MDCT Manifestations Of Transverse Mesocolon In Acute Pancreatitis And Anatomic Basis

Purpose: The transverse mesocolon is made up of two layers of peritoneum, and it is part of mesentery. The mesentery can get the primary affection itself, and the disease of other organs can invade it too. Recently, the disease of mesentery is got more attention. The knowledge of mesentery can help to the imaging diagnosis of a disease, make treatment methods and evaluate prognosis. The MDCT has many advantages to traditional CT. It can get many images with one exposal. The MDCT can reduce respiratory and motorial constructed defect because it scans much faster; it can reduce the partial volume phenomenon because it use thin slice. The AP can invade the transverse mesocolon and the small bowel mesentery. The anatomy of the mesocolic attachment must affect the diffusion way and its MDCT manifestations of AP. We found that there was few literate about the AP invading the transverse mesocolon. The article is composed with two parts. The purpose of part one is to investigate the CT manifestations of the normal transverse mesocolon using multi-detector spiral CT (MDCT) scanning. Combining the MDCT images and the anatomy discussed the normal anatomy of the transverse mesocolon. In part two, we analysed the MDCT images of AP of 68 cases, and discussed the manifestations of the AP involved the transverse mesocolon.Materials and methods: 1. Enhanced-contrast CT scan with 64 and 16 detectors spiral CT scanner were performed in 41 consecutive cases. Emphasis was placed on the following findings: manifestation of major vessels in the transverse mesocolon; location of the transverse mesocolon; the density of fat within the transverse mesocolon; lymph nodes of the transverse mesocolon; the best manifested section showing the transverse mesoncolon. Get the notes of ages and sex of the patients.2. We observed the normal transverse mesocolon of 4 patients who were performed with subtotal gastrectomy and get emphasis as follows: the location of the middle mesocolic vessels; the right attachment of the transverse mesocolon. Get the notes of ages and sex of the patients. 3. Plain and enhanced-contrast CT scan with 64 detectors spiral CT scanner and 16 detectors spiral CT scanner were performed in 68 consecutive patients. Those patients which had AP proved by clinical information, all patients were C, D, or E grade by Balthazar's criterion. Those patients whose CT images were not fit for the analysis were excluded. 68 cases were 39 males, 29 females, and the ages ranged from 14 years to 75 years. Emphasis was placed on the following findings: making out the classification of those CT images by Balthazar's criterion; the attenuation of the fat; effusion within the transverse mesocolon; the thickness of the transverse mesocolon; the mesocolic vessels and the middle colic vessels. Get the notes of ages and sex of the patients.Results: 1. The revealing rates of the middle colic artery was 93.0% (38/41) on axial and coronal MDCT images, the middle colic vein was 85%(35/41) on axial and coronal MDCT images, the gastrocolic trunk was 100%(41/41) on axial and coronal MDCT images. On the axial MDCT images, the transverse mesocolon appeared as the vessels on the level of the transverse colon under the gastric-colic ligament; on the coronal MDCT images, it is hard to distinguish if the transverse mesocolon was plane because the vessels appeared as spots or short bar, it appeared as the vessel net behind the gastro-colic ligament if the transverse mesocolon was oblique; on the sagittal MDCT images, it appeared as the fore-and-aft vessels behind the transverse colic ligament; the attenuation of the fat within the transverse mesocolon was homogenous as the same as the small bowel mesentery; the transverse mesocolon was located in the upper and middle abdomen; the small bowel was showed upon the middle of transverse colon in 22 cases; in 3(7.0%) cases, the normal lymph nodes were revealed in the root of the transverse mesocolon, and were not revealed in the margin and body of the transverse mesocolon. 2. By the normal anatomy we could see that the pancreas were located in the middle of the two layers of the transverse mesocolon; the vessels were located on the posterior layer; the right attachment of the transverse mesocolon was to the inner flexure of the second colon-liver flexure. 3. There were 9 cases of C grade, 20 cases of D grade, 39 cases of E grade by Balthazar's criterion; the rate of the transverse mesocolon involved by the AP was 75%; AP could induce higher attenuation of fat; AP could result the effusion within the transverse mesocolon, and its manifestations were rounded or sheet area with water attenuation, in which, 3 cases' right margin located was on the inner curve of the second colon-liver curve, 8 cases' transverse segment involved by the mesenteric effusion dilated; AP could result thick mesentery, and the transverse mesocolon revealed better on sagittal MDCT images, and its manifestations were thick line upon the vessels and higher attenuation; acute pancreatits could result blurry margin of the superior mesenteric vessels and the middle colic vessels; there were significant difference in the incident rate of the higher attenuation of fat, effusion within the transverse mesocolon, blurry margin of vessels among C, D and E grade pancreatitis. However, there were not significant differences in the incident rate of the thick mesentery of the transverse mesocolon among C, D and E grade pancreatitis.Conclusion: 1. The axial, coronal and sagittal MDCT images can demonstrate the normal manifestations of the transverse mesocolon in a certain extent. Combining the MDCT images and the observation of the normal anatomy of the transverse mesocolon can understand the details of the transverse mesocolon better. The mesocolon can be revealed readily on the MDCT images of AP individuals, and its manifestations were as follows: effusion within mesocolon, the fat attenuation higher, thick mesocolon, blurry margin of vessels. 2. The middle colic artery and vein are the signs of the transverse mesocolon, and the gastro-colic trunk is the lower margin of its root. 3. There are few cases showing lymph nodes in the transverse mesocolon, and their diameters are less than 5mm. 4. The attenuation of the fat located within the small bowel mesentery and transverse mesocolon is the same. 5. The right attachment of the transverse mesocolon locates in the inner flexure of the second colon-liver flexure, and the vessels are on the back sheet of the transverse mesocolon. 6. Effusion caused by AP within the left portion of transverse mesocolon was more often than the right portion of transverse mesocolon. There were significant relations in the incident rate of the higher attenuation of fat, the effusion within the transverse mesocolon, and blurry margin of vessels among C, D and E grade pancreatitis. However, there was no significant relation in the incident rate of thick mesocolon among C, D and E grade pancreatitis.