Intra-arterial digital subtraction angiography for children with idiopathic renal bleeding: a diagnosis of nutcracker phenomenon.

Among children with asymptomatic hematuria, 28 cases of nonglomerular idiopathic renal bleeding were subjected to this series of study. Intra-arterial digital subtraction angiography (DSA) and/or renal venography were performed to investigate the hematuria of unknown etiology. DSA clearly demonstrated the entrapment of the left renal vein (LRV), or nutcracker phenomenon in the majority of our patients (22 out of 28 cases): obstruction of the LRV with well-developed collaterals were found in 8 cases, and in the remaining 14 cases, various degrees of LRV compression were demonstrated. A characteristic real-time DSA image was the congestion of LRV associated with collaterals and/or intermittent venous flow at the compressed segment of LRV. The pullback pressures from LRV to the inferior vena cava (IVC) that were obtained from 5 of these patients demonstrated gradients of 2 mmHg (3 cases), 3 mmHg (1 case), and 5 mmHg (1 case), respectively. The parallel application of ultrasonography has given positive signs for LRV entrapment, although they have not necessarily coincided with the existing criteria of nutcracker phenomenon. Considering the high incidence of LRV entrapment among children with nonglomerular hematuria, most nutcracker phenomenon should be diagnosed on ultrasonography. However, intra-arterial DSA is an important tool to establish the disease entity and ultrasonic criteria.