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1 Department of Radiology, Osaka Medical College, 2-7 Daigaku-machi, Takatsuki
City, Osaka 569-8686, Japan.
2 Department of General and Gastroenterological Surgery, Osaka Medical College,
Takatsuki City, Osaka 569-8686, Japan.
Received May 29, 2003;
accepted after revision January 14, 2004.
Address correspondence to M. Matsuki.
Abstract
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SUBJECTS AND METHODS. Thirty-six consecutive patients scheduled for laparoscopy-assisted distal gastrectomy were evaluated on MDCT. CT was performed at the arterial phase after a bolus IV injection of contrast material. Three-dimensional CT angiography (3D CTA) of the arterial and venous systems was reconstructed separately using a volume-rendering algorithm, and the images were fused. Three-dimensional CTA for the left gastric, right gastric, and replaced left hepatic arteries and the left gastric coronary vein was evaluated prospectively by three reviewers, and then a surgical correlation was made.
RESULTS. In all 36 cases, the left gastric artery was correctly identified on 3D CTA. In 35 of 36 cases, the right gastric artery was correctly identified, whereas in one case, the right gastric artery could not be visualized on 3D CTA because of its small size. In 35 of 36 cases (i.e., one case with agenesis of the left gastric coronary vein was excluded), the left gastric coronary vein was correctly identified. In six cases, the replaced left hepatic artery was correctly identified on 3D CTA. All 36 cases underwent successful laparoscopy-assisted distal gastrectomy on the basis of the 3D CTA. Both the sensitivity and positive predictive values of 3D CTA revealed 100% correct determination of the left gastric artery, replaced left hepatic artery, and left gastric coronary vein. The sensitivity and positive predictive values for the right gastric artery were 97% and 100%, respectively.
CONCLUSION. Three-dimensional CTA using MDCT clearly revealed individual vascular anatomies around the stomach and could play an important role in safely facilitating the laparoscopy-assisted gastrectomy procedure.
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CT Protocol
Images were obtained using the Aquilion MULTI 4-MDCT scanner (Toshiba
Medical Systems). Inflation of the stomach was induced with 6 g of
effervescent granules. Distention of the stomach enabled a clear view of the
courses of the surrounding arteries and veins. A 20-gauge IV catheter was
inserted from the right medial cubital vein. The range of contrast-enhanced CT
was set to cover the area from the point below the dome of the liver to the
lower edge of the stomach; images thus obtained were called
"scout" images. Scanning was performed with the following
parameters: 120 kVp, 300 mA, 0.5-sec gantry rotation speed, helical pitch of
5.5, 1-mm slice thickness, table speed of 5.5 mm per rotation, and
reconstruction intervals of 1 mm. On the contrast-enhanced CT images, nonionic
contrast agent (300 mg I/mL, Omnipaque [iohexol], Daiichi Pharmaceutical) was
infused rapidly at 5 mL/sec using an automated injector (Autoenhance A-250,
Nemotokyorindou) with a total volume of 100 mL for patients weighing less than
40 kg, a total volume equivalent to body weight (kilograms) x 2.5 mL for
patients weighing between 40 and 60 kg, and a total volume of 150 mL in
patients weighing more than 60 kg. The volume of contrast medium administered
ranged from 100 to 150 mL (mean, 122 mL). Arterial phase images were obtained
using the bolus tracking method (called the "real prep method" by
Toshiba Medical Systems), which sets a region of interest (ROI) in the aorta
at the level of bifurcation of the celiac artery and is designed so that
imaging will begin when the CT number of the ROI is 50 H higher than that of
the precontrast imaging. The average scanning delay for the first arterial
phase was 20 sec (range, 17–26 sec).
The volume data obtained from the arterial phase were transferred to a work station (ZIO M900, Zio Software), in which the data were converted to a 3D CTA format using the volume-rendering technique. Three-dimensional CTA of arteries and veins was separately prepared by selecting a CT number tailored to a given target, and the images were colored. These images were then fused. It took between 20 and 46 min to obtain the fused images. On the basis of 3D CTA, the procedure of laparoscopy-assisted distal gastrectomy was preoperatively planned by the surgeons.
