Colonoscopies are primarily performed by gastroenterologists and colorectal surgeons as a matter of routine medical practice, requiring no formal citation.
The claim states that gastroenterologists and colorectal surgeons are the specialists who perform colonoscopies. This is a straightforward, everyday professional fact about medical specialization that is trivially true by direct observation of healthcare systems and professional definitions. Therefore, it falls under COMMON_KNOWLEDGE, and no citation is needed. None of the retrieved papers are cited to support or refute this as a contested matter, as the papers discuss specific comparative quality metrics, procedure volumes, or unrelated medical topics rather than debating whether these specialists perform the procedure.