Risk factors associated with missed colorectal flat adenoma: A multicenter retrospective tandem colonoscopy study

Table 1 Demographic and clinical characteristics of patients with different types of colorectal adenomas n (%)

Patients	Total(n = 2093)	Flat adenoma(n = 177)	Flat and protruding adenoma (n = 514)	Protruding adenoma(n = 1402)	P value
Sex
Male	1369	91 (51.4)	329 (64.0)	949 (67.7)	< 0.001
Female	724	86 (48.6)	185 (34.0)	453 (32.3)	< 0.001
Age (mean ± SD, yr)		55.91 ± 12.68	59.30 ± 12.47	54.78 ± 13.24	< 0.001
Alarm symptoms	1621	134 (75.7)	388 (75.5)	1099 (78.4)	0.341
Diverticulosis	123	10 (5.6)	27 (5.3)	86 (6.1)	0.761
Family history of CRC	131	11 (6.2)	32 (6.2)	88 (6.3)	0.999
History of adenomas	475	40 (22.6)	139 (27.0)	296 (21.1)	0.023
History of abdominal surgery	149	3 (1.7)	35 (6.8)	111 (7.9)	0.010
Cases with adenomas ≥ 3 at first colonoscopy	458	8 (4.5)	222 (43.2)	228 (16.3)	< 0.001

Family history of colorectal cancer (CRC) was defined as the development of CRC in one first-degree relative < 50 years or at least two first-degree relatives 50-70 years; Diverticulosis is defined as the presence of ≥ 2 diverticula. Data are expressed as number (%) unless otherwise indicated.