Right flank pain with diarrhoea: what to know

Diarrhoea can cause cramping and fluid loss, while repeated straining may make the abdominal or side muscles sore. Pain in the right flank can also overlap with discomfort from the bowel, urinary tract, kidney, or nearby muscles. A kidney infection commonly presents with flank pain together with fever, chills, nausea, or painful urination. Kidney stones can cause strong, wave-like pain that moves toward the groin, sometimes with nausea or blood in the urine. Diarrhoea alone does not identify the cause.

Notice whether the pain is constant or comes in waves, whether it changes with movement, and whether urine symptoms or fever are present. A clinician may need to examine your abdomen and back and check urine, hydration, or other findings.

Take frequent small sips of water or an oral rehydration drink, especially after loose stools. Eat light foods if you feel able, and avoid alcohol and foods that clearly worsen cramping. Rest and record the timing of pain, stools, temperature, urine output, and any new urinary symptoms. Do not take anti-diarrhoeal medicine if you have blood in the stool or a high temperature without first getting medical advice. A pharmacist or clinician can help you choose symptom relief that fits your health history.

Seek urgent medical care for severe or rapidly worsening pain, a rigid or very tender abdomen, fainting, confusion, repeated vomiting, inability to keep fluids down, very little urine, blood in the stool or urine, or fever with chills. Arrange prompt assessment if diarrhoea continues, the pain does not settle, or you have urinary burning or frequent urination. These features can point to dehydration, infection, or a stone and should not be assessed by symptom location alone.

Could the pain and diarrhoea have one cause, or might they be separate? Do I need urine or blood testing? Which fluids and medicines are suitable for me? What change should prompt same-day care?