Ch 83 spleen Flashcards
anatomy
- dorsal extremity (head), tethered to the greater curvature of the stomach by the wide gastrosplenic ligament, is generally narrower
- The larger ventral extremity (tail) is quite mobile
- vascular supply arises from the celiac artery (hepatic, splenic, left gastric)
- splenic artery give rise to the pancreatic artery before hilus of the spleen
- continuation of the splenic artery is called the left gastroepiploic artery
- cranial half of the spleen is supplied by short gastric a
How much of the BW is the spleen in dogs and cats?
0.2%
What are the braod functions of the red pulp and white pulp of the spleen?
Red pulp: stores erythrocytes and traps antigens. Site of foetal erythropoietis
White pulp: Site of immune response
What is the main anatomincal 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 connection vetween arterial and venous circulation
List three braod functions of the spleen
Haematopoiesis
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 are filtered out by the spleen due to
- Inelastic cells (spherocytes, acanthocytes)
- RBCs covered with immunoglobulin or intracellular bacteria
Iron is stored in the spleen as ferritin and haemosiderin until transported to the bone marrow for haematopoiesis
Splenic extramedullary hematopoiesis
- in fetus, then changes to BM
- In adult: in response to infiltrative diseases of the bone marrow or with increased demand secondary to peripheral RBC destruction.
- Splenic extramedullary hematopoiesis can manifest as generalized splenomegaly or as focal nodules
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: Approx 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
Physiologic demand mediates splenic contraction via circulating pressors and direct nerve action on splenic smooth muscle, resulting in up to 98% of stored erythrocytes moving into the rapid pool and reducing splenic size to 25% to 50% of normal.
What immune cells 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
List some broad causes of generalised splenomegaly (4)
- Splenitis/inflammation (sepsis, chronic Ix, bacteraemia)
- Immune reaction or cellular hyperplasia (proliferation of normal cellular components, associated with chronic dz)
- Congestion (CHF, vascular outflow obstruction, portal hypertension, capsule relaxation)
- Infiltration (neoplasia - lymphosarcoma, mastocytosis - amyloidosis)**
List some causes of localised splenomegaly
- Nodular hyperplasia (subcapsular nodule, fibrohistiocytic nodule)
- Pseudotumour (benign proliferation of plasma cells, lymphocytes and histiocytes)
- Haemangioma (well-differentiated endothelial cells that connect to well-formed vascular spaces)
- Hamartoma (rare, benign proliferation of mature cells and tissue which are normally present)
- Abscess
- Cysts
- Segmental infarction
- Siderotic and siderocalcific plaques (focal accumulations of stored iron)
- Neoplasia (Hemic: lymphoid, mast cell, histiocytic, plasma cell, and myeloproliferative, Nonhemic: hemangiosarcoma, other sarcoma)
hemangioma, hematoma, and hemangiosarcoma similar gross appearance
Radiography
lateral projection the silhouette of the splenic caudal extremity appears as a triangular, oval, or rounded structure slightly caudal and ventral to the pylorus or liver.
- Large splenic masses often appear in midabdomen
List some differentials for hypoechoic and hyperechoic lesions of the spleen on ultrasound
evaluate all abdomen for effusion, lymphadenopathy, hepatic
Hypoechoic
- Lymphoid infiltration
- Infarction
- Necrosis
- Congestion
Hyperechoic
- Nodular hyperplasia
- Neoplasia
- Fibrosis from healed infarction or haematoma
Contrast-enhanced ultrasonography improves characterization of focal and multifocal lesions
What ultrasound finding is commonly seen with splenic torsion?
Hilar perivenous hyperechoic triangle
color Doppler for intraluminal flow can identify compromised vascular supply
In dogs presenting with splenic hemangiosarcoma, the rate of concurrent right atrial mass was 8.7%
dogs presenting with a right atrial hemangiosarcoma, 9 of 31 dogs (29%) had a concurrent splenic hemangiosarcoma
How can HSA be differentiated from nodular hyperplasia or haematomas on CT scan?
HSA will have lower density (lower Hounsfield units) on pre- and post-contrast images
MRI malignant disease was hyperintense in T2
List options of splenic biopsy
- Tru-cut (not if cavitary)
- Direct surgical (needle biopsy, pinch or punch, partial splenectomy
- Laparoscopic
- Transgastric endoscopic sampling
diagnostic sampling
- risk for hemorrhage is considered very small in dogs and cats using FNA - nonetheless, a baseline hematocrit and coagulation recommended
- Neoplastic dissemination as a result of needle puncture and seeding considered low risk
- guidance is recommended > assess for postsampling hemorrhage
- surgical more likely to yield a diagnostic sample than percutaneous
Diagnostic utility of samples collected by fine needle aspiration or needle biopsy is variable
- cyto vs histo: reported complete agreement in 59% of samples, partial agreement in 29%, and disagreement in 12%.
