Aubrey Bailey, PT, DPT, CHT  is a physical therapist with over 20 years of experience in a variety of healthcare settings.

Jennifer Pollard Ruiz, MD, is a board-certified family physician and has over 20 years of experience as a primary care physician in the public, private, and government sectors.

Flank pain affects one or both sides of the body between your abdomen and back. This symptom can be caused by issues with your muscles, internal organs, or your spine. Physical examination and imaging are often performed to determine the cause of flank pain.

This article will discuss the symptoms of flank pain and the possible causes, diagnosis, and treatment of these conditions.

Sudden-onset flank pain may be caused by a serious problem with the blood vessels. While uncommon, these issues are serious and require immediate medical care. Examples of vascular emergencies include aortic dissection and acute aortic aneurysm.

An aortic dissection occurs when the body's major artery, the aorta, is damaged. When the wall of the aorta tears, blood flows into the layers of the blood vessel walls. This can lead to an aortic rupture or a lack of blood to the organs.

Symptoms of an aortic dissection may include:

An aortic dissection is caused by a tear in the lining of the aorta. This can lead to an abnormal widening of the aorta, known as an aortic aneurysm.

An aortic dissection and aneurysm are medical emergencies and require immediate evaluation and treatment. Your healthcare provider will start with a physical exam and listen to your heart with a stethoscope.

An aortic dissection requires immediate treatment with either surgery or medications, depending on where the tear is. An aortic aneurysm is also treated with surgery or medications.

Flank pain can be caused by injury or spasms in the muscles. Flank muscles include the internal and external oblique abdominal muscles that help to rotate and flex your spine forward and side to side, as well as lumbar (low back) muscles that help you stand up from a bent-over position.

Muscle strains can develop over time from repetitive movements. This causes micro-tearing of the muscle fibers. Sudden movements that strain your muscles can also lead to immediate symptoms of muscle strain.

With severe muscle injury, you might also have swelling or bruising in the affected area.

Oblique abdominal muscle injuries are common in athletes who participate in explosive movements with one side of the body, such as throwing. Lumbar strains typically occur with pushing, pulling, or sudden twisting movements. Damage to these muscles can also be caused by trauma, such as a fall.

Muscle strains are often diagnosed based on the history of your symptoms and a physical exam by your healthcare provider. Additional tests are not usually needed to make this diagnosis.

Muscle strains often improve with rest from aggravating activities and home remedies. These can include:

Medications can also help relieve symptoms, such as:

Conditions that affect the spine can also cause flank pain. These can include lumbar arthritis, spinal stenosis, and disc degeneration. In some cases, these conditions can compress nerves in the lumbar spine that supply your legs.

In addition to flank pain, other symptoms of spine conditions can include:

Many lumbar spine conditions that lead to flank and lower back pain are caused by "wear and tear" on the body as a person ages. Bone spurs can develop between the vertebrae in the spine, and discs (cushions between the vertebrae) become thinner.

Lumbar disc degeneration often causes symptoms around the age of 40 and is particularly common in people who have jobs that require repetitive movements, such as office workers, machine operators, and carpenters.

Diagnosis of spine conditions begins with a thorough history of your symptoms and a physical exam by your healthcare provider. Additional tests, such as X-rays, computed tomography (CT scans), and magnetic resonance imaging (MRIs) are often performed to determine the exact cause of your symptoms.

Home remedies and OTC medications are used to help relieve symptoms of spine conditions. Sometimes, steroid anti-inflammatory medications are injected into the affected area.

When conservative treatment is not effective, surgery may be recommended to treat spine conditions.

Seek urgent medical attention if your flank pain is accompanied by these symptoms:

Flank pain is often a symptom of conditions that affect the urinary system, including kidney stones and infections.

Flank pain is a primary symptom of kidney stones and urinary infections.

Kidney stones are hard deposits that can develop in the kidneys. These stones can leave the kidney and travel through the ureter to your bladder, and out of your body. Flank pain often occurs when a kidney stone enters the ureter. This pain is sudden and severe.

Flank pain from infection can develop more gradually.

When a urinary tract infection spreads to the kidneys, the infection is more serious and is known as pyelonephritis. This condition can rapidly lead to sepsis. Possible symptoms include flank pain, nausea, vomiting, and fever.

Blood and urine tests are used to help diagnose urinary issues. If you have kidney stones, blood tests can help determine the specific minerals that make up your stones. Urine tests assess levels of white blood cells, which can indicate if an infection is present.

Your healthcare provider may also recommend an ultrasound if kidney stones are suspected. Imaging such as X-rays and CT scans are also used to diagnose kidney stones.

Urinary infections are typically treated with antibiotic medications. Treatment of kidney stones depends on the size of the stone. Small stones often pass on their own without any additional treatment.

Larger kidney stones can require additional treatment. Interventions include:

Shingles (Herpes Zoster) is a viral condition that can cause flank pain.

The primary symptom of shingles is a painful, itchy rash on one side of the torso or face.

Other symptoms of shingles include:

Shingles is diagnosed through a physical exam by a healthcare provider. A skin swab might be sent to a lab to confirm your diagnosis.

There is no cure for shingles, but symptoms can resolve on their own without treatment. Sometimes, antiviral medications are used to help reduce the severity of symptoms.

Flank pain can be a symptom of conditions that affect your muscles, lumbar spine, or internal organs. Common causes of flank pain include muscle strain, lumbar spine arthritis, and kidney stones. These conditions are diagnosed through a physical exam, lab tests, and imaging.

Treatment for flank pain depends on the underlying cause. Sometimes flank pain can resolve with rest and home remedies, while other causes might require surgery.

Flank pain is a symptom that can indicate a wide variety of medical conditions. If you know what caused your flank pain, such as a muscle strain after lifting a heavy object, it might be appropriate to treat your symptoms at home.

However, some causes of flank pain are more serious and require medical treatment. When in doubt, see a healthcare provider (sooner than later) to determine the cause of your flank pain.

Flank pain may be caused by muscle strain, lumbar spine arthritis, kidney stones, or other causes.

You may have kidney stones if you suddenly develop severe flank pain. Other symptoms include fever, nausea, vomiting, and blood in your urine.

Kato K, Otoshi K ichi, Yabuki S, et al. Abdominal oblique muscle injury at its junction with the thoracolumbar fascia in a high school baseball player presenting with unilateral low back pain. Fukushima J Med Sci. 2021;67(1):49-52. doi:10.5387%2Ffms.2020-27

Liyew WA. Clinical presentations of lumbar disc degeneration and lumbosacral nerve lesions. Int J Rheumatol. 2020;2020:2919625. doi:10.1155%2F2020%2F2919625

Harvard Health Publishing. Back pain: what you can expect from steroid injections.

Johns Hopkins Medicine. Lumbar strain.

National Institute of Diabetes and Digestive and Kidney Diseases. Diagnosis of kidney stones.

Bueschen AJ. Flank pain. In: Walker HK, Hall WD, Hurst JW, eds. Clinical Methods: The History, Physical, and Laboratory Examinations. 3rd ed. Butterworths; 1990.

National Institute of Diabetes and Digestive and Kidney Diseases. Treatment for kidney stones.

Centers for Disease Control and Prevention. Shingles (Herpes Zoster) signs & symptoms.

By Aubrey Bailey, PT, DPT, CHT Aubrey Bailey is a physical therapist and professor of anatomy and physiology with over a decade of experience providing in-person and online education for medical personnel and the general public, specializing in the areas of orthopedic injury, neurologic diseases, developmental disorders, and healthy living. 

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