Flanks: What Patients Need to Know

The flanks are the areas on the left and right sides of the torso, extending from below the ribs to above the hips. Discomfort in a flank can come from muscles, the urinary system, the digestive tract, skin, or other nearby structures, so its pattern and accompanying symptoms matter.

What Are the Flanks?

The flanks are the broad areas on the sides of the body between the lower ribs and the top of the hips. They include portions of the lower back and side of the abdomen. A person has a right flank and a left flank, and either area may be discussed during a medical examination or when describing symptoms.

Several body structures lie beneath or near the flanks. These include muscles of the back and abdominal wall, ribs, nerves, parts of the spine, the kidneys and ureters, sections of the large intestine, and skin. In some people, pain felt in the flanks can also be referred from organs or tissues elsewhere. For this reason, the location of pain alone cannot confirm its cause.

Healthcare professionals may gently press or tap the flank area during an examination. Tenderness near the kidney region can provide useful information, but it is not by itself a diagnosis. The timing, character, triggers, and associated symptoms are all important when assessing flank discomfort.

How Flank Pain May Feel

Flank pain can vary widely. It may feel like an ache, soreness, pressure, cramping, burning, stabbing pain, or a sharp pain that comes in waves. It may remain in one spot or spread toward the lower abdomen, groin, back, buttock, or upper abdomen. Pain that changes with twisting, bending, coughing, or lifting may be more likely to involve muscles, joints, or the spine.

Pain related to the urinary tract can sometimes occur with burning during urination, a frequent urge to urinate, cloudy or unusually strong-smelling urine, or blood in the urine. A kidney stone may cause intense, wave-like pain that can travel from the flank toward the groin, sometimes with nausea or vomiting. However, symptoms differ among individuals, and similar symptoms can have more than one cause.

It is helpful to note whether the discomfort is on one side or both, whether it began suddenly or gradually, and whether it is constant or intermittent. A person should also consider recent activity, injury, illness, new medicines, changes in bowel habits, and menstrual or pregnancy-related symptoms when relevant. These details can help a clinician decide what evaluation is appropriate.

Common Causes of Flank Discomfort

Muscle strain is a frequent explanation for flank discomfort. It may develop after lifting, repetitive movements, a new exercise routine, prolonged sitting, a fall, or awkward sleeping positions. Strain-related pain often improves with rest and may be reproduced by certain movements or by pressing on the affected muscles. Rib, spinal joint, or nerve-related problems can also create pain along the side of the trunk.

Kidney and urinary conditions are another important group of possible causes. Kidney stones, urinary tract infections that involve the kidneys, obstruction of urine flow, and less commonly other kidney conditions can lead to flank pain. Urinary symptoms, fever, chills, nausea, or changes in urine increase the need for timely medical review. Not every urinary tract infection causes flank pain, and not all flank pain is caused by a kidney problem.

Digestive conditions may also be felt in the side of the abdomen or flank. Constipation, gas, inflammation of the bowel, and some gallbladder or pancreatic conditions can cause pain that is felt beyond the abdomen. Shingles can cause burning, tingling, or tenderness on one side before a rash appears. In women, some gynecological conditions may cause lower abdominal or side pain; in men, pain from the testicle can occasionally radiate upward. A clinician can help distinguish among these possibilities.

Risk Factors and Clues That Can Help

Recent physical exertion, contact sports, heavy lifting, poor workstation posture, and prior back problems can increase the chance that flank pain is musculoskeletal. Dehydration, high heat exposure, certain dietary patterns, a personal or family history of kidney stones, and some medical conditions may increase the likelihood of stones in susceptible people. Previous urinary infections, urinary tract abnormalities, pregnancy, and use of a urinary catheter can raise the risk of more complicated urinary infections.

The pattern of symptoms can offer useful clues without replacing medical assessment. Pain after movement or exercise, especially if there is local muscle tenderness, may point toward a mechanical cause. Fever or chills alongside flank pain may suggest infection. Sudden, severe, one-sided pain that comes and goes in waves can occur with a stone. A new skin rash or sensitive band of skin may indicate shingles, especially when pain is burning or tingling.

Age, pregnancy status, existing kidney disease, diabetes, immune system suppression, and use of blood-thinning medication can affect how urgently flank symptoms should be assessed. Older adults and people with complex health conditions may have less typical symptoms. It is safest not to rely only on online symptom comparisons when pain is significant, persistent, or accompanied by other concerning changes.

How Doctors Evaluate Flank Pain

A medical assessment usually begins with questions about the exact location, onset, severity, duration, and nature of the pain. The clinician may ask about recent injuries, activity, hydration, urinary and bowel symptoms, fever, medications, previous stones or infections, and relevant reproductive health history. They will also ask whether pain spreads to another part of the body and what makes it better or worse.

