Can the use of rectogesic ointment cause perianal abcess? after 4 weeks of usage a small lump has appeared the opening of my anus - far from fissure.

Peek-A-BooBoo: Technically, no.It just makes things relax down there because pain can cause spasms.But think of it this way: you're using your finger(covered or not)to apply it and it ain't all that clean down there(no offense)so there's a chance an open fissure or other area can get infected.Also that ointment relaxes the vessels so maybe there's a small hemorrhoid. If it gets bigger someone should look at it

Abcess: An ointment does not usually treat a perianal abscess, it generally needs to be drained. You could also have a pilonidal cyst, which forms a tract opening above the anus. Get an evaluation.