The general rule is that bathrooms that have opening windows don't require exhaust fans, and ones without opening windows do.
Of course your local building codes should be consulted.
And even if it is an older building, where that may not have been the code when it was built, many localities require landlords to update certain things to current codes any time the space has a change of occupancy, when an old tenant leaves, and before a new tenant moves in.
There are also limits at to what may be the responsibility of the landlord, or the responsibility of the tenant if he's using the space for other than regular commercial space.
So you need to know what the rules are in your area. And there are often different rules for commercial, and residential buildings.
You should speak to the manager of the place where you get dialysis, or find a different place to go. If nobody's complaining, nothing will ever get done.