Post esophagectomy intestinal and digestion pain

My Brother Dennis Male, age 51, stage IV had esophagectomy aprox 4 months ago,  his secondary cancer was a nodule in his shoulder blade, which has been quiet for 2 years now...  with chemo...  he has had no reoccurrence in any soft tissue,  and was considered an exception to the rule no stage IV gets esophagectomy.   anyways,  he has recovered beautifully from this surgery,  has been dilated once, had about 2 weeks of great health, feeling great.  Then all of the sudden, stated to feel lots of abdomen pain, has been scoped, they took biopsy’s of esophagus, stomach, intestines, had pet scans, cat scans, and everything keeps coming back as normal,  has had diarrhea for 3 weeks now, just hospitalized due to excruciating pain in abdomen..  prior to esophagectomy he weighed 180 lbs, now he is at 147... i think the weigh loss is in line with what is expected, he just feels that no matter how much he eats he is not absorbing the nutrients, he is very tired, almost couch bound..   very lot energy.  he is going to be tested for celiac disease....  The Surgeon that did the esophagectomy keeps telling him to be patient, its a long road to recovery.  but trust me, my brother never complained during any of this, he has been battling now for 3 years, and this is just dropping him.   He does all the things that everyone else that has had esophagectomy does.  he doesn’t eat 2-3 hours prior to bed, He sleeps upright practically.. takes his acid blockers.. etc...  he never had any of this abdominal pain before the esophagectomy ?  anyone else experience this?  thanks for any advice, feedback, or support.  regards, Darrin..