Effectiveness of the conservative therapy for spontaneous isolated iliac artery dissection: Preliminary results

Abstract

Purpose

To investigate the effectiveness of conservative therapy for spontaneous isolated iliac artery dissection (SIIAD).

Methods

From February 2006 to May 2016, all patients with SIIAD were included and analyzed. The diagnosis of SIIAD was made based on contrast-enhanced computed tomography. The imaging morphologic characteristics, treatments, and outcomes for each patient were analyzed.

Results

A total of 11 patients (10 male and 1 female, age 71.1 ± 7.8 years) were included in this study. Of the 11 patients, 8 patients were asymptomatic and the SIIADs were discovered during the course of computed tomography for other diseases, and 3 patients were symptomatic. Initial computed tomography findings: iliac arterial calcification (n = 7); compression of the true lumen (n = 6), with stenosis of the true lumen from 25% to 50% (n = 3) and ≥ 50% (n = 3); thrombosed false lumen partially (n = 4), and no thrombosis in false lumen (n = 7); dissecting aneurysm (n = 11); entry points (n = 11); re-entry points (n = 1); no dissection extended to the internal iliac or common femoral artery. Conservative treatment was performed in six patients, and the remaining five patients need no treatment. During 23.3 ± 14.2 months follow-up, none recurred symptoms and signs of symptomatic SIIAD; partial remodeling of SIIAD was achieved in four patients, and the remaining seven patients with no change of SIIAD. There was no presence of new false lumen enhancement on contrast-enhanced computed tomography during follow-up.

Conclusions

SIIAD without arterial rupture or lower limb necrosis can be safely treated with conservative therapy.

Keywords

Iliac artery dissection management

Introduction

Arterial dissection is a serious medical condition, which can lead to artery ruptura, or even patient death.^1,2 Spontaneous isolated iliac artery dissection (SIIAD), an iliac artery dissection without the presence of the aortic dissection, is an uncommon but potentially catastrophic pathology.^3–5 The natural history of SIIAD is unpredictable.^3,4,6 Although several case of SIIAD have been reported,^5,7 there is no clinical study about SIIAD has been reported. Although several treatment options, including conservative treatment, endovascular treatment, and surgical treatment are available. There is currently no consensus regarding optimal management of SIIAD.^3,4,6

The purpose of this retrospective study was to investigate the effectiveness of conservative therapy for SIIAD.

Materials

Study design

This study was approved by our institutional review board with a waiver of informed consent. From February 2006 to May 2016, all patients with contrast-enhanced computed tomography (CT) proven SIIAD were included in this study. Patient demographics and clinical information were gathered from patients’ medical records. The imaging data was gathered from picture archiving and communications system (PACS) of our institution.

Patient evaluation

Ankle brachial index (ABI) was used to assess the degree of lower limb ischemia; the percent compression of the true lumen was measured on CT images using the diameter of the unaffected iliac artery and the diameter of the true lumen at the site of maximal stenosis, and stenosis of the true lumen was classified as from 25% to 50%, and ≥50%⁸; thrombosis of the false lumen was classified as completely, partially, and no thrombosis.⁹

Diagnostic workup

CT scan was performed in using 64-detector row CT (Philips, Rotterdam, Netherlands). CT technical parameters included: 512 × 512 matrix, 5 mm slice, 200–300 mAs; 100–120 kV. Unenhanced and contrast-enhanced CT scan of the whole pelvic cavity was performed. Each patient was administered about 60–80 ml of nonionic iodinated contrast media (Iohexol Injection, 300 mg I/ml, Yangtze Pharmaceutical Co., Ltd., Yangzhou, China) intravenously at a rate of 3.0 ml/s, followed by 20 ml of normal saline. The obtained axial images were transferred to the workstation, and multiplanar reconstruction (MPR), maximum intensity projections (MIP), volume rendered (VR) images were reconstructed.

CT imaging analysis

CT interpretation focused on the morphologic characteristics of SIIAD, including the degree of luminal stenosis, thrombosis of the false lumen, dissecting aneurysm, entry and reentry points, and whether the dissection extended to the internal iliac artery or common femoral artery. The presence or absence of new false lumen enhancement was also evaluated on follow-up CT scans. All images were analyzed separately by two independent radiologists. A third investigator resolved any discrepancies.

Definitions

Lower limb ischemia: patients with any of the “5P” sign, including pulseless, pain, pale, paresthesia, and paralysis.

Lower limb necrosis: patients with an area of tissue death of the lower limb.

SIIAD progression: patients with any of the following finding during follow-up: (a) aggravation of symptoms and signs; (b) aggravation of lower limb ischemia, or new appear lower limb necrosis; (c) new false lumen enhancement, or new increasing size of aneurysmal dilation.²

Failed conservative treatment: patients with SIIAD progression during conservative treatment.

Remodeling of SIIAD: (a) partial remodeling: improvement in the SIIAD, which was characterized by the occlusion of a false lumen and/or reduced stenosis in the true lumen; (b) complete remodeling: morphological recovery of the iliac artery to its normal condition, without any aneurysmal formation.

