Feet swell at lower altitudes?

Hola, When I go from Cuenca to Costa Rica, elev. 2400 ft, my feet swell like balloons within three days of arriving. They stay that way for months.

Walking, for at least a kilo, temporarily relieves the swelling. Holding my feet up or compression socks help a little.

It has baffled the doctors here. Within three days after returning to Cuenca, my feet are back to normal.

Does anyone else have this problem?

Thanks,

Gary Brown