Coral reef aorta (CRA) is a rare disease characterized by hard calcification of the arterial wall, leading to protrusion into the lumen. CRA mainly affects the posterior thoracic and abdominal aortas and often involves the visceral segment [1]. Progressive luminal lesions can result in significant aortic stenosis accompanied by various symptoms. The exact pathophysiology of CRA remains poorly understood. CRA frequently occurs in patients with atherosclerotic risk factors such as hypertriglyceridemia, hypercholesterolemia, tobacco smoking, diabetes, and hypertension [1,2]; however, symptoms typically emerge in patients at approximately 50 years of age, and who are hence younger than those with other arterial occlusive diseases [1,2].

The clinical symptoms vary depending on the severity, location, and number of lesions. According to the literature, the predominant symptoms include hypertension, limb and visceral ischemia resulting from malperfusion, and congestive heart failure [2]. When revascularization is needed, the traditional approach usually involves open aortic surgery such as thromboendarterectomy and bypass surgery [2-4]. However, open surgery is associated with risks of morbidity and mortality, and the choice of the operative method also depends on the characteristics of the lesions, particularly their location and distribution.

Here, we present a case of multiple CRA that manifested as limb and renal ischemia. This report focuses on the diagnostic evaluations and selection of operative methods, considering the postoperative follow-up results.

This study was approved by our Institutional Review Board of Kyungpook National University Hospital (IRB no. 2023-11-009), which waived the requirement for informed consent.

A 54-year-old female with a one-year history of bilateral leg claudication was referred to our outpatient clinic. She complained of claudication after walking 50 m and recent worsening of these symptoms. Her comorbidities included hypertension and hyperlipidemia, and she was taking regular medications. In addition, she was a current smoker with a 15-year history of smoking one pack of cigarettes per day. Furthermore, she had been diagnosed with essential thrombocytosis 13 years previously and had been taking Agrylin and Hydrin.

On physical examination, her bilateral femoral pulses were not palpable. The ankle–brachial index (ABI) values were 0.29 and 0.31 for the right and left ankle, respectively. In addition, waveforms of the bilateral femoral, popliteal, and ankle arteries exhibited monophasic patterns. Computed tomography angiography (CTA) performed at the referring hospital revealed protruding calcified lesions in the descending thoracic aorta (DTA), the upper abdominal aorta (including the visceral segment), and the infrarenal aorta (Fig. 1). The Hounsfield unit of the protruding calcification at the level of the celiac axis was 821, similar to that of the bone. Upon presentation, Takayasu arteritis was initially suspected because of the patient’s relatively young age and the higher prevalence of Takayasu arteritis in East Asia than in Western countries.

Figure 1. Initial computed tomography angiography (CTA) of the patient. Reconstructive CTA image depicted multisegmental involvement of coral reef aorta (CRA) with calcification at the celiac axis measuring 821 Hounsfield units (HU), akin to bone density (A). Axial CTA images illustrated CRA at the levels of the descending thoracic aorta (B), celiac axis (C), left renal artery (D), and infrarenal aorta (E).

Neck CTA was performed to assess the aortic arch vessels; however, it revealed no significant stenosis or occlusion (Fig. 2). Positron emission tomography-computed tomography was then performed to assess the inflammatory status of the aorta, which did not reveal active inflammation in the thoracic or abdominal aorta (Fig. 3). Therefore, CRA was suspected. In addition, a diethylenetriaminepentaacetic acid (DTPA) scan was conducted to evaluate renal function because of the location of calcification in the visceral segment of the aorta. The results indicated decreased left renal function, with a glomerular filtration rate (GFR) of 7.97 mL/min compared with 36.44 mL/min for the right kidney (Fig. 4).

Figure 2. Computed tomography angiography images of aortic arch vessels indicated no significant stenosis or occlusion. (A) Right carotid artery, (B) left carotid artery, (C) right vertebral artery, and (D) left vertebral artery.

Figure 3. Preoperative positron emission tomography-computed tomography (PET-CT) revealed dense calcification (arrows) without evidence of abnormal hypermetabolic lesions, signifying the absence of active vasculitis. Axial PET-CT images depicted the aorta at the levels of the descending thoracic aorta (A), celiac axis (B), left renal artery (C), and infrarenal aorta (D).

Figure 4. The preoperative diethylenetriaminepentaacetic acid scan revealed reduced left renal function, with a glomerular filtration rate of 7.97 mL/min. BKG, background.

