Abstract
Introduction
Abdominal aortic aneurysm (AAA) is the pathologic focal dilation of the abdominal aorta and is defined as a local dilation of the abdominal aorta of at least 150% compared to a relative normal adjacent diameter of that aorta. 1 While common in the elderly population, AAAs are rare in the paediatric population. When present in children, AAAs are usually associated with systemic conditions such as inflammatory conditions, vasculitis or connective tissue disorders. 2 With the increasing use of umbilical artery catheters in premature or unstable neonatal patients, there are rising reports of aortic aneurysms in such high-risk neonates as well. 3
Tuberous sclerosis complex (TSC) is a multi-systemic autosomal dominant disease that was first described by von Recklinghausen in 1862 and coined by Bourneville in 1880. 4 TSC is caused by a mutation in either the TSC1 or TSC2 gene and is characterized by an increased predisposition to the development of hamartomas in almost every organ system. 5 Clinical presentation is variable, and common clinical manifestations include characteristic skin lesions, seizures and harmatomas in the brain, heart, and kidneys. 6 Aortic aneurysms in patients with TSC have been reported presenting at varying age groups. 5
We herein report a case of an incidental finding of an abdominal aortic aneurysm in a child with TSC.
Case report
We present a 3 year 8-month-old girl with a background history of TSC. Her antenatal scans had showed multiple cardiac rhabdomyomas which were present on post-natal echocardiography. She had cortical tubers on her post-natal cranial ultrasound along with renal cysts detected via renal ultrasound. A clinical diagnosis of tuberous sclerosis was therefore made during her neonatal period based on the above mentioned findings. Subsequently; at 14 months of age, she developed focal epilepsy and was started on Carbamazepine by her Neurologist. She had learning disabilities with language delay and was integrated into kindergarten with therapy sessions at an independent non-profit charity organization.
She was admitted for breakthrough status epilepticus secondary to an intercurrent upper respiratory tract infection. On physical examination, her blood pressure was normotensive at 83/40 mmHg and an incidental large pulsatile 3 cm by 4 cm mass was palpated over the right peri-umbilical region. Her abdomen was otherwise soft, non-distended and non-tender. An abdominal ultrasound revealed an intact 3.3 cm by 4.5 cm by 3.3 cm infra-renal aortic abdominal aneurysm. A subsequent computed tomography (CT) angiogram and magnetic resonance imaging (MRI) of her abdomen also confirmed this finding with wall thinning over its right lateral aspect and did not show any further aneurysms (Figure 1). (a–c) Magnetic resonance, computed tomography, and computed tomography angiography images of the aorta in craniocaudal view showing a saccular aneurysm arising from the right aspect of the infrarenal aorta and estimated to measure 3.3 x 4.5 x 3.3 cm. This aneurysm has a lobulated contour with wall thinning noted along its right lateral aspect. (d–e) Magnetic resonance and computed tomography images of the aorta in transverse view showing previously described saccular aneurysm of infra-renal abdominal aorta. Its superior aspect is situated 3.5 cm inferior to the origin of the right renal artery while its inferior aspect is 1.3 cm above the aortic bifurcation.
She subsequently underwent surgical repair of her abdominal aortic aneurysm. Intra-operatively, a large saccular infra-renal abdominal aortic aneurysm was found, with thin layer of clots inside the aneurysm. The aneurysm was repaired by inserting a 12 mm woven Dacron graft into proximal aorta just before level of bifurcation. Histologic analysis (Figure 2) revealed a true aneurysm with dilated lumen of the aortic wall with focal degeneration of media containing disorganized collagen fibres and focal mild chronic inflammation of media and adventitia. Her post-operative recovery was uneventful. She remained normotensive throughout her admission and was discharged from hospital 6 days after surgery. Post-discharge; she remains clinically well, is asymptomatic and is attending childcare. She remains on regular follow-up with multiple subspecialists and is planned for routine surveillance scans. (a) original magnification 4X, Haematoxylin and eosin-stained histology slides showing features of focal degeneration of media with disorganized collagen fibres and mild chronic inflammation. (b) original magnification 10X. (c) original magnification 40X. Media with granulation tissue formation and a few neutrophils.
Discussion
AAAs are rare in children. Most of the reported cases of paediatric AAAs in the literature include mycotic aneurysms, false aneurysms acquired from trauma or are associated with vasculitis or connective tissue diseases such as Marfan syndrome, Ehlers-Danlos syndrome and TSC. Because of their rarity, little is known about the progression and prognosis; and there is no standardized protocol for the treatment of AAA in a child.
In a previous review of patients with tuberous sclerosis and aortic aneurysms, 4 the youngest patient was only 4.5 months of age and the oldest 41 years old. Most had AAAs (86.7%) and a small number had thoracic aortic aneurysms (TAAs). 40% of the patients had passed away due to either ruptured aneurysm or complications during operative repair. Such a high mortality rate for any condition is alarming for patients and physicians alike.
