The patient probably died as a result of an overwhelming infection which spread throughout his body and was carried in the bloodstream - a coliform septicaemia. In the days before modern antibiotic therapy and aseptic or antiseptic environments in operating theatres, septicaemia was the principal cause of post-operative mortality for major surgery. In this case, the source of the septicaemia was probably the patient's acutely inflamed diverticulum. Patients with acute lymphoblastic leukemia are susceptable to infection because of their disease initially. Cytotoxic chemotherapy will also cause immunocompromise.
In this patient chemotherapy proved ineffective but generally this type of leukemia, particularly in childhood responds well.