Treatment is based on what is the immediate concerning issues to be dealt after evaluating patient and reports

If your uncle is been diagnosed with carcinoma  rectum then staging investigations such as CT SCAN ABDOMEN & PELVIS OR MRI OF PELVIS need to be done.  As per staging the required treatment can be suggested.  If operable.  He can undergo surgery,  or else Radiotherapy to the pelvis can be opted.  As he is 88years,  chemotherapy could be omitted.

Please get a MRI pelvis and CT scan done.. treatment would be based on the stage and fitness of patient..

Please share his reports