Left flank pain that comes and goes

Pain in waves, especially when it becomes intense and eases again, can occur with a kidney stone. Kidney infection more often causes a continuing ache with fever, chills, nausea, or marked illness. A urinary tract infection may cause episodes linked with urination, urgency, or frequency. Muscle pain may flare after exercise, lifting, coughing, or a particular posture and settle with rest. Digestive discomfort can relate to meals or bowel movements. None of these patterns is enough to diagnose the cause without considering the whole history.

Keep a simple record of the time, duration, intensity, activity, meals, urination, bowel movements, and other symptoms around each episode. Avoid the activity that reliably provokes pain, maintain ordinary hydration unless restricted, and use suitable pain medicine according to directions. Book an assessment if episodes keep returning or interfere with daily life; urine testing may be useful.

Seek urgent help if an episode is severe or prolonged, or if pain occurs with fever, repeated vomiting, faintness, confusion, blood in urine, inability to urinate, new weakness or numbness, or a significant injury. A short pain-free interval does not remove these warning signs.

Ask what the episode pattern suggests, whether urine or other tests are appropriate, and how to manage another attack safely. Bring your symptom record and mention medicines, previous stones, urinary changes, and recent physical exertion.