Year : 2006 | Volume
: 16 | Issue : 4 | Page : 457--461
CT angiography in evaluation of vascular anatomy and prevalence of vascular variants in upper abdomen in cancer patients
Rajiv Gandhi Cancer Institute & Research Centre, Sect-5, Rohini, New Delhi-110085, India
K S Rawat
Rajiv Gandhi Cancer Institute & Research Centre, Sect-5, Rohini, New Delhi- 110085
Objectives- To evaluate and describe vascular anatomy and the prevalence of vascular variants in upper abdomen in cancer patients with CT angiography to provide roadmap to surgeons to ensure safe surgery.
Materials and Methods- A total of 125 cancer patients were evaluated by a Dual-slice spiral CT scanner with maximum intensity projections (MIP) and 3-D postprocessing.We compared CT angiographic findings with intra-operative findings in 62 patients who underwent surgery.
Results- CT angiography was found very accurate to evaluate vascular anatomy.In our study of 125 patients 76 ( 61%) of patients showed variations:37 (30%) had single variations and 39 (31%) had more than one variation. The classic hepatic arterial anatomy,with the hepatic artery dividing into right and left hepatic arteries is seen in 53% of patients.Left hepatic artery variations in 26 (21%) patients,right hepatic artery variations in29 (23%) patients, and common hpatic artery variations in 4 (3%) patients were noted. Variations were also seen in hepatic veins, inferior phrenic arteries and, renal arteries and veins.Renal artery variations were seen in 33 (26.4) patients and renal veins variations in 19 (15%) patients.
CT angiographic findings were similar to intra-operative findings in 61 (98%) patients who underwent surgery.In one patient we could not visualize an accessory right hepatic artery but it was visualized in retrosperct study arising from gastroduodenal artery.
Conclusion- CT angiography is safe and highly sensitve and accurate modality for evaluation of vascular anatomy.
|How to cite this article:|
Rawat K S. CT angiography in evaluation of vascular anatomy and prevalence of vascular variants in upper abdomen in cancer patients.Indian J Radiol Imaging 2006;16:457-461
|How to cite this URL:|
Rawat K S. CT angiography in evaluation of vascular anatomy and prevalence of vascular variants in upper abdomen in cancer patients. Indian J Radiol Imaging [serial online] 2006 [cited 2019 Dec 10 ];16:457-461
Available from: http://www.ijri.org/text.asp?2006/16/4/457/32246
The vascular patterns are of importance in planning and performance of all surgical procedures in the upper abdomen . Knowledge of anomalous vessels serves as the roadmap before surgery, reduces the risk of trauma to the vessels and ensures thorough vascular ligation and anastomosis. However, surgical mistakes from failing to appreciate vascular anatomy continue to be made with serious consequences to the patient, and with medico-legal implications.Catheter angiography has long been considered the gold standard for evaluation of the vascular anatomy.However,the morbidity and mortality associated with catheter angiography,coupled with few other limitations,have provided impetus for the development of noninvasive procedures of displaying the vascular anatomy .
Material and Methods
Vessels of the upper abdomen were studied in a total of 125 cancer patients in a Dual- slice spiral CT scanner in a period of more than one year from July 2003 to December 2004.Out of 125 patients 62 patients underwent surgery.Remaining 63 patients did not undergo surgery due to different reasons.CT angiographic findings were compared with intra-operative findings of 62 patients.
CT angiography protocol
We performed CT angiogram of 125 patients on a Dual-slice spiral CT scanner (SOMATOM Emotions Duo, Siemens AG Forchheim,Germany).CT angiography of all the patients was done after 6 hrs of fasting. Before CTangiography all patients were trained for breath hold which is required during the examination.An 18-20G Intracath canula was introduced in the antecubital vein or a vein in the forearm. After taking plain topogram of the abdomen the region of interest was taken from the level of upper margin of D12 vertebra to the lower margin of L3 vertebra. For the arterial phase, scan delay was 22seconds and for venous phase it was 70seconds. 125 ml of non-ionic contrast iohexol 300 mg/ml(Omnipaque,Amersham Health,Cork,Ireland) was injected with the use of a power injector (Medrad VISTRON CT,USA) at a rate of 3.5 ml/s and 2mm slices were acquired in a single breath hold using 1.5mm collimation, 110KV, 80 mAS, with table feed of 6mm and reconstruction interval of 0.6mm with a total scan length of 320 mm.
