Background and Study Aims: The depth of insertion
at flexible sigmoidoscopy is variable, depending upon bowel preparation, patient
tolerance and distal colonic anatomy. Many endoscopists routinely aim to insert
the 60 cm flexible sigmoidoscope to the splenic flexure; however internal
endoscopic markers are unreliable, making the true anatomical extent of the
examination difficult to assess. The aim of this study was to assess the depth
of insertion 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 insertion at non-sedated, screening flexible
sigmoidoscopy. In the second (study 2), “real-time” imaging was
utilized to determine sigmoid looping and the anatomical location of the endoscope
tip after 60 cm of instrument had been inserted during total or limited
colonoscopy. A total of 117 consecutive average-risk patients, aged 55 - 65
years participated in study 1, and 136 patients 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. In 61 % of patients
the imaging sytem showed that the descending colon had not been visualized
by the end of the procedure. Failure to reach the sigmoid/descending
junction occurred in 29 (24 %) patients. Reasons for failure included
poor tolerance of the procedure due to pain (23 patients) inadequate 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 endoscope tip had not passed beyond the sigmoid/descending colon junction.
A sigmoid loop formed in 70 % of patients, and unusual loops such as
the alpha, reverse alpha and reverse sigmoid spiral loop occurred more frequently
in women compared to men (P = 0.0249). In those 104 patients
where the splenic 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 approximately one-quarter of patients undergoing screening
flexible sigmoidoscopy, mainly because of discomfort. The descending colon
is intubated in a minority of cases (using standard instruments), even after
60 cm has been inserted. Alternative instruments with different shaft
characteristics (floppy, narrow calibre, 80 - 100 cm
in length) may be necessary to ensure deeper routine intubation in nonsedated
patients.
