The causes could be related to heart like congestive heart failure,cardiovascluar disease,cardiomyopathy,chronic venous insufficiency,
varicose veins,endocarditis,etcHyponatremia,hypothyroidism,kidney failure, liver failure are few other possibilities. Does he also have other symptoms like difficulty in breathing, ankle swelling etc?He needs medical help ASAP.Tests like electrocardiogram,echocardiogram,lipid profile, kidney function tests, liver function tests, serum electrolytes may be needed.