Although the pathogenesis of aortic aneurysms in patients with TSC is unknown, recent observations postulate that the abnormal connective tissue with loss of elastic fibres in these patients have been implicated in aneurysm formation. 5 It has also been reported that vascular dysplasia may result in changes in the vascular architecture such as degeneration of tunica media and elastica that contribute to aneurysm development. 7 As in our case, medial atrophy with disorganized collagen fibres contributed to the reduction of aortic wall strength and the formation of an aneurysm.
The presenting symptoms of an AAA can be varied, and can range from being completely asymptomatic, to symptoms including a pulsatile abdominal mass, hypertension, back pain and even catastrophic rupture. 8 In the study of 15 patients with TSC and AAA, one-third of these patients had a ruptured AAA on presentation. 3 Of note, differentials of a pulsatile abdominal mass include pulsations transmitted from the aorta to a non-vascular mass, but the possibility of AAA should be considered. When a pulsatile mass is present, physical examination should be gentle to reduce the chance of rupture. Appropriate imaging should be conducted early for confirmation of diagnosis, as timely diagnosis is crucial to reduce morbidity.
Given the rarity of vascular involvement in TSC, there is currently no well-established protocol for screening of aneurysms in children with TSC. 5 The 2021 International Tuberous Sclerosis Complex Consensus Group surveillance and management recommendations suggest that there is lack of evidence to encourage routine evaluation for aneurysms. 9 However, physicians should be aware of this association such that the presence of clinical symptoms or other concerning history would prompt investigation and timely intervention.
Ultrasonography is commonly used as a screening modality for aneurysms. In our literature review, some authors have recommended patients with TSC to undergo an abdominal ultrasound and chest radiograph at time of diagnosis to exclude TAA or AAA. At times, an abdominal MRI may be performed together with screening MRI brain, to limit anaesthetic exposure, at the time of diagnosis that may reveal an abdominal aneurysm. 10 If no aneurysm is found, they should continue with regular surveillance for aneurysm development with ultrasound scans every 2 to 3 years prior to puberty and then yearly thereafter, like surveillance of renal neoplasms in patients with TSC. 5 Once an aneurysm is found on ultrasonography, CT or MRI scans are required for a definitive diagnosis and to obtain detailed imaging to determine size of aneurysm and categorize the extent of aneurysm, which will be beneficial in intervention planning.
Management options for AAA include conservative management, surveillance scans eventually leading to surgical repair and immediate surgical repair. 1 Conservative management is mainly indicated in patients in whom surgery is very risky and unlikely to improve life expectancy. 1 Management should be individualized and involves blood pressure control to prevent hypertension as well as the use of antiplatelet therapy to reduce the risk of clot formation. Close serial monitoring and life-long follow-up with ultrasound to monitor aneurysm size and progression as well as monitoring of renal function is indicated. 2
In the surgical repair of AAA, the two modalities available are open and endovascular repair. However, there are many factors to consider in paediatric AAA repair. Compared to the adults, the size of the paediatric aorta is much smaller and the increasing aortic size with growth of the child may cause endoleak, therefore limiting the feasibility of endovascular options. Open surgical repair with a graft thus remains the leading surgical intervention, although a standardized operative approach has not been recognized. Open surgical repair options include aneurysmorrhaphy and synthetic graft placement (Dacron or Gortex). Aneurysmorrhaphy has been found to have higher recurrence rate because the dysplastic aortic segment is retained. 8
In a systemic review on paediatric patients with congenital abdominal aneurysms, 1 a higher mortality rate was reported amongst those undergoing conservative management compared to those undergoing operative interventions (44.4% vs 11.8%). However, risks of major vascular surgery are high and thus those eligible for surgical repair of their aneurysm should be extensively counselled regarding these inherent risks. If left unrepaired, on the other hand, there are other unexpected risks of sudden rupture or complications including renovascular disease. 2
Conclusions
Childhood abdominal aortic aneurysm (AAA) is a rare but life-threatening condition. It is more common in patients with connective tissue disorders or certain genetic conditions such as tuberous sclerosis complex (TSC). Patients with TSC should be monitored closely for signs and symptoms of aortic aneurysms and proceed with screening scans for an early diagnosis. Due to the high risk of rupture, early elective open surgical repair should be recommended when an aortic aneurysm is identified in a patient with TSC. If left untreated, AAA carries a high-risk of morbidity and mortality in the event of a rupture.
Footnotes
Author contributions
KYCK and SRC researched literature and conceptualized the study. KYCK drafted the initial manuscript. CYT and SRC reviewed as well as revised the manuscript for intellectual content. All authors reviewed and edited the manuscript and approved the final version of the manuscript as submitted.
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.
Ethical approval
KK Women’s and Children’s Hospital does not require ethical approval for reporting individual cases or case series.
Informed Consent
Written informed consent was obtained from the patient for anonymised information to be published in this article.