- successful diagnosis is good for hematopoietic hyperplasia and neoplasia
- Nondiagnostic common with with structural problems (trauma or torsion), vascular
pre-op consdierations
- risk for intraoperative hemorrhage and coagulopathies, a coagulation profile and blood typing
- transfusion pre-op if packed cell volume of less than 20% (autotransfusion if non-neoplastic)
- Blood pressure and electrocardiograms (ECGs)
- dopamine and dobutamine > hypotension
- ventricular arrhythmias can be placed on a lidocaine constant rate infusion (CRI; 25 to 80 µg/kg/min)
What suture/pattern is recommended for splenorrhaphy
4-0 to 5-0 monofilament rapidly absorbable in an interrupted mattress pattern, capscule
for small lacerations or punctures weighed against the future risk for hemorrhage
Hemostatic agents such as gelatin sponges
List some options for partial splenectomy
- Suture (continuous with second line of continuous or interrupted mattress)
- CO2 laser
- Ultrasonic cutting device
- Vessel sealing device
- Bipolar electrosurgical devices
preserves splenic function > for cases with a focal splenic abscess or injury; not neoplasia
Complete Splenectomy
indicated with neoplasia, splenic torsion, severe trauma, generalized infiltrative disease, and some immune-mediated disease processe
- greater vessels vs peri-hilar
- LigaSure; Covidien) seal vessels up to 7 mm in diameter
- Hemostatic clips, which are appropriate for vessels no greater than 3 mm
- portal vein and remaining splenic vein should be carefully inspected for evidence of thrombus.
- prophylactic gastropexy for large-breed dogs to preven GDV> conflicting conclusions
- torsed splenic pedicle, manual ligation or use of a vessel sealing device is preferred over stapling devices.
- Derotation of the pedicle before ligation is contraindicated
- laproscopic
- Splenosis—the formation of small collections of splenic parenchyma attached to omentum
Splenic Trauma
- penetrating, iatrogenic, trauma
- may lead to massive hemorrhage
- hemoabdomen is present > centesis for PCV/TP
- abdominal compression
- Significant splenic trauma generally requires partial or complete splenectomy;
What breeds are overrepresented for splenic torsion?
Great Danes, Saint Bernards, GSD, Irish Setters
splenic torsion pathophys
- torsion of the splenic pedicle initially occludes venous drainage, resulting in splenic congestion. Subsequent arterial occlusion results in splenic infarction
- c-shaped gross appearnce
- pathogenesis is unknown,
- hypothesized that splenic torsion may occur in conjunction with spontaneously resolving GDV (stretched the gastrosplenic ligaments)
- acute (shock) or chronic (non-specific signs)
torsion dx
- CT: failure of splenic contrast enhancement and presence of a “corkscrew-like” soft tissue mass
- Ultrasound: splenomegaly and lacy, diffusely hypoechoic splenic parenchyma, hilar perivenous hyperechoic triangle
- Doppler ultrasonography is particularly useful for detecting the absence of flow through hilar vessels
What substances can be released if a splenic torsion if derotated (4)?
- Sequestered blood, thrombi and microthrombi
- Free radicals
- TNF
- vasoactive compounds
Prophylactic gastropexy is strongly recommended at the time of splenectomy unless the patient is not sufficiently stable
torsion sx
Splenic Neoplasia
incidence: 1/3 -2/3 neoplastic in dogs, cats less known
- HSA common cause of non-traumatic haemabdomen
- With hemangiosarcoma, rapid growth and widespread metastasis are typical because of its vascular endothelial origin
- often confined to abodmen, but may spread to thorax (right atrium/auricle, lung, l.n.)
- older dogs 9-11
What % nontraumatic heamoabdomin is from the spleen?
What % are HSA?
Splenic haemorrhage in 73.6%
HSA in 63.3%
List DDX for splenic neoplasia in dogs (10)
- HSA
- undifferentiated sarcoma
- FSA
- OSA
- LSA
- myxosarcoma
- MCT
- Chondrosarcoma
- Lymphoma
- metastatic
What are the 2 most common forms of splenic neoplasis in cats?
Lymphoma
MCT
diagnosis
Hematocrit may be predictive of neoplasia: odds of malignancy increased threefold for every 10% decrease in PCV
- Thoracic radiographs, abdo ultrasound or CT (sonographic splenic abnormalities are nonspecific findings in dogs and cats)
Tx neoplasia
- patient stabilization and complete splenectomy with biopsy of other abdominal sites
- fully warn owners
- multiple liver lesions, actively bleeding nodules, and dark-colored hepatic nodules were highly associated with malignancy
- Ventricular arrhythmias were reported in 14 (23.7%)
prognosis
- Hemangiosarcoma: aggressive with a very poor prognosis > some variability in survival depending on stage
- hemoperitoneum: tachycardia, bicavitary effusion, severe respiratory disease, massive transfusion = negative prognostic indicators
- Uncontrolled hemorrhage from metastatic lesions and coagulopathic syndromes most common causes of peri-op death.
