Flank pain

Overview

Flank pain is pain on one side of your body, between your ribs and your hip. It often feels like a dull ache or a sharp, stabbing sensation. Flank pain can come from muscles, bones, or organs in that area, most commonly the kidney or urinary tract.

Yes, flank pain is a common reason people visit their doctor. Kidney stones alone affect about 1 in 10 people at some point in their lives.

Flank pain can affect anyone, but it is more common in people aged 30 to 60, and slightly more common in men than women for conditions like kidney stones.

Symptoms

Common symptoms

• A dull ache or sharp pain on one side of your back (between the ribs and hip)
• Pain that comes and goes in waves (often with kidney stones)
• Pain that spreads to your lower belly or groin
• Pain when you urinate
• Blood in your urine (pink, red, or brown)
• Fever or chills (if there is an infection)

Symptoms in children

• Fussiness or crying that seems unexplained
• Pain in the side or belly
• Fever without a clear cause
• Vomiting or poor feeding

Symptoms in older adults

• Vague or less specific pain that may be harder to describe
• Confusion or sudden change in behaviour (can be a sign of infection)
• Loss of appetite or feeling generally unwell
• Fever or chills

Causes

Main causes

• Kidney stones – hard deposits that form in the kidney and can cause sharp, wave-like pain as they move
• Urinary tract infection (UTI) – especially a kidney infection (pyelonephritis) which causes pain, fever, and chills
• Muscle strain or injury – overstretching or tearing back muscles can cause dull or sharp flank pain
• Kidney disease – such as polycystic kidney disease or a blocked kidney (hydronephrosis)
• Shingles – a viral infection that can cause a painful rash in the flank area
• Other causes – problems with the spine, ribs, or organs like the pancreas or gallbladder can sometimes be felt in the flank

Risk factors

• Not drinking enough fluids
• A diet high in salt, sugar, or animal protein (can increase kidney stone risk)
• Being overweight or obese
• Having a family history of kidney stones
• Having had a UTI before
• Being over 60 (higher risk of kidney infection and stones)
• Certain medical conditions like gout, diabetes, or high blood pressure

When to see a doctor

See a doctor urgently if:

• Severe pain that comes on suddenly and doesn't go away
• Pain with a high fever or chills
• Blood in your urine
• Unable to pass urine
• Pain after a fall or injury
• Nausea or vomiting that is severe

Book a routine appointment if:

• Mild or moderate flank pain that lasts more than a day or two
• Pain that comes and goes (like waves)
• You feel generally unwell but not in severe pain
• You need advice about managing your symptoms at home

Diagnosis

Your doctor will ask about your pain, any other symptoms, and your medical history. They will also examine your back and belly. Based on that, they may order tests to find the cause.

Tests that may be done

• Urine test (urinalysis) – to check for infection, blood, or minerals that can form stones
• Blood tests – to check kidney function and look for infection
• Imaging tests – such as an ultrasound, CT scan, or X-ray to see the kidneys, ureters, and bladder
• Sometimes a cystoscopy (a thin camera tube inserted into the bladder) if other tests are unclear

What to expect at your appointment

Most tests are done as an outpatient (you go home the same day). Your doctor will explain the results in simple terms. If tests show a problem, they will discuss treatment options with you. It may take a few days to get results, so try not to worry in the meantime.

Treatment

Treatment depends on what is causing your flank pain. The goal is to relieve your symptoms, treat the underlying problem, and prevent it from coming back. Many conditions can be managed with simple home care, while others need medical treatment or procedures.

Self-care at home

• Drink plenty of water (unless your doctor tells you otherwise) – aim for 6-8 glasses a day
• Get plenty of rest and avoid heavy lifting or strenuous activity
• Apply a warm compress or heating pad (wrapped in a cloth) to the painful area for 15-20 minutes
• Take over-the-counter pain relievers like paracetamol or ibuprofen – always follow the label and ask your pharmacist or doctor if they are safe for you
• For a kidney stone, try to stay active – gentle walking may help the stone pass

Medical treatments

Your doctor may prescribe antibiotics if you have a urinary tract infection. For kidney stones, they may give medicines to help you pass the stone more comfortably and reduce pain. If stones are large or causing problems, procedures like shock wave lithotripsy (sound waves to break stones) or a scope to remove them may be needed. Always ask your doctor what treatment is best for your situation.

When is surgery considered?

Surgery is rarely needed for flank pain. It may be considered if you have a large kidney stone that does not pass, a blocked kidney, or an abscess (a pocket of infection) that needs draining.

Living with this condition

Flank pain caused by a kidney stone or infection usually gets better within a few days to a week. While you recover, take things slowly. Listen to your body – if an activity makes the pain worse, stop and rest. Keep up with your fluids and any medicines your doctor prescribes.

Lifestyle tips

• Drink enough water every day to keep your urine light yellow
• Reduce your salt intake – avoid processed foods and adding salt at the table
• Eat a balanced diet with plenty of fruits and vegetables
• Maintain a healthy weight
• If you smoke, consider quitting – smoking can increase the risk of kidney cancer and other kidney problems

Diet and exercise

A healthy diet rich in calcium (from food, not supplements) can actually help prevent kidney stones. Avoid foods high in oxalates (like spinach, rhubarb, and nuts) if you are prone to certain stones – ask your doctor for specific advice. Exercise regularly (like walking or swimming) but avoid heavy lifting if you are in pain.

Mental health and emotional wellbeing

Living with flank pain can be frustrating and worrying, especially if the cause is not clear. It is normal to feel anxious or low. Talk to your doctor about your feelings – they can offer support or refer you to a counsellor if needed.

Prevention

Not all flank pain can be prevented, but you can reduce your risk of many causes. Staying well hydrated, eating a balanced diet, and maintaining a healthy weight are the most important steps. If you have had kidney stones before, your doctor may give specific dietary advice to prevent new ones.

Vaccines

There are no vaccines that directly prevent flank pain. However, staying up-to-date with vaccines (like the flu shot) can help prevent infections that might lead to kidney problems.

Screening programmes

There is no routine screening for flank pain. If you have risk factors (like a family history of kidney disease or stones), your doctor may check your urine or blood occasionally. Always tell your doctor if you have any concerning symptoms.

Complications

If left untreated

• A kidney infection can spread to the bloodstream (sepsis), which is life-threatening
• A large kidney stone can block the flow of urine, causing kidney damage or infection
• Chronic (long-term) kidney problems may develop if the cause is not addressed
• Severe pain can lead to difficulty sleeping, eating, and daily activities

Long-term outlook

The outlook for flank pain is very good. Most people recover fully with simple measures or treatment. Even serious causes like kidney stones or infections can be treated effectively. By working with your doctor and taking care of your health, you can manage your symptoms and prevent future episodes.

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