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After going through history most likely he suffered a infection by amoeba or bacteria,but colitis it may be chronic and thickning of cecum makes to suspect other diseases like TB and Malignancy.
Another thing is Fatty liver
common causes are Diabetes
level and Alcohol consumption.
You should check for FBS,PPBs and Lipid Profile
If by chance he takes alcohol then stop it completely,rest depend on test result.
If thickning in cecum and colon persist after treatment go for Colonoscopy
with biopsy to know exact cause of thckning and once cause is known it can be treated accordingly.
He should take light and easily digestible diet and take care of potable water.
Plenty of fruits and green vegetables cooked in less spicy way may be taken.
Good Luck to you.