Computed tomography and magnetic resonance imaging features of intrapancreatic accessory spleen

Abstract

Intrapancreatic accessory spleen (IPAS) is rarely seen in clinical practice.Its imaging presentation was similar to that of the pancreatic solid tumor.Familiarity with the computed tomography (CT) and magnetic resonance imaging (MRI) features is helpful for the diagnosis and treatment of IPAS,and thus avoid unnecessary operations.From August 2007 to August 2012,5 patients with IPAS were admitted to the Affiliated Hospital of Ningbo University and 5 patients to the Changhai Hospital.All the 8 patients underwent CT scan.Seven patients received concomitant MRI examination [5 patients received diffusion weighted imaging (DWI)].The IPAS of 8 patients were located at the tail of pancreas (the shapes of 3 cases were round,4 were oval and 1 was triangular).The longest diameter was (2.3 ± 1.0) cm and the shortest diameter was (1.4 ± 0.6) cm.The results of CT plain scan showed that the density of the IPAS of the 8 patients was similar to that of the orthotopic spleen.The results of artery phase of the enhanced CT showed zebra patterns enhancement in 5 patients,and homogenous enhancement in 3 patients.The results of venous phase of the enhanced CT showed remarkable high signal intensity consistent with spleen,and the signal intensity decreased gradually in the delayed phase.The patterns of enhancement of the lesions were similar to those of orthotopic spleen in 8 patients,and the lesions of 7 patients had higher signal intensity than those of pancreatic parenchyma.The signals of 7 patients in T1 weighted images and T2 weighted images were similar to those of orthotopic spleen.On DWI images (b =600 s/mm2),IPAS showed remarkable high signal intensity,and the ADC600 value was (0.868 ± 0.046) mm2/s,which showed no significant difference compared with (0.870-± 0.045) mm2/s of the orthotopic spleen (t =0.522,P ＞ 0.05).Two patients were complicated with hepatic cirrhosis,and 1 of them was with concomitant primary liver cancer.Other accessory spleens around the orthotopic spleen were found in 2 patients.In conclusion,IPAS has similar characteristics to those of the spleen on both the precontrast and contrast-enhanced images of all imaging modalities.CT and MRI combined with DWI examination have great value in diagnosing IPAS. Key words: Accessory spleen, pancreas ; Tomography, computed; Magnetic resonance imaging; Diffusion-weighted imaging