Spleen Flashcards
True or false? Rarely the left gastric and splenic arteries arise from a short common trunk?
True
What are the functions of red and white pulp in the spleen?
Red pulp: stores erythrocytes and traps antigens. Loose meshwork of endothelial cells containing lymphocytes, macrophages, and circulating blood cells.
White pulp: site of immune response (follicles of B-cells surrounded by T-cells)
What is the difference in the sinus structure of the spleen between dogs and cats?
Dogs: Sinusoidal (i.e. some RBCs must traverse a region of red pulp between vessels before entering the venous side).
Cats: Non-sinusoidal
Where are congenital accessory spleens most commonly found?
Gastrosplenic ligament
What are the primary functions of the spleen?
Filtering of microorganisms and antigenic particles from blood, synthesis of immunoglobulin and cytokines, maturation of newly formed erythrocytes, storage of RBCs and platelets, and removal of abnormal and senescent RBCs.
How much of a dogs RBC mass can be stored in the spleen?
10-20%, and 30% of platelet mass
What are the three pools of RBCs in the spleen?
Rapid pool: 90% of blood, 30 second transit
Intermediate pool: 9% of blood, 8 minute transit
Slow pool: 1% of blood, 1 hour transit
Splenic contraction can result in up to 98% of stored erythrocytes moving into the rapid pool
What are the primary causes of generalized splenomegaly?
Infectious splenitis, immune reaction or cellular hyperplasia, congestion, infiltration
What are the primary causes of a congested spleen?
Congestive heart failure, portal hypertension, vascular outflow obstruction, relaxation of the splenic capsule allowing blood to pool within sinusoids (often caused by barbiturates).
Why is the feline spleen less likely to have physiologic enlargement compared to the canine spleen?
Because it is non-sinusoidal
What are the most common infiltrative causes of generalized splenomegaly?
Myeloproliferative neoplasms, i.e. lymphoma, mastocytosis. Histiocytic sarcoma also described in Flat coated retrievers, rottweilers, Bernese mountain dogs and Golden retrievers. Rarely lysosomal storage diseases and splenic amyloidosis may cause generalized splenomegaly.
Metastatic disease of the spleen is uncommon.
What are some potential causes of localized splenomegaly?
Hematoma, hemartoma, hemangioma, siderotic or siderocalcific plaques, abscess, nodular hyperplasia, segmental infarction, neoplasia.
What are some common conditions concurrent with splenic infarction?
Hypercoaguability, splenomegaly, cardiac disease, neoplasia, liver or renal disease, corticosteroids, sepsis, splenic hematoma, vasculitis.
Due to concurrent comorbidities care should be taken when considering the need for splenectomy.
What are some imaging techniques that can be used to detect splenic infarction?
Contrast enhanced CT or MRI
Is nodular hyperplasia more common in dogs or cats?
Dogs - possibly due to the sinusoidal nature of the spleen in this species (less opportunity for venous pooling in cats).
What is the difference between a hamartoma and nodular hyperplasia?
Both involve normal cells of the spleen, but the harmartoma does not reproduce the normal architecture of the surrounding tissue
What are fibrohistiocytic splenic nodules?
These are a histologically distinct form of nodular hyperplasia seen in dogs. Most likely represents a variety of diseases ranging from lymphoid hyperplasia (good prognosis) to histiocytic lymphoma (poor prognosis). Additionally testing should be performed to more accurately delineate the disease in these instances.
What is the difference between siderotic and siderocalcific plaques?
Siderotic plaques: due to accumulation of hemosiderin from erythrophagocytosis. Typically secondary to hemorrhage.
Siderocalcific plaques: accumulation of hemosiderin, calcium and bilirubin. Considered a senile change.
True or false? Dogs with benign splenic masses had a significantly higher mean mass-to-splenic volume ratio and mean splenic weight as a percentage of body weight.
True
Is splenic neoplasia more commonly localized or generalized in dogs?
Localized (more commonly generalized in cats). Can be classified as hemic (lymphoid, mast cell, histiocytic, plasma cell), or nonhemic (hemangiosarcoma, other sarcomas).
What percentage of dogs presenting with splenic hemangiosarcoma had a concurrent right atrial mass?
9% (whereas 29% of dogs presenting with a right atrial mass had concurrent hemangiosarcoma).
Do target lesions (nodules with a hypoechoic rim and hyperechoic center) have a positive predictive value for malignancy on ultrasound?
Yes
What can be used to improve the ultrasonographic characterization of focal and multifocal lesions of canine and feline spleens?
Contrast enhanced (microbubble) ultrasonography.
What is the appearance of malignant splenic neoplasia on MRI?
Hyperintense in T2 and post-contrast. On contrast enhanced CT tended to have a lower density.