Thank you for your reply. What sort of surgery can cure it?
I am so sorry to listen this health issue but there is nothing to worry about it may be cure by simple surgery and nothing big. This is a general issue for men. I am giving some explanation here which I found from different source which may be helpful for you.
The rectus abdominis muscles should meet in the midline at the linea alba. Superior to the umbilicus, some people have a congenital defect that results in a wider gap between them. As a result, when a patient flexes the abdominal muscles as when doing a sit-up, the rectus muscles spread apart (divaricate). The divarication is made more obvious when the patient lifts their head or legs off the bed when supine.