FDG avid small bowel lesions: Significance in an oncologic population

Objectives Many incidental colorectal lesions with focal FDG uptake discovered on F-18 FDG PET/CT performed for an unrelated reason are neoplastic, often malignant. There is paucity of data on the PET/CT findings of small bowel (SB) lesions. A large retrospective study of incidental focal FDG uptake in bowel reported a very low incidence of pathologic FDG uptake within the SB (1). In daily clinical practice, FDG uptake within SB is not infrequently encountered and often considered physiologic in the absence of a perceived anatomic abnormality on CT. The actual incidence of SB tumors detected with FDG PET/CT is unknown.

Methods We will present a retrospective analysis of the significance of focal FDG avid SB lesions identified in a series of 11 patients during oncologic PET/CT imaging. Our series includes malignant SB lesions confirmed with histopathology (endoscopic or surgical) and/or long-term clinical follow-up. Pathologies include primary SB adenocarcinomas, enteropathic lymphomas, GIST and small bowel metastases.

Results Of the 11 patients, three had primary adenocarcinoma of the duodenum/jejunum, two had jejunal metastases from lung cancer, three had enteropathic SB involvement with lymphoma, one had duodenal GIST, one had direct extension of a hepatic flexure colon cancer into the duodenum, one had ileal metastasis from previously resected jejunal adenocarcinoma and one had duodenal GIST. Interestingly, many of these lesions were not initially detected on preceding contrast enhanced CT (CECT). In the future we hope to conduct a prospective determination of the incidence and significance of focal small bowel FDG uptake in oncology patients referred for PET-CT imaging.

Conclusions Malignant primary or metastatic lesions of the SB are rare and frequently missed on CECT, Focal areas of FDG avidity on PET/CT should trigger a careful anatomic evaluation of the corresponding SB segment. If abnormal, the likelihood of a malignant SB lesion is high in an oncologic population. Their early detection may influence patient outcome