Emergency Radiology (2000) 7:47-55
Ha Hyun Kwon, Rha Sung Eun, Kim Jung Hoon, Auh Yong Ho, Maglinte Dean D.T.
The pathophysiology of strangulating small bowel obstruction and the limitations of known CT criteria of strangulation are reviewed. The concept of coronal mapping of the course of the superior mesenteric vessels based on axial abdominal CT in order to aid the radiologic diagnosis of intestinal strangulation is introduced.
There is a paucity of clinical and laboratory findings for diagnosing intestinal strangulation [1, 2]. Dr. Wangensteen, a well-known and respected surgeon, has stated: "There are no absolute criteria by which simple and gangrenous bowel obstruction can be differentiated with finality, short of operation." Radiological studies, such as abdominal radiographs or barium studies, are also of limited value for establishing a correct diagnosis [3, 4, 5]. Therefore, the high diagnostic accuracy (83-85%) achieved in many studies using CT is somewhat surprising [6, 7]. Using the CT criteria reported in the literature [6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16], this most difficult clinical conundrum is often resolved. Nonetheless, interpretive difficulties and limitations of the method exist. With more experience, we realized that CT indicators previously described as highly specifically suggestive of intestinal strangulation are also seen in simple obstruction [6, 12]. This pverlap is presumed to arise from changes in the pathophysiological status of the obstruction between the time of CT examination and surgery, from visual errors at surgical inspection, or from incorrect use of diagnostic criteria by the radiologist.
Another problem encountered using CT as the imaging method in an attempt to distinguish simple from strangulated obstruction is the wide range of accuracy rates among interpreters. This variation seems to result mainly from perceptual errors or from imprecise definitions of known criteria.
We review the pathophysiology of strangulation, clarify definitions, and examine the limitations of known CT criteria in order to improve the reliability of CT for diagnosing strangulation in small-bowel obstruction and to introduce the concept of coronal mapping of the course of the superior mesenteric vessels based on axial abdominal CT in the diagnosis of intestinal strangulation.