Endovascular Repair of Splenic Artery Aneurysm

ABSTRACT

Splenic artery aneurysm (SAA) is the most common form of visceral artery aneurysm (VAA). Most present asymptomatically with incidental findings on CT or ultrasound which are diagnostic although about 20% present with vague left upper quadrant abdominal pain. Rupture presents with a high mortality rate and treatment should be initiated in any patient with symptoms or other high risk patients.

Results

Endovascular treatment with coils was found to be an effective management for a mid-distally located SAA without compromising splenic blood flow and function.

Discussion

Treatment should be aimed at preserving splenic function whenever possible and endovascular treatments offer a less invasive option to patients than open surgical ligation or resection.

Introduction

Splenic artery aneurysms (SAA) are the most common, accounting for nearly 60%, of all visceral artery aneurysm (VAA), which as a whole are relatively uncommon.^1,2 SAA present with a high risk of rupture (3-9%) and a coinciding high mortality risk with rupture (up to 36%),⁹ which is further increased in patients with underlying portal hypertension (>50%) or pregnancy (70% mother, 95% fetus).^4,7 They occur more commonly in women than men (4:1). Most patients present asymptomatically with incidental findings on either CT or ultrasound, which are diagnostic; although plain abdominal x-ray may occasionally show signet ring calcifications. The number of cases has been increasing secondary to the widespread diffusion of medical imaging. Approximately 20% of patients with SAA present with vague left upper quadrant or epigastric abdominal pain. Traditionally the preferred treatment of SAA was repair or ligation, with a rise in the laproscopic approach, and concomitant splenectomy when necessary. More recently there have been reports of cases being successfully treated with endovascular procedures (ie, embolization). Open surgeries are now performed much less often for VAAs. The treatment plan varies based on the morphology of the aneurysm, the condition of the patient and the availability of resources. This must be assessed in every patient to prevent potential life-threatening complications.

Case Report The patient was a 42-year-old male who presented to the emergency room with sudden onset of severe abdominal pain. The patient denied any prior similar symptoms. His medical history is significant for hypertension well controlled with diet. On admission, he was noted to have a normal hemoglobin, hematocrit and red blood cell count with a markedly elevated white blood cell count (21.5x10⁹/L). His chemistry findings were all within normal limits, however his creatinine was in the upper limit of normal at 1.1 mg/dL, as well as normal liver function tests, amylase and lipase readings. Computed Tomography (CT) examination showed a retroperitoneal hematoma around the tail of the pancreas adjacent to the greater curvature of the stomach with inferior extension toward the left kidney. There was also a moderate amount of free fluid noted within the pelvis; all of unknown origin. Based on clinical history and CT findings the diagnosis of ruptured SAA was considered as well as peptic ulcer disease with perforation. (Figures 1 and 2)

(Fig 1 - Coronal CT showing the splenic artery with cloverleaf aneurysm appearance)

(Fig 2 - CT scan showing tortous splenic aneurysm and free fluid in abdomen)

After obtaining informed consent from the patient, which included advisement of the risks and benefits and potential complications surrounding the different treatment options the patient was prepared for angiography. An angiogram was performed using a #5 French diagnostic catheter and initial flush injection revealed a tortuous splenic artery with a cloverleaf or bi-lobed type aneurysm arising from the mid-distal junction of the splenic artery. (Figure 3) At this point, this was presumed to be the site of leakage and resultant hematoma seen on CT. Selective injection through the celiac artery revealed that the aneurysm was supplied mainly by the splenic artery with collateral from the pancreatic branch. Due to its tortuous nature the 0.035 system was only able to be advanced to the first initial turn in the splenic artery. A 0.018 system tracker was able to be advanced past this point. Six millimeter coils were used to embolize distal to the aneurysm. The 0.018 system was then switched for a 0.035 system and a #6 French guiding sheath was then placed into the celiac access. Coils were then laid in the mid-aspect of the splenic artery. There was noted to be a thrombus due to sluggish flow that occurred during advancement of the 0.035 system as well as some spasm of the splenic artery. A combination of 8 and 10 mm coils were used to the main portion of the mid section of the splenic artery with some coils laid more proximally. Flow appeared to be maintained through large branches from the pancreatic tail. There was still noted to be some flow at the hilum but the aneurysm could not be identified to fill with certainty at the conclusion of the procedure.

