Although generally considered quite safe,<unk>  does carry the very rare possibility of tearing of the intestinal wall by the instrument, which could require immediate surgery to repair the tear; in addition, removal of a polyp may sometimes lead to localized bleeding which is resistant to cauterization by the instrument and must be stopped by surgical intervention.
Sigmoidoscopy
Stool test
Dry enema
EGS 
Defecography
Rectal examination
Lower gastrointestinal series
Magnetic resonance enterography