Ayurvedasutra 4.21

4.21

virasadravyādanājīrṇajanyasirāmārgasthitapavanavigatyā sirārasātiprasravaṇād ajīrṇādāmāmbuvṛddherudaraṃ jāyate

Abdominal disease arises from the obstruction of the passage of wind situated in the channels caused by eating unwholesome substances and indigestion, from excessive exudation of fluid from the channels, and from the increase of undigested matter and watery fluid due to indigestion.