Sudhakar Kundapur Venkatesh, MD, MBBS

The celiac artery is the largest artery in the abdomen and supplies a number of major upper abdominal organs, including the liver, spleen, stomach, and pancreas, through its branches. An appreciation of this arterial anatomy is important when planning surgery and image-guided interventions.

The success of procedures such as liver transplantation, intestinal anastomosis, intra-arterial chemotherapy, chemoembolization, and radioembolization, requires a detailed knowledge of the celiac artery and its branches. This should include an awareness of any anatomical variants, which are extremely common in these vessels. For instance, when embolization in the liver is planned, it is essential that interventional radiologists know of any variations in the blood supply feeding the liver tumors and surrounding organs. This knowledge may help achieve complete embolization at the target site and also prevent embolic materials from straying into other vessels.

Angiography is the gold standard for demonstrating vascular anatomical variants. But it is invasive and carries the risk of procedural complications. The use of noninvasive techniques, such as CT and MRI, in this role has been limited by the low resolution of images and slow acquisition speeds. The introduction of multislice CT (MSCT) scanners, which enable large volumes of data to be acquired within a few seconds, means that high-resolution 3D imaging can now be performed easily.

Reformatted CT images, obtained with various software tools, can be used to demonstrate the celiac vascular anatomy and its relationship to other structures, the bile duct and portal vein, for example. CT angiography can also display arterial anatomy in different planes and projections, similar to the images obtained with angiography. MSCT has consequently become a valuable noninvasive tool for imaging normal vascular anatomy and its variants and pathological conditions affecting major abdominal vessels.

The celiac artery arises from the ventral surface of the abdominal aorta at the level of the 12th thoracic vertebra and T12-L1 intervertebral disc space. It courses caudally for a short distance, then forms a branching structure. The classic description of normal celiac anatomy is that the main trunk trifurcates into the left gastric artery, the splenic artery, and the common hepatic artery

 (Figure 1). In fact, the length and course of the celiac artery are variable and its branches frequently arise separately from the trunk. Several other branches may additionally arise from the celiac trunk, for example, inferior phrenic arteries, the dorsal pancreatic artery, and the middle colic artery.

Variations on normal celiac arterial anatomy are also often associated with branching pattern variants of the superior mesenteric artery.

Variations to the aorta’s anterior branches can be explained embryologically. 

 The paired dorsal aorta gives rise to a series of paired vitelline arteries, also called primitive digestive trunks, which are the precursor to the future digestive vessels. As the vitelline arteries fuse, the 10th pair usually forms the celiac artery, the 13th pair forms the superior mesenteric artery, and the 21st or 22nd pair forms the inferior mesenteric artery.

A ventral longitudinal arterial anastomosis exists between the 10th, 11th, 12th, and 13th roots. The 11th and 12th roots normally disappear, leaving the anastomizing vessel with the 10th root. This gives rise to the celiac artery, which divides into the left gastric artery, the splenic artery, and the common hepatic artery.

Variations of the celiac artery and superior mesenteric artery are explained by the persistence of some or all of the primitive ventral anastomoses of the vitelline arteries and associated variations in the 10th and 13th vitelline roots.

Several authors have studied and classified anatomical variants in celiac anatomy. This work includes the identification of eight types of celiac artery based on celiac and mesenteric artery branching, and 10 types based on hepatic artery origins.

The trifurcation of the celiac artery into the hepatic, splenic, and left gastric arteries was accepted as the description of normal anatomy for many years. A gastrosplenic trunk is formed when the hepatic artery is absent, a hepatosplenic trunk is formed when the left gastric artery is missing, and a hepatogastric trunk is formed when there is no splenic artery arising from the celiac artery.

If two main branches are absent, there will be no celiac trunk and all three main branches may then originate independently from the aorta (1% to 2% of cases).

 The three main branches of the celiac artery and the superior mesenteric artery can sometimes arise from a common (celiacomesenteric) trunk (2%). Absent branches may also originate from the aorta or one of the remaining two main arteries.

