Diagnosis of the nutcracker phenomenon using two-dimensional ultrasonography.

We aimed to establish new criteria for the diagnosis of the nutcracker phenomenon (N phenomenon) using ultrasonography (US). The left renal vien (LRV) was examined with US in 125 children, divided into three groups, namely the macroscopic hematuria group (23 children), the microscopic hematuria group (52 children) and the control group (50 normal children) all without nephritis, urolithiasis and tumor. The following parameters were calculated: (1) the ratio of the diameter of the dilated part of the LRV (D) to that of the narrowed part of the same vein (N) (D/N ratio), (2) the ratio of D to the aortic diameter (A) (D/A ratio) and (3) the difference in diameter between the LRV and the right renal vein (RRV) (RVD difference). The D/A ratio and the RVD difference correlated significantly with the D/N ratio. This indicates that not only the D/N ratio but also the D/N ratio but also the D/A ratio and RVD difference can be used for diagnosing the N phenomenon. The cutoff levels for the three parameters were set at the mean + 2 SD of the values of the normal controls, that is, at 3.7 (D/N ratio), 0.75 (D/A ratio) and 1.7 mm (RVD difference). We made diagnoses of the N phenomenon when two or more parameters were over the cutoff level. According to these criteria, most patients with macrohematuria and one third of patients with microhematuria were positive for the N phenomenon. The D/A ratio and RVD difference were useful for diagnosing the N phenomenon, and as a result our criteria can reduce misdiagnosis for normal children.