Preoperatively, the patient exhibited normal heart function, with an ejection fraction of 62% and no regional wall motion abnormalities. In addition, the pulmonary function test results were within the normal limits. Considering the patient’s multiple lesion locations, which included a heavily calcified visceral segment, and the presence of acceptable comorbidities for a surgical approach, open surgery was decided. Bypass surgery was planned, extending from the proximal DTA above the proximal CRA lesion to the aortic bifurcation. As the patient did not present abdominal symptoms, and the orifices of the superior mesenteric artery (SMA) and inferior mesenteric artery (IMA) were patent, visceral revascularization was not planned for this patient (Fig. 5). The patient was placed on a bean bag in the right lateral decubitus position. For proximal anastomosis, the sixth intercostal space was selected by posterolateral thoracotomy. A long midline abdominal incision was made for abdominal aortic dissection and distal anastomosis. Intraoperatively, the peritoneum was opened, and anterior mobilization of the colon, spleen, and left kidney was performed using a retroperitoneal approach. After completing the proximal anastomosis, a 16 mm tube graft (Hemashield; Maquet) was tunneled through the opening in the left posterolateral diaphragm, and distal anastomosis was performed at the level of the aortic bifurcation. As the function of the left kidney was impaired due to the calcified ostial lesion associated with CRA, the left renal artery was severed and reimplanted into the graft.

Figure 5. Initial computed tomography angiography (CTA) of the patient. Reconstructive CTA images revealed a patent superior mesenteric artery (SMA, arrow) and inferior mesenteric artery (IMA, dashed arrow) without significant stenosis (A) and well-developed collaterals (arrows) between the celiac axis, SMA, and IMA (B).

Postoperatively, pleural effusion developed after removal of the chest tube. Percutaneous catheter drainage was performed 11 days postoperatively, and the catheter was removed 17 days postoperatively. No other significant complications occurred, and a follow-up DTPA scan revealed improved left renal function, with the GFR of the left kidney increasing from 7.97 to 18.50 mL/min 10 days postoperatively. The ABI also showed improvement, reaching 1.15 and 1.13 for the right and left ankle, respectively. A follow-up CTA before discharge confirmed patent grafting and reimplantation of the left renal artery (Fig. 6). The patient was discharged on postoperative day 21 without claudication. During the 45-month follow-up period, no CRA-associated symptoms, such as claudication or mesenteric ischemia, developed. However, the right kidney function deteriorated during follow-up, with the GFR of the right kidney on the DTPA scan decreasing to 5.81 mL/min three years postoperatively (Table 1).

Figure 6. Postoperative computed tomography angiography before discharge demonstrated a well-patent graft (arrow) (A) and the reimplanted left renal artery (arrow) (B).

Table 1 . Serial follow-up results of serum creatinine (s-Cr), estimated glomerular filtration rates (eGFR), and diethylenetriaminepentaacetic acid (DTPA) scan.

	Preoperative	Postoperative	1 yr	3 yr	4 yr
s-Cr (mg/dL)	0.96	0.66	1.06	1.37	1.79
eGFR (mL/min)	61	93	54	40	30
GFR on DTPA scan (mL/min)
Right kidney	36.44	40.86	NA	5.81	NA
Left kidney	7.97	18.50	NA	36.88	NA

GFR, glomerular filtration rate; NA, not available..

CRA is an uncommon condition, and only 124 cases were summarized and reviewed in a recently published systematic review [2]. However, this condition must be identified because it can progress to ischemia, affecting vital organs, and potentially leading to life-threatening consequences [5,6]. This section focuses on key points regarding the terminology and operative methods used in the treatment.

Atherosclerotic occlusive disease primarily affects the distal aortic portions, including the infrarenal abdominal aorta and the bilateral iliac arteries. However, CRA involves severe obstructive calcifications predominantly found in the visceral part of the aorta, encompassing the suprarenal and juxtarenal aortas. Despite ongoing research, the exact causes and mechanisms underlying this condition remain unclear [7]. The terminology surrounding CRA is complex, and it must be distinguished from similar vascular conditions. Middle aortic syndrome (MAS), aortic coarctation, aortic stenosis caused by inflammatory disorders such as Takayasu arteritis, and CRA are sometimes used interchangeably for upper abdominal aortic stenosis. Despite causing aortic stenosis, these conditions exhibit distinct characteristics.

MAS is usually defined as segmental constriction of the distal DTA and upper abdominal aorta. It accounts for 0.5%-2% of all aortic coarctations and can develop later in life because of acquired inflammatory conditions, unlike congenital aortic coarctation near the ductus arteriosus [8,9]. Although most cases of MAS are idiopathic [10], some acquired inflammatory diseases can cause MAS. In adults, 50.9% of MAS cases are linked to inflammatory diseases, predominantly Takayasu arteritis [8]. Although Takayasu arteritis, known as “pulseless disease”, typically affects the aortic arch and its major branches, it can also involve the abdominal aorta and renal arteries in type III or IV Takayasu arteritis (type III involves the DTA, abdominal aorta, and/or renal arteries, and type IV affects only the abdominal aorta and/or renal arteries) [11]. Therefore, Takayasu arteritis is one of the main causes of MAS.

