Optimized protocol of multiple post-processing techniques improves diagnostic accuracy of multidetector computed tomography in assessment of small bowel obstruction compared with conventional axial and coronal reformations

Table 1 Worksheet for readers to use for interpretation of multidetector computed tomography post-processing images

Presence or absence of obstruction	External hernias
Presence (≥ 2.5 cm)	Bezoars/stones
Absence (< 2.5 cm)	Vascular lesions
Severity of obstruction	Inflammatory lesions
Mild (2.5 to < 3 cm)	Others (e.g., foreign body, abdominal cocoon, hematoma and so on)
Moderate (3 to < 4 cm)	Findings of secondary bowel ischemia
Severe (≥ 4 cm)	Main sings
Obstruction site	Increased bowel wall attenuation
Proximal (duodenum to proximal jejunum)	Decreased bowel wall enhancement
Middle (distal jejunum to mid-ileum)	Vascular embolus/thrombosis
Distal (distal ileum)	Vascular stenosis/occlusion
Multisegmental (more than one segment)	Pneumatosis/portomesenteric gas
Cause	Secondary sings
Adhesions	Bowel wall thickening
Neoplasms	Increased bowel wall enhancement
Intussusception	Mesenteric fluid/haziness
Neoplasms	Mesenteric vascular engorgement
Non-neoplasms	Small bowel feces sign
Volvulus	Ascites
Hernias	Others (solid organ infarction, free gas and so on)
Internal hernias	Other findings (fistula, leakage or perforation, pneumoperitoneum and so on)

Table 2 Use frequencies of multiple post-processing techniques in the protocol 3 n (%)

Assessment parameter	Reader 1	Reader 2	P-value
Presence or absence of SBO (n = 106)	1 (0.9)	2 (1.9)	1.000
Severity (n = 106)	0	0
Obstruction site
No (n = 16)	1 (6.3)	2 (12.5)	1.000
Proximal (n = 9)	0	0
Middle (n = 37)	2 (5.4)	1 (2.7)	0.556
Distal (n = 44)	3 (6.8)	4 (9.1)	0.694
Total (n = 106)	6 (5.7)	7 (6.6)	1.000
Cause
No (n = 16)	1 (6.3)	2 (12.5)	1.000
Adhesions (n = 20)	2 (10.0)	1 (5.0)	0.548
Neoplasms (n = 11)	1 (9.1)	3 (27.3)	0.269
Intussusception
Neoplasms (n = 9)	2 (22.2)	2 (22.2)	1.000
Nonneoplasms (n = 5)	3 (60.0)	2 (40.0)	0.527
Volvulus (n = 8)	6 (75.0)	7 (87.5)	0.522
Hernias
Internal hernias (n = 6)	6 (100)	6 (100)	1.000
External hernias (n = 9)	1(11.1)	2 (22.2)	0.527
Bezoars/stones (n = 7)	0	2 (28.6)	0.127
Vascular lesions (n = 8)	8 (100)	8 (100)	1.000
Inflammatory lesions (n = 7)	1 (14.3)	2 (28.6)	0.515
Total (n = 106)	31 (29.2)	37 (34.9)	0.377
Findings of secondary bowel ischemia
Increased bowel wall attenuation	0	0
Decreased bowel wall enhancement	0	0
Vascular embolus/thrombosis	5 (4.7)	5 (4.7)	1.000
Vascular stenosis/occlusion	18 (17)	15 (14.2)	0.570
Pneumatosis/portomesenteric gas	1 (0.9)	2 (1.9)	1.000
Bowel wall thickening	0	0
Increased bowel wall enhancement	0	0
Mesenteric haziness/fluid	2 (1.9)	0	0.477
Mesenteric vascular engorgement	8 (7.5)	10 (9.4)	0.622
Small bowel feces sign	0	0
Ascites	0	0
Total (n = 106)	34 (32.1)	32 (30.2)	0.767

SBO: Small bowel obstruction.

