Flank pain radiating to the leg: what to know

Pain from the side of the back may spread downward when muscles, the lower spine, or nearby nerves are irritated. A kidney stone can cause severe, wave-like pain that moves toward the groin; urinary changes may occur with it. Kidney infection more often brings a steady flank ache with fever, chills, nausea, or burning when passing urine. A urinary tract infection can cause urinary discomfort and may need assessment if pain reaches the flank.

Notice whether movement, coughing, or a particular position changes the pain. Also record its start, side, intensity, and any numbness or weakness in the leg.

Rest from lifting and twisting while keeping gentle movement as tolerated. Sip fluids normally unless a clinician has told you to restrict them. A warm compress may ease muscle tightness; protect your skin from heat. Use only a pain medicine that is suitable for you and follow its label, especially if you have kidney disease, stomach ulcers, are pregnant, or take blood thinners.

Arrange a medical review if the pain persists, returns, or comes with urinary symptoms. A clinician may examine your back and abdomen, check strength and sensation, and test a urine sample.

Seek urgent help for new leg weakness, numbness around the inner thighs or genitals, or loss of bladder or bowel control. Get prompt assessment for fever with flank pain, repeated vomiting, blood in the urine, inability to pass urine, or pain that is sudden and severe. These features can signal a problem needing timely treatment.

Ask whether the pattern fits a kidney, back, or nerve problem; which examination or urine tests are useful; and which pain medicines are safe with your health history. Ask what changes should prompt same-day care.