CT interpretation and 3-D postprocessing
Post processing and CT image interpretation were done using various techniques like multiplanar reconstructios, maximum intensity projection (MIP) and volume rendered technique (VRT),on a Siemens Syngo 3-D workstation.Axial source images were also evaluated and are most helpful in evaluation of vascular anatomy,as reported in previous studies . 3-D reconstructed images are helpful in evaluating complex vascular anatomy.
Overall, vascular anomalies were seen in 76 ( 61%) of patients: 37 (30%) had single variation, 39 (31%) had more than one variation.Hepatic artery variations were seen in 59 (47%) patients and renal artery variations were seen in 33 (26.4%) patients.
Common hepatic artery (CHA)
CHA variation is noted in 4 (3%) patients. It had its origin from superior mesenteric artery (SMA) in 3 (2%) patients [Figure 1] and from aorta in 1(1%) patient.
Left hepatic artery (LHA)
Left hepatic artery variations were noted in 26 (21%) patients. This had its origin from the left gastric artery (LGA) in 21 (17%) patients [Figure 2],out of which it was the only supply to the left lobe of liver in 5 patients, dominant in 5 patients and accessory in 11 patients. Its origin from celiac trunk (CT) was seen in 3 patients .Two left hepatic arteries from hepatic artery proper was seen in one patient. Gastroduodenal artery (GDA) arising from left hepatic artery was seen in one patient.
Right hepatic artery (RHA)
Of 125 patients, the right hepatic artery variations were noted in 29 (23%) patients, it took origin from the superior mesenteric artery in 22 (18%) patients [Figure 3] ,out of which it was the only supply to the right lobe of liver in 13, dominant in 5 and accessory in 4 patients. As accessory its origin from gastroduodenal artery was seen in 3 patients. Two right hepatic arteries from hepatic artery proper were seen in one patient. It arose from coeliac trunk in one patient. Anomalous branches, superior pancreaticoduodenal artery from dominant right hepatic artery in one patient and gastroduodenal artery from right hepatic artery in one patient were also seen .
We have found accessory right hepatic vein ( RHV )in 11(9%) patients draining separately into inferior vena cava ( IVC).
Inferior phrenic arteries
Inferior phrernic arteries variations were noted in 9(8.8%) patients. Right inferior phrenic artery from common hepatic artery in one, left inferior phrenic artery from left gastric artery in two,both inferior phrenic arteries from renal arteries in two, both inferior phrenic arteries from celiac trunk in one, right inferior phrenic artery fron right renal artery in one, right inferior phrenic artery from celiac trunk in two patients were seen.
Total renal artery variations were noted in 33 (26.4%) patients. Multiple left renal arteries were found in 20(16% ) patients and multiple right renal arteries in 19(15%) patients [Figure 4],[Figure 5].
In 15 (12%) patients two right renal veins and in 4 (3%) patients two left renal veins were seen.
Out of 125 patients,62 patients underwent surgery.We compared CT angiographic findings of these 62 patients with intra-operative findings and found that CT angiographic findings of 61 (98%) patients matched with intra-operative findings.In one patient we could not detect an accessory right hepatic artery on CT angiogram.However in retrospect study this accessory right hepatic artery was seen arising from GDA.
Coeliac trunk (CT) is wide ventral branch of aorta and normally divides into left gastric artery ( LGA), common hepatic artery (CHA) and splenic artery. Coeliac trunk may also give off one or both inferior phrenic arteries. LGA is the smallest coeliac branch.LGA may take origin directly from aorta [Figure 6] . An accesory LGA may arise from the left branch of the heaptic artery. Common hepatic artery (CHA) is intermediate in size between the LGA and splenic artery. GDA arises from hepatic artery and divides into right gastro-epiploic and superior pancreatico-duodenal arteries. Superior pancreaticoduodenal arteries are usually double- anterior and posterior . The classic hepatic arterial anatomy,with the proper hepatic artery branching into right and left hepatic arteries, is seen in 55% patients,as reported in previous studies [5,6,7].Our study is comparable to previous studies in regard to normal pattern and variants.
