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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.