Nutcracker phenomenon in two siblings of a Japanese family

Abstract

Sirs, Compression of the left renal vein (LRV) between the aorta and the superior mesenteric artery (SMA), known as the nutcracker phenomenon (NCP), can cause gross or microscopic hematuria, flank pain, proteinuria, or a combination of these clinical features [1, 2, 3]. The phenomenon causes hypertension of the LRV, consequently causing LRV compression, left gonadal vein varices, and unilateral hematuria [2, 4]. A recent report documented orthostatic proteinuria associated with the NCP [1, 5, 6, 7]. We describe two siblings with microscopic hematuria caused by NCP. These patients were a 3-year-old brother and a 5-year-old sister born to healthy non-consanguineous parents. Their family history manifested no renal diseases. Microscopic hematuria was first indicated in both patients by an annual screening urinalysis at their kindergarten. Their respective blood chemistries and urinary calcium/creatinine ratios were normal. Urine was normal except for sediment containing 5–20 red cells per high-power field. Repeated urine cultures showed no pathological organisms. Urinary red cell morphology revealed predominantly (>90%) isomorphic cells. Serum complement, IgA, IgG, and IgM concentrations, as well as antistreptolysin O titer, antinuclear antibody, antidouble-stranded DNA antibody, and rheumatoid factor were in the normal range. Ultrasonography of the kidneys showed marked dilatation of the LRV in the hilar portion and severe compression of the LRV between the aorta and the SMA, which was an indirect finding that is typical of NCP. Entrapment of the LRV is not easily detectable using conventional means. Selective renal venography, with the measurement of the gradient pressure between the LRV and the inferior vena cava, or intra-arterial digital subtraction angiography has been used for the diagnosis of NCP [8]. Doppler ultrasonography, three-dimensional helical computed tomography, and magnetic resonance angiography have been employed recently as useful noninvasive diagnostic tools [1, 3, 4, 5]. Abnormal branching of the SMA from the aorta is suggestive of the fundamental pathophysiology of NCP [1]. Nevertheless, it remains unclear why so few patients have experienced compression of the LRV and why LRV hypertension causes hematuria. Additional studies have demonstrated a new variant of NCP with different anatomical details [9]. The urinary red cell morphology is not sufficiently reliable to distinguish a glomerular source of bleeding from a non-glomerular source [2]. Clarification of non-glomerular hematuria in patients with NCP, who also have other co-existing renal disorders causing hematuria, is more complicated. Concomitant IgA nephropathy or membranous nephropathy associated with the NCP has been reported [2]. NCP is not a hereditary disease: occurrence of NCP within the same family or in close relatives is rare. NCP may have occurred coincidentally, causing hematuria in both siblings. Alternatively, they may have had underlying familial benign hematuria in association with NCP despite a negative family history. Further evaluation is necessary to elucidate the etiology of non-glomerular hematuria of these siblings.