Hello CHUGH and thank you for posting.
I am sorry you are going through this worrying time with your brother-in-law.
Perforation of the bowel can happen in bowel cancer, particularly in stage 4 as the tumour may have broken through the bowel wall. Any further pressure through an obstruction or from treatment shrinking the tumour can leave a hole behind, this can cause a leakage. Any fluid from the bowel leaking out into the abdomen can cause infection, so close monitoring and intravenous antibiotics are needed until the patient has improved. Once your brother-in-law is more stable they will be able to re-assess him and his treatment plan.
Take care and if you or any member of your family would like to contact our nurse helpline the number to call is Freephone 0808 800 4040. The lines are open from 9 am till 5 pm, Monday to Friday.
Sarah.