A proportion of people who have had treatment for cancer suffer difficulties with sudden loss of control over bowel movements, and indeed some suffer from chronic diarrhoea issues. Dr Jervoise Andreyev, the gastroenterologist from Royal Marsden, and his colleague Ann Muls, have been in the forefront of treating these problems, and there is a Pelvic Radiation Disease Association that specialises in this sort of problem.
Macmillan Cancer relief have now produced a guide for health professionals based on Jervoise Andreyev's work, with his colleagues, and I am including a link to this as some may find it helpful to take it to their doctor for a referral to a gastroenterologist. It is not specifically for people who have had an oesophagectomy / gastrectomy, but some aspects of it might be relevant to some problems you might face.
This problem is a considerable assault on quality of life after otherwise successful cancer treatment, and I hope it helps people to make progress towards light at the end of the tunnel.