MST HSA
- 2-month: 31% for hemangiosarcoma and 83% nonneoplastic hematomas
- 19 to 65 days treated solely by splenectomy
- Factors that influence prognosis: tumor stage, number of gross lesions and age
- Adjunctive chemotherapy after splenectomy has been shown to increase survival times
- dogs with gross evidence of metastasis (stage III) are least likely to gain survival time with chemo
Prognosis for other splenic neoplasms depends upon the tumor type
What are some negative prognostic indicators in dogs undergoing splenectomy of mass lesions?
- Marked preoperative thrombocytopaenia or anaemia
- Intraop ventricular arrhythmias
What is the main chemotherapeutic agent used for splenic HSA?
Doxorubicin - shown to increase survival after splenectomy
survival times for various protocols range from 140 to 202 days.
What are some other, less common, options for adjunctive Tx of splenic HSA?
- Liposomal encapsulated immunotherapy
- oral continuous low-dose therapy (etoposide/cyclophosphamide/piroxicam)
prognosis for cats
prognosis for cats with splenic mast cell tumor is guarded; survival ranges from 2 to 34 months after splenectomy
Benign Splenic Masses
- most common splenic hematoma and reactive hyperplasia
- hyperplastic nodules indistinguishable from neoplasms, complete splenectomy is indicated for any splenic cavitary lesion.
- Benign splenic hematomas can be massive and sequestering a large proportion of the patient’s blood
- nontraumatic hemoabdomen, 26.6% had a ruptured splenic hematoma
- The long-term prognosis is excellent for nodular hyperplasia and hematoma after surgery
List potential post-op complications after splenectomy
- Haemorrhage
- Vascular compromise (left pancreatic artery, portal vein thrombosis)
- Arrhythmias 35-44%
- SIRS, ARDS, DIC, PTE (marked oreop thrombocytopaenia and anaemia and intraop arrhythmias identified as risk factors)
- GDV
- Infection Splenectomies animals are at higher risk of infection
- Oxygen transport - higher risk of hypoxia and ischaemia as have no splenic reserve
haemorrhage
- Hemorrhage from inadequately ligated vessels and from other abdominal tumor sites (e.g., liver) is the most commonly cited complication
- Hematocrit should be evaluated immediately after surgery
- thrombosis at the time of surgery may undergo thrombolysis, permitting significant blood loss many days after the procedure.
Vascular Compromise
- Vascular compromise to the left limb of the pancreas > artial pancreatectomy may be required if the pancreas becomes ischemic
- Acute portal vein thrombosis (PVT) reported 24 to 48 hours after splenectomy > All dogs died or were euthanized
arrythmias
ventricular premature contractions, or ventricular tachycardia (44% at prsentation)
- more common in dogs with anemia, hypotension, leukocytosis, and splenic mass rupture
- Continuous ECG monitoring is recommended during the recovery period
- tx with membrane stabilisers
When should VPCs be treated?
- Haemodynamic instability
- Multiform ECG complexes
- Very rapid v-tach
- R-on-T complexes
Tx: lidocaine CRI 25 to 80 µg/kg/min or procainamide CRI of 20 to 50 µg/kg/min
What are hypothetised causes of arrhythmias?
What medication can be sent home if the arrhythmias have not resolved?
- Myocardial ischaemia and hypoxia secondary to reduced cardiac return and hypovolaemic shock as well as impaired venous return from compression
- Acid-base imbalances, microemboli, myocardial depressant factors associated with pancreatic ischaemia
- Can go home on mexiletine or sotalol
Systemic Inflammatory Derangement
- Consequences of disruption of normal coagulation and inflammatory pathways can include disseminated intravascular coagulation, pulmonary thromboembolism, acute respiratory distress syndrome, and systemic inflammatory response syndrome (SIRS),
- marked preoperative thrombocytopenia or anemia and development of intraoperative ventricular arrhythmias have been identified as risk factors
Gastric Dilatation Volvulus
- Postsplenectomy gastric dilatation volvulus (median 352d post-op)
- tretching of the supporting gastrosplenic, hepatoduodenal, or hepatogastric ligaments by an expanding splenic mass may predispose the stomach to twist
- prophylactic gastropexy is recommended
Infection
- Active and passive removal of inflexible RBCs and antigen-covered RBCs from the blood no longer occurs
- spleen is also the primary site for removal of RBCs infected by bacteria > higher risk of infection
Oxygen Transport
- higher risk for hypoxia and ischemia in the event of acute blood loss (no splenic reservoir)
Minimally invasive splenectomy is associated
with a low perioperative complication rate
and short operative time in cats
Fairfield 2024
17 cats, retrospec
treatment of splenomegaly or modestly sized splenic masses
total or lap assisted splenectomy
- 2 converted to open sx (11%)
Diagnostic value of the ultrasonographic description
of a splenic mass or nodule as cavitated in 106 dogs
with nontraumatic hemoabdomen
Millar
AJVR
there was no evidence to support a diagnosis of malignancy on the basis of ultrasonographic detection of a cavitated lesion, and such a finding should not influence any recommendation or decision regarding euthanasia. Other preoperative tests, such as thoracic radiography, hemangiosarcoma likelihood predictor scoring, and contrast-enhanced imaging, may be of higher clinical value in predicting the presence of malignant lesions in this population of dogs.