(Fig 3 - Angiogram of splenic artery showing tourtuosity and bilobed aneurysm)

On follow-up CT after embolization of the splenic artery, the patient was still complaining of similar pain but was hemodynamically stable with a large left upper quadrant hemorrhage related to the splenic artery aneurysm that appears stable. Coils were visualized in the mid aspect and distal hilar aspect of the splenic artery. There was a small amount of filling noted in the distal hilar region superiorly and in the mid aspect. There was no apparent filling noted in the region of the aneurysm. (Figure 4) There was an increase in free pelvic fluid seen most likely secondary to redistribution of intraperitoneal blood. The celiac artery appeared normal and the SMA origin remained patent. The spleen showed normal opacification without any evidence of infarction. The patient’s creatinine and WBC returned to normal.

(Fig 4 - Angiogram showing embolization distal and proximal to the aneurysm site without apparent filling of the aneurysm. Collateral blood flow to the spleen is also seen.)

One week after procedure patient presented for follow-up in office without any complaints or apparent complications of embolization treatment. Patient presented similarly without complaints or complications at two month follow-up. (Figure 5)

(Fig 5 - CT of abdomen showing clearance of free fluid in abdomen and coils in place in splenic artery)

Discussion

Splenic artery aneurysms are the third most common reported site of intra-abdominal artery aneurysm after abdominal aorta (AAA) and iliac arteries.⁷ However, autopsy reports suggest that SAA may have a prevalence of up to 10% while AAA show an incidence of 0.5%.4,5 SAA are the most common visceral artery aneurysm and are often saccular and located at the splenic hilum.⁴ These lesions are typically slow growing and have a diameter related risk of rupture, occurring more frequently with a diameter greater than 2cm.¹

There are a variety of different factors that are believed to either contribute or directly cause SAA. Pancreatitis, whether acute or chronic, has been shown to be a direct cause often resulting in rupture and bleeding into the GI tract. Septic emboli, Polyarteritis Nodosa, Systemic Lupus Erythematosis, Ehlers-Danlos Syndrome, Neurofibromatosis, fibrodysplasia, atherosclerosis, renal failure, portal hypertension, trauma and orthotropic liver transplantation have also been shown to have some contribution to the development of SAA. Pregnancy, particularly multiparous women with an average of 4.5 pregnancies, has been shown to have a correlation to increased incidence of SAA.⁴ This may be due to the increase in blood flow to the spleen or to the direct effect of estrogen on elastic tissue of the arteries.⁴ Approximately 95% of cases occurring in pregnancy occur in the second trimester and pregnancy demonstrates the highest risk of rupture (Most common in the third trimester).⁸

The major risk associated with splenic artery aneurysms is massive hemorrhage and hemosuccus pancreatitis which increases with increasing size of the aneurysm. The risk of rupture is believed to be between 3% and 10%.6 Bleeding may initially be contained in the lesser sac and re-rupture into the peritoneal cavity resulting in a “double rupture phenomenon”.^4,7 There is also a potential for rupture into adjacent viscera resulting in potential gastrointestinal tract bleeding and other related complications. Left lower lobe atelectasis, subphrenic abscess formation, showing as a left pleural effusion, or postoperative thrombocytosis are possible complications. Surgical guidelines recommend resection or endovascular treatment of all symptomatic and any asymptomatic aneurysms larger than 2cm and all pseudoaneurysms (due to their extremely high chance of rupture). Also any pregnant patient or patients wishing to become pregnant should be treated.^1,2 Primary excision of the splenic artery aneurysm with arterial repair is associated with a high failure rate.

