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

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

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

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

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)

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

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

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

- 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)

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

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

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

Materials and Methods ~ Statistical Analysis Unweighted κ: interobserver agreement for binary CT signs Weighted κ: agreement between readers for CT variables - fair agreement: 0.21-0.4 - moderate agreement: 0.41-0.6 - substantial agreement: 0.61-0.80 - almost perfect agreement: 0.81-1.0 Association between each CT sign and small bowel ischemia: χ2 or Fisher exact tests

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

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

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)

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

Results~ imaging findings

Results~ imaging findings

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

Results~ Prospective and retrospective interpretations

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%)

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

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

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

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

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

Thanks for your attention!

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