Back-Side Flank Pain: What to Know

The flank is the area between the ribs and hip on either side of the back. Pain that changes with movement, twisting, or pressing the area may be muscular. Kidney stones can cause intense, wave-like pain that may move toward the groin, sometimes with nausea or blood in the urine. A kidney infection may cause flank pain with fever, chills, vomiting, or painful and frequent urination. A urinary tract infection can cause urinary symptoms and may spread upward if untreated. Other causes include skin, nerve, or digestive problems.

Write down which side hurts, when it started, whether it is constant or cramping, and whether movement changes it. Notice fever, urine colour, burning, urgency, nausea, vomiting, or a rash. Drink normally unless a clinician has told you to restrict fluids; do not force large amounts when severe pain or vomiting is present. Seek medical advice before using leftover antibiotics. A clinician may examine your abdomen and back, test urine, and decide whether further testing is needed.

Get urgent medical help for flank pain with fever and chills, repeated vomiting, confusion, fainting, inability to pass urine, or severe pain that does not settle. Blood in the urine, pregnancy, a single functioning kidney, or known kidney disease lowers the threshold for prompt assessment. Emergency care is appropriate for sudden severe pain with weakness, collapse, or a rigid or very tender abdomen. Mild pain after a clear muscle strain still needs review if it persists or urinary symptoms develop.

Could this be muscular, a kidney stone, a kidney infection, or a urinary tract infection? Do I need a urine test or imaging? What pain relief is safe for my kidneys and other conditions? How much should I drink? Which changes mean I should seek urgent care?