What should you know about differential diagnosis for left flank pain?

Pain that comes in waves and travels towards the groin can occur with kidney stones. Flank discomfort with fever, chills, nausea, or painful urination can occur with a kidney infection. A urinary tract infection may cause burning, urgency, or lower abdominal discomfort, though flank pain can signal involvement higher in the urinary tract. A strained muscle often hurts more with movement or touch. Shingles can cause burning pain followed by a one-sided rash. These patterns overlap, so location alone cannot identify the cause.

Arrange medical assessment for new, persistent, or recurrent left flank pain, particularly with urinary changes. A clinician may examine your abdomen and back, check urine, and decide whether blood tests or imaging are appropriate. Note when the pain began, whether it moves, what worsens it, and any fever, vomiting, rash, or blood in urine. Drink normally unless a clinician has given different fluid advice.

Seek urgent help for severe or sudden pain, fever with flank pain, repeated vomiting, faintness, confusion, inability to pass urine, or visible blood in urine. Pregnancy, one functioning kidney, or significant kidney disease lowers the threshold for prompt assessment.

Ask whether the pain pattern suggests a kidney, urinary, muscular, or nerve cause, which tests are appropriate, and which changes should trigger urgent review.