Celiac arterial anatomy most commonly consists of a hepatogastrosplenic trunk with either a branching trifurcation (Figure 1), a hepatosplenic bifurcation (type I, Figure 2), or a gastrosplenic bifurcation (73% to 85%).

 A hepatosplenic trunk (type II, Figure 3) will be seen in 3% to 13% of cases, a hepatogastric trunk (type III) in 2% of cases, and a hepatosplenomesenteric trunk (type IV, Figure 4) in 1% of cases. A variant of type IV would be a hepatomesenteric trunk (Figure 5).

Less common arterial structures include the existence of a gastrosplenic trunk (0.5% to 12%) (type V), a celiacomesenteric trunk (type VI, Figure 6) (0.5% to 2%), and a celiacocolic trunk (type VII) (1.5%), where the middle colic artery arises from the celiac artery. The absence of the celiac trunk, discussed above, is referred to as type VIII. The right hepatic artery will often arise from the superior mesenteric artery. This common variation can occur with any of the above variants.

Multislice CTA enables rapid acquisition of thin-slice, high-resolution images of the abdominal arteries during the phase of maximum contrast enhancement. Volumetric data acquisition permits 3D image reconstruction, allowing the relationship of arteries to adjacent organs and the biliary tree to be displayed. The course of the aberrant vessel is also delineated clearly. This may be of great value because direct visualization of the surgical field is often limited in patients with pancreatic and hepatobiliary malignancy.

Recognition of a variant splanchnic arterial supply has important diagnostic and therapeutic implications. Preoperative knowledge of variant anatomy may reduce the need for extensive dissection to identify vessels, and may avert vascular damage. CTA has a reported accuracy of more than 95% for the detection of arterial variants.

An awareness of celiac artery variants is extremely important. If a patient with a celiacomesenteric trunk undergoes pancreatic surgery, for example, most abdominal organs will be at risk of ischemic injury when the clamp is applied across the trunk because the usual collateral supply from the superior mesenteric artery is not present. Similarly, embolization in a patient with a hepatogastric artery variant could result in reflux of the chemotherapeutic or radioembolization agent into the gastric artery. This may cause severe complications, such as gastric ulcers and perforation. Preemptive embolization of the gastric artery with coils may be carried out if the anatomy is known in advance, thereby minimizing complications.

The identification of variants such as a replaced hepatic artery is critical when performing pancreatico-duodenectomies and for dissection of the porta hepatis. Using palpation to detect the presence of an artery can be unreliable when there is portal inflammation, enlarged portal lymph nodes, or an existing biliary stent.

In conclusion, celiac artery variants can influence surgical procedures and the planning of image-guided interventions. It is consequently important for radiologists to know of the different celiac artery variants that can be demonstrated easily on CTA.

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Multislice CTA depicts celiac artery variants

Parenteral drug abuse is relatively uncommon in Singapore compared with other forms of substance abuse.1 The recent trend, however, of addicts injecting self-dissolve tablets with other drugs, bringing risk of serious limb morbidity, is causing concern.

One such drug that has been linked to this practice is buprenorphine hydrochloride. This agent, better known as Subutex, has U.S. Food and Drug Administration approval and was originally introduced to treat opioid dependence.2 Buprenorphine is also a Schedule III narcotic under the Controlled Substances Act. Subutex is sold as uncoated oval white tablets that are intended for sublingual administration. Each tablet also contains lactose, mannitol, cornstarch, povidone K30, citric acid, sodium citrate, and magnesium stearate.3 Buprenorphine is a partial agonist at the micro-opioid receptor and an antagonist at the k-opioid receptor.