Table 3 Average confidence scores among three protocols for assessment of small bowel obstruction (n = 106)

Assessment parameter	Protocol 1			Protocol 2			Protocol 3			P-value
	Reader 1	Reader 2	P-value	Reader 1	Reader 2	P-value	Reader 1	Reader 2	P-value
Presence or absence of SBO
Presence	4.8 ± 0.5	4.7 ± 0.6	0.070	4.8 ± 0.4	4.9 ± 0.3	0.103	4.9 ± 0.4	4.8 ± 0.4	0.184	0.110
Absence	4.6 ± 0.7	4.8 ± 0.6	0.270	4.9 ± 0.3	4.8 ± 0.4	0.164	4.7 ± 0.5	4.9 ± 0.3	0.188	0.341
Severity of obstruction
No	4.6 ± 0.7	4.8 ± 0.6	0.270	4.9 ± 0.3	4.8 ± 0.4	0.164	4.7 ± 0.5	4.9 ± 0.3	0.188	0.341
Mild	4.4 ± 0.7	4.5 ± 0.7	0.162	4.8 ± 0.5	4.7 ± 0.5	0.428	4.7 ± 0.6	4.6 ± 0.6	0.666	0.753
Moderate	4.8 ± 0.4	4.7 ± 0.4	0.323	4.8 ± 0.4	4.8 ± 0.4	0.710	4.7 ± 0.6	4.8 ± 0.4	0.133	0.418
Severe	4.9 ± 0.4	4.8 ± 0.4	0.326	4.9 ± 0.4	4.9 ± 0.4	1.000	4.9 ± 0.3	4.9 ± 0.4	0.663	0.872
Obstruction site
Proximal	4.4 ± 0.7	4.4 ± 0.5	1.000	4.8 ± 0.4	4.9 ± 0.3	0.594	4.7 ± 0.5	4.8 ± 0.4	0.681	0.323
Middle	4.2 ± 0.9	4.3 ± 0.8	0.054	4.6 ± 0.5	4.7 ± 0.5	0.058	4.4 ± 0.7	4.6 ± 0.6	0.710	0.004b
Distal	4.4 ± 1.0	4.5 ± 0.9	0.083	4.7 ± 0.5	4.7 ± 0.5	0.570	4.6 ± 0.6	4.6 ± 0.6	0.660	0.221
Cause
Adhesions	3.6 ± 0.8	3.7 ± 0.8	0.083	4.7 ± 0.5	4.8 ± 0.4	0.428	4.5 ± 0.6	4.6 ± 0.6	0.163	0.001b
Neoplasms	4.1 ± 0.7	4.2 ± 0.6	0.341	4.9 ± 0.3	4.8 ± 0.4	0.588	4.7 ± 0.5	4.6 ± 0.5	0.588	0.001b
Intussusception
Neoplasms	4.1 ± 1.1	4.2 ± 1.0	0.594	4.9 ± 0.3	4.8 ± 0.4	0.594	4.7 ± 0.5	4.6 ± 0.5	0.594	0.019a
Nonneoplasms	4.2 ± 0.8	4.0 ± 0.7	0.374	4.8 ± 0.4	4.8 ± 0.4	1.000	4.6 ± 0.5	4.8 ± 0.4	0.374	0.029a
Volvulus	4.4 ± 0.7	4.5 ± 0.8	0.351	5.0 ± 0.0	4.9 ± 0.4	0.351	4.6 ± 0.5	4.8 ± 0.5	0.598	0.041a
Hernias
Internal hernias	3.3 ± 1.4	3.5 ± 1.0	0.611	4.7 ± 0.5	4.8 ± 0.4	0.611	4.3 ± 0.8	4.5 ± 0.5	0.695	0.002b
