The phrase "anal region" refers to the area around the anus, which is the opening at the end of the digestive system where stool or waste exits the body. Full definition
You'll need a washcloth to stimulate the kitten's abdomen and anal region so that your kitty can «go». (petcentric.com)
And some will notice a dark line on the midline of the lower abdomen, known as the linea nigra (or linea negra), as well as hyperpigmentation (darkening of the skin) of the nipples, external genitalia, and anal region. (kidshealth.org)
Also during the birth itself, there is a great deal of pressure being exerted on the anal region, which can lead to hemorrhoids. (authenticparenting.info)