The action of buprenorphine on opioid receptors, and their ability to produce euphoria and opioid-like effects, creates the potential for this drug to be abused.4 Intravenous drug users are known to crush the tablets and attempt to dissolve the powder before injecting the mixture.5 This practice is becoming more common in Singapore.4-6 The reported abuse rate of buprenorphine in France and Australia ranges from 37% to 57%.7,8

Complications related to this practice are well documented.9 Intravenous drug users aim for the "black blood" (vein) and not the "pinkie" (artery) when injecting.10 Peripheral veins become "used," or sclerosed, after a while. Chronic intravenous drug users then resort to injecting in the groin for access into the femoral vein or above the elbow for brachial vein access.

Addicts may inadvertently inject drugs intra-arterially, due to the close proximity of arteries to veins (e.g., brachial and femoral arteries). Intra-arterial injection can also be deliberate. Either way, the practice may lead to distal embolic occlusion, pseudoaneurysm formation, or retained broken needle tips. Management of these limb-threatening arterial injuries can be problematic because this patient group often has significant comorbidities.11

Imaging can play an important role in identifying complications associated with intra-arterial injection. Diagnoses can be made using plain-film x-ray, ultrasound, CT, and digital subtraction angiography.

Arterial embolic occlusions most likely occur when drugs are not dissolved completely before injection. Incompletely dissolved constituents may then contribute to thrombus formation.4 Occlusion occurs at the distal branches, which is more in keeping with embolic phenomenon than direct vessel injury. Other possible etiologies for distal artery occlusion include chemical endothelial injury and vasospasm.12

The severity of limb ischemia at presentation depends on several factors. These include symptomatic duration, site of occlusion, and severity of occlusion. We found that patients with slow or delayed flow on DSA had better clinical outcomes than patients with no blood flow in arteries distal to the injection site. Patients with higher levels of occlusion in the forearm and leg arteries, and delayed presentation to the hospital, have worse outcomes that often result in amputation.13

Our experience shows DSA to be an excellent modality for detecting arterial occlusions in this patient group. It provides a dynamic visualization of blood flow and a clear demonstration of occlusion points, which often occur in the tiny digital vessels (Figures 1 and 2). Collateral flow, incomplete stenoses with poor flow, and vasospasm may be seen as well. The same changes may not be detected as reliably on CT or MR angiography. DSA may also help when planning interventional procedures to treat occlusions.

The vessel in question should preferably be imaged proximal to the injection site. This may help demonstrate any coexisting pseudoaneurysms and/or arteriovenous fistula formation. Larger trials and greater experience with this patient group is required to evaluate the value of angiography in predicting the need for early surgical intervention and the efficacy of thrombolysis in the acute setting. Optimal management may remain difficult, however. This group of patients is unlikely to provide a reliable history of drug use, symptomatic onset, and duration of symptoms. They also may not comply with the recommended treatment strategy.

Pseudoaneurysms can form as a result of direct injury to the vessel wall or secondary to local infection adjacent to an artery that causes arterial wall breakdown. Rupture of the pseudoaneurysm is a serious complication that can lead to the loss of the limb or to death by exsanguination.14 It is important to distinguish a pseudoaneurysm from an abscess. Inappropriate incision and drainage could lead to catastrophic blood loss. The overall amputation rate may reach up to 33% in patients with pseudoaneurysms.15

Most femoral pseudoaneurysms less than 3 cm in diameter will spontaneously thrombose. This may be observed with serial ultrasound examinations in symptomatic patients. Open repair is usually undertaken when there is associated soft-tissue infection/collection and/or rapid expansion of the pseudoaneurysm observed over a period of time.16

All patients we have treated for pseudoaneuryms so far have been asymptomatic, with involvement of the femoral artery. Both CT and DSA were useful in delineating the pseudoaneurysm's arterial supply and its relationship with the surrounding vascular structures (Figures 3-5).

Intravenous drug users are at risk of retained needle fragments. Chronic drug users reuse needles for multiple injections, which makes the needles prone to fracture. Addicts also inject into areas of scar tissue and sometimes bend needles to inject in difficult-to-access central areas when peripheral sites are no longer available. This practice again may fracture the needle. Retained needles and needle fragments represent a potential hazard for the patient and attending healthcare workers, even more so if the patient has HIV or hepatitis B. The needles may also migrate within tissues and embolize vessels.

