a bag of skin in which urine collects in human and animal bodies

pouch

small swelling under the skin filled with liquid (caused by rubbing, burning etc)

swelling

a ball formed of liquid and containing air or gas, e.g. one that forms in boiling water

globule of air

a hollow growth in the body containing liquid matter

unusual growth

a paper covering for a letter etc

wrapper

a tiny opening in the skin through which fluids (e.g. sweat) pass; to examine, study, something in detail

small aperture in skin

a bag of skin (usually containing liquid) in an animal or plant

bag