During the physical examination, the clinician may check the abdomen, back, hips, spine, skin, and flank area. They may assess for tenderness, muscle spasm, signs of dehydration, and fever. Depending on symptoms, a urine test may look for blood, infection markers, or other abnormalities. Blood tests can assess kidney function, signs of inflammation, or other possible concerns.

Imaging is not needed for every person with mild flank pain. However, ultrasound, computed tomography, X-ray, or other imaging may be considered when a stone, obstruction, injury, abdominal condition, or another structural cause is suspected. The choice of test depends on the person’s symptoms, examination findings, health history, and need to limit unnecessary radiation exposure.

Treatment and Self-Care Depend on the Cause

Treatment for flanks or flank pain is directed at the underlying cause. Mild muscle-related discomfort may improve with relative rest, gradual return to normal movement, heat or cold packs as tolerated, and attention to posture and lifting technique. A clinician or pharmacist can advise whether an over-the-counter pain reliever is suitable, particularly for people with kidney disease, stomach ulcers, heart conditions, pregnancy, or regular medications.

Urinary infections may need prescription antibiotics, while kidney stone management depends on the stone’s size, location, symptoms, and whether urine flow is blocked. Some stones pass without procedures, while others require specialist treatment. Severe pain, infection with a blockage, reduced kidney function, or inability to keep fluids down needs prompt medical care rather than home management.

People should avoid trying to treat persistent flank pain solely with supplements, restrictive diets, or repeated pain medication without knowing the cause. Drinking adequate fluids is generally sensible for overall health unless a clinician has advised fluid restriction. For recurring kidney stones, individualized prevention plans may include urine testing, dietary guidance, or medication based on the type of stone.

Acibadem International’s multidisciplinary specialists and JCI-accredited hospitals evaluate and treat kidney, urinary, musculoskeletal, and abdominal causes of flank pain for international patients when specialist assessment is needed.

When to Seek Medical Care

Urgent medical assessment is appropriate for severe or rapidly worsening flank pain, particularly if it begins suddenly or prevents normal activity. A person should also seek urgent care if flank pain occurs with fever, chills, repeated vomiting, confusion, fainting, difficulty breathing, significant abdominal swelling, or an inability to pass urine. These symptoms can sometimes indicate an infection, obstruction, injury, or another problem that needs prompt treatment.

Prompt evaluation is also important for visible blood in the urine, pain after a significant injury, pain during pregnancy, new pain in a person with one kidney or known kidney disease, and symptoms in someone with a weakened immune system. Pain with testicular swelling or severe pelvic symptoms should not be delayed, as these concerns require timely examination.

A routine appointment is reasonable for mild but persistent flank discomfort, repeated episodes, unexplained symptoms, or pain that does not improve after several days of avoiding strain. Keeping a brief record of the pain, urinary changes, fever, activity, fluid intake, and medicines can make the consultation more useful. Early assessment can clarify the cause and help prevent unnecessary discomfort or complications.

Frequently asked questions

Where are the flanks located on the body?

The flanks are on the right and left sides of the torso, between the lower ribs and the upper hips. They include areas beside the lower back and the side of the abdomen. The kidneys sit deeper within the upper part of the flank region, but many other tissues are also located there.

Is flank pain always caused by the kidneys?

No. Flank pain can come from muscles, ribs, the spine, nerves, skin, bowel, urinary tract, or other nearby structures. Kidney-related pain is more likely when urinary symptoms, fever, nausea, or pain radiating toward the groin are also present, but medical evaluation may be needed to determine the cause.

What does kidney pain usually feel like?

Kidney pain is often felt deeper in the flank, under the lower ribs and toward the back. It may be a persistent ache with infection or sharp, severe pain that comes in waves with a stone. Symptoms such as fever, burning urination, blood in the urine, nausea, or vomiting should be discussed with a healthcare professional.

Can dehydration cause flank pain?

Dehydration does not always directly cause flank pain, but it can contribute to concentrated urine and may increase stone risk in people who are prone to kidney stones. It can also occur alongside illness that causes fever, vomiting, or diarrhea. Persistent pain should not be assumed to be dehydration without assessment.

Can a muscle strain cause pain in the flanks?

Yes. Strain of the back, abdominal, or side muscles can cause soreness or sharp pain in a flank, especially after lifting, exercise, twisting, coughing, or prolonged awkward posture. Pain that is clearly worse with movement or pressing on the area may support a musculoskeletal cause, but does not rule out other conditions.

Should a person exercise with flank pain?

It is usually sensible to avoid activities that worsen pain until the cause is clearer. Gentle movement may be appropriate for mild muscle soreness, but strenuous exercise, heavy lifting, and contact sports should be postponed if pain is significant or unexplained. A clinician can advise on a safe return to activity after injury or illness.

References

• National Institute of Diabetes and Digestive and Kidney Diseases
• National Kidney Foundation
• Mayo Clinic
• Merck Manual Consumer Version
• U.S. National Library of Medicine

This article is for general information only and is not a substitute for professional medical advice. Please consult a qualified doctor about your individual situation.