Splenic Artery Aneurysms and Hepatic Artery Dissection

Abdominal aorta aneurysms (AAAs) are common in the vascular fi eld. Testing for this phenomenon is rather easy; simply order an AAA screening via ultrasound. What is not common, however, is fi nding an aneurysm of the much smaller branches of the splanchnic arteries. These arteries consist of the celiac artery (CA), common hepatic artery (CHA), splenic artery (SA), gastric artery, and superior mesenteric (SMA) and inferior mesenteric arteries (IMA). The most common aneurysm location in these vessels is the SA. These aneurysms can prove fatal if ruptured and are most dangerous in young women who are pregnant and of child bearing age. Even more rare than SA, aneurysms are hepatic artery aneurysms and dissections. In one case study from 1995, there had only been 12 cases documented with isolated hepatic artery dissection. With the increase in technology and imaging modalities, small visceral aneurysms are now found much more prevalently. Treatment options for these unique problems are still under debate, as there are a limited number of occurrences and the ability to accurately track the progression of the aneurysms has improved. Accreditation Statement: This activity has been planned and implemented in accordance with the Essential Areas and policies of the Accreditation Council for Continuing Medical Education through the joint sponsorship of the University of Cincinnati and the Society for Vascular Ultrasound. The University of Cincinnati is accredited by the ACCME to provide continuing medical education for physicians. The University of Cincinnati designates this journal activity for a maximum of 1 AMA PRA Category 1 Credit(s)TM. Physicians should claim only the credits commensurate with the extent of their participation in the activity. Address correspondence to: Adam E. Jackson, RDCS, RVT, 465 Emerald Parkway, Sugar Hill, GA 30518. E-mail: [email protected] JACKSON JVU 40(4) 186 of the population. They were most frequently incidental fi ndings or found during autopsy.1 In more recent case studies, the prevalence of these aneurysms is found with a reported rate from 0.1% to 10% of people.2 The increase in prevalence is due to improved and more frequent imaging. With increased imaging these rare, and occasionally, life-threatening disorders are still most frequently found as incidental fi ndings. SA aneurysms are the third most common intraabdominal aneurysm (after aortic and iliac) and most common of the splanchnic artery aneurysms, accounting for up to 60% of splanchnic aneurysms.2 These aneurysms are four times more likely to occur in women than in men, and most dangerous during pregnancy.2 Etiology and Dangers of SA Aneurysms SA aneurysms are defi ned as abnormal dilation of the vessel to more than 1 cm in diameter.2 The pathogenesis is not fully known for these aneurysms but risk factors include trauma, hormonal and local hemodynamic events in pregnancy, portal hypertension, arterial degeneration, and atherosclerosis.2 As of 2009, there were only 400 reported cases of SA aneurysms, with 100 during pregnancy.3 Rupture risk of a SA aneurysm is 3%, with a 25% mortality rate. During pregnancy, the mortality rate jumps to 75% upon rupture.2 The majority of ruptures will occur in pregnancy, representing 95% of the total ruptures of SA aneurysms.2 With these high percentages of ruptures in pregnant women, diagnosis and quick intervention become key. It is fair to conclude the population that carries the greatest risk for not only an SA aneurysm, but also a fatal rupture of the aneurysm, is pregnant females and multiparous women having a greater risk of developing SA aneurysms. Ultrasound and SA Aneurysms There is little information on SA aneurysms and ultrasound found in the literature. This lack of data is probably due to the fact that the SA is not visualized often with ultrasound during an examination and could be due to the limitations of the equipment, sonographer, and imaging protocols. Looking for a SA aneurysm is not a routine test. Performing this type of unique examination requires excellent knowledge of the visceral vascular anatomy. The SA is a naturally tortuous vessel that dives deep into the abdomen, possibly limiting visualization of the test with obese patients, pregnant women, or patients with bowel gas. Even without these limitations, this examination can be challenging due to the size of the vessel and experience of the sonographer. The examination should be scheduled in the AM with the patient NPO from midnight to help increase the chance to visualize this vessel. The patient should be in the supine position and the test should begin under the xiphoid process at the proximal aorta. With normal vasculature, the CA should be the fi rst branch off the aorta and demonstrate a low-resistance waveform. The celiac will bifurcate into the common hepatic artery (CHA) and SA. This area of bifurcation is commonly called the “seagull sign” and can be used as a landmark to fi nd the SA, as shown in Figure 1. The SA will then course in a “candy cane” shape as it moves proximally from the bifurcation and then turns distally. Following the vessel from this point becomes a challenge as it dives deep into the abdomen. Color Doppler and waveform analysis will help identify this vessel as it courses to the spleen, as shown in Figure 2. The vessel should show a low-resistance waveform and proper angulation of the Doppler curser is needed for accurate velocities. To see the SA move into the spleen, the patient may need to be moved into the right lateral decubitus position, as was the case with this study, to adequately visualize the distal SA. This is the area where most SA aneurysms will be seen and was found in this case study. On ultrasound, these appeared as round cyst-like structures sitting just outside and on the border of the spleen, as shown in Figure 3. Knowing the patient’s history was helpful as the aneurysm could have easily been mistaken as cysts without color Doppler to ensure there was arterial fl ow in the lumen. Flow in the aneurysmal vessel appeared in a ying-yang color pattern in the largest aneurysm suggesting a possible pseudoaneurysm, as shown in Figure 4 and once again in Figure 6 accompanied by multidirectional fl ow inside the aneurysm. Pulsed wave Doppler was used and demonstrated low-resistant waveforms with elevated velocities seen in the largest aneurysm, as shown in Figure 5. After confi rming arterial fl ow inside the aneurysm, I then measured all the dilated areas, with and without color fl ow, to help delineate the borders, as shown in Figure 6. Next color Doppler was used on the spleen to check for blood fl ow in this organ. The measurements of all four aneurysms were very close to the measurements taken from the CTA performed earlier, with the largest measuring 1.84 × 1.79 cm, as shown in Figure 7. Ultrasound examinations of the SA can be greatly limited by bowel gas, obesity, and sonographer skill. In patients with clear images, it can be used as a useful tool in