Flank Pain

Flank pain, or side pain, is pain emanating from just one side of the abdomen and limited to the area between the ribs and the pelvic bone. While the most common causes are kidney problems (such as infection, kidney stones, blood clots, abscess, or tumor), there are a number of other organs nearby—including the gallbladder, appendix, and spine—and it can take a bit of detective work to determine the root cause of the pain.

Flank pain can be accompanied by a variety of symptoms, can come on suddenly (acute) or intensify slowly over weeks or months (chronic). Acute flank pain is more often due to an obstruction (such as stones, clots or cysts), while chronic flank pain may signal kidney or renal pelvis disease.

Reasons for Flank Pain

Flank pain is often urological in nature and come with a variety of associated symptoms. They include:

  • Ureteral obstruction and dilation: A blockage can occur anywhere along the urinary tract and can cause the tubes (ureters) that carry urine from the kidneys to the bladder to swell when urine gets trapped. Ureteral blockages are typically due to stones, but can also be caused other factors, including blood clots, cysts, tumors, congenital defects, and inflammation or infection.
    • Associated symptoms include blood in semen (hematospermia), bloody or dark urine (hematuria), difficulty urinating, frequent urges to urinate, incontinence, pelvic pain, abdominal swelling, fever, nausea, and vomiting.
  • Kidney disease: Some of the kidney disorders that cause flank pain are polycystic kidney disease and Berger's disease (which occurs when protein is retained in the kidney and disrupts tits function).
    • Associated symptoms include headaches, high blood pressure, discolored or bloody urine, and swelling of the hands and feet.
  • Stones: When urine is too concentrated, hard mineral deposits can form anywhere along the urinary tract and cause mild to severe pain.
    • Symptoms include lower abdomen and groin pain; painful urination; discolored, cloudy or foul-smelling urine; vomiting; frequent urge to urinate; fever; infection; and chills.
  • Kidney abscesses: A puss-filled mass can form within a hollow spot in the kidney during a result of a bacterial infection.
    • Symptoms include fever, abdominal pain, chills, and painful urination.
  • Urinary tract infections: UTIs typically occur when bacteria (such as E. coli) enter the urinary system through the urethra (the tube that transports urine out of the body) and travel as far as the kidneys.
    • Associated symptoms include painful or frequent urination, fever, genital discharge, nausea, vomiting, cloudy or bloody urine, and abdominal swelling or pressure.

Other, non-urological conditions that can cause flank pain include:

  • Shingles, which cause pain with a rash on one side
  • Spinal fracture
  • Back problems, such as disc disease
  • Gallbladder disease
  • Abdominal hemorrhage
  • Gastrointestinal disease
  • Muscle spasm
  • Liver disease
  • Arthritis or infection of the spine
  • Appendicitis

Diagnosing Flank Pain

When looking for the underlying cause of flank pain, a physician will perform a physical exam and ask about the patient's medical history and symptoms. Based on that information, the following tests may be done:

  • CT scan to image the abdomen to and look for tumors, infections, injuries, or kidney stones. It will also reveal an inflamed appendix
  • Blood tests to check kidney and liver function
  • Intravenous pyelogram to examine bladder, kidney, and ureter function, as well look for as any stomach injuries, infections, tumors, or kidney stones
  • Abdominal ultrasound to image abdominal organs, including the kidneys, gallbladder, liver, pancreas, and spleen and look for hernias, tumors, cancers, kidney and gallbladder stones, liver diseases, or internal injury
  • Urinalysis to do a physical, chemical, and microscopic exam of a patient's urine and determine whether he might have diabetes, kidney disease, urinary tract infections, blood in the urine, urinary tract stones, chronic renal failure, or signs of cancer
  • Urine culture to look for bacteria and other microbes
  • Voiding cystourethrogram to image the bladder while full and while emptying and diagnosebirth defects of the urethra or bladder, enlarged prostate, neurogenic bladder, and urinary reflux


Ozturk C, et al. Far lateral thoracic disc herniation presenting with flank pain. (2006) Journal of the Spine.

Flank Pain. (2009). UCLA Health Encyclopedia

Pyelonephritis: kidney infection. (2012). National Kidney and Urologic Diseases Information Clearinghouse. NIH Publication No. 12–4628

Flank Pain. (2013). A.D.A.M Encyclopedia.

Bueschen A. (1990). Clinical methods: The history, physical laboratory examinations. Causes of flank pain. Butterworth Publishers

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