The gastrointestinal tract or gut runs from top (mouth) to tail (anus). Its function is to allow intake, digestion and absorption of food and disposal of waste in the form of faeces. The gut is involved in up to 90% of patients with systemic sclerosis. Any part of the gut can be affected from mouth to anus. Gut involvement can occur at any time in the course of the disease and it can be progressive but not invariably so.