Compared with the other minimal invasive lithotripsy techniques, PCNL is generally considered a safe technique offering the highest stone-free rates11. However, serious complications still occur following this percutaneous procedure. Severe bleeding requiring transfusion is a relatively rare complication associated with PCNL. Most bleeding complications can be well controlled with conservative treatments12. The post-PCNL transfusion rates ranging between 1% and 55% have been documented in recent studies. The use of selective renal artery angiography and embolization has ranged from 0.6–1.5%3,13. In our study, 45 (1.4%) of 3148 patients underwent TAE following PNL. This rate is in accordance with the literature.
In most countries, men are predisposed to urolithiasis, with male-to-female ratio ranging from 1.3 to 514. Therefore, the proportion of male patients requiring TAE after PCNL was significantly higher than that of female patients in our study. We found that patients requiring TAE after PCNL had twice hospital stays and hospitalization costs than patients without complications,and it is statistically significant. This was not reported in previously related studies. Patients requiring TAE after PCNL have a high proportion of previous kidney surgery (22.22%) in our results. A recent meta-analysis also shows that PCNL in patients with previous open renal surgery is associated with a significantly higher risk of requiring TAE15. Possible reason may be that previous kidney surgery is usually associated with anatomical alterations, inflammation, and adhesions. Performing PCNL at this site could lead to vascular problems. Furthermore, retroperitoneal and caliceal scarring surrounding the kidney may reduce its mobility16. Therefore, intraoperative manipulation of the nephroscope may produce enough torque to cause lacerations to the kidney, with bleeding. Performing PCNL should be more cautious for patients with previous kidney surgery.
There is currently no standard classification for postoperative bleeding from PCNL. Based on the International Study Group of Pancreatic Surgery and Liver Surgery17,18, early bleeding was defined as post-hemorrhage occurring within the first 24 h postoperatively, whereas > 24 h is considered delayed bleeding. Vascular injury during surgical procedures or underlying perioperative coagulopathy may be the main cause of early post-PCNL bleeding. Delay post-PCNL bleeding is typically a surgical complication, with the usual delay from days to weeks6. Post-PCNL bleeding is usually caused by pseudoaneurysm, AVF, and arterial laceration in previous related studies. When renal arterial bleeding does occur, blood from the injured artery can leak freely due to the high pressure, drain into the injured adjacent vein resulting in AVF, or into renal parenchyma or hilar areolar tissue resulting in pseudoaneurysm5,6,19. However, in our cases, these life-threatening hemorrhages are usually caused by arterial laceration (28, 62.20%) and AVF (7, 15.60%). The main reason is that our radiologist did not report pseudoaneurysm directly, but attributed it to arterial laceration. This study evaluated the therapeutic effect of TAE on post-PCNL bleeding. Successful embolization was performed in all 38 patients, including 35 with vascular lesions and three prophylactic embolizations. Primary clinical success was achieved in 35 (92.1%) patients, and only 2 patients developed second TAE owing to uncontrolled persistent bleeding after initial embolization. With regard secondary embolization, one patient showed different bleeding sites in the two angiographic results, and another patient showed bleeding at the first embolization site. One patient did not find bleeding site in the two angiographic results; hence, prophylactic embolization was performed. In most cases, the success rate of embolization is high, but a small number of patients may need secondary embolization because of the poor first embolization effect or undetected bleeding site. For patients with negative first-time angiography, most of the bleeding was gradually stable, no further embolization was needed, and only one case continued to bleed. No bleeding was found after re-angiography; hence, prophylactic embolization was performed on the artery near the puncture site. We recommend that patients with bleeding from multiple negative angiographic findings can be considered for prophylactic embolization.
For urologists, uncontrolled bleeding after PCNL is a stressful complication. The selection of continued conservative treatment or TAE can be difficult. Therefore, a clear indication for TAE is very important. Oguz et al. recommended emergent surgical intervention should be performed if metabolic acidosis and anuria/oliguria accompanied the decrease of hemoglobin20. Jinga et al.21 reported that the variations of hemoglobin, together with the quantity of transfused units, is an indication for TAE. However, these indications lack specific indices and have not been validated. Currently, there are still a lack of strict indications for TAE in post-PCNL bleeding. Hemoglobin decrease is the most common indicator, which is used to assess the severity of bleeding in clinical surgery 22,23. Li et al.6 proposed that TAE should be the recommended treatment for delayed post-PCNL hemorrhage in patients with hemodynamic instability and/or corrected hemoglobin decrease of > 30 g/L following conservative management. However, relying solely on the hemoglobin decrease to determine the timing of TAE is not adequate. For some patients, hemoglobin decrease may be not obvious, but it occurs in a short time. This situation also requires timely TAE. Hence, we proposed the concept of hemoglobin decrease rate. In our study, we calculated the changes in hemoglobin and hematocrit during bleeding episode to TAE, TAE to the first post-TAE day, and the first post-TAE day to the third post-TAE day, respectively. The decrease of hemoglobin/hematocrit and hemoglobin decrease rate were significantly reduced after TAE therapy, suggesting a good treatment effect. Moreover, we found that some patients still had minimal bleeding after TAE, but most tend to be stable within 1–3 days. Based on these findings, we recommend that hemoglobin decrease of > 25 g/L or hemoglobin decrease rate of > 5.5 g/L·d following conservative management of bleeding as one of the indications for TAE.
In our study, 10 patients had negative angiographic findings. Choi et al.24 reported that angiographic findings were not significantly associated with age, sex, and PCNL, and only percutaneous nephrostomy was associated with a higher rate of negative angiographic findings. Our subgroup analysis also shows similar results. However, we found that the decrease of hemoglobin/hematocrit levels in patients with negative angiographic finding was significantly lower than that in patients with positive angiographic finding. Patients with negative angiographic findings also had a lower hemoglobin decrease rate. The minimal bleeding rate required for angiographic detection is 0.5 mL/min. Angiography becomes optimally sensitive when the bleeding rate reaches 1 mL/min, which is equivalent to three units per day25. Slow bleeding rate may be one of the reasons of negative angiographic findings. Vasospasm or minor vascular laceration is also an important factor6. Vasospasm may occasionally account for a negative result shortly after bleeding26. In addition, selective angiography is limited in showing venous bleeding. For the patients with negative angiographic findings, post-PCNL bleeding may be controlled by conservative treatment; hence, embolization may be worth considering. More research is needed to further explore the timing of embolization for these patients.
The present study had some limitations. First, it was a single-center retrospective study, which makes obtaining relevant information difficult. Second, our radiologist did not directly report pseudoaneurysm, but attributed it to arterial laceration. Another limitation was this study lacks control and randomization. Multi-center studies with larger samples and longer follow-up periods are needed for further validation.