What should you know about persistent left flank pain?

The flank is the area between the lower ribs and the hip, toward the side or back. Pain there may follow lifting, twisting, prolonged posture or a muscle strain, and often changes with movement or touch. Kidney-related pain can be deeper and may occur with burning urination, urinary frequency, blood in the urine, nausea or fever. A stone may cause severe waves of pain that travel toward the groin, while a kidney infection may cause a steady ache with fever or feeling unwell. These patterns overlap, so left-sided pain alone cannot identify its cause.

Record when the pain began, whether it is constant or wave-like, what makes it better or worse, and any urine, bowel, fever or skin changes. This information helps a clinician choose an examination and tests.

Arrange a routine appointment if pain persists, recurs or has no clear muscle-related trigger. Until assessed, avoid activities that clearly worsen it, maintain normal fluids unless a clinician has restricted them, and use only pain relief that is suitable for you. Do not ignore urinary symptoms or rely on leftover antibiotics. A clinician may check your abdomen, back and urine, then decide whether further testing is needed.

Seek urgent care for flank pain with fever, chills, vomiting, inability to pass urine, visible blood in urine, severe worsening pain, fainting or marked weakness. Get immediate help for pain after a serious injury, new abdominal rigidity, or pregnancy with significant pain or bleeding. Kidney infection and an obstructing stone can need prompt treatment.

Ask whether the pattern suggests a muscle, kidney or urinary cause, whether urine testing or imaging is appropriate, and which pain medicines are safe with your health history. Ask what changes should trigger urgent review while you wait.