Unexpected superimposition of nutcracker effect in various conditions: is it an unrecognized confounding factor?

Abstract

Sir, We read with great interest the recent contribution by Harada et al. in Eur J Pediatr [1]. They reported a 5-year old girl with Henoch–Schonlein purpura (HSP) presenting duodenal involvement which might be associated with superior mesenteric artery syndrome (SMAS). She showed compression of the third segment of the duodenum by a short aortomesenteric distance and a narrow angle between the aorta and the superior mesenteric artery (nutcracker effect). Nutcracker effect can cause SMAS or left renal vein entrapment syndrome (nutcracker syndrome), because the third portion of the duodenum and left renal vein normally traverse between the two arteries. We also reported previously an HSP child with hematuria, which was associated with nutcracker syndrome rather than the vasculitic involvement of the kidney [4]. We would never have diagnosed this syndrome if we had not used renal Doppler ultrasound, because anyone who sees an HSP patient with hematuria generally regards that patient as having HSP nephritis. Recently, we have also experienced additional cases of nutcracker syndrome superimposed on HSP or post-streptococcal glomerulonephritis (PSGN). Patient 1 A 13-year-old girl was shown to have HSP nephritis on renal biopsy and was treated with prednisolone, leading to resolution of proteinuria. However, intermittent and exercise-induced hematuria persisted. Renal Doppler ultrasound had also demonstrated the superimposition of nutcracker syndrome (peak velocity ratio 7.4, normal <4.0). Although HSP nephritis was mainly responsible for the hematuria and proteinuria in this case, nutcracker syndrome might also have aggravated them. Patient 2 A 6-year-old boy presented with gross hematuria, which was coke-like, but sometimes pinkish. He was normotensive and had no acute nephritic features. Laboratory findings showed that antistreptococcal O (ASO) titer was increased (570 todd units, normal <200 todd units) and C3 was decreased (43 mg/dl, normal 77–195 mg/dl). ASO titer was much increased 4 weeks later (811 todd units) but gradually decreased 7 weeks later (398 todd units). C3 level had normalized 4 weeks later (107 mg/dl). Therefore, the diagnosis of PSGN was made. However, we also performed a renal Doppler ultrasound in this case, because the color of gross hematuria was sometimes pinkish, which demonstrated the superimposition of nutcracker syndrome (peak velocity ratio 6.9). Gross hematuria disappeared 1 month later, but microscopic hematuria persisted for more than 2 years. We performed a follow-up renal Doppler ultrasound at 14 months, which showed persistent elevation of the peak velocity ratio (peak velocity ratio Eur J Pediatr (2007) 166:1089–1090 DOI 10.1007/s00431-006-0382-y