What are the common causes of splenomegaly in dogs and cats?

Splenomegaly can result from many causes, including infections, immune-mediated diseases, haematological disorders, and tumours. The vet will typically start with blood work and imaging (ultrasound or X-ray) to identify the most likely cause, and may recommend tissue sampling if needed. Follow your vet's guidance on which tests to proceed with.

What tests will the vet use to confirm splenomegaly?

Routine workup includes physical palpation, a complete blood count and biochemistry panel, and abdominal ultrasound or radiography to evaluate splenic shape and detect any masses. Advanced imaging (CT) or fine-needle aspiration and biopsy may be recommended if further characterisation is needed.

Does splenomegaly always require surgical removal of the spleen?

Not necessarily. Whether splenectomy is required depends on the underlying cause, the risk of haemorrhage, and the findings from imaging or tissue sampling. Surgery is typically recommended when a tumour is suspected or splenic rupture has occurred; in other cases, medical management with monitoring may be appropriate.

What kind of monitoring is needed after surgery or during treatment?

After surgery or during medical treatment, regular blood tests are usually needed to monitor cell counts and biochemistry values, along with ultrasound or X-ray rechecks to track splenic size and lesion changes. The recheck interval and specific tests will be tailored to the underlying cause and your vet's recommendations.

How much do the tests and treatment usually cost?

Costs vary by clinic and region — ask your vet for an estimate before proceeding.

Disease Guide

Splenomegaly in Dogs & Cats: Symptoms, Diagnosis & Treatment [2025]

Abnormal enlargement of the spleen that requires investigation to identify the underlying cause

Take 1 minute to check the symptoms first

Last updated: 2026/01/06

Pethealthmap Editorial Team

Sources: ACVIM, AVMA, National Taiwan University Veterinary Hospital

When to See a Vet

Seek Emergency Care Immediately

•Gums or oral mucous membranes are visibly pale and the pet appears weak
•Sudden collapse or loss of consciousness with poor responsiveness
•Rapid breathing or obvious difficulty breathing

Schedule a Clinic Visit Soon (within 24–72 hours)

•Persistent lethargy or noticeably decreased activity level
•Significantly reduced appetite or repeated refusal to eat accompanied by weight loss
•Repeated vomiting or diarrhea lasting more than one day

01What symptoms indicate something is wrong?

Splenomegaly in dogs and cats typically presents with non-specific signs involving energy levels and blood-related changes; diagnostic workup is needed to identify the cause.

Lethargy, reduced activity, or noticeably increased sleeping
Persistent weakness and reluctance to stand for long or engage in play
Markedly reduced appetite or prolonged refusal to eat
Repeated vomiting or diarrhoea, or a change in bowel habits
Elevated heart rate, faster breathing, or easy tiring during mild exertion

Seek emergency care immediately if you notice the following symptoms:

⚠️ Visibly pale or white gums and oral mucous membranes accompanied by weakness
⚠️ Sudden collapse or loss of consciousness with poor responsiveness
⚠️ Rapid breathing or obvious respiratory distress
⚠️ Sudden rapid abdominal distension that is clearly painful to the touch

02How should you assess the situation at home? Key observations and emergency criteria

Systematic at-home monitoring with notes and recordings helps the vet quickly prioritise diagnostics and narrow down potential causes.

Note the onset date and trend of changes in energy and activity level
Weigh your pet daily and log the readings for comparison
Record the frequency, timing, and character of any vomit
Track stool consistency and frequency, and watch for any blood in the stool
Use your phone to film the abdomen and side profile for the vet to review
If you notice anything alarming — such as pale gums or collapse — arrange an appointment promptly

03How will the vet make a diagnosis? Common diagnostic steps

In-clinic workup centres on physical examination combined with blood tests and imaging, with the goal of identifying the cause of splenomegaly and assessing for complications.

Physical examination

abdominal palpation to assess spleen size and tenderness

Complete blood count (CBC)

checking for anaemia or platelet abnormalities

Biochemistry panel

evaluating liver and kidney function and electrolyte status

Abdominal ultrasound

assessing splenic architecture, masses, or signs of haemorrhage

Radiography (X-ray)

ruling out other abdominal or thoracic pathology

CT scan if indicated, to further evaluate the spleen or surrounding tissues

04How is it treated and managed after diagnosis? Medications, dietary adjustments, and care guide

Treatment depends on the underlying cause and may involve surgery or medical management; regular blood work and imaging follow-up are required in both cases.

If a lesion or haemorrhage is confirmed, splenectomy or other surgical intervention may be required
Infectious or immune-mediated causes are typically managed with medication and monitored closely
Regular blood tests are needed during the post-operative or treatment period to track recovery
Ultrasound or X-ray follow-ups monitor changes in splenic size and lesion appearance
Home care includes dietary adjustments, restricted activity, and attending scheduled rechecks as directed
Referral to an oncology or internal medicine specialist is recommended when tumour involvement or complex aetiology is suspected

05What should you prepare before the vet visit? Key information to help the vet identify the cause

Record the onset date and a timeline of how symptoms have progressed

List recent diet, all current medications, and any supplements being given

Note the frequency, content, and duration of any vomiting or abnormal stools

Bring photos and videos of the abdomen or any unusual behaviour for the vet to review

Bring previous test results or imaging if available

Call ahead to ask whether fasting or any other preparation is required before the visit

This content is for reference only and cannot replace a professional veterinary diagnosis. If your pet shows signs of illness, please seek veterinary care promptly.