If urine cannot drain from the kidney, it builds up and the kidney swells. Causes include kidney stones, an enlarged prostate, urinary infections, pregnancy and, less often, a tumour. Symptoms are pain in the back or side, needing to urinate often, cloudy or bloody urine, and sometimes fever or difficulty passing urine. Doctors first drain the urine, usually with a thin tube (catheter), and then treat the cause. Quick treatment protects the kidney from lasting damage.
Kidney cysts and polycystic kidney disease
Single, simple cysts become more common with age and usually cause no symptoms. Polycystic kidney disease is different. It is an inherited condition in which many fluid-filled cysts grow in the kidneys. It usually causes no problems until a person is in their 30s or 40s, when it can lead to pain in the tummy or side, high blood pressure, blood in the urine, urinary infections and kidney stones. A child has a one in two chance of inheriting it if a parent has the faulty gene. There is no cure, but treatment controls blood pressure and complications and can slow the damage.
Dehydration
Not drinking enough can cause a dull ache around the kidneys and raises your risk of kidney stones. Dark urine is the easiest sign to spot. The ache should ease once you are drinking enough again. If it does not, look for another cause.
Injury
A blow to the back or side from a fall, a car accident or a contact sport can bruise or damage a kidney. Blood in the urine after an injury needs urgent assessment.
Less common causes
A blood clot in a kidney vein, bleeding in the kidney and kidney cancer can all cause pain in the side. These are much less common, but they are the reason ongoing one-sided pain or blood in the urine should always be checked.
Symptoms that point to the cause
| Likely cause | Typical clues |
|---|---|
| Kidney stone | Severe pain in the side or lower back that may come and go and spread to the groin, nausea, cloudy urine |
| Kidney infection | Fever, pain in the lower back or side, burning when urinating, cloudy urine |
| Blocked kidney | Pain in the back or side, urinating often or with difficulty, cloudy or bloody urine |
| Polycystic kidney disease | Pain in the tummy or side from your 30s or 40s, high blood pressure, a family history |
| Dehydration | Dull ache, dark urine, improves with fluids |
| Injury | Pain after a blow to the back or side, sometimes blood in the urine |
How is kidney pain diagnosed?
Your doctor will ask about your symptoms and examine you. A urine test checks for infection and blood, and blood tests show how well your kidneys are working. An ultrasound or CT scan may be needed to look for stones, a blockage or cysts.
Left kidney pain treatment
Treatment depends on the cause: antibiotics for an infection, fluids and pain relief or a procedure for stones, drainage for a blocked kidney, and long-term monitoring for polycystic kidney disease. While you wait to be seen:
- Drink water regularly, unless a doctor has told you to limit fluids.
- Take paracetamol for pain or fever.
- Avoid ibuprofen and other anti-inflammatory painkillers unless a doctor advises them, because they can affect the kidneys.
- Rest, and keep track of your temperature.
When to see a doctor
See a doctor the same day if you have pain in your side or back together with any of the following:
- fever or shivering
- pain or burning when you urinate
- blood in your urine
- nausea or vomiting
- a constant ache on one side that is not settling
- pregnancy
Call 10177, or 112 from a cellphone, or go to the nearest emergency unit if the pain is sudden and severe, if you cannot pass urine, or if the person is confused, drowsy or struggling to speak.
Can you prevent kidney pain?
- Drink enough to keep your urine pale. People who have had a kidney stone are usually advised to drink more, up to 3 litres a day.
- Cut down on salt.
- Treat bladder infections early so they do not reach the kidneys.
- Have your blood pressure checked, especially if kidney disease runs in your family.
This article is for general information and does not replace advice from your doctor.
Medically reviewed by the ASAIPA clinical team.
