Hi thanks for contacting us.... Your main concern is difficulty in passing stool.... Your father also old aged ...so problem is there of constipation.... Here advise him to take more fiber food like apple, whole grain , wheat bran , carrot etc... Water intake more... Regular mild exercise done... Chamomile in tea useful.... Fiber supplement given..... Green tea also good herbal remedy... Avocados highly rich in fiber ..so useful.for digestion.... Red beetroots rich in fiber , pottasium and magnesium so help to remove waste..... If still needed over the counter laxative can be given..... Take care.... Dr.Parth