Peritonitis is an inflammation of the peritoneum, the serous membrane which lines part of the abdominal cavity. It may result from infection or from a non-infectious process. Perforation of part of the gastrointestinal tract is the most common cause of peritonitis

Perforation of Brookelyns colon is the cause of the peritonitis she contracted. It is treated with antibiotics. In Brookelyns case it is extremely difficult to treat, because she has a VP Shunt which would act as a highway for the infection to travel from the peritoneum to the brain so her shunt had to be externalized for the treatment of the peritonitis. It was then replaced into her peritoneum when the infection was treated.