Chapter 83: Spleen Flashcards
Describe the splenic blood supply:
Three major branches come off the celiac artery:
Hepatic a.
Left Gastric a.
Splenic arteries:
The splenic artery runs along the left pancreas and gives of the pancreatic before running along the spleen. It gives off two short gastrics to the cranial spleen, these anastomose with the left gastric to create the left gastroepiploic artery.
Where are accessory spleens most likely to be found?
Gastrosplenic ligament - can also be found in thoracic cavity, inguinal canal, scrotum
Name 5 functions of the spleen?
Storage of RBCs and platelets
Maturation of RBCs
Filter microorganisms and antigens
Synthesis of IgG and cytokines of complement pathway
Removal of abnormal and senescent RBCS
What % of body weight is the spleen in dogs and cats?
0.2%
What are the broad functions of the red pulp and white pulp of the spleen?
- Red pulp: stores erythrocytes and traps antigens. Site of fetal erythropoiesis
- White pulp: Site of immune response
What is the main anatomical difference between the spleen in the dog and cat?
Dogs have a sinusoidal spleen - combo of direct arteriovenous endothelial connections and some areas where RBCs must traverse a region of red pulp between vessels prior to entering the venous side
Cats have a nonsinusoidal spleen - direct connections
What are three broad functions of the spleen?
- Hematopoiesis
- Reservoir function
- Immunologic function
How does the spleen take part in maturation of RBCs?
After production in the bone marrow, RBCs spend several days in the spleen maturing:
- Intracellular material is removed
- Cell membrane is shaped into a disc
- Cell size is reduced
What are some causes for the spleen to filter out/cull RBCs?
Damaged or senile RBCs:
- Inelastic cells (spherocytes, acanthocytes)
- RBCs covered with immunoglobulin or intracellular bacteria
How much of a dogs RBC mass and platelet mass can the spleen store?
10-20% RBC mass
30% platelet mass
What are the three pools of blood travelling through the spleen?
Rapid pool: 90% of the blood entering the spleen, takes less than 30 seconds to rejoin systemic circulation
Intermediate pool: 9% circulating blood, 8 minutes to rejoin systemic circulation
Slow pool: 1% of circulating blood, takes 1 hour
Splenic contraction moves what % of stored erythrocytes into the rapid pool?
How much does splenic volume decrease?
98%
Decrease to 25-50% of normal
What immune cells and what immunoglobulin is the spleen the largest producer of?
B-cells
T-cells
IgM
What is the main method by which the spleen filters microorganisms from the blood?
Phagocytosis
What are (4) causes of generalized splenomegaly?
- Splenitis/inflammation (sepsis, chronic infections, bacteremia)
- Immune reaction or cellular hyperplasia (IMHA, ITP/EMH)
- Congestion (CHF, vascular outflow obstruction, GDV, portal hypertension, capsule relaxation from drugs)
- Infiltration (neoplasia, amyloidosis)
What are (10) causes of focal/localized splenomegaly?
Nodular hyperplasia
Pseudotumor (benign proliferation of plasma cells, lymphocytes and histiocytes)
Hemangioma
Hamartoma
Abscess
Cysts (in humans only)
Segmental infarction
Siderotic and siderocalcific plaques
Neoplasia
Which is better for splenic nodules on ultrasound, hyperechoic or hypoechoic?
Hypoechoic
Multiple nodules are also more suspicious
Types of splenic sampling?
- Tru-cut (not if cavitary)
- Direct surgical
- Laparoscopic
- Transgastric endoscopic sampling
When should you reassess for hemorrhage after splenic sampling?
15-20 min post
What is the PALS in the spleen?
Periarteriolar lymphoid sheath (T-cells here)
What % of dogs with splenic hemangiosarcoma have a right atrial mass?
8.1%
What percent of dogs with a right atrial hemangiosarcoma have a splenic mass?
30%
What ligament tethers the head of the spleen to the greater curvature of the stomach?
The gastroslpenic ligament
What is the venous drainage of the spleen?
Splenic vein to gastrosplenic vein to portal vein
