What causes flank pain?

The flank is the area between the lower ribs and the side of the hip, often toward the back. Pain that follows lifting, twisting, or a tender muscle may be musculoskeletal. Severe pain that comes in waves and travels toward the groin can occur with Kidney Stones. A Kidney Infection may cause one-sided flank discomfort with fever, chills, nausea, or urinary symptoms. A lower Urinary Tract Infection usually causes burning or frequent urination, but symptoms can move upward if infection spreads.

Note whether the pain is sudden or gradual, constant or wave-like, and whether movement changes it. Drink normally unless a clinician has advised fluid restriction, and avoid strenuous activity until the cause is clearer. Do not ignore blood in the urine, painful urination, fever, or vomiting. A clinician may need an examination and urine testing, with further assessment depending on the pattern.

Seek urgent help for severe or rapidly worsening pain, fever with shaking chills, repeated vomiting, fainting, confusion, blood in the urine, or difficulty passing urine. Prompt assessment is also needed if pain occurs during pregnancy, follows a significant injury, or is accompanied by marked weakness.

Describe the exact side and location, onset, severity, movement pattern, and any spread toward the abdomen or groin. Mention urinary changes, fever, nausea, injury, exercise, pregnancy, previous stones, and medicines. Ask whether urine testing or imaging is appropriate.