Acute renal bleeding is a common emergency in urology. It can be due to a number of factors such as closed or open renal trauma. Commonly, iatrogenic renal vascular injuries represent 50% of renal vascular lesions and can occur during renal biopsies, PCNL, or PCN [7,8,9,10]. Renal tumors, such as renal angiomyolipoma or renal cell carcinoma and renal arteriovenous malformations, are also important causes of acute renal bleeding. Bleeding from these causes might be in the form of aneurysm, pseudoaneurysm (PA), extravasation, AVF, ACF, or perinephric hematoma [4, 5]. In our study, trauma represented 86.6% of our patients. Most of them were iatrogenic.
Diagnosis of cases and accurate detection of lesions depended on CT and US but still angiography is the best modality above with the highest accuracy in detecting the bleeding and its cause . Angiography is surely diagnostic but can be therapeutic also at the same session [12, 13]. In this study, 16 patients were diagnosed with CT and the remaining 29 patients were evaluated with angiography on the first imaging modality because they needed emergency RAE. CT with its CT angiographic assessment provided an accurate description of the bleeding lesions in the kidney that facilitates interventions.
The angiographic picture of bleeding varies based on the severity and cause of the acute renal bleeding. In the study of Wang et al., they found contrast extravasation as a most common finding representing 49.4% of cases (41/83) while traumatic AVF in 14.4%, renal pseudoaneurysm in 8/83 patients (9.6%) . However, the study of Ząbkowski et al. reported the pseudoaneurysms as the most common finding . In our study, pseudoaneurysms were the most common picture seen where bleeding was discovered as pseudoaneurysms in 35/55 lesions (63.6%) and as free extravasation 11/55 lesions (20%) that is running with Ząbkowski et al.
It is essential to mention that the clinical response of RAE depends on the type of the embolic agent and the adequacy of the embolization process. When selecting an embolic agent, several factors should be taken into consideration. These factors are the lesions site, size, and flow of pattern of vessels to be occluded, the availability of embolic agents, the comprehension of the radiologist who will perform the procedure, the speed and reliability of delivery, the duration of the occlusive effect, and the avoidance of non-target embolization [15, 16]. In our study, we used permanent occlusive agent, namely, the coils, NBCA glue, and PVA particles to avoid recanalization of the lesion and so, bleeding recurrence will be less.
Regarding the clinical success, our study reported a primary clinical success rate of 91.1% after the first session while the overall rate after the second session was 93.3%. This agreed with Limtrakul et al. who reported clinical success of 91.5% for their 94 patients treated with RAE . Moreover, Du et al. reported clinical success of 100% of RAE compared to conservative therapy that was 73.6% in their cases of bleeding after PCNL . Regarding treatment failure, RAE failed to control bleeding in 3 cases of our patients. This ran with Wang et al. who reported 4/81 (4.8%) cases of failure. The majority of their patients (3/4) were post-severe renal trauma. In our study, all failed patients were post-traumatic with either multiple injuries. For those patients, nephrectomies were done. In our study, one patient got recurrence of bleeding after 6 months of embolization of his AVM due to incomplete nidus obliteration.
Specifically, as for the coil sub-group, we successfully used coils in 23 patients representing (51.1%). All coils were of detachable delivery technique and fibered surface benefiting of its advantage of controlled and accurate positioning as well as strong occlusive effects. The main disadvantage of using coils is that more than one coil is usually needed for proper occlusion increasing the cost and time of the procedure or additional embolic may be added . Haochen et al. used pushable coils to treat bleeding after biopsy. In all patients, they used additional gel foam to efficiently occlude the lesion . In our study, we found that detachable fibered coils are effective as we did not use additional agents. This may be due to the longer length of the detachable coil compared to pushable. We used two coils in one patient when total occlusion could not be achieved. One important complication is the coil mal-position that occurred in one of our patients with no clinical significant event.
Yamakado et al.  and Parildar et al.  reported the use of NBCA glue in renal arterial bleeding. Moreover, Contasdemir et al.  reported five cases while Mavili et al.  reported 4 cases. Both concluded that using NBCA glue provides permanent and accurate embolization in a cost-effective manner. The use of NBCA glue is preferred due to its low viscosity for easy injection through small or tortuous catheters and it provides quick and stable thrombosis with cost-effective privilege. In this study, NBCA glue was successfully used in 15 patients. The results of our study coincide with the results of these authors mentioned above. Despite its advantages, using liquid embolic agent that can cause unpredictable embolization is a major concern which was observed in one patient. A common effect that may occur after embolization is reflux. It can occur due to either using larger volume of NBCA glue or due to rapid non-intermittent injection of the glue. A test injection is usually performed to avoid this incident. In our study, we always use microcatheter to prevent gluing of the catheter tip to the vessel wall and to prevent inadvertent embolization during retrieval of the microcatheter.
PVA is bio-compatible and inert that provides fast occlusion. It is accepted as permanent embolic material and classified as spherical and non-spherical. PVA particles were used in many studies. These particles occlude variable-sized arteries according to their size range [22,23,24]. In our study, we used PVA 100-300 μc to occlude subsegmental branches of traumatic bleeding. Large vessels were incompletely occluded as the particles become embedded in the walls [22, 23]. PVA control during injections is easy but reflux is common and occurred in one of seven studied cases. We used PVA in the tumor to occlude the intra-tumor vasculatures as well using 100-300 and 300-500 μc particles. Finally, PVA controlled the bleeding well in all our patients.
Post-embolization syndrome was the most common complication in our study, reported in 14 patients (31.1%). It was mild in 12 cases, and we attributed this to the use of co-axial technique with micro-catheterization of the bleeding arterial branches. Therefore, tissue loss was limited to that caused by the original trauma itself . Only two patients developed severe post-embolization syndrome. In these patients, non-target embolization of a main segment branch from PVA reflux and spillage of NBCA-glue into its lumen. There was one patient having dissection. These complications ran well with those of other studies [20, 21].
Our study has some limitations. The most important limitation is the retrospective design of the study. The second is the med term evaluation and so, the durability of such embolization is limited by 1 year only. The third limitation is the small number of subgroups compared to needed in sample size. The last limitation is the non-randomization of the studied subgroups. In the future, we need a controlled randomized study to compare efficacy of each embolic agent.