Thank you for your query on Healthcare Magic.
Toddlers usually have a big belly in comparison to their body because :
1. The size of intestine is more than their abdomen
2. They have exaggerated lumbar lordosis
while walking so the tummy looks protruded
As the age grows the space of abdomen will increase and it accommodates the intestines completely so the size of belly decreases with the age.
also lead to increased belly because of retention of stool and with associated gas formation.
If the constipation is treated with dietary fiber
rich food, plenty of water, and laxatives the problems will be solved.
The chances of having a tumor is rare and it can be ruled out by doing an ultrasound abdomen and pelvis.
also causes a large belly, so it has to be ruled out by doing blood investigation with thyroid function test.
I advise you to consult your pediatrician
for physical examination and for investigations if required depending on his examination.
Hope I have answered your query.