Occult small bowel melanoma metastases on whole body PET

Full text: A 72-year-old man with a history of malignant melanoma with pulmonary and chest wall metastases presented with acute gastrointestinal (GI) bleeding and occasional right iliac fossa pain. Upper GI endoscopy, a small bowel series, and colonoscopy failed to demonstrate a source of bleeding The patient continued to have further large rectal bleeds and became cardiovascularly unstable A 99mTc labelled red blood cell scan was performed, acquiring images for up to 4 hours, and again no active bleeding site was identified. A 18-fluorine fluoro-deoxy glucose (FDG) whole body Positron Emission Tomography (PET) scan was performed following routine protocol. This scan showed widespread and multiple foci of FDG avid disease. Uptake was seen in the caecum, ascending colon, sigmoid colon and rectum, and a number of discrete foci within the small bowel. Although the colonic uptake may have been physiological, malignant involvement could not be excluded. The other intra-abdominal foci were not consistent with physiological activity and were thought likely to represent metastatic deposits within the small bowel. These were assumed to be the cause of the GI bleeding, not able to be demonstrated by conventional imaging modalities. In this difficult case the FDG PET scan was able to demonstrate small bowel melanoma deposits and the probable cause for the GI bleeding, unable to be demonstrated by conventional imaging modalities. Copyright (2002) The Australian and New Zealand Society of Nuclear Medicine Inc