The Compendium of Caraka 6.13.37

6.13.37

tasya plīhā kaṭhino+&aṣṭhīlevādau vardhamānaḥ kacchapasaṃsthāna upalabhyate; sa copekṣitaḥ krameṇa kukṣiṃ jaṭharamagnyadhiṣṭhānaṃ ca parikṣipannudaramabhinirvartayati//

Its plīhan, enlarging initially hard like an aṣṭhīlā stone, is felt in the shape of a tortoise; and when neglected, gradually enclosing the belly, stomach, and the seat of the digestive fire, it brings about abdominal enlargement.