Flank Pain with Uncertain Cause

The flank is the area between your upper belly (abdomen) and your back. Pain there is often caused by a problem with your kidneys. It might be a kidney infection or a kidney stone. Other causes of flank pain include spinal arthritis, a pinched nerve from a back injury, a rib injury, a bruise, a back muscle strain, inflammation, or spasm.

The cause of your flank pain is not certain. You may need other tests.

Home care

Follow these tips when caring for yourself at home:

  • You may use acetaminophen or ibuprofen to control pain, unless your healthcare provider prescribed another medicine. If you have chronic liver or kidney disease, talk with your provider before taking these medicines. Also talk with your provider first if you’ve ever had a stomach ulcer or digestive bleeding.

  • If the pain is coming from your muscles, you may get relief with ice or heat. During the first 2 days after the injury, put an ice pack on the painful area for 20 minutes every 2 to 4 hours. This will reduce swelling and pain. A hot shower, hot bath, or heating pad works well for a muscle spasm. You can start with ice, then switch to heat after 2 days. You might find that alternating ice and heat works well. Use the method that feels the best to you.

Follow-up care

Follow up with your healthcare provider if your symptoms don’t get better over the next few days.

When to seek medical advice

Call your healthcare provider right away if any of these happen:

  • Repeated vomiting

  • Fever of 100.4ºF (38ºC) or higher, or as directed by your healthcare provider

  • Chills

  • Flank pain that gets worse

  • Pain that spreads to the front of your belly (abdomen)

  • Dizziness, weakness, or fainting

  • Blood in your urine

  • Burning feeling when you urinate or the need to urinate often

  • Pain in one of your legs that gets worse

  • Numbness or weakness in a leg

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