Angiography and possible angioembolization should be considered for all patients who are hemodynamically stable in order to attempt to preserve splenic function whenever possible. Percutaneous transarterial embolization of the splenic artery using coils distal and proximal to the aneurysm neck has proven successful for treating aneurysms located in the proximal portion of the splenic artery. The percutaneous transarterial approach has also been shown successful with the use of detachable balloons, covered stents, gelfoam and N-butyl cyanocrylate.² Typically this method is not used for treatment of distal aneurysms due to the risk of splenic infarct when working in such close proximity to the splenic hilum. Collateral blood flow from the short gastric arteries determines preservation of the splenic tissue.² More recently, there have been reports of success with treatment of hilar SAA with coil embolization and balloon remodeling.¹⁰ Embolization may result in painful infarct and abscess formation with subsequent splenectomy required. In some cases, splenectomy is still needed following the initial procedure due to blood supply compromise. For larger aneurysms embolization is likely to be incomplete but may be accomplished. Primary success rates reported with endovascular treatment are between 75-98%.³ Possible complications being refilling of the aneurysm and post embolization syndrome.^1,3 There is increased failure rate when this technique is attempted with distal or wide neck aneurysms or in splenic arteries that are long and tortuous and surgical intervention may be warranted in these patients.^1,3

Open surgery is often reserved for relatively stable patients who are allergic to contrast medium, where angioembolization has failed or inpatients with other contraindications to contrast injection, surgical treatment may be the preferred treatment method for distal aneurysms. Surgical exploration has also been employed, following aggressive resuscitation, in cases of rupture when there is no interventional radiology availability or when endovascular approaches has already failed treatment. With surgery there is the possibility of encountering a phelgmon or having the inability to find the plane of dissection. Aneurysm resection with preservation of splenic function, with or without reconstruction of the splenic artery, is the preferred method in order to preserve host immune resistance and prevent infection in the perioperative period.¹ Although in distal hilar and intraparenchymal aneurysms this may be impossible and splenectomy may be unavoidable.^1,8 Ligation of the pseudoaneurysm and repair of the splenic artery have been reported but there is a 43% failure rate.² Morbidity and mortality rates following elective surgery for SAA are around 10% and 1% respectively,² but remain greater than 20% in emergent cases.⁸

Laparoscopic repair or resection is also possible but difficult to perform. Favorable outcomes have been indicated when surgeons utilize a combination approach with contact ultrasonography to recognize deficient residual flow to the spleen after aneurysm exclusion. Like open surgery, laparoscopic management is preferred in young patients and those who are unable or unwilling to undergo the imaging control protocol needed to perform endovascular measures. With the laparoscopic approach, there is the obvious benefit of a less invasive procedure, when compared to open surgery, with decreased hospital stay and comparable results to endovascular treatments. In patients with distally located aneurysms, it is advisable to simply exclude rather than excise the aneurysm for fear of damage to the splenic vein. The laparoscopic approach, as opposed to open procedures, may also have fewer incidences of pancreatic injury and irritation.³ Laparoscopic surgery should never be attempted in patients who are not hemodynamically stable.⁵

For patients who do not need surgical intervention (ie, those with asymptomatic SAA <2cm diameter) medical management with beta-blockers can help prevent the growth of the aneurysm.

CT examinations are necessary for follow-up of patients treated with embolization to monitor for recurrence and splenic infarction.² When successful embolization is confirmed at one year after treatment, further follow-up is probably no longer needed although this must be individualized for each patient. If there is reopening and partial aneurysm filling additional embolization or other surgical methods may be warranted.³

Conclusion

A high index of suspicion is warranted in any patient with a chief complaint of vague left upper quadrant or epigastric abdominal pain or in patients presenting with hemodynamic instability without any other obvious cause. When addressing these patients the differential diagnosis includes PUD, pancreatitis, abscess, intestinal ischemia, cancer, splenomegaly and rupture or infarction of the spleen and need to also be excluded. Diagnosis is made on CT or ultrasound although occasionally signet ring calcifications may be seen on plain abdominal x-ray. In deciding treatment modality the patient’s condition, morphology of the aneurysm and resources available need to all be taken into account. The options for treating these patients are repair of ligation, either by traditional open or laproscopic approach, or endovascular treatment. Endovascular treatment may utilize stents, coils, balloons, gelfoam or N-butyl cyanocrylate. Asymptomatic patients with SAA <2cm and who are not pregnant do not necessarily require treatment and may be followed with observation.

Author information:

Ruth Carroll, MS III

New York College of Osteopathic Medicine.

rcarroll@nyit.edu

Michael Aronis, MD, FACS

United Medical Associates

Wilson Memorial Hospital, Johnson City, NY

Mike_Aronis@me.com

Andrew L. Isenberg, MD, FACS

Clinical Assistant Professor of Surgery SUNY Upstate Medical Center

Beansurg@aol.com

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