1. Radiology: Volume 241: Number 3—December 2006
CT of Small-Bowel Ischemia Associated with Obstruction in Emergency Department Patients: Diagnostic Performance Evaluation
Shannon P. Sheedy,MD
Frank Earnest IV,MD
Joel G. Fletcher,MD
Jeff L. Fidler,MD
Tanya L. Hoskin,MS
Radiology: Volume 241: Number 3—December 2006

2. Date: 2007/01/16 Place: MRI會議室 Presenter: Intern 洪柏聖
From the Division of Abdominal Imaging, Department of Radiology (S.P.S., F.E., J.G.F., J.L.F.) and Division of Biostatistics,Department of Health Sciences Research (T.L.H.), Mayo Clinic College of Medicine, Mayo W2, 200 First St SW, Rochester, MN 55905
Date: 2007/01/16
Place: MRI會議室
Presenter: Intern 洪柏聖
Supervisor: VS 鍾達榮

3. Introductions: Improve dx accuracy improve p’t care
Selection of a patient cohort for review
Retrospective review of patient data
Practice experience biases
Thoroughness of the reviewing radiologist
No ideal methods for measuring quality of dx imaging

4. Introductions: ER abd. CT interpretations
rapid management of acute nontraumatic abd. pain
Small-bowel obstruction (moderate, severe): accuracy of CT dx Small-bowel ischemia with obstruction:
reported sensitivities: 75~100%
reported specificities: 61~93%
Delay in dx high morbidity and mortality
Purpose: Dx of CT in pts with abd. pain in ER
Surgical or pathologic findings as reference
standard
prospective and retrospective

5. Materials and Methods~ Patients
2000/12002/10:
61CT in 60 p’ts with acute abdominal pain
 small-bowel surgical procedure for obstruction of
segmental ischemia within 7 days
25 male and 35 female, aged 1-89y/o (median 67)
Exclusion: surgery on other GI, gyn, primary mesenteric vascular dz, trauma (533/7306)
Approved by institutional review board
and was Health Insurance Portability and Accountability Act compliant (HIPAA)

6. Materials and Methods~ CT technique
one of two multisection CT scanners
5-mm reconstruction thickness and 5-mm intervals
or a single section helical scanner
7-mm reconstruction thickness and 7-mm intervals.
Bowel opacification: 50~600 ml of 2% dilute oral
meglumine diatrizoate solution
IV CM: 20~140 ml of iohexol, iopamidol, or ioversol, 3ml/s
Image acquisition: portal venous phase after 70-s delay
5: no oral or iv CM, 6: only oral CM, 5: only iv CM
45: both

7. Materials and Methods~ Image Review
Remove: names and identifying p’t record No.
Not remove: age, sex, date of CT exam.
Two experienced GI radiologists(5yrs&9yrs):
reviewed each CT and were blinded to pt identification and clinical information
 only know: abdominal pain presented in ER and surgery of small bowel within 7 days

8. Materials and Methods~ Image Review
CT signs of bowel obstruction and segmental ischemia or strangulation:
- subjective presence of circumferential bowel wall thickening
- bowel-wall edema determined by the presence of submucosal
edema with a visible target or halo sign
- presence of any intramural gas
- extraalimentary air
- portal venous or mesenteric venous gas
- increased attenuation of the bowel wall, compared with attenuation of adjacent bowel-wall segments in the absence of intravenous contrast enhancement

9. - subjective decreased relative enhancement of the bowel wall,
compared with other bowel-wall segments after intravenous
contrast enhancement
- presence of mesenteric fluid, defined as hazy fluid attenuation,
in the mesentery adjacent to the involved segment of small bowel
- presence of mesenteric vascular engorgement, defined as relative
dilatation of mesenteric vessels
- a transition point of small-bowel obstruction
- presence of a C- or U-shaped loop of small bowel suggesting a
closed loop obstruction or volvulus
- presence of ascites, defined as any peritoneal fluid in men or more
than a small quantity of cul-de-sac fluid in women
- presence of mottled intraluminal gas and debris within the
small bowel lumen (small-bowel feces sign)

10. Materials and Methods~ Image Review
Diagnosis of obstruction, ischemia or both:
-not present,
-possible,
-probable,
-definite
Third radiologist (10 yrs in GI images):
blinded consensus review of each case
 resolve discrepancies analysis

