Depth of insertion at flexible sigmoidoscopy: Implications for colorectal cancer screening and instrument design

Background and Study Aims: The depth of insertion at flexible sigmoidoscopy is variable, depending upon bowel preparation, patient tolerance and dista l colonic anatomy, Many endoscopists routinely aim to insert the 60 cm flex ible sigmoidoscope to the splenic flexure; however internal endoscopic mark ers are unreliable, making the true anatomical extent of the examination di fficult to assess. The aim of this study was to assess the depth of inserti on at flexible sigmoidoscopy. Patients and Methods: Two separate studies were done. In the first (study 1 ), magnetic endoscopic imaging was used to determine the final depth of ins ertion at non-sedated, screening flexible sigmoidoscopy. In the second (stu dy 2), "real-time" imaging was utilized to determine sigmoid looping and th e anatomical location of the endoscope tip after 60 cm of instrument had be en inserted during total or limited colonoscopy. A total of 117 consecutive average-risk patients, aged 55-65 years participated in study 1, and 136 p atients underwent either limited, (33) or attempted total colonoscopy (103) in study 2, Results: In study 1 the median insertion distance was 52 cm, range 20-58. I n 61 % of patients the imaging sytem showed that the descending colon had n ot been visualized by the end of the procedure. Failure to reach the sigmoi d/descending junction occurred in 29 (24 %) patients. Reasons for failure i ncluded poor tolerance of the procedure due to pain (23 patients) inadequat e preparation (3 patients) and, excessive looping (3 patients). In study 2, after 60 cm of instrument had been inserted, the splenic flexure or beyond was reached in 29 % and the descending colon in 9 %, whilst in 62 % the en doscope tip had not passed beyond the sigmoid/descending colon junction. A sigmoid loop formed in 70 % of patients, and unusual loops such as the alph a, reverse alpha and reverse sigmoid spiral loop occurred more frequently i n women compared to men (P = 0.0249). In those 104 patients where the splen ic flexure was reached the mean maximum length of instrument inserted prior to reaching the flexure was 75.4 cm, (SD = 21.9). Conclusions: Examination of the entire sigmoid was not achieved in approxim ately one-quarter of patients undergoing screening flexible sigmoidoscopy, mainly because of discomfort. The descending colon is intubated in a minori ty of cases (using standard instruments), even after 60 cm has been inserte d. Alternative instruments with different shaft characteristics (floppy, na rrow calibre, 80-100 cm in length) may be necessary to ensure deeper routin e intubation in nonsedated patients.