Brief Answer:
You require some investigations

Detailed Answer:
Hello Sir,

Swelling in feet and ankle is common in old age. You require some test to know its cause These include
Complete blood count, Liver function tests, kidney function test, thyroid profile, echocardiogram to know cardiac status and diabetes profile.
Common causes include low protein in body, kidney diseases, hear related diseases.
Do not worry as all of these are treatable.
For reducing swelling take less of salt in diet. You may also require diuretics drugs which increase urine output.

Please revert back with the investigations and meet a physician soon.

Thanks and regards.

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