Transcatheter Arterial Embolization of Splenic Artery Aneurysms: A Single-Center Experience.

PURPOSE: The purpose of this study was to report on splenic artery aneurysms (SAAs) treated by transcatheter embolization in our single-center institution and to evaluate the clinical outcomes of patients with SAA by aneurysm location.
MATERIALS AND METHODS: The original medical records and imaging results of 52 patients with SAA treated in our center between January 1, 1995 and December 31, 2013 were reviewed. Of these cases, 7 patients (13.5%) underwent surgery, 4 patients (7.5%) underwent serial observation, and 1 patient had stent insertion only, leaving 40 patients (78.9%) who underwent endovascular treatment using a coil, with or without N-butyl-2-cyanoacrylate.
RESULTS: Aneurysms were located in the distal third of the splenic artery in 27 patients (67.5%), in the middle third in 9 cases (22.5%), and in the proximal third in 4 cases (10%). Of the 40 included patients, 25 were female (62.5%). Twenty-eight patients (70%) were asymptomatic. The mean aneurysm diameter was 2.48 cm (range, 0.8-6.0 cm). Complications involved pancreatitis (n=1) and early spleen infarction (n=29: <1/3 in 14, 1/3-2/3 in 10, and >2/3 in 5). Postembolization syndrome was noted in 26 patients (65%). There were no significant differences by aneurysm location in the postoperative increase in the values of white blood cells, amylase, lipase, and C-reactive protein (P=0.067, P=0.881, P=0.891, and P=0.188, respectively).
CONCLUSION: At our institution, endovascular management is safe, has high technical success, and represents the first-line treatment for SAA, regardless of aneurysm location.

INTRODUCTION

Although rare, splenic artery aneurysms (SAAs) are clinically important because they are life-threatening when a rupture occurs. The true prevalence of SAAs is unknown, varying between 0.04% and 0.10% at autopsy and at 0.8% on nonselective angiogram [1]. With the increasing use of high-resolution imaging techniques, SAAs are being detected with greater frequency than before. The reported risk of rupture ranges between 3% and 10% and, if rupture occurs, it is fatal in 20%–100% of patients [2,3]. Open surgical treatment has traditionally been performed [4,5], although the first minimally invasive surgical treatment–laparoscopic management of a SAA was reported in 1993 [6]. Recently, a percutaneous endovascular embolization procedure has gained popularity, and it is now performed as the first-line treatment for SAA. Although no randomized controlled trials have assessed the safety and efficacy of endovascular embolization, there have been several case reports and small or generalized retrospective reviews [7-11].

In our current study, we retrospectively reviewed patients with SAA treated by transcatheter embolization in our single-center institution and evaluated the clinical outcomes of patients with SAA by aneurysm location.

MATERIALS AND METHODS

Patients

Patients who presented at the Asan Medical Center, Seoul, Korea and were diagnosed with a SAA between January 1, 1995 and December 31, 2013 were identified and reviewed. Patients (n=52) were identified during this study interval using the International Classification of Diseases-9 code 442.83 (SAA). Seven patients (13.5%) underwent surgery and four patients (7.5%) underwent serial observation. Forty-one patients underwent elective endovascular treatment. One patient who underwent percutaneous endovascular treatment received a stent insertion alone, without coil embolization. Leaving 40 patients (78.9%) who underwent endovascular treatment using a coil, with or without N-butyl-2-cyanoacrylate. SAAs were located in the proximal (n=4), middle (n=9), and distal (n=27) segments of the main splenic artery.

The records of all patients were identified using the Asan Medical Center Record Registry, and a chart review was used to collect patients’ demographic information, clinical characteristics, aneurysm features, imaging studies, including spiral computed tomography (CT) and angiography, and clinical outcomes. All patients underwent CT to confirm the diagnosis and assess the anatomical characteristics of the aneurysm and the possibility of endovascular treatment. Transcatheter embolization was always performed with coils and sometimes with the additional injection of N-butyl-2-cyanoacrylate (Histoacryl). Technical success was defined as complete exclusion of the aneurysm on the postembolization arteriogram, without major complications. Postembolization syndrome (PES) was defined as fever, abdominal pain, nausea, or vomiting, or the elevation of pancreatic enzymes over preprocedural values after infarction.

