111Indium-labelled red-cell scintigraphy to detect intermittent gastrointestinal bleeding from synchronous small- and large-bowel adenocarcinomas.

A 70-year-old woman presented with symptoms of profound anaemia and evidence of intermittent gastrointestinal haemorrhage. Oesophagogastroduodenoscopy, colonoscopy, abdominal computerised tomography, sulphur colloid scintigraphy and selective mesenteric angiography were non-diagnostic. An indium-labelled red-cell scan was performed, which suggested bleeding from the ileum at 36 h. At laparotomy, a primary small-bowel adenocarcinoma was resected. Six weeks later, she was again anaemic. Repeat colonoscopy showed a synchronous primary colonic adenocarcinoma, which had been masked by intraluminal blood during the original indium scan. The lesion was impalpable, even after full mobilisation of the colon. A right hemicolectomy was performed. Indium has a longer half-life (67 h) than the more commonly used technetium isotope (18 h). This allows serial imaging for up to 5 days, which may increase diagnostic efficiency in intermittent gastrointestinal bleeding. Clinicians should be aware that persisting activity from intraluminal blood may mask synchronous lesions.