Multiphasic MDCT in small bowel volvulus
Introduction
Small bowel volvulus (SBV) is one type of abdominal volvulus, or acquired twisting of intra-abdominal structures. The twisted structure can be gastrointestinal tract, omentum, mesentery and other organs. It is one of the common surgical emergencies in adult populations of Central Africa, India, and the Middle East, where annual incidence is 24–60/100,000 population. But this condition occurs rarely in North America and Western Europe, where the incidence is 1.7–5.7 cases/100,000 [1], [2]. SBV is defined as the clockwise or counterclockwise rotation of all or part of the small bowel around its mesenteric axis [3], [4]. It is associated with high morbidity and mortality rate, resulting from twisting and obstruction of the arterial supply, venous stasis, bowel wall edema and closed loop obstruction, leading to ischemia and even infarction [3]. To prevent these complications, immediate diagnosis and surgical intervention is essential. However, clinical diagnosis of SBV is difficult due to its non-specific clinical findings and laboratory investigations. Doppler sonography can be used to diagnose SBV; however, technical difficulties and inadequate information available from the examination limit its use as a routine diagnostic tool [5]. Mesenteric vessel abnormalities as determined on digital subtraction angiography (DSA) have been reported to be useful for diagnosis of SBV in a small number of cases, which usage is however limited by the invasive nature of the technique [3]. Currently CT plays a key role in early diagnosis of SBV. Whirl sign has been reported as an important sign of SBV on axial CT [6], but its specificity was questioned in later study [7].
We hypothesize that depiction of mesenteric vascular anatomy using multiphasic contrast enhanced MDCT with CT angiography (CTA) and CT portal venography (CTPV) reconstruction can be used to improve diagnostic accuracy of SBV. In addition, the vessels running into ligaments or the mesenteries as demonstrated on CTA can serve as landmarks that help to define abnormal ligaments or mesenteries that define the location of SBV. Direction and number of turns of SBV can also be assessed by the appearances of abnormal vessels. In this study, we aim to evaluate the use of multiphasic MDCT for diagnosis of SBV and to compare location, orientation and degree of SBV as demonstrated on CTA/CTPV with operative findings.
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Patients
All consecutive patients who suffered from operatively confirmed SBV and had undergone preoperative MDCT over a period of 4 years from May 2004 to April 2008 were retrospectively reviewed. The cases were recovered after the search for relevant keywords in operative records and images are retrieved from the picture archiving and communication system (PACS). Altogether, 12 patients who were diagnosed with SBV based on CT findings. 11 of these patients underwent surgery subsequently, of which 9
Imaging findings
The summary of imaging findings is shown in Table 1. There was only one case for which the radiologists differ in their initial evaluation with regard to the degree of rotation. Both radiologists record the same findings independently for all the other cases.
On axial MDCT images, all cases showed segmental or global dilatation of small intestine. Other findings included circumferential bowel wall thickening in eight cases, halo appearance and hyperemia in seven cases, whirl sign in six cases (
Discussion
SBV is a rare but potentially fatal surgical emergency. There is a predilection ratio of 2:1 for males and its peak incidence is in the sixth to eighth decade [7]. Common symptoms of SBV include acute abdominal pain, usually in periumbilical or epigastric regions, with early persistent nausea and vomiting [7], [8], [9]. Associated abnormal laboratory tests include elevation of leukocyte counts and transaminase, inconsistent elevation of amylase and lactate levels. SBV is usually secondary to
Conclusion
Multiphasic contrast enhanced MDCT with CTA/CTPV reconstruction is useful in the diagnosis of SBV. The location, direction and degree of SBV can be accurately defined preoperatively based on CTA/CTPV. When SBV is suspected based on CT findings, CTA/CTPV reconstruction should be performed to provide additional information for preoperative planning.
Conflict of interest
There is no conflict of interest.
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