Triphragmium ulmariae affects Meadowsweet Filipendula ulmaria.  There is no host plant alternation.  The bright orange aecial stage causes galls on the leaves and petioles, which become twisted and distorted.  It is mainly recorded on the underside leaf-veins and petioles.  The uredinia are orange, on the leaf undersides, and are not gall causing.  Later on, blackish telia are present on leaf undersides.

host

Photograph the rust on the host plant; ensure you have noted the host plant species in your comments.

on Meadowsweet