Snakes pass both digestive-tract waste and filtered body waste out of a single opening called the cloaca, says Snake Removal. They excrete waste infrequently. The resulting waste tends to be a soft, slimy mass that might have white streaks in it.
Like most reptiles, the snake's kidneys are designed to conserve water. The waste filtered out of the blood by the kidneys is converted into uric acid. That waste is then deposited into the snake's cloaca, where most of the water is reabsorbed, leaving only a thick white paste.
Snakes generally swallow their prey whole. After being swallowed, food is digested in the stomach and intestines. The digested food is absorbed through the wall of the small intestine. Remaining residue moves through the large intestine into the upper chamber of the cloaca, where some water is reabsorbed. It then passes into the posterior chamber of the cloaca to mix with the uric acid waste, says Reptile Magazine. The resulting substance is excreted.