The Compendium of Caraka 8.3.20

8.3.20

prapīḍya caikagrahaṇena dattaṃ netraṃ śanaireva tato 'apakarṣet/
tiryak praṇīte tu na yāti dhārā gude vraṇaḥ syāccalite tu netre//

and pressing it, given with a single squeeze, he should then withdraw the pipe slowly.
If introduced obliquely, the stream does not flow; if the pipe moves, an ulcer forms in the rectum.