Regarding the differential diagnosis of Takayasu arteritis and CRA, these two clinical entities may share some clinical features because they can present with aortic stenosis in the suprarenal and juxtarenal aortic segments, often accompanied by heavy calcifications, and they exhibit female predominance [2,12]. Notably, aortic calcification is not uncommon in Takayasu arteritis, affecting 58%-75% of patients [12,13]. Some investigators have suspected infections, local amyloidosis, or Takayasu arteritis as the underlying causes of CRA [14,15]. Nevertheless, these conditions can be differentiated based on some key factors. In Takayasu arteritis, late-phase aortic stenosis presents with a reduction in aortic diameter itself, whereas CRA typically presents with a normal aortic diameter complicated by extensive calcified plaques. Most patients with CRA exhibit typical atherosclerotic risk factors such as heavy smoking, which is uncommon in Takayasu arteritis [16].

The treatment options for CRA depend on factors such as the extent and severity of aortic stenosis, patient comorbidities, and clinical symptoms. While recent advances in endovascular techniques, including stent grafts and lithotripsy, have shown promise in managing aortic stenosis in CRA, their use is limited to specific cases because of potential occlusion of the vital aortic branches, particularly in cases with visceral involvement. Additionally, lithotripsy carries the risk of embolization and requires the use of protection devices [17,18]. The systematic review by Baldaia et al. [2], which involved 124 CRA cases, revealed that 88.7% of patients underwent open surgery, 8.9% received endovascular treatment, and 2.4% had laparoscopic surgery. Open surgery remains the primary treatment approach in most cases, primarily because of the visceral location of CRA.

The surgical method for CRA also depends on the location and extent of the condition. For example, trapdoor endarterectomy with primary closure is a viable option in cases confined to the upper abdominal aorta, involving the celiac, superior mesenteric, and renal arteries [3]. Notably, the most common open surgery for CRA is endarterectomy via a retroperitoneal approach, accounting for 79.1% of the 110 open repairs [2]. The advantages of trapdoor endarterectomy include a reduced cross-clamping time, shorter operation duration, and decreased use of prosthetic materials, thereby potentially lowering the risk of graft-related infections [3]. A prosthetic patch for aortotomy closure was required in only 2.3% of endarterectomy cases reported in the literature [2]. However, not all CRA cases are amenable to endarterectomy, particularly those with multiple lesions and those involving the thoracic aorta. In such cases, bypass surgery, including both extraanatomical and anatomical options, is considered to address and bypass multiple lesions with a single graft [4,19].

In the present case, CRA lesions were present in three main segments: the DTA, the upper abdominal aorta involving the visceral part, and the infrarenal aorta. The most severe stenosis was observed in the infrarenal aortic segment, and decreased left renal function was caused by the obstructive CRA. Therefore, a bypass was performed from the DTA to the aortic bifurcation, with left renal artery reimplantation. In addition, mesenteric revascularization was not considered during the initial operation because the SMA and IMA orifices did not exhibit significant stenosis, and well-developed collaterals between visceral arteries were visible in the initial CTA. Furthermore, retrograde flow from the bypass graft to the IMA was deemed sufficient to maintain mesenteric circulation via collaterals. However, during the three-year follow-up, CRA progression in the visceral part led to deterioration of the right renal function. To prevent this complication in future cases, an additional bypass from the aortic graft to the right renal artery or endarterectomy of the visceral lesions may be considered during the initial operation. Fortunately, this patient did not experience mesenteric ischemia during follow-up; however, there remains a possibility of its occurrence when the CRA progresses or collateral flow from the IMA becomes occluded. In such a scenario, the feasibility of retrograde bypass to the SMA or hepatic artery from the distal graft or iliac arteries can be considered. This is supported by the fact that we refrained from extensive dissection of the celiac artery and SMA during the initial operation. Various factors influence the selection of operative methods for CRA; however, these should also account for long-term postoperative outcomes and anticipated disease progression.

In summary, this case highlights the importance of precise terminology in distinguishing CRA from other vascular conditions and underscores the preference for open repair in cases of complex multisegment involvement. The surgical method should be individualized based on the patient and lesion characteristics, taking into account the expected disease progression. Long-term follow-up is crucial to monitor patient outcomes and disease progression in CRA management.

None.

Hyung-Kee Kim has been the editor-in-chief of the VSI since 2023. Woo-Sung Yun has been the senior editor of the VSI since 2023. They were not involved in the review process. Otherwise, no potential conflict of interest relevant to this article was reported.

Conception and design: HKK, SH. Analysis and interpretation: all authors. Data collection: HKK, SP, DH, WSY. Writing the article: HKK, SP, WSY. Critical revision of the article: DH, WSY, SH. Final approval of the article: all authors. Statistical analysis: none. Obtained funding: none. Overall responsibility: SH.