Upper back flank pain

Muscle strain is more likely to vary with twisting, lifting or touch, particularly after unusual activity. Kidney stones can cause intense pain that comes in waves and may travel toward the groin, sometimes with nausea or blood in urine. A kidney infection may cause flank pain with fever, chills, feeling ill or painful frequent urination. A urinary tract infection can cause burning or urgency, though flank pain with fever needs prompt attention. The symptom pattern matters more than location alone.

Rest from lifting while keeping gentle movement if it does not worsen the pain. Drink normally unless a clinician has told you to restrict fluids, and note urine colour, frequency, burning, fever, nausea and whether the pain moves. Do not use leftover antibiotics. A clinician may need a urine test and examination to separate a muscle problem from urinary disease.

Arrange prompt care for flank pain with fever, chills, vomiting, painful urination, blood in urine or difficulty passing urine. Seek emergency help for unbearable or rapidly worsening pain, fainting, confusion, severe weakness or a single functioning kidney with new pain. Pain after major injury also needs urgent assessment.

Could this be muscular, a kidney stone, kidney infection or urinary tract infection? Do I need urine testing or imaging? What changes in fever, urine or pain should make me seek urgent help?