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.
True or false? Chance of successful diagnosis with splenic FNA or needle biopsy is good with nodular hyperplasia and neoplasia?
True, both readily exfoliate. Not recommended to perform needle biopsy on cavitary lesions due to risk of hemorrhage.
Nondiagnostic FNA of the spleen is most common with which disorders?
Structural problems (trauma, torsion), vascular disorders (infarction, thrombosis), fibrosis, lymphoid atrophy, and amyloidosis.
What are diagnostic imaging techniques that can be used in evaluation of the spleen?
Radiology, ultrasound +/- contrast enhanced with microbubble injection, CT and MRI.
What peri-operative testing is recommended prior to splenectomy?
Coagulation profile, blood typing, serum chemistry, CBC, ECG, blood pressure.
When is splenorrhaphy appropriate?
If salvage of the spleen is preferred and capsular hemorrhage can be controlled by direct pressure. The capsule is apposed in an interrupted mattress pattern with 4-0 or 5-0 monofilament.
What conditions might be appropriate for treatment with partial splenectomy?
Trauma or abscess. Should never be used for neoplasia.
What techniques can be used for partial splenectomy?
TA stapling device, digital separation of the parenchyma, clamping and transection with suturing of the capsule (alternatively bipolar vessel sealing devices, CO2 lasers, ultrasonic cutting devices can be used).
What vessels are ligated in non-hilar splenectomy?
Short gastric arteries and veins, left gastroepiploic artery and veins, splenic artery and veins distal to the pancreatic vessels.
What size vessels can hemostatic clips be safely applied to?
3mm
Should gastropexy be performed at the same time as splenectomy?
Inconsistent conclusions about risk of GDV following splenectomy. Should base decision on patient specific risk factors.
Can a stapling device be used for splenectomy in instances of splenic torsion?
Not recommended due to the thickening of the perivascular tissues. Recommended either manual ligation in sections or use of bipolar vessel sealing device.
Why do you have to be careful when using an abdominal compression bandage in cases of splenic trauma?
It may worsen respiratory compromise, particularly in cases of concurrent thoracic or diaphragmatic injury.
What is the expected signalment of a patient with splenic torsion?
Large to giant breed deep chested dogs. Male dogs more commonly affected.
What is one proposed pathogenesis of splenic torsion?
Spontaneously resolving GDV may stretch the gastrosplenic ligaments leading to torsion
What are the two timeframes for presentation with splenic torsion?
Acute and chronic. Acute cases generally have evidence of hypovolemic or toxic shock. Chronic cases have less specific findings related to abdominal pain.
What imaging techniques can be used for diagnosis of splenic torsion?
Abdominal radiographs (C-shaped spleen +/- loss of detail, gas density), CT (failure of contrast enhancement), ultrasound (hilar perivenous hyperechoic triangle, Doppler ultrasound particularly useful).
Do acute or chronic splenic torsion carry a better prognosis?
Chronic as generally more cardiovascularly stable
What proportion of splenic lesions are neoplastic in dogs?
1/3 to 2/3
Which breeds of dogs are overrepresented for canine hemangiosarcoma?
German shepherds, Labrador Retrievers, Golden retrievers
What is the most common cause of spontaneous non traumatic hemoabdomen in dogs?
Malignant neoplasia
What are the most common splenic neoplasms in cats?
Mast cell tumours and lymphosarcoma
What hematologic changes are common in dogs with splenic neoplasia?
Anemia, mature neutrophilic leukocytosis, hyperbilirubinemia, elevated liver enzymes.
What percentage of dogs recorded ventricular arrhythmias following splenectomy for hemangiosarcoma?
25% (44% if causing non-traumatic hemoabdomen)
How is PCV predictive of splenic malignancy in dogs?
Every 10% decrease in PCV associated with a threefold increase in the odds of malignancy. The presence of peritoneal effusion also identified as a predictor of malignancy (lesion diameter measurement on ultrasound or CT were not useful).
What staging tests should be performed in cases of splenic neoplasia?
Abdominal ultrasound (most common sites of metastasis are abdominal organs), thoracic radiographs or CT (atrial lesions may represent metastasis or synchronous primary tumour, spread can also occur to the lungs or sternal and tracheobronchial LNs).
What are some factors that might influence survival following splenectomy for hemangiosarcoma?
Tumour stage, number of gross lesions, age at diagnosis (older dogs live longer)
What is the MST for dogs with splenic hemangiosarcoma undergoing surgery alone v. with chemotherapy?
MST 26 days with surgery alone (although for stage I and II tumours may be higher, 86 days).
With chemotherapy MST have ranged from 140 - 202 days.
What is the most common chemotherapeutic drug used in the treatment of hemangiosarcoma?
Doxyrubicin (least effective in dogs with macroscopic disease, i.e. stage III). Immunotherapy and use of NSAIDs have also been investigated with varied results.
What is the MST for dogs with nonangiogenic and nonlymphomatous sarcomas?
2.5 months
What is the MST for cats with splenic mast cell tumour?
2 - 34 months after splenectomy
What percentage of dogs with non-traumatic hemoabdomen had a ruptured splenic hematoma?
