Talk to Gastroenterologist on Chronic Constipation

my father (80+ year-old bed-bound and suffering from severe chronic constipation). His condition recently has progressed to very hard, stone like stools, often requiring manual evacuation every 3-5 days, despite regular use of Duphalac and fiber supplements.

I’m very concerned about fecal impaction, complications from repeated forceful evacuation and his overall safety at this age.

Would appreciate some advise on meds and procedures we should follow.