Management of SIIAD

The decision to manage conservatively, to undergo endovascular therapy or surgical treatment was based on patient’s symptoms and signs, as well as the morphologic characteristics of SIIAD on CT scan. Conservative treatment was underwent initially of symptomatic patients or patients with risk factors, which consisted of pain control, strict blood pressure control, intravenous use of vasodilators, and anticoagulation²; vasodilators was admitted to patients with lower limb ischemia; anticoagulation was only given to patients who with thrombosis of the true lumen. Endovascular therapy can be considered in patients with SIIAD progression during follow-up or failed conservative treatment.^2,10 Surgical treatment should be performed without delay to patients with artery rupture, or failed/unsuitable of endovascular therapy.

Contrast-enhanced CT scan was additionally checked at any time when aggravation of symptoms and signs during the treatment or recurred symptoms and signs of SIIAD during follow-up.

Clinical follow-up

Clinical follow-up was scheduled on the first, third, and sixth month after the diagnosis of SIIAD, and annually thereafter until complete remodeling of the SIIAD according to a pre-established follow-up protocol. More frequent evaluations were done when needed. During follow-up, ABI and contrast-enhanced CT were obtained.

Results

Patients

From February 2006 to May 2016, a total of 11 patients were diagnosed of SIIAD and included in this study. There was no patient presented with iliac artery rupture who were treated as emergencies without the specific diagnosis of ruptured dissection being made. There were 10 male and 1 female, with mean age of 71.1 ± 7.8 years (range 57–87 years). The demographic information, disease characteristics, and symptoms are detailed in Table 1. Of the 11 patients, asymptomatic in 8 patients (the SIIAD were discovered during the course of CT for other diseases), and symptomatic presented with lower abdomen pain in 3 patients.

Table 1.

Baseline characteristics of the 11 patients.

	Patients, n
Age (years)	71.1 ± 7.8 (range, 57–87)
Gender
Female	1
Male	10
Smoking
Yes	3
Quit	4
Never	4
Atherosclerotic risk factors
Hypertension	5
Diabetes	2
Dyslipidemia	7
Atherosclerosis	7
Without atherosclerosis	4
Asymptomatic	8
Symptomatic (pain)	3
Lower limb ischemia/necrosis	0
D-dimer (normal <0.5 µg/ml)	0.3 ± 0.1
ABI	1.0 ± 0.1

Initial CT findings

Initial CT findings: iliac arterial calcification was found in seven patients (Figure 1); compression of the true lumen occurred in six patients (Figures 2 and 3), with the stenosis of true lumen from 25% to 50% in three patients, and ≥50% in three patients; thrombosed false lumen partially was in four patients, and the remaining seven patients with no thrombosis in the false lumen (Figure 4); dissecting aneurysm occurred in all patients (Figures 4 and 5), with the mean diameter of dissecting aneurysm of 4.2 ± 2.4 mm (range 1.5–16 mm); entry and reentry points were in 11 and 1 patient (Figure 4); no dissection extended to the internal iliac artery or common femoral artery. The initial CT findings are detailed in Table 2.

Figure 1.

(a, b) Short segment dissection of the right external iliac artery without true lumen stenosis; and no thrombosis in the false lumen (white arrowhead). (c, d) Stable chronic short segment dissection of the right external iliac artery by CTA 5 years later (white arrowhead).

Figure 2.

(a, b) Initial CTA shown dissection of the right common iliac artery, with dissecting aneurysm (white arrowhead. (c, d) Thrombosed of the distal false lumen (white arrowhead), with severe compressed of the true lumen (>50%, black arrowhead).

Figure 3.

Stable right common iliac artery dissection with no change compared with images 4.5 years before (same patient to Figure 2). (a, c, d) A huge dissecting aneurysm can be seen (white arrowheads). (b) Thrombosed of the distal false lumen (white arrowhead), with partial remodeling of SIIAD.

Figure 4.

(a, b) The short segment well fenestrated dissection of the left external iliac artery, and flap can be seen between the true and false lumen (black arrowhead). (c, d) Stable focal dissection, and no expansion and thrombosis of either true or false lumen on CTA 3 years later.

Figure 5.

(a, b) Initial CTA shown dissection of the left iliac artery, maximum dimensions of 14 mm of the dissecting aneurysm (white arrowhead). (c, d) Stable appearance of dissection of the left iliac artery and dissecting aneurysm on 1 year follow-up (white arrowhead).

Table 2.

Initial CT findings of the 11 patients.

