You are correct to worry about disclosure as insurance companies may say that it was a fraudulent misrepresentation.  The type of illness and procedure may or may not have mattered in issuing the policy but you don't want to worry that your beneficiaries will have a fight on their hands.  You should contact the agent or the broker who helped you in applying or if there is a contact number for the insurer, call them.  They will know the procedure you need to follow.