Page 582 - Atlas of Small Animal CT and MRI

5.7

Spleen

Introduction Trauma

CT and MR imaging have not been widely used for CT has not been widely used for evaluation of the trau­
evaluation of patients with splenic disease because matic acute abdomen in veterinary medicine, largely
conventional radiography and ultrasonography are both because ultrasonography has historically been a more
excellent alternative imaging approaches. Many splenic accessible alternative imaging modality. In people, CT is
lesions are identified on thoracic or abdominal studies often used in trauma patients to identify fractures of the
acquired for other purposes. Some of these lesions may spleen and liver, which can lead to surgical hemoabdo­
be incidental findings, while others may represent a key men. Although CT has not been widely used for this
component of the animal’s primary disorder. Abdominal purpose in veterinary medicine, CT should be consid­
CT to evaluate the spleen may be appropriate for accu­ ered as a presurgical diagnostic step in trauma patients
rate cancer staging and in animals with acute abdominal with uncontrolled hemoabdomen when parenchymal
disease in which traumatic, vascular, or inflammatory organ fracture is suspected but cannot be verified using
disease of the spleen is suspected. CT for characteri­ other imaging approaches. Experimental splenic trauma
zation and diagnosis of diffuse splenic disease is less results in a discontinuous splenic capsule and local peri­
compelling since CT features can be nonspecific, and toneal effusion, with a nonenhancing focal splenic lesion
diagnosis can usually be made using ultrasound and (Figure 5.7.4). Intraparenchymal contrast collections
guided fine‐needle or tissue core biopsy. and extraparenchymal contrast leakage may also be
On unenhanced CT images, the spleen has a uniform seen. CT performed under sedation can provide rapid
2
density of approximately 50 HU. The splenic parenchyma assessment of traumatic injuries. 3
consists predominantly of reticular connective tissue and Splenic hematomas are periodically identified as com­
blood vessels (red pulp) and lymphoreticular nodules plex, heterogeneously contrast‐enhancing masses that
(white pulp). The open circulatory (venous sinus) archi­ distort the splenic capsule. These can occur as the result
tecture of the red pulp causes a nonuniform distribution of known trauma or can be apparently spontaneous.
of contrast medium in early arterial phase contrast‐ Splenic hematomas may be difficult or impossible to dis­
enhanced imaging of the spleen. The mottled appearance tinguish from splenic neoplasia since the constellation of
of the parenchyma becomes increasingly uniform as con­ imaging findings overlaps. Unfortunately, fine‐needle
trast concentration equilibrates within the venous sinuses aspiration biopsy and tissue core biopsy may be mislead­
during portal and delayed phases (Figure 5.7.1). ing because of the presence of concurrent hemorrhage in
The feline spleen is hypointense to liver on T1 images association with splenic neoplasia.
and hyperintense to liver on T2 images (Figure 5.7.2). Ectopic splenic tissue may be present as a result of
1
The canine spleen has similar MR imaging characteris­ congenital causes, trauma, or splenectomy. This tissue
tics (Figure 5.7.3). has the same imaging characteristics as normal spleen

Atlas of Small Animal CT and MRI, First Edition. Erik R. Wisner and Allison L. Zwingenberger.
© 2015 John Wiley & Sons, Inc. Published 2015 by John Wiley & Sons, Inc.
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