27%
What are some risk factors for perioperative death with splenectomy for mass lesions of the spleen?
Tachycardia, bicavitary effusion, massive transfusion, respiratory disease, thrombocytopenia/anemia, development of intraoperative arrhythmias
What are some potential post-operative complications following splenectomy?
Hemorrhage (most common), arrhythmias, GDV, increased risk of infection, decreased oxygen transport (cannot contract spleen for RBC reserve), systemic inflammatory derangement, vascular compromise (portal vein thrombus, pancreatic ischemia)
What are some proposed causes of arrhythmias with splenic disease?
Myocardial ischemia and hypoxia secondary to reduced cardiac return and hypovolemic shock from mass rupture and loss. Impaired venous return from mass effect. Derangements in acid-base, electrolyte imbalances, micro emboli, and myocardial depressant factors released from the pancreas.
What are 4 factors that increase the risk of arrhythmias following splenectomy in dogs?
Anemia, hypotension, ruptured splenic mass, leukocytosis.
What are 4 triggers for the treatment of ventricular arrhythmias in dogs?
Hemodynamic instability, multiform ECG complexes, rapid ventricular tachycardia, R-on-T complexes.
What are two drugs that can be used for the initial treatment of ventricular arrhythmias?
Lidocaine, procainamide.
If a patient is still having ventricular arrhythmias at the time of discharge post-splenectomy, what oral drugs can be considered?
Sotalol and mexiletine
Why is splenectomy thought to potentially increase the risk of GDV?
Stretching of the hepatogastric, gastroduodenal or gastrosplenic ligaments by an expanding splenic mass may predispose the stomach to twist.
According to Sirochman 2020 in Vet Surg, what 3 factors were associated with a increased risk of mortality after splenectomy?
Intra- or post-operative blood products, increased duration of anesthesia, intraoperative ventricular arrhythmias.
In a study by Story 2020 in Vet Surg what was the MST for small and large breed dogs treated for hemangiosarcoma, respectively?
Small: 116 days (207 with chemo)
Large: 97 days (139 with chemo)
No difference between groups.
What 8 clinical variables were used for creation of the T-STAT model for discrimination of benign from malignant splenic masses in dogs in the study by Burgess 2021 in JAVMA?
- Serum total protein
- Presence of >2 nRBCs/100WBCs
- Ultrasonically assessed splenic mass diameter
- Number of liver nodules
- Presence of multiple splenic masses or nodules
- Mesenteric, omental, or peritoneal nodules
- Moderate to marked splenic mass inhomogeneity
- Moderate to marked abdominal effusion
In a study by Cudney 2021 in JAVMA, in what percentage of cases with non-traumatic hemoabdomen were differences identified between gross and ultrasonographic findings?
54%. Sensitivity of ultrasound for detecting masses in the liver (37%) and mesentery (31%) were low.
In a study by McGaffey 2022 in JAVMA, what was the conversion rate for lap-assisted splenectomy? What size of neoplastic mass was this technique considered appropriate for?
6% conversion rate.
Masses up to 55.2 cm cubed/kg were able to be removed.
In a study by Millar 2022 in JAVMA, what percentage of cases with nontraumatic nonmalignant hemoabdomen died prematurely following splenectomy?
17% - suspected due to potentially undiagnosed hemangiosarcoma. Patients with low protein and elevated hemangiosarcoma prediction scores were at increased risk of premature death (MST 49 days).
In a study by Michael 2023 in JAVMA, what 3 factors were associated with an increased risk for ventricular arrhythmias in patients undergoing splenectomy for splenic masses?
Increasing body weight, hemoabdomen, increasing heart rate.
Ventricular arrhythmias were associated with increased risk of mortality, although overall mortality rate was only 7%.
In a study by Rossanese 2023 in JAVMA, what were the 4 most commonly diagnosed splenic neoplasms in cats undergoing splenectomy? What was the MST for cats with neoplastic lesions? What 2 factors were associated with poorer survival?
Mast cell tumour (42%), hemangiosarcoma (40%), lymphoma and histiocytic sarcoma (6% each) were the most commonly diagnosed neoplasms.
The MST was 136 days (and was significantly longer for cats with MCT [348 days] compared to hemangiosarcoma [94 days]).
The presence of metastasis and anemia were both associated with poorer survival.
Anemia, hemoabdomen and splenic mass on imaging were associated with a diagnosis of hemangiosarcoma.
In a study by Schick 2023 in JAVMA evaluating the accuracy of the 2/3 rule for non-traumatic hemoabdomen, what percentage of dogs evaluated had benign v. malignant neoplasms? What percentage of neoplasms were hemangiosarcoma?
Malignant neoplasia was diagnosed in 75% of dogs, benign in 25%.
87% of malignant neoplasia was hemangiosarcoma.
According to Clarke 2020 in JAVMA what percentage of liver biopsies taken during splenectomy for neoplastic disease had evidence of malignancy when the liver was grossly normal?
3% (compared to 29% when grossly abnormal). Dogs with a grossly abnormal liver were 16 times more likely of being diagnosed with liver neoplasia on biopsy.
