Flank pain and swelling: what to know

Flank pain with swelling can have local, digestive or urinary causes, and new swelling should be assessed when it persists or worsens. A visible lump, one-sided fullness, fever, urine changes or severe pain deserves closer attention than temporary bloating.

A muscle or soft-tissue injury can cause tenderness and local swelling, especially after lifting, exercise or a blow. Bowel gas or constipation may cause fullness that changes after passing stool or wind. Kidney stones can cause flank pain, nausea and urinary blood, while kidney infection may cause flank pain with fever, chills or feeling unwell. A urinary tract infection can cause burning or frequency but does not explain every type of swelling. A clinician may inspect the area, feel the abdomen and arrange urine tests or imaging.

Note whether the swelling is visible, tender, firm, changing with position, or linked to meals or bowel movements. Avoid heavy lifting and protect a recently strained area. Do not press repeatedly on a painful lump. Maintain normal fluid intake unless advised otherwise, and arrange an appointment for unexplained swelling, recurring pain or any urinary symptoms.

Seek urgent medical attention for rapidly increasing swelling, severe pain, fever, repeated vomiting, faintness, a rigid abdomen, blood in urine, inability to pass urine, or swelling after significant injury. These signs can indicate infection, obstruction, bleeding or tissue damage.

Is the swelling in the skin, muscle, bowel area or deeper? Do I need urine testing or imaging? Which activities and medicines should I avoid while the cause is being assessed?