Smaller needle fragments may not always be seen easily on plain-film x-rays, even though they are metallic and hence radiopaque. CT not only helps detect needle fragments, but it also provides important anatomic information prior to surgery (Figures 5 and 6). Retained needle fragments can be a source of infection and result in local abscess formation. Surgical removal of the needle fragment is the treatment of choice.

In summary, the trend of injecting self-dissolved drug preparations may lead to serious limb morbidity. A high index of suspicion is warranted when patients present with unusual arterial complications that may be inconsistent with their clinical history. Radiologists should be familiar with the various arterial complications of self-injection and the role of imaging in their detection.

DR.TAN is a resident and DR. VENKATESH is an assistant professor and consultant radiologist in the department of diagnostic radiology at National University Hospital, Yong Loo Lin School of Medicine, National University of Singapore.

This article is adapted from Tan CH, Venkatesh SK, Lim A, Tsai L. Arterial complications of self-prepared drug injections: imaging a recent trend. Educational exhibit presented at the annual meeting of the Radiological Society of North America, Chicago; November 2006:971.

National Council against Drug Abuse. Singapore drug situation in 2005 [www.drugfree.org.sg/drugs]

FDA/Center for Drug Evaluation and Research. Subutex (buprenorphine hydrochloride) and Suboxone tablets (buprenorphine hydrochloride and naloxone hydrochloride) [www.fda.gov/cder/drug/infopage/subutex_suboxone]

FDA/Center for Drug Evaluation and Research. Patient information leaflet Subuxone (buprenorphine HCl/naloxone HCl dihydrate, sublingual tablet) and Subutex (buprenorphine HCl, sublingual tablet). [www.fda.gov /cder/foi/label/2002/20732lbl.pdf]

Yeo AK, Chan CY, Chia KH. Complications relating to intravenous buprenorphine abuse: a single institution case series. Ann Acad Med Singapore 2006;35(7):487-491.

Lo HY, Leong CS. Surgical complications in parenteral Subutex abusers. Singapore Med J 2006;47(11):924-927.

Loo HW, Yam AK, Tan TC, et al. Severe upper limb complications from parenteral abuse of Subutex. Ann Acad Med Singapore 2005;34(9):575-578.

Obadia Y, Perrin V, Feroni I, et al. Injecting misuse of buprenorphine among French drug users. Addiction 2001;96(2):267-272.

Jenkinson RA, Clark NC, Fry CL, Dobbin M. Buprenorphine diversion and injection in Melbourne, Australia: an emerging issue? Addiction 2005;100(2):197-205.

Alcantara AL, Tucker RB, McCarroll KA. Radiologic study of injection drug use complications. Infect Dis Clin North Am 2002;16(3):713-743.

Roszler MH, McCarroll KA, Donovan KR, et al, The groin hit: complications of intravenous drug abuse. Radiographics 1989;9(3):487-508.

Woodburn KR, Murie JA. Vascular complications of injecting drug misuse. Br J Surg 1996;83(10):1329-1334.

Calder KK, Severyn FA. Surgical emergencies in the intravenous drug user. Emerg Med Clin N Am 2003;21(4):1089-1116.

Rautio R, Keski-Nisula L. Inadvertent intra-arterial drug injections: the role of angiographic and clinical findings. Acta Radiol 2006;47(6):554-558.

O'Leary MR. Subclavian artery false aneurysm associated with brachial plexus palsy: a complication of parenteral drug addiction. Am J Emerg Med 1990;8(2):129-133.

Behera A, Menakuru SR, Jindal R. Vascular complications of drug abuse: an Indian experience. ANZ J Surg 2003;73:1004-1007.

Corriere MA, Guzman RJ. True and false aneurysms of the femoral artery. Semin Vasc Surg 2005;18(4):216-223.

Sudhakar Kundapur Venkatesh, MD, MBBS

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Multislice CTA depicts celiac artery variants

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