Why is 90-day mortality used and not 30-day?

NBOCA reports 90-day rather than 30-day mortality. From a patient’s perspective the risk of post-operative death at 3 months is just as significant an outcome as death within 1 month of surgery. Post-operative death at 3 months captures those deaths that occur after prolonged critical care support which is now a much more common feature of colorectal cancer resection and adds significantly to the procedure-associated death rate. A previous study showed that the vast majority of deaths occurring within 90 days of surgery were as a result of complications of the surgery [Archives of Surgery 2009; 144: 1021-1027].