Paraileostomy hernia: a clinical and radiological study. Forty-six patients who underwent colectomy with end ileostomy for ulcerative colitis (n = 33) or Crohn's disease (n = 13) have been reviewed for paraileostomy hernia (PIH) formation 1-16 years after surgery. PIH developed in 13 of these patients (28 per cent) and was not related to the original disease or excessive weight gain. Twenty-eight patients underwent limited computed tomography (CT) scanning of the stomal region. Eight of these had a clinically detectable PIH, which was demonstrated on CT. A further two patients had PIH demonstrated on CT which was not detected by clinical examination. The rate of PIH was similar where the stoma emerged lateral to the rectus abdominis muscle (six out of 16 patients, 37 per cent) to where the stoma emerged through the rectus (four out of 12 patients, 33 per cent). Recurrence following operative repair of PIH was common. PIH occurs more frequently than previously supposed. CT can detect PIH and may be useful in evaluating a patient with stoma-related symptoms for occult PIH formation. 