Experience with five patients has shown facilitation of insertion of the colonoscope if a guidestring was passed beforehand. The string was swallowed and allowed to pass through the entire gastrointestinal tract. The thinness of the string made it possible to perform diagnostic examinations, biopsy, and polypectomy. A marked saving of time and a substantial decrease in patient discomfort ensued from this technique.
Smith JH, Roberts GW, Ohan AH, Worth F. Use of an Oral-Anal String as a Guideline for Colonoscopy. Arch Surg. 1974;108(6):879. doi:10.1001/archsurg.1974.01350300109027