The Compendium of Caraka 8.3.24

8.3.24

vimathya saṃyojya punardravaistaṃ bastau &nidadhyānmathitaṃ khajena/
&vāmāśraye hi grahaṇīgude ca tat pārśvasaṃsthasya sukhopalabdhiḥ//

churning them together, one should then combine them with liquids, churn with a churning stick, and place into the bladder.
Because the duodenum and rectum lie on the left side, one lying on that side attains comfort.