How to politely ask for an update from the visa office

[Magnificent-Moe]

I've been approved for a visa and have been informed that the visa office is processing one visa per week -- I have time sensitive circumstances as i my son in the US will have brain surgery soon soon (to which the consular is aware as that is why i have applied)

I would like to email them and ask for an update, but i would like to make sure that i sound respectful while still communicating the urgency of my situation.