Brief Answer:
Need further tests.

Detailed Answer:
Hi MR. XXXXXXX

I understand your concern.
Well gross splenomegaly is said when spleen is very large in size.
The common causes are,
Tropical splenomegaly seen in malaria
Blood cancers
Extrahepatic portal hypertension
Kalaazar
Chronic liver disease etc

The basic test needed are
Complete blood count, peripheral smear
Liver function test for liver disease
Venous doppler of portal vein
If deemed necessary bone marrow examination

Some time even after extensive workup exact cause may not be found.
Treatment depends on the cause of it.
Sometimes if very large causing pain may need to be operated too.

In the nutshell, gross splenomegaly needs further evaluation. Treatment will be based on the investigation results.

Hope this answers your query.
Best wishes

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