Flank pain on one side

Flank pain is felt at the side of the back between the ribs and hip. Kidney stones can cause sudden, intense waves of pain on one side that may move toward the groin. Kidney infection commonly presents with flank pain and may occur with fever, chills, nausea or urinary changes. A urinary tract infection may cause painful urination, urgency or frequent trips to the toilet. Muscles, joints, nerves and bowel problems can also produce one-sided discomfort. The side alone cannot identify the cause; movement, onset and associated symptoms provide more useful clues.

Describe the pain precisely: front or back, steady or wave-like, and affected by movement, food or urination. Pause strenuous activity and keep normally hydrated unless fluid restriction has been prescribed. Use medicines only after checking that they suit your health history and other treatments. Arrange a clinical review when the pain persists, recurs or affects sleep. A urine check and physical examination can help separate urinary causes from problems in the muscles or abdomen.

Seek urgent care if pain is severe, rapidly worsening or accompanied by repeated vomiting, faintness, confusion, blood in the urine, inability to pass urine, or a rigid abdomen. Fever or chills with flank pain need prompt assessment. Pregnancy, known kidney disease or a single functioning kidney also warrant early medical advice rather than prolonged self-monitoring.

What features make a urinary cause more likely? Should I have a urine test or scan? Which symptoms require emergency assessment? How long should I monitor this before review?