White blood cell (WBC), serum amylase, and lipase values were assessed before endovascular treatment and during hospitalization, depending on the clinical status of the patient. The highest pre- and postoperative values and the changes in the WBC, amylase, and lipase values were considered for analysis. No specific protocol was followed for SAA management: surgeon preference and judgment dictated all management decisions.

Statistical analysis

The demographic and clinical characteristics of the three study groups were analyzed with a chi-square test and the differences among the groups were compared with a one-way analysis of variance (ANOVA). All statistical analyses were performed with PASW Statistics ver. 18.0 (IBM Co., Armonk, NY, USA), and a P-value of ≤0.05 was considered statistically significant.

RESULTS

A summary of patient demographics and clinical characteristics is provided in Table 1. In total, 40 patients were diagnosed with SAA and managed using endovascular treatment. Of these 40 patients, aneurysms were located in the distal third of the splenic artery in 27 (67.5%), in the middle third in 9 (22.5%), and in the proximal third in 4 (10%). The mean age at diagnosis was 55.2 years (range, 28–76 years). Of the 40 patients, 25 were female (62.5%). SAAs were located in the distal third of the splenic artery in 13 of the male patients (48.1%) and in 14 of the female patients (51.9%). Although 28 patients (70%) were asymptomatic, 12 patients (30%) presented with symptoms (10 with abdominal pain, 2 with abdominal discomfort). Comorbid illnesses and risk factors included hypertension (n=9, 22.5%), diabetes mellitus (n=9, 22.5%), pre-existing pancreatitis (n=6, 15%), portal hypertension (n=10, 25%), hyperlipidemia (n=9, 22.5%), and tobacco use (n=10, 25%). The mean follow-up period was 30.1 months (range, 1–101 months).

Table 1.

Patient demographics and clinical characteristics by aneurysm location

Factor	Total (n=40)	Proximal (n=4)	Middle (n=9)	Distal (n=27)	P-value
Age (y)	55.17±11.2	53.25±15.0	52.22±10.5	56.44±11.1	<0.752
Sex (female)	25 (62.5)	3 (75.0)	8 (88.9)	14 (51.9)	<0.116
Symptoms (symptomatic)	12 (30.0)	0 (0.0)	2 (22.2)	10 (37.0)	<0.429
Diabetes mellitus	9 (22.5)	1 (25.0)	0 (0.0)	8 (29.6)	<0.188
Hypertension	9 (22.5)	1 (25.0)	2 (22.2)	6 (22.2)	<1.000
Pancreatitis	6 (15.0)	0 (0.0)	0 (0.0)	6 (22.2)	<0.288
Portal hypertension	10 (25.0)	0 (0.0)	1 (11.1)	9 (33.3)	<0.323
Hyperlipidemia	9 (22.5)	2 (50.0)	2 (22.2)	5 (18.5)	<0.347
Smoking	10 (25.0)	3 (75.0)	9 (100.0)	18 (66.6)	<0.133
Follow-up (mo)	30.1±26.3	26.5±36.9	25.5±28.6	32.2±24.8	<0.880

Values are presented as mean±standard deviation or number (%).

For a summary of aneurysm characteristics, see Table 2. Of the 40 patients, 34 had true aneurysms (85%) and 6 had false aneurysms (15%). Thirty-five patients (87.5%) had one aneurysm, whereas five had multiple aneurysms. All multiple aneurysms were located in the distal third of the splenic artery. Four patients with multiple SAAs had two aneurysms and one patient had four SAAs in the distal third of the splenic artery. Calcification was present in 14 patients (35%). The mean aneurysm diameter was 2.48 cm (range, 0.8–6.0 cm). The mean±standard deviation (SD) aneurysm diameters by location (proximal, middle, and distal segments) were 2.70±0.24 cm, 1.80±0.57 cm, and 2.76±1.52 cm respectively. There were no ruptured aneurysms among the patients who underwent endovascular treatment.

