Intrapancreatic accessory spleen
Images consist of an axial contrast-enhanced CT, axial T2-weighted, axial gradient
echo, axial T1 precontrast, axial T1 with fat saturation during arterial phase
of contrast administration, and an axial T1 with fat saturation after a 15-minute
An ovoid-enhancing lesion is present within the pancreatic tail. Relative to
pancreatic parenchyma, the lesion is hyperintense on T2-weighted images,
hypointense on T1-weighted images, hypointense on gradient echo images, and
enhances on arterial phase and delayed images. The lesion follows splenic
attenuation on CT and splenic signal intensity on all MRI sequences.
Accessory spleens are found in at least 10% of the population with approximately
15% of these occurring within or near the pancreatic tail. These lesions are
incidental findings with no clinical significance. However, these lesions have
been mistaken for enhancing neuroendocrine tumors with resultant unnecessary
Intrapancreatic accessory spleens are most commonly discovered
incidentally during CT examinations for other causes. On CT, the lesion will be
round or ovoid, enhanced, and follows the attenuation of splenic parenchyma on
all phases of contrast material administration. A definitive diagnosis cannot
be made by CT, but should be mentioned as a diagnostic consideration if the
morphology and attenuation are appropriate. The diagnosis is ultimately made by
MRI or nuclear scintigraphy using technetium-99m-labeled sulfur
colloid or 99m Tc-labeled heat-damaged RBCs. While nuclear
scintigraphy may make the diagnosis, it lacks the anatomic resolution of MRI
and could result in a misdiagnosis. On MRI, accessory spleens will follow the
signal intensity of splenic parenchyma on all imaging sequences including all
phases of contrast material administration. It is important to compare the
signal intensity of pancreatic lesions to spleen as the signal intensity of the
lesion relative to pancreatic parenchyma is worrisome for a neuroendocrine
tumor — hyperintense on T2WI, hypointense on T1WI, hypointense on gradient echo
sequences, and enhancing on arterial phase images.
Familiarity with the diagnosis of an intrapancreatic accessory spleen is
crucial to avoiding unnecessary invasive procedures and the associated
- Kim SH, Lee JM, Choi BH, et al. Intrapancreatic accessory spleen: Findings on MR imaging, CT, US, and scintigraphy, and the pathologic analysis. Korean J Radiol. 2008;9:162-174.
- Harris GN, Kase DJ, Bradnock H, Mckinley MJ. Accessory spleen causing a mass in the tail of the pancreas: MR imaging findings. AJR Am J Roentgenol. 1994;163:1120–1121.
- Boraschi P, Donati F, Volpi A, Campori G. Intrapancreatic accessory spleen: Diagnosis with RES-Specific contrast-enhanced MRI. AJR Am J Roentgenol. 2005;184:1712-1713.