GUN DOG VET
Don’t fret! When some large masses are removed, dead space is left behind.
The body hates this and so puts fluid into the space that’s created.
This can delay healing and, because of gravity and body movement, further damage can occur as the fluid moves around.
Most likely, your vet will make a small wound near the main one and pull a small rubber tube, called a penrose drain, through this hole and into the dead space, allowing any fluid to drain away.
The drain will need to be removed after a few days, to avoid it becoming a wick for infection.
The opening and surrounding area will also need to be kept clean.
The drain holes almost invariably heal quickly after the tube is removed.
If you look at the picture sequence here, all is revealed!