Superior mesenteric artery (SMA) arises from the front of aorta about 1 cm below the coeliac trunk. SMA may be the source of common hepatic, gastro-duodenal, accesory right hepatic, accessory pancreatic or splenic arteries .
Inferior phrenic arteries arise from the aorta just above the celiac trunk .
There are three main hepatic veins draining into IVC .The right hepatic vein ( RHV) drains hepatic segments V-VII,the middle hepatic vein ( MHV ) drains segments IV,V and VIII, and the left hepatic vein ( LHV) drains segments II and III ,.A variable number of venous branches can also drain part of posterior segment of right lobe of liver directly into IVC  .Such accessory right hepatic veins are estimated to occur in 6% of people .In our study we found accessory right hepatic vein in 9% of patients.An accessory hepatic vein can cause increased bleeding if not recognized before surgery.
Renal arteries arise laterally from the aorta, just below the inferior mesentric artery. The right is longer and often higher. The left renal artery is little lower. One or two accesory renal arteries frequently occur, especially on the left, usually from the aorta above or below the main artery .
Renal veins join the IVC and each lies in front of the corresponding artery.The right vein is shorter.The left renal vein crosses in front of aorta .Multiple renal veins are more common on the right side.
This current study shows that there is a pattern to the variation of the vessels, even though the possibilities of individual variation are myraid. The study demonstrates an anomalous variation of the vessels in nearly 76 (61%) of the patients. When there were variations, about 39 ( 31%) had more than one variation. The observation of one variation, therefore, should alert about the possibility of more variations. The most puzzling anomalies are those involving the celiac axis. However, an anomalous left hepatic artery and an anomalous right hepatic artery, in the absence of celiac axis, can be difficult to follow .
Jones et al reported anatomical variations of the right or left hepatic arteries in nearly 50% of patients. This is comparable to current study in which anatomical variation in hepatic arteries was seen in 47% of patients,and this is presented in Table 1.
When RHA does not arise from common hepatic artery, it most commonly arises from SMA. This variation was seen in 18% of patients.Anomalous origin of RHA was also seen from gastroduodenal artery(2%), celiac trunk(1%). Similar observation was reported by Jones et al. This result shows that anomalous RHA usually traced from aorta or any of the arteries on the right side of aorta e.g. SMA, GDA, right gastric artery (RGA).
Anomalous LHA was found to arise from LGA (17%), GDA(1%) and CT(2%). This result was comparable to the study by Jones et al. LHA has the same pattern, origin traced from the arteries to the left of the aorta, namely LGA, splenic artery or left side of aorta.
These results of CT angiography are comparable to the digital subtraction angiography study by Convey et al who reported LHA variation in 19.8%,RHA variation in 14.8% and CHA variation in 4% patients,CHA arising from either the SMA or the Aorta.
Total renal artery variations were noted in 26.4% patients. Multiple renal arteries are more common on left side(16%) than right side (15%).Multiple renal veins are more common on right side(12%) than left side(3%).Our study showed similar results as reported in previous studies ,,,. Determination of the detailed anatomy of the accessory renal vessels forms a important factor in the selection of the donor kidney.
On comparison with intra-operative findings ,our study showed an accuracy rate of 98% with dual-slice spiral CT scanner.
The advantage of CT angiography over conventional angiography is that former is non invasive and it can be performed on outpatient basis. After conventional angiography 8-12hours of bed rest is required. Though the contrast requirement in CT angiography is 2-3 times more than convetional angiography, nephrotoxicity with non ionic contrast agents is rarely encountered in individuals with normally functioning kidneys .
MR angiography is also a non invasive modality for angiography. CT angiography is better than MR angigraphy as less procedure time and less patient compliance is required in CT angiography. MR angiography images are usually unacceptable if breath holding is inadequate.Disadvantages of CT angiography are ionizing radiation and the administration of iodinated contrast material to the patients.
In conclusion,our study showed CT angiography is an excellent modality for pre-operative evaluation of vascular anatomy and it is safe,cost effective,time saving and highly accurate.Hence CT angiography can be used as a primary modality for evaluation of vascular anatomy.
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