A Rare Clinical Presentation of Pediatric Hypertension due to Unilateral Renal Artery Stenosis with the Middle Aortic Syndrome

ABSTRACT

Renal artery stenosis is one of the secondary causes of pediatric hypertension. Cases with critical unilateral renal artery stenosis associated with the middle aortic syndrome are rare phenomena. The middle aortic syndrome (MAS) is a rare vascular disease representing an important cause of severe hypertension in children. MAS are mostly idiopathic, but also may occur in genetic and acquired disorders.

INTRODUCTION

Hypertension in children is a rare phenomenon. MAS is an important but rare etiology of paediatric hypertension. The extent of involvement in MAS is determined by the genetic disorders and is more often associated with suprarenal stenosis and extra-aortic involvement.[1] Management of hypertension can be difficult, and each patient needs individualised therapy. The extent of vascular disease depends on the type of genetic disorder.[1] Pediatric hypertension is defined as systolic blood pressure > 95^th percentile for age, sex, and height. Establishing the diagnosis of HTN requires obtaining three abnormal systolic and/or diastolic BP readings.[2] A detailed history should be obtained from all patients as it frequently provides clues for possible etiologies[2] There are multiple possible etiologies for secondary HTN. About 50–60% of HTN cases are induced by a renal disease or renal artery stenosis.[2] Cardiac disease is the next most common etiology, mainly due to coarctation of the aorta or mid-aortic syndrome.[2]

CASE PRESENTATION

We describe a nine-year-old boy presented with complaints of vomiting every alternate day in the last six months. The child was clinically evaluated; relevant investigations were sent. The child showed features of hypocalcemia, so calcium gluconate loading dose was given and serum calcium and ionized calcium were normal. The child’s BP was 170/120 mm/Hg which was above 99^th percentile, controlled with antihypertensives. Preliminary investigation showed hypokalemia which was corrected. Expert cardiology opinion was obtained in view of hypertension; 2D echo showed moderate AR mild MR, TR, and mitral valve prolapse. To rule out the other causes of hypertension, renal artery Doppler technique was done which showed left renal artery low velocity and low RI and suggested for CT renal angiography. CT renal angiography [Figure 1] was done which showed left main and left accessory renal artery stenosis and diffusely enhancing soft tissue thickening noted around the visualized thoracic and abdominal aorta [Figures 2 and 3]. PET CT ESR.CRP.IL-1.IL-6 and if no active disease in PET CT child can be taken up for elective renal artery angioplasty or stenting. PET CT showed mildly metabolically active mediastinal, right hilar, and bilateral axillary lymph nodes. Small FDG non-avid peri-broncho-vascular lung nodule/tree in bud opacity in posterior right lower lobe was observed. Could represent inflammatory/infective etiology. Suggested lymph nodal HE correlation. Mild circumferential mural thickening in the thoracoabdominal aorta with no metabolic activity. No evidence of luminal narrowing/thrombus. May represent sequelae of vasculitis with no evidence of active inflammation in the present scan. Focal severe narrowing of the ostio-proximal left main and accessory renal arteries with no metabolic activity no evidence of metabolically active disease anywhere else in the body. However, there were mildly metabolically active mediastinal, right hilar, and bilateral axillary lymph nodes. CRP, C3, C4, and ANA were negative and ESR was 53. Renin level was >500 and aldosterone level was >100, hence diagnosed as RVH due to left renal artery stenosis. The balloon angioplasty was done and left renal blood flow improved [Figures 4 and 5]. Post procedure the child became normotensive and is on follow-up.

Figure 1.

CECT Renal Angiogram

Figure 2.

Renal Perfusion Angiography showing Left Renal artery Stenosis

Figure 3.

CECT angiogram showing Left Renal artery stenosis

Figure 4.

CECT Renal angiogram Showing introduction Balloon for Renal artery Dilation

Figure 5.

CECT Renal angiogram Showing stenotic dilatation post Balloon angioplasty for stenotic Left Renal artery

DISCUSSION

RVH can be caused by numerous pathologies both syndromic and non-syndromic. RVH can be caused by an isolated renal artery stenosis (RAS) and/or the middle aortic syndrome (MAS). In patients with renal artery stenosis, the chronic ischemia produced by the obstruction of renal blood flow leads to adaptive changes in the kidney which include the formation of collateral blood vessels and secretion of renin by juxtaglomerular apparatus. The renin enzyme has an important role in maintaining homeostasis in that it converts angiotensinogen to angiotensin I. Angiotensin I is then converted to angiotensin II with the help of an angiotensin-converting enzyme (ACE) in the lungs. Angiotensin II is responsible for vasoconstriction and release of aldosterone which causes sodium and water retention, thus resulting in secondary hypertension or renovascular hypertension.

The middle aortic syndrome is a rare disease characterized by segmental or diffuse narrowing of the abdominal and/or distal descending aorta with involvement of the renal and visceral branches and represents an important cause of severe hypertension in children.

A genetic form of MAS is encountered in children and young adults encountered in 7–36%. The most common genetic causes of MAS are neurofibromatosis type 1, Williams syndrome, Alagille syndrome, tuberous sclerosis, and mucopolysaccharidosis.

The common causes of acquired MAS are Takayasu arteritis, congenital rubella, and other nonspecific arteritis.

The most common blood vessels involved in idiopathic MAS are the renal and splanchnic branches of the aorta.

Investigation- Computed tomography angiography (CTA), magnetic resonance angiography (MRA), ultrasonography, captopril renal scintigraphy, and the captopril test for the diagnosis of renal artery stenosis in patients suspected of having renovascular hypertension.[3]

Management- The mainstay of treatment for renal artery stenosis lies in restoration of intravascular volume, prevention of acute insult of hypertensive crisis, and correction of underlying renal arterial stenosis.[4] Angioplasty The goal of treatment is restoration of renal perfusion. Preservation of renal function Reduction in polypharmacy. Temporizing hypertension in younger patients before surgical repair during/after puberty. Stenting Generally repeated angioplasty is considered more appropriate than stenting.[5] Stent insertion is generally avoided in children because stents themselves can act as a site of stenosis as the child grows.

CONCLUSION

RVH, though a very rare clinical presentation, can have a deleterious effect on the health of the child, so any child with vague complaints of vomiting and/or headache should be screened for hypertension. Angioplasty is the treatment of choice initially. Surgery is preferred for recurrent stenosis. Early diagnosis and early referral reduced morbidity and mortality in children. In terms of clinical practice, we recommend evaluating the children with MAS in detail because they may present other specific manifestations for certain genetic diseases, and on the other hand, it is necessary to detect the presence of MAS in children who were already diagnosed with certain genetic diseases.

Conflicts of interest

There are no conflicts of interest.

Funding Statement

Nil.