This proverb (for which cf. Zenobius 1.52 and other paroemiographers) comes from the fourth book of the lost Prose Works of Aristophanes, the comic playwright (fr. 903 Kock, now 934 Kassel-Austin), "Akesias healed the anus," as a warning not to trust a witless doctor. Libanius uses it thus, "I fear that if I touch the matter I will become Akesias" (Epistulae 476.5). The proverb clearly implies that Akesias made things worse than they were before. It may be that the possible etymology of Akesias's name from a verb that means both to heal and to stitch provides the comedy (alpha 856, cf. alpha 841, alpha 851). "Dr.Stitcher" is the wrong person to trust when it comes to choosing a proctologist.
[1] i.e. in trying to heal someone made things worse.