Nutcracker syndrome in children with orthostatic proteinuria: diagnosis on the basis of Doppler sonography.

OBJECTIVE: To evaluate the Doppler sonographic findings of the left renal vein in children with orthostatic proteinuria in comparison with healthy children and to propose more reliable sonographic criteria for diagnosing nutcracker syndrome in children.
METHODS: Doppler sonographic findings in 47 children with orthostatic proteinuria and in 27 healthy control subjects were compared. The diagnosis of orthostatic proteinuria was made on the basis of clinical and laboratory findings. The peak velocity and anteroposterior diameter were measured at the hilar and aortomesenteric portions of the left renal vein. The means +/- 2 SD of the anteroposterior diameter ratio and peak velocity ratio between the 2 portions were calculated for control subjects and used as the cutoff levels for nutcracker syndrome.
RESULTS: The peak velocity ratios between aortomesenteric and hilar portions were 5.21+/-2.55 in the patient group and 2.57+/-0.70 in the control group. The anteroposterior diameter ratios between the 2 portions were 5.31+/-2.65 in the patient group and 2.77+/-0.69 in the control group. We set the cutoff level of anteroposterior diameter and peak velocity ratios for the diagnosis of nutcracker syndrome at mean +/- 2 SD of the value for the control group (3.98 for the peak velocity ratio and 4.16 for the anteroposterior diameter ratio). When these cutoff levels were applied, the patients with orthostatic proteinuria had abnormal levels of anteroposterior diameter in 27 (57.4%) of 47, peak velocity in 30 (63.8%) of 47, and both in 23 (48.9%) of 47.
CONCLUSIONS: Nutcracker syndrome may be an important cause of orthostatic proteinuria in children. Doppler sonography of the left renal vein may be a useful screening tool in patients with suspected orthostatic proteinuria to evaluate whether the cause is nutcracker syndrome.