Table 2.

Aneurysm characteristics by aneurysm location

Feature	Total (n=40)	Proximal (n=4)	Middle (n=9)	Distal (n=27)	P-value
Type (true)	34 (85.0)	4 (100.00)	9 (100.00)	21 (77.78)	0.288
Multiplicity (single)	35 (87.5)	4 (100.00)	9 (100.00)	22 (81.48)	0.440
Size (cm)	2.48±1.33	2.70±0.24	1.80±0.57	2.76±1.52	0.099
Thrombus	5 (12.5)	1 (25.00)	1 (11.11)	3 (11.11)	0.760
Calcification	14 (35.0)	2 (50.00)	5 (55.56)	7 (25.93)	0.210

Values are presented as number (%) or mean±standard deviation.

For a summary of postoperative outcomes, see Table 3. All patients achieved technically successful endovascular treatment. Although 15 patients were treated with coils alone, the other 25 aneurysms were treated with coils and the injection of N-butyl-2-cyanoacrylate. There was no perioperative mortality. The mean hospital stay was 8.95 days (range, 1–55 days). The mean±SD hospital stays for aneurysms located in the proximal, middle, and distal segments were 2.75±0.50 days, 7.44±8.72 days, and 10.37±13.73 days, respectively (median±interquartile range: 3.00±0.50 days, 3.00±4.00 days, and 4.00±11.00 days, respectively). Three patients were hospitalized again within 1 month but access site complications did not occur. Thirty-six patients underwent follow-up CTs within 1 month after the procedure to evaluate the short-term results and complications. Complications involved pancreatitis (n=1) and early spleen infarction (n=29: <1/3 in 14, 1/3-2/3 in 10, and >2/3 in 5); no spleen abscesses developed. One patient who had a false SAA with acute pancreatitis before the procedure had fluid collection. Other complications included portal vein thrombosis (n=1), recurrent pseudocysts (n=2), and celiac dissection (n=1) (Table 4). PES was noted in 26 patients (65%); 15 of these patients had a distal aneurysm. In patients with PES, eight had fever, six had abdominal pain, two had nausea and vomiting, five had fever and abdominal pain, and five had nausea and abdominal pain. With regard to the postoperative increase in the values of WBCs, amylase, lipase, and C-reactive protein, there was no significant difference by aneurysm location (P=0.067, P=0.881, P=0.891, and P=0.188, respectively). Postoperative clinical outcomes showed no significant differences among the three groups.

Table 3.

Postoperative outcome by aneurysm location

Variable	Total (n=40)	Proximal (n=4)	Middle (n=9)	Distal (n=27)	P-value
Hospital stay (d)	8.95±12.12	2.75±0.50	7.44±8.72	10.37±13.73	0.379
Complication	6 (15.00)	0 (0.00)	2 (22.22)	4 (14.81)	0.474
Postembolization syndrome	26 (65.0)	4 (100.00)	7 (77.78)	15 (55.56)	0.181
Splenic infarction					0.203
None	7 (17.5)	2 (66.67)	1 (14.29)	4 (15.38)
<1/3	14 (35.0)	1 (33.33)	5 (71.53)	8 (30.77)
1/3–2/3	10 (25.0)	0	1 (14.29)	9 (34.62)
>2/3	5 (12.5)	0	0	5 (19.23)
ΔAmylase (U/L)	42.6±136.10	23.67±21.59	125.86±282.70	31.30±79.98	0.881
ΔLipase (U/L)	33.2±154.91	17.00±24.27	151.17±336.97	13.00±98.60	0.891
ΔWhite blood cell (×103/μL)	10.13±4.28	9.50±0.62	13.71±4.84	9.38±3.42	0.067
C-reactive protein (mg/dL)	5.14±7.02	0.1	5.47±6.38	7.36±7.77	0.188

Values are presented as mean±standard deviation or number (%).

