Fast MRI outperforms CT in detecting bowel obstruction
If the alternative in imaging bowel obstruction is single-slice CT, then fast MRI should be the modality of choice, according to researchers at the Mayo Clinic and Johns Hopkins University.
CT imaging had replaced the previous gold standard of small bowel follow through for detecting bowel obstructions, said Dr. Douglas Beall, who performed the research at Mayo. He is now division chief of musculoskeletal radiology at the U.S. Air Force Wilford Hall Medical Center.
?Compared with single-slice CT, MR provides the benefit of multiplanar imaging and can accurately diagnose the presence and location of bowel obstruction,? he said.
Researchers prospectively evaluated 44 patients who presented with clinical evidence of bowel obstruction. Beall and colleagues imaged the patients using 1.5T HASTE MR and helical CT. They did not administer contrast media in the MR acquisition, while they did use oral and intravenous contrast medium in the consecutive helical CT imaging through the abdomen and pelvis. The study was published in the August issue of Clinical Radiology.
The researchers used laparotomy or radiography to confirm the presence of bowel obstruction in 28 patients: 25 presented with small bowel obstruction and three with colonic obstructions.
Beall and colleagues discovered the following: · fibrous adhesions in nine patients · metastases or primary carcinoma in seven patients · Crohn?s disease in four patients · hernias in two patients · inflammation or abscess in two patients
Additional causes of obstruction included lymphoma, intussusception, and anastomotic stricture.
The researchers found that MR correctly diagnosed 95% of the cases of obstruction compared with 71% for CT. HASTE MR imaging showed a sensitivity of 95% and a specificity of 100%, compared with 71% for both for CT.
Despite the favorable MRI results in the study, Beall said that the advent of multidetector CT means the advantages of MRI over CT may not outweigh the increased costs and longer scan times involved.
?MR is more suitable for a stable patient who is to be scanned when an MR technologist is available and the CT alternative is a single-slice CT,? he said. ?Although no study has been done comparing MDCT versus MRI, the high-resolution multiplanar imaging seen with MDCT will likely take away most of the current advantages of fast MR imaging.?
Studies should be done to compare the accuracy of MDCT versus fast MRI in diagnosing the presence, location, and etiology of small bowel obstruction, as well as the effectiveness of MDCT and fast MRI for distinguishing between benign and malignant causes of obstruction, according to Beall.
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