[Characteristic imaging features of carcinoid tumors of the small bowel in MR enteroclysis].

PURPOSE: To determine the value of MR enteroclysis (MRE) in the localization and characterization of primary carcinoid tumors of the small bowel and to describe typical imaging features.

MATERIAL AND

METHODS

Twenty patients with suspicion of primary small bowel carcinoid tumors (pCT) were recruited to undergo MRE following nasojejunal intubation and small bowel filling with 2.5 l of 0.5% methylcellulose solution under MR fluoroscopic guidance. MRE was performed on a 1.5 T MR scanner including T2w SSFSE, SSFP and contrast enhanced T1w GRE sequences with fat saturation. Fifteen patients, who subsequently had surgery for resection of their pCT, were retrospectively included in the study. All MRE were analyzed as for the presence, location, number, size, multiplicity and morphologic appearance of the pCT by two board certified radiologists in consensus. The conspicuity of the tumors was rated for each sequence type separately, according to a 4-point rating scale. Signal intensity measurements were performed in tumor and muscle. The presence of desmoplastic reaction, vascular involvement and lymph node metastases was also analyzed.

RESULTS

pCT were correctly identified and localized in 14/15 patients. Due to their hyperenhancement tumors was best detected on contrast-enhanced T1w fat saturated GRE sequences. SSFSE was clearly inferior with the tumors being either hyperintense or isointense to muscle. pCT appeared as nodular intraluminal masses in 40% of the cases, as focal wall thickening in 33.3% and in 20% with both. Mean size was 25 (7-46 mm) with a tendency to smaller size for ileal tumors. MRE failed to depict superficial micronodular peritoneal spread in one patient. Desmoplastic reaction was observed in 73.3% of the cases with mesenteric masses exhibiting lower signal than the pCT due to fibrotic changes.

CONCLUSION

MRE is a valuable method for the detection and localization of primary carcinoid tumors, provided that appropriate bowel distension is achieved. Various characteristic morphologic features could be identified which may contribute to characterize pCT and their loco-regional metastases.