Loin pain

What are the common causes of loin pain?

Common causes include:

• Kidney stones: A hard deposit moving through your urinary system can cause sudden, severe pain that comes in waves, sometimes spreading to your groin – it often, but not always, comes with blood in your urine
• A kidney infection: This usually causes a dull, constant ache, along with a high temperature, chills and feeling generally unwell, often alongside urinary symptoms
• A muscle strain or back problem: Pain from your back muscles or spine can be felt in the loin area – it tends to be worse with lifting, bending or twisting, and the area is often tender to touch
• Shingles: Causes a burning pain in a band across one side of the body, which can appear before the blistering rash does.

Less common but more serious causes include:

• An abdominal aortic aneurysm: A bulge in the body's main blood vessel, which can cause pain similar to a kidney stone, particularly in older adults having a first episode of this type of pain
• A kidney tumour: This tends to cause pain that builds up gradually, sometimes with painless blood in the urine
• A fractured or injured rib: This can cause sharp pain in a similar pattern to a kidney stone, often worse with movement or breathing in deeply.

Are there different types of loin pain?

Beyond the common causes above, there's a specific and rare condition called loin pain haematuria syndrome (LPHS) that's worth knowing about.

It's rare condition combining loin pain with haematuria (blood in your urine), where no other cause can be found. The pain may be continuous or come and go, and it's often worse at night or after exercise. It mostly affects young adults, and most people diagnosed with it are women.

LPHS is diagnosed only once more common causes, such as kidney stones, infection or other kidney diseases, have been ruled out. Its exact cause isn't known, though it's been linked to abnormalities in the tiny filtering structures inside the kidney.

How is loin pain diagnosed?

Your GP will ask when the pain started, whether it came on suddenly or gradually, whether it's constant or comes and goes, and whether you have any urinary symptoms, fever, nausea or vomiting. They'll examine your abdomen and back, and check your temperature, pulse and blood pressure. Tests that may be used include:

• a urine test, to check for blood, infection or crystals
• blood tests, to check how well your kidneys are working and look for signs of infection
• an ultrasound or CT scan, to look for kidney stones, tumours or other abnormalities – CT scans are usually preferred for adults, while ultrasound is preferred for children and during pregnancy.

If these tests don't find a clear cause, and you have persistent loin pain with blood in your urine, your doctor may consider loin pain haematuria syndrome. This sometimes involves further tests, such as a kidney biopsy or an angiogram, which looks at the blood vessels in the kidney.

How is loin pain treated?

Treatment depends entirely on the cause:

• Kidney stones: Drinking plenty of fluids can help smaller stones pass naturally, alongside pain relief – larger stones may need a procedure, such as shockwave treatment to break up the stone, or a minimally invasive procedure to remove it
• Kidney infection: Usually treated with antibiotics
• Muscle or back-related pain: Usually eases with rest, pain relief, and gradually returning to normal activity, alongside stretching or physiotherapy
• More serious causes: Such as a tumour or aneurysm, are treated by a specialist team, with options that may include surgery.

Treating loin pain haematuria syndrome

There's no cure for LPHS, so treatment focuses on managing the pain:

• Painkillers: Usually starting with paracetamol, moving to stronger options such as codeine if needed, with careful monitoring
• Blood pressure medicines (ACE inhibitors or ARBs): Which may help by reducing pressure inside the kidney
• A nerve block injection: For pain that is severe and hasn't responded to other treatments
• Surgery: Such as moving the kidney to a new position (renal autotransplantation) or disconnecting some of its nerves, is rarely recommended – it's usually considered only as a last resort, since symptoms can return afterwards.

Although LPHS pain can be severe, it does not cause kidney damage or kidney failure, and symptoms may ease with time.

When should I see a doctor?

See a GP if you have loin pain that:

• is persistent, recurring, or severe
• doesn't have an obvious cause, such as a recent injury
• comes with blood in your urine.

Get urgent medical help if you have loin pain along with:

• a high temperature, chills, or feeling very unwell
• pain that is sudden, severe, and makes it hard to keep still
• nausea or vomiting
• difficulty or pain when passing urine.

If you're an older adult having a first episode of severe, sudden loin pain, it's important to get this checked promptly, as it can occasionally be linked to a serious problem with a major blood vessel.