Image Analysis
All 3D CTA images were prospectively evaluated by one radiologist and two
surgeons in consensus. On the basis of the 3D CTA findings, we divided
individual cases into six types (I–VI), according to the Michels
classification [6]
(Fig. 1) of the branching
patterns of the left gastric, common hepatic, and splenic arteries. Six types
were defined according to the following characteristics: type I
(hepatosplenogastric trunk), the left gastric, common hepatic, and splenic
arteries originate from the celiac trunk; type II (hepatosplenic trunk), the
common hepatic and splenic arteries originate from the celiac trunk, whereas
the left gastric artery originates from the aorta, the splenic artery, or the
hepatic artery; type III (hepatosplenomesenteric trunk), the left gastric
artery originates from celiac trunk, whereas the common hepatic and splenic
arteries originate from the superior mesenteric artery; type IV (hepatogastric
trunk), the left gastric and common hepatic arteries originate from the celiac
trunk, whereas the splenic artery originates from the superior mesenteric
artery; type V (splenogastric trunk), the splenic and the left gastric
arteries originate from the celiac trunk, whereas the common hepatic artery
originates from the superior mesenteric artery or from other structures; type
VI (celiacomesenteric trunk), the left gastric, common hepatic, splenic, and
superior mesenteric arteries form a common trunk. In each type, the origins of
the left gastric artery and right gastric artery were evaluated on 3D CTA.
Moreover, the replaced left hepatic artery originating from the left gastric
artery and the course of the left gastric coronary vein were evaluated on 3D
CTA. The sensitivity and positive predictive value of 3D CTA for determining
the left gastric, right gastric, and replaced left hepatic arteries and the
left gastric coronary vein were computed using the surgical findings as the
reference standard.
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Of the 31 type I cases, 13 showed the right gastric artery originating from the proper hepatic artery, 11 showed the right gastric artery originating from the left hepatic artery (Fig. 3A), six showed the right gastric artery originating from the gastroduodenal artery (Fig. 3B), and one showed the right gastric artery originating from the right hepatic artery. Of the two type II cases, one showed the right gastric artery originating from the common hepatic artery, and another showed the right gastric artery originating from the proper hepatic artery. The right gastric artery originating from the gastroduodenal artery in one type IV and from the left hepatic artery in one type V case was shown on 3D CTA. Also, a replaced left hepatic artery, originating from the left gastric artery, was noted in six cases (17%). In all six cases, the replaced left hepatic artery was confirmed at surgery (Fig. 4A, 4B). In 35 of 36 cases, the course of the left gastric coronary vein on 3D CTA correlated with the surgical findings. In one case in which the left gastric coronary vein was not visualized on 3D CTA, the left gastric coronary vein was not identified and the dilated right gastric vein was confirmed at surgery.
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The patterns of inflow of the left gastric coronary vein were classified into five types, as defined by our criteria (Fig. 5). Twelve cases were classified as type 1A (joining the splenic vein after running along the ventral side of the proper hepatic artery, the common hepatic artery, or the splenic artery), four cases were rated as type 1B (joining the splenic vein after running along the dorsal side of the proper hepatic artery, the common hepatic artery, or the splenic artery), four cases were rated as type 2A (joining the junction of the superior mesenteric vein and the splenic vein after running along the ventral side of the proper hepatic artery, the common hepatic artery, or the splenic artery), two cases were rated as type 2B (joining the junction of the superior mesenteric vein and the splenic vein after running along the dorsal side of the proper hepatic artery, the common hepatic artery, or the splenic artery), and 13 cases were rated as type 3B (joining the portal vein after running along the dorsal side of the proper hepatic artery, the common hepatic artery, or the splenic artery) (Fig. 6A, 6B).
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All 36 cases underwent successful laparoscopy-assisted distal gastrectomy on the basis of the 3D CTA images. Both the sensitivity and positive predictive values of 3D CTA were 100% in terms of correctly determining the left gastric artery, replaced left hepatic artery, and left gastric coronary vein. The sensitivity and positive predictive values for the right gastric artery were 100% and 97%, respectively.
