Diagnosis of nut-cracker phenomenon using renal Doppler ultrasound in orthostatic proteinuria

Background. We evaluated the efficacy of non-invasive renal Doppler ultraso und (US) to detect the nutcracker phenomenon (NCP) and we studied the preva lence of NCP in children with orthostatic proteinuria. Methods. Among a total 66 cases of orthostatic proteinuria, 39 cases of NCP were found, with 27 cases being detected in a normal control group. Using Doppler US, the anteroposterior (AP) diameter and peak velocity (PV) of the left renal vein (LRV) were measured at the hilar and aortomesenteric porti on. We calculated the ratio of AP and PV diameters between the two portions . The parameters were analysed using Student's t-test. Results. The AP diameters and the ratio in the hilar and narrow portions we re all significantly different between the two groups (P<0.01). The PV in t he narrow portion and the ratio of PV were significantly different (P < 0.0 1), but the PV in the hilar portion was not statistically different between the two groups (P>0.05). If the diagnostic criteria for NCP was that the r atio of PV was more than 5, then 22 subjects (56.4%) in the orthostatic pro teinuria group and none in the control group could be diagnosed as NCP. If, however, the cut-off values for the diagnosis of NCP were set at the mean +/- 2 SD of the ratio (PV ratio 3.98 and size ratio 4.16), then the orthost atic proteinuria group showed abnormal AP diameter in 25 (64.1%), peak velo city in 28 (71.8%), and both in 21 patients (53.8%), and the control group showed an abnormal AP diameter in one subject (3.7%). Conclusions. NCP may be one of the leading causes of orthostatic proteinuri a, and non-invasive renal Doppler US may be a useful diagnostic tool in the screening of NCP. In the future, the diagnostic criteria of NCP must be re defined in children.