11. Materials and Methods ~ Reference Standard
Charts reviewed retrospectively:
surgical or pathologic diagnosis as reference standard
Review of the original CT reports:
 small-bowel dilatation, small-bowel obstruction,
closed loop obstruction, or volvulus
Interval between CT and surgery: 1h31m to 175h42m
43(70%): previous bowel surgery
24(39%): enteric dz
 6 with IBD, 7 with colon ca, 5 with diverticulosis, 4 with hx of small bowel
obstruction, 1with metastatic carcinoid, 1with hx of volvulus
2 with hx of prostate ca, 3 with hx of TCC

12. Materials and Methods ~ Statistical Analysis
SAS, version 8.2
Descriptive statistics: reported as mean and SD or median and range for continuous variables
Categoric variables: frequencies and percentages
P value <0.05: statistically significant difference
Sensitivity and specificity: surgical or pathologic findings as reference standard
95% exact binomial confidence intervals
Surgery within 24hrs of CT & 24hrs after CT

13. Materials and Methods ~ Statistical Analysis
Unweighted κ: interobserver agreement for binary CT signs
Weighted κ: agreement between readers for CT variables
- fair agreement:
- moderate agreement:
- substantial agreement:
- almost perfect agreement:
Association between each CT sign and small bowel ischemia: χ2 or Fisher exact tests

14. Results~ surgical findings
21/36=58%
6/25=24%

15. Results~ surgical findings
The presence or absence of bowel obstruction was not specifically noted in 18 of 61 surgical notes.
Small-bowel obstruction with bowel dilatation was confirmed at surgery or at consensus CT reading in 56 of 61 studies

16. Results~ imaging findings
Prospective CT interpretation of small bowel obstruction
Sensitivity: 88%(49/56),
Specificity:60%(3/5)
7 with small bowel obstruction and dilatation: not described in prospective CT interpretation
4 noted in the consensus reading
(1: free air, 2:109hrs & 139hrs)

17. Results~ imaging findings
2 without small bowel obstruction and dilatation
but described positive in prospective CT
One no findings of small-bowel dilatation and
obstruction at consensus review
One false-positive prospective interpretation,
175hrs between CT and OP

18. Results~ imaging findings

19. Results~ imaging findings

20. Results~ Interobserver Agreement
There was generally substantial or almost perfect interobserver agreement between the blinded readers and the consensus reading
fair
moderate
substantial

21. Results~ Prospective and retrospective interpretations

22. Discussion (I)
Previous investigations of CT for the diagnosis:
Sensitivity: 76% & 100%
Specificities: 93% & 61%
(inclusion criteria, proportion of pt with surgery and studies without contrast enhancement, and nonsurgical pts)
Previous study: two or more CT signs as positieve indicator good sensitivity
-our cases in such criteria only 23/27(85%)
sensitivity
-helped identify only 8/34 CT pt without
ischemia(specificity:24%)

23. Discussion (II) Reduced segmental bowel-wall enhancement:
100% specific for the dx of small bowel ischemia
only 6/18 with ischemia sensitivity: 33.3%
* in prospective interpretation:
noting bowel-wall enhancement ↑sensitivity
The use of arterial phase helpful in:
- primary mesenteric vascular dz
- improve bowel-wall enhancement

24. Discussion (III)
Small-bowel feces sign: first reported by Mayo-Smith et al
obstruction, undigested food, secondary bacterial growth, water absorption proximal to an obstruction
Limitations of this study:
selecting the sample (abd. Pain, surgery within 7 days), analysis criteria, reference standards
 44% pts with small-bowel ischemia didn’t undergo CT or surgery was excluded

25. Discussion (IV) Review of the prospective reports:
use of specific terms  easily considered to conclude negative finding
Criteria for CT signs were subjective:
rely on experience and judgment of the reviewers
 mesenteric vascular engorgement, transition point in the caliber of the small bowel, decreased bowel wall enhancement
 reduced sensitivity

26. Discussion (V)
For the reference standard of surgical or pathologic findings:
- thought to be ischemic no pathologic findings
- extensive adhesiolysis complicated identification
of closed loop obstruction

27. Discussion (VI) Prospective sensitivity of CT in our ER:
much lower than that of previously published reports
Decreased segmental bowel-wall enhancement and the presence of the small-bowel feces sign
 significantly associated wit small-bowel ischemia in
patients
Maximizing bowel-wall enhancement and accurately identifying decreased segmental bowel-wall enhancement substantially improve the dx performance

28. Thanks for your attention!

29. Decreased enhancement of bowel wall: the most specific sign no false-positive findings, 6 true-positive findings