Pain in both sides of the flank

The flanks are the areas between the upper abdomen and the back, below the ribs. Pain on both sides may follow muscle strain, prolonged posture or vigorous activity. Urinary causes include infection involving the kidneys, a urinary tract infection, or stones, although stones often cause intense pain that may move toward the groin. Burning urine, frequent urination, fever, chills, nausea or blood in the urine make a urinary cause more concerning. Pain can also come from the spine, ribs, skin or digestive organs.

Note whether the pain is aching, cramping or sharp, and whether movement, meals, urination or deep breathing changes it. Rest from strenuous activity, use comfortable support and drink normally unless a clinician has advised fluid restriction. Arrange a medical review if pain continues, returns, limits normal activity or occurs with urinary symptoms. A clinician may examine your abdomen and back and decide whether urine testing or imaging is useful.

Seek urgent care for severe or rapidly worsening pain, fever with chills, repeated vomiting, fainting, confusion, inability to pass urine, visible blood in urine, a rigid abdomen, or new weakness or numbness. Pregnancy, one functioning kidney, known kidney disease or recent injury lowers the threshold for prompt assessment. Do not wait for pain to settle if you feel seriously unwell.

Tell your doctor when the pain began, what affects it, and whether urinary, bowel, fever or skin symptoms accompany it. Ask whether you need urine tests, blood tests or imaging and which pain medicines fit your health history.