The Compendium of Caraka 8.3.25

8.3.25

līyanta evaṃ valayaśca tasmāt savyaṃ śayāno 'arhati bastidānam/
viḍvātavego yadi cārdhadatte niṣkṛṣya mukte &praṇayedaśeṣam//

Thus the rectal folds yield; therefore, one lying on the left side is fit for the administration of an enema.
And if an urge for feces or flatus arises when half is given, he should withdraw it, and once released, administer the remainder.