Table 4.

Types of complication in the study series

Complication	n (%)
Fluid collection	1 (2.5)
Portal vein thrombosis	1 (2.5)
Pancreatitis	1 (2.5)
Recurred pseudocyst	2 (5.0)
Celiac dissection	1 (2.5)

DISCUSSION

The treatment of choice for SAAs has now changed from either open surgery or laparoscopic surgery to transcatheter embolization. Endovascular treatment should be the first-line treatment for all SAAs because of its safety, lower mortality, and sufficient short- and long-term results [8,11,12]. Lakin et al. [13] noted that endovascular ablation remains a durable, effective treatment for SAAs that present with a larger size or grow over time. There is no consensus in the literature on the size criteria for endovascular management of asymptomatic SAAs. Abbas et al. [3] reported that asymptomatic SAAs >2 cm in size are at an increased risk of rupture, a finding supported by Mayo clinic data. Smaller SAAs (<2 cm) grow slowly and carry a negligible rupture risk. Some evidence has suggested that SAAs should be treated if women are anticipating pregnancy and in liver transplant candidates, regardless of their size [14-16]. In our present study, the mean aneurysm diameter was 2.48 cm, and the mean aneurysm diameters by location (proximal, middle, and distal) were 2.70 cm, 1.80 cm, and 2.76 cm, respectively. The mean size of SAAs located in the middle segment of the splenic artery was <2 cm because, of the nine patients who had a middle SAA, one was a liver transplantation candidate and one was a living donor for liver transplantation. Their respective SAA sizes were only 0.8 cm and 1.5 cm.

In a previous literature review, various articles discussed the transcatheter arterial embolization of SAAs but few articles specified the SAA outcomes by aneurysm location. Here, we have focused on perioperative outcomes by aneurysm location. Because of the differences in outcomes by aneurysm location, we believed that there was an intervention limitation if the aneurysm was close to the celiac axis, if pancreatitis developed in the branches from the splenic artery to the pancreas in the middle part, or if splenic infarction occurred in the distal part of the splenic artery. Regardless of aneurysm location, we achieved technical success and found no significant differences in the rates of pancreatitis, spleen infarction, or PES, or in the postoperative laboratory findings by aneurysm location.

Postembolizational pancreatitis is rare. Guillon et al. [17] observed an early, transient elevation of pancreatic enzyme levels, which occurred more frequently for proximal aneurysms. In our current series, one patient with a middle SAA developed acute pancreatitis after the procedure. Tokuda et al. [18] concluded that the reason for the pancreatitis was the direct embolization of the pancreatic terminal arteries by N-butyl-2-cyanoacrylate. In our one case, the splenic artery proximal and distal to the aneurysm was embolized using seven coils and with one N-butyl-2-cyanoacrylate.

Splenic infarction was the most common postprocedural complication but most cases resolved without sequelae. In the literature, most splenic infarctions occurred after distal SAA treatment [11-13]. In our institute, 22 patients (84.6%) with distal segment SAAs, 6 patients (85.7%) with middle segment SAAs, and 1 patient (33.3%) with a proximal segment SAA showed splenic infarction (P=0.203). No patient had adverse clinical outcomes that included a splenic abscess.

CONCLUSION

In this retrospective study, PES and splenic infarction were common but most resolved without sequelae. There were no differences in complications or laboratory findings such as WBCs, C-reactive protein, serum amylase, and lipase by aneurysm location. All patients achieved technical success. These results indicate that endovascular management is a safe and feasible procedure for patients with SAA, regardless of aneurysm location. Transcatheter embolization represents the first-choice treatment for SAAs in any location.