How do trematode flukes get rid of undigested food?

Trematode flukes typically lack an anus, meaning they do not have a dedicated exit for solid waste at the end of their digestive tract. Consequently, undigested food residue is expelled back out through the mouth.1

In cases where these parasites feed on blood, the digestion process is largely intracellular. This results in the formation of hematin, an insoluble pigment derived from the breakdown of hemoglobin, which is eventually eliminated by the disintegration of gut cells.2