Can internal rectal intussusception cause constipation, painful defecation, and flat & thin stools? what test is typically ordered to confirm a dx?

That is a : Rare problem, you could try MiraLAX (polyethylene glycol) for constipation. I would get seen and consider a colonoscopy. An intussuseption is rare but a GI doc with a scope is likely ur best bet.

Usually not: But regardless would be very unusually after a lar you mentioned in your previous note, other than exam the best test is a voiding proctogram. (defecography).