Which one is correctly spelt?

Diarrhoea (British) / Diarrhea (American) - উদরাময়; পেটের অসুখ; ঘন ঘন পাতলা পায়খানা।

diarrhoea(noun)

an illness in which the body's solid waste is more liquid than usual and comes out of the body more often:
diarrhoea and sickness
an attack of diarrhoea

Source: Oxford Dictionary, Bangla Academy Dictionary