	Patients, n
Location of dissection
Left common iliac artery	2
Right common iliac artery	2
Left external iliac artery	4
Right external iliac artery	3
Iliac arterial calcification	7
Compression of true lumen	6
25–50%	3
≥50%	3
Thrombosis of false lumen
Completely	0
Partially	4
No thrombosis	7
Dissecting aneurysm
Yes	11
Diameter of dissecting aneurysm (mm)	4.2 ± 2.4
Entry points	11
Reentry points	1
Internal iliac artery	0
Common femoral artery	0

Treatments and outcomes

Of the 11 patients, conservative treatment was performed in six patients, and the remaining five patients need no treatment. There was no patient received anticoagulation. Of the three symptomatic patients, the median interval between beginning of conservative treatment and symptoms disappeared was 2 days (range 1–2 days). All patients were recovered uneventfully, and none of them recurred symptoms and signs of symptomatic SIIAD. None developed arterial rupture or lower limb ischemia/necrosis.

Subsequent CT findings

During 23.3 ± 14.2 months (range 5–51 months) follow-up, partial remodeling of SIIAD was achieved in four patients, and the remaining seven patients with no change of SIIAD on follow-up CT scans. There was no presence of new false lumen enhancement.

Discussion

This study demonstrated: (1) SIIADs are stable, and some of them can be achieved partial remodeling of SIIAD during follow-up; (2) SIIAD without arterial rupture or lower limb necrosis can be safely treated with conservative therapy.

Although multiple case reports have been performed previously in patients with SIIAD,^5,11–15 the underlying causes and etiology of SIIAD are still unclear.^12–16 According to this study, SIIAD occurred in 90.9% male patients with the mean age of 71.1 ± 7.8 years, 63.6% patients have been smoking, and 45.5% patients have hypertension. Previous reports have also identified several risk factors for SIIAD, including atherosclerosis, vascular type Ehlers–Danlos syndrome, fibromuscular dysplasia, cystic medial degeneration Erdheime–Gsell.^5,11–15 Although 11 patients were included in this study, there was no patient was approved with vascular type Ehlers–Danlos syndrome, fibromuscular dysplasia, cystic medial degeneration Erdheime–Gsell. The statistical analysis of potential risk factors was not possible in our study because of the small sample size.

The natural history of SIIAD is variable and unpredictable.^3,4,6 Although patients with SIIAD can be resolved spontaneously without specific treatment or in stable condition,⁷ the progress to true lumen occlusion, false lumen expansion, aneurysmal dilation, and iliac artery rupture have been reported.^3,4,6 The primary objective of treatment of SIIAD is to limit the extension of dissection, to preserve the blood flow distally through the true lumen, and to prevent the artery rupture. Conservative treatment, endovascular treatment and surgical treatment were reported in the management of SIIAD.^3,4,6 There is currently no consensus regarding optimal management of SIIAD.¹⁰

A major clinical problem in treating SIIAD is arterial aneurysm rupture.⁴ It was reported dissecting aneurysm was common in SIIAD patients, which carries a risk of rupture.⁴ Surgical treatment should be performed in patients with rupture of a iliac artery aneurysm.⁴ The present study, although dissecting aneurysm was found in all patients, there was no patient need endovascular or surgical treatments, and 36.4% patients were achieved partial remodeling of SIIAD and the remaining 63.6% patients were in stable condition with no change of SIIAD during follow-up.

Another major clinical problem in treating SIIAD is lower limb ischemia/necrosis. The lower limb has rich collateral circulations anatomically. There have been no case reports of lower limb necrosis associated with SIIAD. Thus, the lower limb has a subtle but rich microcirculation, and has the potential to develop collaterals over time. Conservative treatment is sufficient in SIIAD is lower limb ischemia. Of this study, there were three patients with the stenosis of true lumen ≥50%, and there was no lower limb ischemia/necrosis occurred with the mean ABI of 1.0 ± 0.1.

The present study included 11 SIIAD patients with 23.3 ± 14.2 months follow-up, and partial remodeling of SIIAD was achieved in four patients, and the remaining seven patients with no change of SIIAD on follow-up CT scans, which proved conservative treatment is a promising option and can be applied successfully in patients with SIIAD.

Endovascular therapy has been reported in the treatment of patients with SIIAD, and can be reserved for patients who failed conservative therapy.^3,6 Although endovascular stent placement provided immediate symptomatic improvement and prevented further progression of the false lumen,^3,6 there are many drawbacks of stent placement, including stent restenosis and obliteration of side branches of the iliac artery.

Surgical treatments of SIIAD have been reported.⁴ These patients need a laparotomy and complex visceral artery reconstruction. The morbidity and mortality of surgery is high with lengthy hospital stay. With the advent of endovascular repair, the indications for surgery are narrowing and the number of patients receiving surgery is decreasing. However, open surgery should be performed in complicated patients who are unsuitable/failed of endovascular therapy, or patients with artery rupture. According to our study, we believe conservative therapy will be more popular in the treatment of patients with SIIAD.

The present study is limited by its retrospective nature and the number of patients included in this study was small; also, statistical analysis of relationship among the pain, stenosis of true lumen, and dissecting aneurysm was not possible because of the small sample; furthermore, a prospective randomized clinical trials with a large sample size are needed to validate the conservative therapy.

In conclusion, SIIAD without arterial rupture or lower limb necrosis can be safely treated with conservative therapy.

Footnotes

Declaration of conflicting interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

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