We appreciate the interest of and comments by Park et al. Nutcracker syndrome is certainly an under-recognized cause of hematuria in children. It was noted that left renal venography is the most accurate modality to identify nutcracker syndrome, and it was concluded that renal Doppler ultrasonography should be considered as an initial screening tool in children with hematuria. We agree with this opinion; however, we would like to make additional comments.

We described nutcracker syndrome as an uncommon but under-recognized cause of hematuria in children. Yang et al. also consider nutcracker syndrome as a rare clinical condition [3]. Our case report is an attempt for physicians to consider this diagnosis, especially in the emergency department, when evaluating children with hematuria, especially hematuria associated with abdominal pain.

We agree with the opinion of ultrasonography being the initial investigation in children with isolated hematuria. However, in the emergency department when patients present with undifferentiated abdominal pain, other alternative diagnoses should be considered. Computed tomography (CT) scans are helpful in identifying and excluding other causes of acute abdominal pain. Reports from emergency departments indicate the use of CT scan for the diagnosis of nutcracker syndrome [2]. The diagnostic value of CT scan is well established in the evaluation of nutcracker syndrome and is well correlated with renal venography and renocaval pressure gradient [1]. An important limitation of the use of ultrasound is that it is operator-dependent and may not be feasible in the emergency departments at all times.