Thanks for your question on Health Care Magic. I can understand your father s situation and problem. Constipation in CA stomach patient needs investigations to rule out internal abdominal causes. Common causes are obstruction, paralytic ilius, loaded fecal matter etc. Intestinal obstruction is common in CA stomach patient due to enlarged abdominal lymphnodes. Hypokalemia (low potassium)is also common due to decreased oral intake and poor absorption. And this can cause paralytic ilius. So better to first get done ultrasound examination of abdomen, serum potassium level and if needed CT abdomen to search for the cause of constipation. If hypokalemia is the cause than potassium supplements should be given. But if obstruction is there than he needs surgery. High fiber diet, plenty of fluids can also helpful in constipation. So first rule out above mentioned causes for constipation and start appropriate treatment. Hope I have solved your query. Wishing good health to your father. Thanks.