Learn more about what could be causing your flank pain

Musculoskeletal problems are the most common cause of back pain, but occasionally, it could be kidney pain. If you are experiencing pain that moves towards your side and groin area, or if you have a fever or urinary symptoms, then your kidneys could be the source.

Where Are Your Kidneys?

Your kidneys are located below your ribs, which is why a problem with these organs can often be felt in your upper back or flank, or side area.

The kidneys perform several important functions for your body, including:

  • Removing waste products, excess fluid, and drugs
  • Regulating salt, potassium, and acid content
  • Producing hormones that control red blood cell production, blood pressure, and more
  • Providing vitamin D for bone health

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Symptoms of Kidney Pain

Kidney pain, or flank pain, typically feels like a dull ache on one side of your upper back. The pain usually begins on your side or back. Attributes of kidney pain, including how severe it is, how often it occurs, and whether it’s isolated or radiating, vary. Those characteristics can help determine the cause of your pain.

Other associated symptoms of kidney pain include:

  • Fever
  • Nausea and vomiting
  • Blood in urine

Kidney and Flank Pain Causes

A number of different infections or injuries can cause kidney or flank pain. The most common causes include:

  • Kidney stones: Masses made up of crystals that form in your urine and build up in your kidneys that can cause severe pain, especially during urination. They can be passed manually or, in more serious cases, removed surgically.
  • Pyelonephritis — An infection caused by bacteria traveling up from the bladder or from the blood into the kidneys.
  • Polycystic kidney disease (PKD): A genetic disease in which normal kidney tissue is replaced by cysts, PKD can cause the kidney to stop working.
  • Kidney infarction: A rare condition in which kidney blood flow is disrupted. This can lead to acute kidney injury, decreased kidney function, kidney disease, and death.
  • Hemorrhage of the kidney: A bleed in the kidney, possible from multiple causes.
  • Kidney canceror tumor: Benign or cancerous masses in the kidney. Kidney cancer is found most often in older adults, with more men affected than women.
  • Renal vein thrombosis: A clot that develops in the vein that drains blood from the kidneys.

In addition to kidney problems, upper back and side pain also can be caused by physical injury, arthritis, or gallbladder or gastrointestinal diseases. It’s important to know when to seek care.

Kidney Pain vs. Back Pain

Many people experiencing back pain believe the pain is linked to their kidneys. But more often than not, that’s not the case.

Helbert Rondon, MD, MS, FACP, FASN, said most back pain is just that: back pain.

“(Most) back pain is not kidney-related – it’s musculoskeletal,” says Dr. Rondon, an associate professor of medicine in the University of Pittsburgh School of Medicine’s Renal-Electrolyte Division and director of UPMC’s Nephrology Fellowship Training Program. “There’s a problem with muscle or bones or something along those lines.”

Common causes of back pain include:

  • Overuse, strain, or injury
  • Aging
  • Herniated disc
  • Arthritis
  • Compression fracture
  • Illness
  • Spine disorders

Kidney pain is usually deeper and doesn’t get better or worse depending on whether you move, Dr. Rondon says. Dr. Rondon says other kidney-related symptoms can help you tell if you’re experiencing kidney pain, but even those aren’t 100 percent accurate.

“The best way to tell in the end is just to do an imaging of the kidneys, like a kidney ultrasound and a urine tests,” he says. “That helps to rule out all these other conditions.”

When Should I See My Doctor About Kidney Pain?

You should see your doctor immediately if you are experiencing the following symptoms:

If you suddenly experience severe kidney pain, with or without blood in your urine, you should seek emergency medical care. Sudden, severe pain can often be a sign of a blood clot or hemorrhage, and you should be evaluated immediately.

Dr. Rondon says if you notice symptoms like a change in your urine’s color, a fever, or if your pain doesn’t improve, seek a doctor. For emergency situations, you should go to the emergency department. For other situations, contact your primary care physician for a referral to a nephrologist or urologist.

For more information on kidney pain, talk to your doctor or visit the UPMC kidney disease webpage. Do you have flank pain? Check out our article on the 3 Common Causes of Flank Pain to learn more.

Editor's Note: This article was originally published on , and was last reviewed on .

American Kidney Fund. Kidney Pain. Anton J. Bueschen. Clinical Methods: The History, Physical, and Laboratory Examinations, 3rd Edition, Flank Pain. National Center for Biotechnology Information, U.S. National Library of Medicine. National Kidney Foundation. 3 Early Warning Signs of Kidney Disease. National Kidney Foundation. How Your Kidneys Work. Yun Kuy Oh, MD, PhD, Chul Woo Yang, MD, PhD, Yong-Lim Kim, MD, PhD, Shin-Wook Kang, MD, PhD, Cheol Whee Park, MD, PhD, Yon Su Kim, MD, PhD, Eun Young Lee, MD, PhD, Byong Geun Han MD, PhD, Sang Ho Lee, MD, PhD, Su-Hyun Kim, MD, PhD, Hajeong Lee, MD, Chun Soo Lim, MD, PhD. Clinical Characteristics and Outcomes of Renal Infarction. American Journal of Kidney Diseases.

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