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Laparoscopy-assisted distal gastrectomy is less invasive than open surgery. However, one disadvantage of laparoscopy-assisted distal gastrectomy is that it is difficult to obtain an image of the entire lesion. In addition, using this approach, we cannot manipulate lesions directly. For these reasons, a relatively long intraoperative time is required to deal with the origins of arteries and veins, of which the particular anatomy can vary greatly from case to case [3].
Important technical considerations during laparoscopy-assisted distal gastrectomy are as follows: During gastrectomy on the pyloric side, the area facing the greater curvature is first approached, and the left and right gastroepiploic arteries are ligated. Then, the right gastric artery is ligated. In cases in which the right gastric artery originates from the proper hepatic artery, the left hepatic artery, or the right hepatic artery, the right gastric artery is identified after careful dissection of the first portion of the duodenum, and the right gastric artery is ligated at its origin (Figs. 3A and 7A). In other cases in which the right gastric artery bifurcates from the gastroduodenal artery, the greater curvature of the stomach is everted, and the origin of the right gastric artery can be depicted and easily ligated (Figs. 3B and 7B). Then, the area facing the lesser curvature is manipulated.
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Excision of the lymph nodes in the anterosuperior region of the common hepatic artery (Japanese classification 8a) proceeds in the proximal direction. The left gastric coronary vein must first be confirmed and ligated before excision of the lymph nodes (Japanese classification 8a). If the ligation of the left gastric coronary vein is not performed in advance, the left gastric coronary vein can be erroneously injured during local lymph node excision. This damage leads to massive bleeding that prevents the surgeon from having access to a good view of the operative field [4] (Fig. 6A, 6B). Excision en bloc of the lymph nodes around the celiac artery (Japanese classification 9) exposes the left gastric artery, which typically originates from the celiac artery. However, in cases in which the left gastric artery originates from the aorta or the splenic artery, further exploration for the left gastric artery is required (Figs. 2B and 2C). In addition, in cases in which the replaced left hepatic artery bifurcates from the left gastric artery, the origin of the left gastric artery can be erroneously dissected (Fig. 4A, 4B). To prevent postoperative liver dysfunction, the surgeon should preserve the replaced left hepatic artery while dealing with the left gastric artery distal to the origination. Therefore, to safely facilitate the laparoscopy-assisted gastrectomy procedure, we consider it important to preoperatively assess the vascular anatomy around the stomach using 3D CTA with MDCT.
Improvement in CT scanner technology has enabled the accurate reconstruction of the images of various vessels [8–16]. Studies have shown the clinical usefulness of 3D-CTA in various diagnostic fields. In recent years, MDCT scans, which use a larger number of detectors than single-detector helical CT, have enabled the collection of a considerable amount of thin-slice data within a short time [10–16]. The increased spatial resolution has enabled the preparation of 3D reconstruction images with higher accuracy than had previously been possible. Moreover, high iodine concentrations obtained by infusing a large amount of iodine at a high flow rate permit excellent 3D CTA [17]. In assessing abdominal vessels, 3D CTA has become a suitable diagnostic procedure for disorders of the aorta and its major branches (e.g., the hepatic and renal arteries). In the field of abdominal surgery, the clinical usefulness of 3D CTA has been reported for the preoperative estimation of aortic aneurysms and pancreatic cancer and for the preoperative assessment of and planning for liver and kidney transplantation candidates [8–16]. Before our study, to our knowledge, no published studies have examined the detectability of gastric arteries and veins and analyzed their anatomic variety with the purpose of devising a plan for laparoscopy-assisted gastrectomy. In our study, 3D CTA using MDCT clearly showed the vascular anatomy around the stomach; this approach proved to be useful to preoperatively assess individual vascular variation. This technique made possible safe and rapid manipulation of the origins of the arteries and vein and lymph node excision without incurring injury to the involved arteries and veins.
In conclusion, 3D CTA using MDCT gave a clear visualization of the origins of the gastric arteries and the course of the left gastric vein. This technique was found to be useful for the safe and rapid performance of laparoscopy-assisted surgery for the treatment of patients with gastric cancer.
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