How serious is belly button hernia after laparoscopic surgery of colectomy in adults?

NOT serious: After major laparoscopic surgery like colectomy , some times incisional hernia develops , if it happens will need simple surgery to repair it.

Port site hernia: Your "belly button hernia" may actually be a laparoscopic port site hernia following your laparoscopic colon removal. Generally speaking, if an abdominal wall hernia is symptomatic (tenderness, protrusion, obstruction), we advise repair. Some small asymptomatic hernias may be safely watched. Consult with your surgeon.

Port site: This is most likely a laparoscopic port site hernia. They are usually small and relatively easily fixed. Options include approaching it by reopening the trocar site directly, or to approach it laparoscopically through other incisions. Either way successful repair should be expected.

Depends: The size and what is protruding through hernia and if the contents get stuck. All these things determine how serious. If it hurts or bothers you or is stuck go see your surgeon.