Multimodal imaging approach in hyponatremic hypertensive syndrome. A rare case of pediatric unilateral hypoplasia of the main renal artery combined itself with stenosis and review of literature

Abstract

Renal artery stenosis (RAS) accounts for approximately 5%-10% of secondary renovascular hypertension in the pediatric population. It can occur as an isolated entity, or as a hypoplasia combined itself with stenosis. Hypoplasia, or long-segment developmental narrowing, is a rare cause of renovascular hypertension. Hyponatremic hypertensive syndrome (HHS) is a malignant complication of unilateral RAS and/or renal artery hypoplasia. Hyponatremia, hypokalemic hypochloremic metabolic alkalosis, nephrotic range proteinuria, polyuria, polydipsia, and weight loss are the most common findings. In particular, hypertension remains refractory despite aggressive antihypertensive therapy. Laboratory findings of elevated plasma levels of renin in most case suggest that the stimulation of renin release from the ischemic kidney plays an important pathophysiologic role. HHS is a diagnostic and therapeutic challenge in children. We report a case of a unilateral right renal artery hypoplasia, complicated by a segmental narrowing, in a 17-month-old male, clinically symptomatic for hypertension. We emphasize the role of ultrasound, computed tomography, and digital subtraction angiography that should be planned as reliable and non-invasive multimodal imaging approach.

Keywords: Angioplasty; Computed tomography angiography; Hyponatremic hypertensive syndrome; Hypoplasia; Renovascular hypertension; Ultrasound.

Fig. 1

B-MODE US renal arteries in comparative. (A) right renal artery (0.9 mm, arrow) vs (B) left renal artery (1.9 mm, arrow).

Fig. 2

Color-Doppler US (CD-US) of right kidney interlobar arteries: a significantly lower than the norm resistive index (RI 0.45) and an increased acceleration time. A “parvus and tardus” pulsus waveform.

Fig. 3

Color-Doppler US (CD-US) of left kidney interlobar arteries: a resistive index within normal limits (RI 0.69). Absence of pulsus waveform alterations.

Fig. 4

Axial computed tomography (CT) images (slice thickness 3 mm) of both kidneys. The right kidney is significantly decreased in size (right long axis R: 48 mm vs left long axis L:72 mm). A low enhancement was appreciated by the time of acquisition.

Fig. 5

A-B, 6 A-B: Three-dimensional CT reconstruction of the renal arteries / volume multiplanar MPR reconstructions, axial and coronal images. Arrows RRA: right renal artery; LRA: left renal artery; mRRA: multiple right renal artery; mLRA: multiple left renal artery. Arrowhead stenosis in RRA at about 6 mm from abdominal aorta diramation for a maximum extension of approximately 4 mm.RRA a right renal artery with a caliber half than the contralateral (1 mm vs 2.1 mm). Arrowhead a stenotic tract at about 6 mm from abdominal aorta diramation for a maximum extension of approximately 4 mm. mRRA a right filiform accessory renal artery, originating just above the main vessel. LRA a left renal artery, homogeneous along the whole course. mLRA a left accessory renal arter with a smaller caliber and a caudal emergence in relation to the main artery. N.B.: the right kidney had no enhancement when the left kidney was completely represented.

Fig. 7

Follow-up B-MODE US post-angioplasty: renal arteries calibers in comparative. RRA: a regular caliber (1.5 mm) nearby the emergence and in its first tract with a rescued length of the right kidney (63.4 mm), at this time.

Fig. 8

Follow-up color-Doppler US (CD-US) post-angioplasty: a great vascularization in the right kidney, overall the parenchima to the outer portion of the subcortex.

Fig. 9

Follow-up color-Doppler US (CD-US) post-angioplasty: a resistive index value within the normal limits (RI 0.62) as well as the acceleration gradient. No more evidence of “parvus and tardus” pulsus waveform.