CT characteristics included an enlarged (8/8),
rounded (7/8), folded C-shaped spleen (8/8) with a difference of median parenchymal attenuation
between pre- and postcontrast of +1.15 HU
A “whirl sign” was seen in the majority of cases (7/8)
Evaluation of the validity of the double two-thirds rule for diagnosing hemangiosarcoma in dogs with
nontraumatic hemoperitoneum due to a ruptured splenic mass: a systematic review
Schick 2023
A total of 1,150 dogs were evaluated, with 73.0% malignant splenic lesion and 27.0% benign splenic lesion.
87.3% were hemangiosarcoma.
88.Levels of evidence were low, and bias was high (retrospective)
double two-thirds rule underestimates HSA for non-traumatic ruptured
splenic mass
This rule states that two-thirds of splenic masses will be malignant, and of those malignancies, two-thirds will be hemangiosarcoma
benign lesions are grossly indistinguishable from malignant lesions and no preoperative factors have been found to be sufficiently accurate for diagnosis
Diagnostics such as contrast harmonic ultrasound, CT, and MRI may show characteristics that can differentiate malignant from benign lesions
Prevalence of malignancy and factors
affecting outcome of cats undergoing splenectomy
Matteo Rossanese 2023
62 cats
50 out of 62 cats (81%) were diagnosed with splenic neoplasia. Mast cell tumor ([MCT], 42%), hemangiosarcoma ([HSA], 40%), lymphoma and histiocytic sarcoma (6% each)
Benign splenic lesions were uncommon in this cohort of cats. Spontaneous hemoabdomen should prompt the clinician to suspect neoplasia in cats with splenic disease. Anemia and evidence of metastasis at diagnosis were poor prognostic factors regardless of the final diagnosis.
Development of perioperative premature ventricular
contractions as an indicator of splenic hemangiosarcoma
and median survival times
Panissidi 2021
peri-operative VPC not associated with median survival times
- 18/45 (40%) HSA dx → 13/18 (72%) post-operative VPC
- post-op VPC more likely with HSA vs other masses
- HSA 2.3x more likely to be thrombocytopenic
Clinical utility of liver biopsies in dogs
undergoing splenectomy
E. Clarke 2020
grossly normal liver at the time of splenectomy → low yield diagnostic test
- 44.2% malignant splenic neoplasia → 2.5% neoplastic dz with grossly normal liver bx
- 28.9% with grossly abnormal liver bx → ~16x higher chance of neoplastic dx
- hemabdomen → increased likelihood of liver bx positive for neoplasia
Influence of use of a bipolar vessel sealing device on shortterm
postoperative mortality after splenectomy: 203 dogs
(2005-2018)
Anna L. Sirochman 2020
bipolar vessel sealing device → no difference in short-term post-op mortality
after splenectomy
- overall mortality prior to discharge 7.4%
- administration of blood products, increased anaesthesia and intra-op ventricular
arrythmia associated with death prior to discharge
- administration of blood products (intra- or post-) associated with death prior to suture
removal
Outcomes of 43 small breed dogs treated for splenic
hemangiosarcoma
Ashton L. Story 2020
no difference in survival time for small vs large breed dogs with splenic HSA
- overall MST: small 116d, large 97d
- sx+chemo: small 207d, large 139d; sx alone: small 47d, large 38d
- mDFI: small 446d, large 80d
- metastasis → decreased ST; chemotherapy → increased ST in small breeds
Complications and outcomes associated with laparoscopic-assisted splenectomy in dogs
McGaffey 2022
laparoscopic-assisted splenectomy in 136 dogs
- conversion 8/136 (5.9%)
- complications 78/136 (57.4%) - all grade 1-2
- applicable for total splenectomy for moderate-sized splenic masses without hemorrhage
and PCV cut-off 36%
Latifi 2020 – localised splenic histiocytic sarcoma treated by splenectomy +/- chemotherapy, n=14
- MST 427 days, 5/14 (35.7%) → suspected/confirmed metastatic disease, mPFI 158d
- 11/14 tumour-related death
