Visualization of the renal vein filled with contrast agent may indicate the renal vein injury during percutaneous nephrolithotomy: two case reports.

BACKGROUND: Intravenous misplacement of a nephrostomy tube is a rare complication of percutaneous nephrolithotomy (PCNL) or percutaneous nephrostomy. The mechanism of misplacement of a nephrostomy tube into the vascular system is seldom investigated. One type of the possible mechanism is that the puncture needle penetrates a major intrarenal tributary of the renal vein and enters the collecting system. However, the guidewire is located outside the collecting system near the large branches of renal vein or perforates into the renal vein. The dilation is performed and causes a large torn injury. Subsequently, the nephrostomy tube is placed inside the vessel when radiological monitoring is not used. However, there is no imaging evidence and the scene of procedure is not demonstrated. This paper reports two cases of visualization of the renal vein filled with contrast agent during PCNL. The findings may be good evidence to support the step of renal vein injury in patients with intravenous nephrostomy tube misplacement. CASE PRESENTATION: We presented two cases with visualization of the renal vein filled with contrast agent during PCNL. In the process of injecting the contrast agent through the puncture needle, we could see the renal vein. Moreover, it was identified that the puncture needle tip was not on the optimal position. The position of puncture needle tip lay outside the collecting system, which was close to the calyceal infundibulum and branches of renal vein. CONCLUSIONS: Visualization of the renal vein filled with contrast agent may be good evidence to verify the renal vein injury in patients with intravenous nephrostomy tube misplacement during PCNL or percutaneous nephrostomy. The suboptimal location of the puncture needle tip and visualization of the renal vein filled with contrast agent indicate the renal vein injury. One type of mechanism of intravenous nephrostomy tube misplacement is as following. Firstly, the guidewire stays outside the collecting system. Subsequently, dilatation directed by the guidewire results in the injury of the vein. Then, the nephrostomy tube migrates into the venous system due to prompt tube inserting and the direction of the sheath and/or the guidewire to the injured vein.

Real-Time Calibration of Magnetometers Using the RLS/ML Algorithm.

This study presents a new real-time calibration algorithm for three-axis magnetometers by combining the recursive least square (RLS) estimation and maximum likelihood (ML) estimation methods. Magnetometers are widely employed to determine the heading information by sensing the magnetic field of earth; however, they are vulnerable to ambient magnetic disturbances. This makes the calibration of a magnetometer inevitable before it is employed. In this paper, first, a complete measurement error model of the magnetometer is studied, and a simplified model is developed. Then, the real-time RLS algorithm is introduced and discussed in detail, and the unbiased optimal ML is utilized to improve the accuracy of the parameter estimation. The proposed algorithm is advantageous in correcting the parameters in real time and simultaneously obtaining unbiased parameter estimation. Finally, the simulation and experimental results demonstrate that both the accuracy and computational speed of the proposed algorithm is better than those of the widely used bath-processing method. Moreover, the proposed calibration method can be adopted for calibrating other three-axis sensors.

Failure of initial renal arterial embolization for severe post-percutaneous nephrolithotomy hemorrhage: a multicenter study of risk factors.

PURPOSE: Severe hemorrhage after percutaneous nephrolithotomy is a rare but alarming event. If local tamponade fails to control bleeding, the current treatment of choice is superselective renal arterial embolization. If initial embolization is unsuccessful, repeat embolization or nephrectomy is often required. To our knowledge we report the first study of risk factors for failed initial superselective renal arterial embolization. MATERIALS AND METHODS: We retrospectively reviewed the records of 17,619 patients who underwent a total of 19,185 percutaneous nephrolithotomies from January 2007 to April 2012 at 6 centers. Study inclusion criteria were percutaneous nephrolithotomy and severe postoperative renal hemorrhage requiring superselective renal arterial embolization. Data on patients in whom initial embolization failed were compared to those on patients with successful embolization on univariate and multivariate analysis. RESULTS: Of the 17,619 patients 117 (0.6%), met study inclusion criteria, including 90 males and 27 females. Initial treatment failed in 12 patients (10.3%), 8 underwent repeat superselective renal arterial embolization, 3 required 3 embolizations and 1 underwent nephrectomy. Complete bleeding cessation was achieved in all 11 repeat embolization cases. We identified 3 risk factors for failure of initial superselective renal arterial embolization, including multiple percutaneous access sites, more than 2 bleeding sites identified on renal angiogram and gelatin sponge alone used as the embolic material. CONCLUSIONS: Carefully selecting patients for multitract percutaneous nephrolithotomy, making an extra effort to identify all bleeding vessels during angiography and not using gelatin sponge as the only embolic material could potentially decrease the risk of failure of initial superselective renal arterial embolization after percutaneous nephrolithotomy.