Radiology 2005;236:712-715 Intern 陳君豪 2005/08/17 Evaluation of Bowel Ischemia with Contrast-enhanced US: Initial Experience Radiology 2005;236:712-715 Intern 陳君豪 2005/08/17

Introduction – (1) Bowel ischemia is a potentially fatal disorder often caused by vascular embolism and bowel strangulation The diagnosis is not necessarily easy owing to the lack of specific physical or laboratory findings

Introduction – (2) The definitive diagnosis is usually established at angiography, this method is not suitable for the evaluation of patients who are only suspected of having the disease

Introduction – (2) Contrast material–enhanced ultrasonography (US): evaluate transmural bowel wall perfusion after the injection of SHU-508A Evaluate patients with radiographic evidence of small-bowel dilatation

Materials and Methods – (1) 51 patients (mean age, 67.1 years) with evidence of small-bowel dilatation at conventional radiography

Materials and Methods – (2) Detect any distended small-bowel loops (>2 cm) for 10 mins SHU-508A flushed with saline for 10 seconds Most dilated or the least peristaltic small-bowel were scanned with contrast-enhanced power Doppler US (interval, 4 seconds) for 2 minutes

Normal (A), diminished (B), and absent (C)

Materials and Methods – (3) When more than one type of signal was observed, the signal with the poorest enhancement was used. Absent and diminished color signals bowel ischemia

Materials and Methods – (4) Definitive diagnosis was established at the time of surgery (n=18) and/or autopsy (n=2) in patients with bowel ischemia. For patients with obstruction, CT (n=10), contrast-enhanced studies (n=14), or colonoscopy (n=7), together with clinical course, established the diagnosis

Materials and Methods – (5) 31 patients Bowel obstruction Cancer (n=7) Adhesions (n=24) 20 patients Bowel ischemia Bowel strangulation (n=15) SMA thromboembolism (n=5)

35 y/o woman with simple obstruction Color signals: normal in the bowel wall

72 y/o man with bowel strangulation Segment with ischemia has diminished (B) and absent (C) color signals

78 y/o woman with SMA thromboembolism Color signals are absent in all bowel segments

Result Sensitivity was 85% Specificity was 100% Positive predictive value was 100% Negative predictive value was 91.2% P < .01 was considered to indicate a significant difference

Discussion – (1) Contrast-enhanced US shows promise for the noninvasive diagnosis of bowel ischemia based on initial experience in patients with radiographic evidence of small-bowel dilatation

Discussion – (2) Contrast-enhanced CT is one of the methods used for the diagnosis of this disorder. However, the contrast agents move into the extravascular space, which results in difficulty differentiating between mild ischemia and congestion Radiation exposure and the potential renal toxicity of the contrast agents

Discussion – (3) Limitations in this study: First, the assessment of color signals was subjective Second, interobserver agreement was not assessed

Discussion – (4) Third, the exclusion of patients with disseminated intravascular coagulation and cardiac failure may have biased our results Our results may not be generalizable to patients with DIC, acute/chronic cardiac failure, microcirculatory diseases, or obesity

Discussion – (5) Further studies with a greater number of patients are needed to determine the effectiveness of contrast-enhanced US in the differentiation between early strangulation and simple obstruction.

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