De or het dialysebehandeling?

The correct Dutch article is:

de dialysebehandeling

Rule Words ending in -ing: almost always de. See the rule

How to use dialysebehandeling

the dialysebehandelingde dialysebehandeling
this dialysebehandelingdeze dialysebehandeling
that dialysebehandelingdie dialysebehandeling
our dialysebehandelingonze dialysebehandeling
your dialysebehandelingjouw dialysebehandeling
every dialysebehandelingelke dialysebehandeling
which dialysebehandeling?welke dialysebehandeling?
a big dialysebehandeling / the big dialysebehandelingeen grote dialysebehandeling, de grote dialysebehandeling