Right iliac fossa pain with a palpable mass

An appendix mass (phlegmon) or appendiceal abscess. The differential includes Crohn’s ileitis, caecal carcinoma in older patients, ileocaecal tuberculosis, a psoas abscess, and in women an ovarian or tubo-ovarian mass.

Contrast-enhanced CT of the abdomen and pelvis in adults: it distinguishes a phlegmon from a drainable abscess, defines size and location, and excludes an underlying tumour. Ultrasound is first-line in children and in pregnancy, with MRI as the radiation-free alternative.

No. A well-formed appendix mass without generalised peritonitis is treated non-operatively (the Ochsner–Sherren regimen in its modern form): intravenous fluids, broad-spectrum antibiotics, analgesia and serial observation of pulse, temperature and mass size. An abscess larger than about 3–4 cm is drained percutaneously. Failure to settle, spreading peritonitis or clinical deterioration mandates surgery.

It is selective rather than routine. Recurrence after successful conservative treatment is roughly 10–20%. Patients over 40 need interval colonoscopy or CT colonography because an appendiceal or caecal neoplasm underlies a minority of cases; interval appendicectomy is offered for recurrent symptoms or when malignancy cannot be excluded.

Alvarado and AIR scores combine migratory pain, anorexia, nausea, tenderness, rebound, fever and inflammatory markers. They are useful for stratifying risk and reducing negative appendicectomy rates, but they do not replace imaging in equivocal cases.