Had colon resection 4 mo ago. Having pain and nausea. Had ct. No diver but found 5cm free fluid in abdomen. No leaks will this be reabsorbed into body?

Depends. Unusual to find 5 cm of free fluid 4 months following a colon resection in otherwise healthy person. The identity of this fluid will determine its course- e.g. Ascites, blood, pus, etc. If no other cause for the nausea and pain, perhaps aspiration to determine what the fluid is may be indicated if your symptoms persist or worsens. Please consult with your surgeon or gastroenterologist.