All about the Spleen
Updated: Oct 12
Splenic Masses in Dogs:
Practical Rules of Thumb for Diagnosis, Prognosis and Surgical Decision-Making
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Video showing how to perform Splenectomy with the Fourlimb MarClamp
Filmed at VSS Jindalee.
All about the Spleen
One of the most common questions veterinarians face when a splenic mass is identified is:
"What are the chances it's cancer?"
Unfortunately, unlike many tumours, splenic masses often require splenectomy before a definitive diagnosis can be obtained. Yet owners frequently need guidance before deciding whether to proceed with surgery.
We can use several useful "rules of thumb" and clinical clues that help guide these conversations with owners. None are perfect, or replace histopathology. However they can help give clues, and then it is for the owner to roll the dice....
Rule of Thumb #1
Start With The Double Two-Thirds Rule
When discussing a ruptured splenic mass with hemoabdomen, I usually start here.
Double Two-Thirds Rule
Of dogs presenting with a bleeding splenic mass:
Approximately two-thirds are malignant
Approximately one-third are benign
Of the malignant masses:
Approximately two-thirds are hemangiosarcoma
Approximately one-third are other malignancies
This isn't exact. In reality, slightly more than one-third of bleeding masses are benign in several studies. However, it is an easy starting point for conversations with owners.
Rule of Thumb #2
Incidental Splenic Masses Are Different
This is probably the most important concept owners and veterinarians forget.
The double two-thirds rule applies primarily to:
Ruptured masses
Dogs presenting with hemoabdomen
It does not apply to incidentally discovered masses. In fact the statistics effectively flip in the opposite direction.
Rule of Thumb #3
Breed Matters
Certain breeds should increase suspicion.
More Likely Malignant
German Shepherd Dogs
Golden Retrievers
Working breeds
Sighthounds
More Likely Benign
Spaniels
Breed should never be used in isolation, but it is another clue that can help move the probability dial one way or the other
Rule of Thumb #4
Ultrasound Can Provide Clues
Ultrasound is rarely definitive. However, several findings can influence our level of concern.
Clues Suggesting Benign Disease
✅ Mass <2 cm
✅ Mass >7 cm
✅ Homogenous appearance
The >7 cm finding often surprises clinicians. The proposed explanation is that malignant masses frequently rupture before reaching this size.
Clues Suggesting Malignancy
⚠️ Heterogeneous appearance
⚠️ Target lesions
⚠️ Additional lesions elsewhere
⚠️ Liver nodules
However, remember:
Approximately 50% of liver lesions identified alongside splenic masses are benign.
Don't euthanase based on ultrasound appearance alone.
Rule of Thumb #5
Cavitation Doesn't Help
For many years, cavitated splenic masses were considered suspicious for hemangiosarcoma.
Current evidence suggests otherwise.
Both benign and malignant splenic masses can be cavitated.
Rule of Thumb #6
FNA Is Safe, But Often Unhelpful
A common question is:
Should we sample the mass?
The answer depends on whether the result will genuinely alter decision-making.
The Good News
FNA is generally safe
Seeding risk is minimal
Bleeding complications are uncommon
The Bad News
Cytology often yields blood
Agreement with histopathology is only around 60–70%
Practical Interpretation
If cytology says:
✅ Malignant → probably malignant
If cytology says:
❌ Benign → don't trust it
A benign result should never be used to confidently exclude malignancy.
Rule of Thumb #7
Thoracic Metastasis Changes Everything
Owners often ask:
"Can we know before surgery?"
The unfortunate answer is usually no. The one major exception is obvious metastatic disease. If thoracic radiographs contain obvious metastatic lesions:
➡️ Assume malignancy until proven otherwise.
Otherwise, splenectomy often remains the only route to a definitive diagnosis.
Putting It All Together
Clues Supporting Malignancy
Hemoabdomen
Large-breed predisposed patient
Heterogeneous mass
Target lesions
Thoracic metastasis
Malignant cytology
Clues Supporting Benign Disease
Incidental discovery
Small breed
Homogenous appearance
Mass <2 cm
Mass >7 cm
No single clue is definitive and in fact even predictive algorithms combining multiple factors are generally only correct around 70–80% of the time.
Surgical Considerations
Rule of Thumb #8
Stabilise Before You Cut
Many splenic mass patients present with hypovolaemic shock. Current thinking has moved away from aggressive fluid replacement and toward:
"Bolus and Reassess"
10–20 mL/kg crystalloid bolus
Reassess endpoints
Repeat as required
Monitor:
Mental status
Pulse quality
Heart rate
Mucous membrane colour
Blood pressure
Lactate
Avoid over-resuscitation and clot disruption.
Rule of Thumb #9
Replace Blood With Blood
If the patient is bleeding significantly:
Use blood products early.
Particularly consider transfusion when:
PCV <20%
Persistent tachycardia
Weak pulses
Rising lactate
Ongoing shock despite fluid therapy
Autotransfusion remains a valuable and under-utilised tool.
Rule of Thumb #10
Never Regret A Larger Incision
A good exploratory celiotomy starts with exposure.
Ideally;
Xiphoid to pubis incision
Remove falciform ligament
Suction available
Full exploratory performed
Remember:
Incisions heal side-to-side, not end-to-end.
Poor exposure causes more complications than large incisions.
The Gastropexy Question
Should every splenectomy receive a prophylactic gastropexy?
The evidence remains debated.
Potential reasons for increased GDV risk following splenectomy include:
Sectioning of the gastrosplenic ligament
Increased abdominal space
Altered gastric support structures
Equally, many splenectomy patients belong to breeds already predisposed to GDV.
My approach is simple:
If the patient is stable and I am already in the abdomen, I generally perform a gastropexy.
The procedure is quick, low morbidity, and may prevent a future life-threatening emergency.
Final Take-Home Messages Summary
Splenic Mass Rules of Thumb
Bleeding mass = start with the double two-thirds rule.
Incidental mass = most are benign.
Breed matters.
Homogenous masses are reassuring.
Cavitation is not useful.
FNA is specific but not sensitive.
Thoracic metastasis changes the conversation.
Stabilise before surgery.
Replace blood with blood.
If in doubt, histopathology wins.
The most important lesson for clinicians is that owners are not necessarily asking for certainty - they are asking:
"Given everything we know today, what are the chances?"
Our job is to use the available clues to help them make an informed decision while recognising that, with splenic masses, the final answer often still comes from the pathologist.
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