What should you know about sudden left flank pain?

Flank pain is felt between the ribs and hip on the side of the back. A Kidney Stone can cause severe, wave-like pain that travels toward the groin, sometimes with nausea or blood in urine. A Kidney Infection may cause flank pain with fever, chills, feeling unwell, or painful and frequent urination. Muscle strain is more likely to change with movement or touch, but the pattern alone cannot confirm the cause. A Urinary Tract Infection can sometimes involve upper urinary symptoms and needs attention if fever develops.

Stop strenuous activity and find a comfortable position. Sip fluids normally unless you have been given a fluid restriction, and do not force large volumes to flush out a suspected stone. Record when the pain began, whether it moves, its relationship to movement or urination, and any fever, vomiting, or urine change. A clinician may examine your abdomen and back, test urine, and decide whether imaging is needed.

Seek urgent care for severe or worsening pain, fever with flank pain, repeated vomiting, faintness, confusion, inability to pass urine, or blood in the urine. Pregnancy, one functioning kidney, or significant medical illness lowers the threshold for prompt assessment. Pain after a substantial injury also needs urgent review.

Ask whether your symptoms fit a stone, infection, muscle problem, or another source, and whether urine testing or imaging is appropriate. Mention prior stones, urinary infections, recent exercise or injury, bowel symptoms, fever, and every medicine you take.