Flank pain can be a sign of a kidney problem. But, since many organs are in this area, other causes are possible. If you have flank pain and fever, chills, blood in the urine, or frequent or urgent urination, then a kidney problem is the likely cause. It could be a sign of kidney stones.

Flank pain may be caused by any of the following:

• Arthritis or infection of the spine
• Back problem, such as disk disease
• Gallbladder disease
• Gastrointestinal disease
• Kidney stone, infection, or abscess
• Liver disease
• Muscle spasm
• Shingles (pain with one-sided rash)
• Spinal fracture

The treatment depends on the cause.

Rest, physical therapy, exercise, and nonsteroidal anti-inflammatory drugs (NSAIDs) may be recommended if the pain is caused by muscle spasm or spinal arthritis. You will be taught how to do these exercises at home.

Antibiotics are used to treat most kidney infections. You will also receive fluids and pain medicine. You may need to stay in the hospital.

Contact your health care provider if you have any of the following:

• Flank pain along with a high fever, chills, nausea, or vomiting
• Blood (red or brown color) in the urine
• Unexplained flank pain that continues
• Difficulty eating or drinking fluid

The provider will examine you. You will be asked about your medical history and symptoms, including:

• Location of the pain
• When the pain began, if it's always there or comes and goes, if it's getting worse
• If your pain is related to activities or bending over
• What the pain feels like, such as dull and aching or sharp
• What other symptoms you have

The following tests may be done:

• Abdominal CT scan
• Blood tests to check kidney and liver function
• Ultrasound to look at your internal organs
• Chest or abdominal x-ray
• Kidney or abdominal ultrasound
• Lumbosacral spine x-ray
• Tests to check the kidneys and bladder, such as urinalysis and urine culture, or cystourethrogram

Pain - side; Side pain

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McQuaid KR. Approach to the patient with gastrointestinal disease. In: Goldman L, Cooney KA, eds. Goldman-Cecil Medicine. 27th ed. Philadelphia, PA: Elsevier; 2024:chap 118.

Millham FH. Acute abdominal pain. In: Feldman M, Friedman LS, Brandt LJ, eds. Sleisenger and Fordtran's Gastrointestinal and Liver Disease. 11th ed. Philadelphia, PA: Elsevier; 2021:chap 11.

Seller RH, Symons AB. Abdominal pain in adults. In: Seller RH, Symons AB, eds. Differential Diagnosis of Common Complaints. 7th ed. Philadelphia, PA: Elsevier; 2018:chap 1.

Updated by: C. Benjamin Ma, MD, Professor, Chief, Sports Medicine and Shoulder Service, UCSF Department of Orthopaedic Surgery, San Francisco, CA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.