When and why a colonoscopist should discontinue colonoscopy by himself?

Table 1 Kudo’s colonoscopist level classification

Colonoscopist level	Presentation of correlative level
I	Mostly beginners, able to push forward the colonoscope body in the colon cavity; unable to use the method of the colon axis constriction to shorten the length of the colon
II	Able to push the colonoscope through the descending sigmoid flexure by α-loop or N-loop, and pull back the colonoscope to set free the loop when the colonoscope head reaches the transverse colon; then, use the method mentioned above
III	Able to control the colonoscope passing through the descending sigmoid flexure by α-loop or N-loop, and pull back the colonoscope to set free the loop when it reaches the descending colon; then, use the above-mentioned method
IV	Able to control the colonoscope and keep the colon axis constriction from rectosigmoid flexure, pushing the colonoscope passing through the descending sigmoid flexure without loop formation

Table 2 Kudo’s classification of colonoscopy difficulty

Difficulty classification	Presentation of correlative pattern
Grade A	Relatively short sigmoid colon, easy to be shortened. Applied to most young and middle-aged men. 2-3 min taken to reach the cecum
Grade B	Lengthy sigmoid colon and relatively tortuous descending sigmoid flexure, easier to form a loop
Grade C	Sigmoid colon with local or partial adhesion after abdominal disease, surgery, or unusually long sigmoid colon, with or without obvious tortuous descending sigmoid flexure, easier to form a loop

Table 3 Sites for colonoscopy discontinuation and reasons for discontinuation n (%)

Site	Value	Fixation	Tortuosity	Laxity	Redundance
Right hemicolon
Ascending colon	10 (5.1)	9	4	3	3
Hepatic flexure	45 (23.1)	41	30	5	12
Transverse colon	26 (13.3)	22	15	2	7
Left hemicolon
Splenic flexure	9 (4.6)	8	8	2	0
Descending colon	14 (7.2)	13	11	4	1
Descending sigmoid flexure	40 (20.5)	35	39	6	2
Sigmoid colon	29 (14.9)	27	26	2	1
Rectosigmoid flexure	22 (11.3)	22	19	0	0
Total	195 (100)	177	152	24	26

Table 4 Factors related to sites for colonoscope reaching left hemicolon and right hemicolon

	Left hemicolon			Right hemicolon
	OR	95%CI	P value	OR	95%CI	P value
Preoperative variable
Sex (female vs male)	0.69	0.41-1.17	0.17	0.35	0.20-0.63	< 0.001
Age (> vs ≤ 60 yr)	1.63	0.95-2.80	0.08	0.88	0.50-1.52	0.64
Anesthesia (yes vs no)	0.74	0.43-1.30	0.30	0.98	0.55-1.75	0.93
Type of colonoscope (yes vs no)	0.88	0.50-1.53	0.64	1.11	0.62-2.00	0.72
Intraoperative variable
Fixation (yes vs no)	0.06	0.03-0.16	< 0.001	0.16	0.06-0.39	< 0.001
Tortuosity (yes vs no)	0.04	0.02-0.08	< 0.001	0.23	0.13-0.43	< 0.001
Laxity (yes vs no)	0.56	0.24-1.33	0.19	1.16	0.50-2.71	0.73
Redundancy (yes vs no)	0.80	0.21-3.10	0.75	0.12	0.05-0.26	< 0.001

Table 5 Factors related to insertion time (> 10 min) in left hemicolon and right hemicolon

	Left hemicolon			Right hemicolon
	OR	95%CI	P value	OR	95%CI	P value
Preoperative variable
Sex (female vs male)	1.30	0.86-1.96	0.22	1.47	0.96-2.26	0.08
Age (> 60 yr vs ≤ 60 yr)	1.18	0.78-1.79	0.43	1.35	0.88-2.06	0.17
Anesthesia (yes vs no)	0.68	0.44-1.03	0.07	0.84	0.54-1.30	0.43
Type of colonoscope (yes vs no)	0.68	0.45-1.04	0.08	0.61	0.39-0.94	0.02
Intraoperative variable
Fixation (yes vs no)	0.99	0.55-1.79	0.98	1.92	1.04-3.52	0.04
Tortuosity (yes vs no)	1.80	1.14-2.86	0.01	2.40	1.51-3.82	< 0.001
Laxity (yes vs no)	1.62	0.92-2.85	0.10	1.53	0.87-2.70	0.14
Redundancy (yes vs no)	2.44	1.09-5.44	0.03	4.65	2.30-9.39	< 0.001