My father has severe diarrhea after chemotherapy for colon cancer. Please help.

Hello doctor,

My 43 years old father has colon cancer. He had undergone hemicolectomy laparoscopic surgery, and he is currently undergoing chemotherapy with Xelox (Oxaliplatin and Capecitabine). I am here to ask you about the side effects of chemo that my father is experiencing from the first cycle. The first cycle was hard, as he had to deal with some gas problems. Now in this second cycle, he is having extreme diarrhea. My questions are as follow.

My father was given Loperamide, Rabeloc 20, Folic acid tablets, and ORS to control diarrhea. But diarrhea is still there, and frequency is 4 to 5 times a day. The stool is complete watery. Also, he is not on Capecitabine tablets. It is a rest week of the second cycle. If the diet is a concern, then we are giving diarrhea strict food like banana, rice, potatoes, etc. Why is diarrhea not getting well? He is also having pain between the two rib cages, which is like the pain in gastritis. Is it possible that he could have gastritis?

He is losing weight drastically. Before everything, his weight was 68 kg. But after surgery, it was only 58 kg. And after the first cycle of chemo, it was 55 kg. This decreasing trend is very worrisome, which also affects his mental strength. How to deal with it? Can he pause chemo for a while? He is losing body strength and weight. I think that his body is not well enough to receive the next cycle. The patient is also experiencing pain at the site of surgery. Is it normal? The surgery was done about two and a half months back.