External hernias	4.7 ± 0.5	4.6 ± 0.7	0.347	4.9 ± 0.3	5.0 ± 0.0	0.347	4.9 ± 0.3	4.9 ± 0.3	1.000	0.054
Bezoars/stones	4.6 ± 0.5	4.7 ± 0.5	0.356	5.0 ± 0.0	4.9 ± 0.4	0.356	4.9 ± 0.4	4.7 ± 0.5	0.356	0.492
Vascular lesions	3.2 ± 1.3	3.3 ± 1.1	0.594	4.7 ± 0.5	4.6 ± 0.5	0.594	4.4 ± 0.5	4.3 ± 0.5	0.681	0.001b
Inflammatory lesions	3.9 ± 1.3	4.1 ± 1.1	0.356	4.7 ± 0.5	4.4 ± 0.5	0.172	4.3 ± 1.0	4.4 ± 0.5	0.604	0.581
Findings of secondary bowel ischemia
Increased bowel wall attenuation	4.4 ± 0.5	4.5 ± 0.5	0.539	4.7 ± 0.5	4.7 ± 0.5	1.000	4.7 ± 0.5	4.6 ± 0.5	0.664	0.819
Decreased bowel wall enhancement	4.5 ± 0.5	4.4 ± 0.5	0.572	4.6 ± 0.5	4.7 ± 0.5	0.536	4.6 ± 0.5	4.7 ± 0.5	0.721	0.282
Vascular embolus/thrombosis	4.0 ± 0.9	4.1 ± 1.0	0.598	4.9 ± 0.4	4.8 ± 0.5	0.598	4.6 ± 0.5	4.5 ± 0.5	0.598	0.010a
Vascular stenosis/occlusion	3.8 ± 0.8	3.9 ± 0.9	0.503	4.8 ± 0.4	4.7 ± 0.5	0.265	4.4 ± 0.5	4.5 ± 0.6	0.574	0.001b
Pneumatosis/portomesenteric gas	4.1 ± 0.3	4.3 ± 0.7	0.447	4.4 ± 0.5	4.7 ± 0.4	0.081	4.6 ± 0.5	4.7 ± 0.5	0.681	0.814
Bowel wall thickening	4.5 ± 0.5	4.6 ± 0.5	0.321	4.6 ± 0.5	4.7 ± 0.5	0.109	4.6 ± 0.5	4.7 ± 0.5	0.254	0.059
Increased bowel wall enhancement	4.6 ± 0.5	4.8 ± 0.4	0.231	4.7 ± 0.5	4.8 ± 0.4	0.161	4.8 ± 0.4	4.7 ± 0.5	0.536	0.441
Mesenteric haziness/fluid	4.3 ± 0.6	4.3 ± 0.6	0.571	4.7 ± 0.5	4.8 ± 0.4	0.292	4.6 ± 0.5	4.7 ± 0.5	0.571	0.003b
Mesenteric vascular engorgement	4.2 ± 0.6	4.1 ± 0.6	0.748	4.8 ± 0.4	4.9 ± 0.4	0.494	4.7 ± 0.5	4.8 ± 0.4	0.716	0.001b
Small-bowel feces sign	4.4 ± 0.5	4.6 ± 0.6	0.329	4.7 ± 0.5	4.6 ± 0.5	0.576	4.5 ± 0.5	4.6 ± 0.6	0.428	0.748
Ascites	4.7 ± 0.5	4.6 ± 0.5	0.583	4.9 ± 0.4	4.8 ± 0.4	0.671	4.8 ± 0.4	4.7 ± 0.5	0.583	0.848

