Hi. UC causes inflammation of the inside of abdomen from where the nerves go down. There is some reflex relation between the UC and backache and lower limb pain. You might have noticed that the pain must be reducing after you pass the poof. If so , nothing much to worry. IF the pain is severe and not relieved, better to have an MRI of the lower spine on a safer side. Consult a Gastro Doctor for treatment of UC.