^aP < 0.05,

^bP < 0.01. SBO: Small bowel obstruction.

Table 4 Inter- and intra-reader agreement (κ value) among three protocols for assessment of small bowel obstruction

Assessment parameter	Inter-reader agreement			Intra-reader agreement
	Protocol 1	Protocol 2	Protocol 3	Reader 1			Reader 2
	Reader 1-2	Reader 1-2	Reader 1-2	Protocol 1-2	Protocol 1-3	Protocol 2-3	Protocol 1-2	Protocol 1-3	Protocol 2-3
Presence or absence of SBO (n = 106)	0.902	0.897	0.966	0.866	0.902	0.964	0.933	0.897	0.967
Severity of obstruction (n = 106)	0.868	0.869	0.894	0.830	0.882	0.895	0.881	0.907	0.921
Obstruction site (n = 106)	0.873	0.926	0.925	0.855	0.890	0.925	0.908	0.870	0.963
Cause
No (n = 16)	0.902	0.897	0.966	0.866	0.902	0.964	0.933	0.897	0.967
Adhesions (n = 20)	0.725	0.820	0.820	0.725	0.786	0.759	0.820	0.820	1.000
Neoplasms (n = 11)	0.946	1.000	0.946	0.946	0.946	1.000	1.000	0.946	0.946
Intussusception
Neoplasms (n = 9)	0.927	0.935	0.935	0.863	0.927	0.935	0.863	0.935	0.935
Nonneoplasms (n = 5)	0.738	0.883	0.883	0.883	0.738	0.883	0.738	0.883	0.883
Volvulus (n = 8)	0.927	0.927	0.927	0.845	0.927	0.927	1.000	0.927	0.927
Hernias
Internal hernias (n = 6)	0.554	0.903	0.788	0.789	0.649	0.903	0.739	0.739	1.000
External hernias (n = 9)	0.935	0.935	1.000	0.935	1.000	0.935	0.935	0.935	1.000
Bezoars/stones (n = 7)	0.917	0.917	1.000	0.917	1.000	0.917	0.917	0.917	1.000
Vascular lesions (n = 8)	0.554	0.927	0.751	0.522	0.419	0.845	0.518	0.711	0.845
Inflammatory lesions (n = 7)	0.371	0.586	0.637	0.444	0.411	0.637	0.363	0.333	0.751
Total (n = 106)	0.733	0.861	0.848	0.748	0.760	0.848	0.772	0.797	0.924
Presence or absence of secondary bowel ischemia (n = 106)	0.572	0.863	0.840	0.675	0.645	0.795	0.690	0.696	0.863

SBO: Small bowel obstruction.

Table 5 Detection rates for assessment parameters among three protocols for assessment of small bowel obstruction n (%)

Assessment parameter	Protocol 1			Protocol 2			Protocol 3			P-value
	Reader 1	Reader 2	P-value	Reader 1	Reader 2	P-value	Reader 1	Reader 2	P-value
Presence or absence of SBO
Presence (n = 90)	85 (94.4)	87 (96.7)	0.469	89 (98.9)	87 (96.7)	0.312	88 (97.8)	88 (97.8)	1.000	0.378
Absence (n = 16)	15 (93.8)	14 (87.5)	0.544	15 (93.8)	16 (100)	0.310	15 (93.8)	16 (100)	0.310	0.430
Obstruction site
No (n = 16)	15 (93.8)	14 (87.5)	0.544	15 (93.8)	16 (100)	0.310	15 (93.8)	16 (100)	0.310	0.430
Proximal (n = 9)	8 (88.9)	7 (77.8)	0.527	9 (100)	8 (88.9)	0.303	8 (88.9)	8 (88.9)	1.000	0.570
Middle (n = 37)	34 (91.9)	33 (89.2)	0.691	34 (91.9)	35 (94.6)	0.643	35 (94.6)	34 (91.9)	0.643	0.775
Distal (n = 44)	40 (90.9)	41 (93.2)	0.694	43 (97.7)	43 (97.7)	1.000	42 (95.5)	43 (97.7)	0.557	0.160
Total (n = 106)	97 (91.5)	95 (89.6)	1.000	101 (95.3)	102 (96.2)	1.000	100 (94.3)	101 (95.3)	1.000	0.129
Cause
No (n = 16)	15 (93.8)	14 (87.5)	0.544	15 (93.8)	16 (100)	0.310	15 (93.8)	16 (100)	0.310	0.430
Adhesions (n = 20)	18 (90.0)	19 (95.0)	0.548	19 (95.0)	20 (100)	0.311	19 (95.0)	20 (100)	0.311	0.434
Neoplasms (n = 11)	10 (90.9)	11 (100)	0.306	11 (100)	11 (100)	1.000	11 (100)	10 (90.9)	0.306	0.597
Intussusception
Neoplasms (n = 9)	7 (77.8)	8 (88.9)	0.527	9 (100)	8 (88.9)	0.303	8 (88.9)	9 (100)	0.303	0.414
Nonneoplasms (n = 5)	4 (80.0)	4 (80.0)	1.000	5 (100)	4 (80.0)	0.292	4 (80.0)	5 (100)	0.292	0.749
Volvulus (n = 8)	7 (87.5)	8 (100)	0.302	7 (87.5)	8 (100)	0.302	8 (100)	7 (87.5)	0.302	1.000
Hernias
Internal hernias (n = 6)	4 (66.7)	3 (50.0)	0.558	6 (100)	5 (83.3)	0.296	5 (83.3)	5 (83.3)	1.000	0.045a
External hernias (n = 9)	9 (100)	8 (88.9)	0.303	8 (88.9)	9 (100)	0.303	9 (100)	9 (100)	1.000	0.595
Bezoars/stones (n = 7)	7 (100)	6 (85.7)	0.299	6 (85.7)	7 (100)	0.299	7 (100)	7 (100)	1.000	0.592
Vascular lesions (n = 8)	3 (37.5)	4 (50.0)	0.614	8 (100)	7 (87.5)	0.302	6 (75.0)	7 (87.5)	0.522	0.004b
Inflammatory lesions (n = 7)	6 (85.7)	6 (85.7)	1.000	6 (85.7)	5 (71.4)	0.515	6 (85.7)	5 (71.4)	0.515	0.857
Total (n = 106)	90 (84.9)	91 (85.8)	1.000	100 (94.3)	100 (94.3)	1.000	98 (92.5)	100 (94.3)	1.000	0.001b
Presence or absence of secondary bowel ischemia
Presence (n = 38)	28 (73.7)	27 (71.1)	1.000	36 (94.7)	35 (92.1)	0.644	34 (89.5)	36 (94.7)	0.395	0.001b
Absence (n = 68)	65 (95.6)	67 (98.5)	0.308	65 (95.6)	66 (97.1)	0.647	66 (97.1)	65 (95.6)	0.647	0.928

^aP < 0.05,

^bP < 0.01. SBO: Small bowel obstruction.

Table 6 Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of three protocols for assessment of small bowel obstruction

Assessment parameter	Protocol 1		Protocol 2		Protocol 3
	Reader 1	Reader 2	Reader 1	Reader 2	Reader 1	Reader 2
Presence or absence of SBO
Sensitivity	94.4%	96.7%	98.9%	96.7%	97.8%	97.8%
Specificity	93.8%	87.5%	93.8%	100%	93.8%	100%
PPV	98.8%	97.8%	98.9%	100%	98.9%	100%
NPV	75.0%	82.4%	93.8%	84.2%	88.2%	88.9%
Accuracy	94.3%	95.3%	98.1%	97.2%	97.2%	98.1%
Obstruction site
Sensitivity	94.3%	96.4%	98.9%	96.6%	97.7%	97.7%
Specificity	78.9%	63.6%	78.9%	94.1%	78.9%	84.2%
PPV	95.3%	91.0%	95.6%	98.9%	95.5%	96.6%
NPV	75.0%	82.4%	93.8%	84.2%	88.2%	88.9%
Accuracy	91.5%	89.6%	95.3%	96.2%	94.3%	95.3%
Cause
Sensitivity	93.8%	96.3%	98.8%	96.6%	97.6%	97.7%
Specificity	57.7%	53.8%	75.0%	84.2%	71.4%	80.0%
PPV	87.2%	86.5%	94.4%	96.6%	93.3%	95.5%
NPV	75.0%	82.4%	93.8%	84.2%	88.2%	88.9%
Accuracy	84.9%	85.8%	94.3%	94.2%	92.5%	94.3%
Secondary bowel ischemia
Sensitivity	73.7%	71.1%	94.7%	92.1%	89.5%	94.7%
Specificity	95.6%	98.5%	95.6%	97.1%	97.1%	95.6%
PPV	90.3%	96.4%	92.3%	94.6%	94.4%	92.3%
NPV	86.7%	85.9%	97%	95.7%	94.3%	97%
Accuracy	87.7%	88.7%	95.3%	95.3%	94.3%	95.3%

SBO: Small bowel obstruction; PPV: Positive predictive value; NPV: Negative predictive value.