Transcatheter arterial embolization as therapy of renal angiomyolipomas: the evolution in 15 years of experience

The radiomics-clinical nomogram for predicting the response to initial superselective arterial embolization in renal angiomyolipoma, a preliminary study

Purpose

The aim of this study was to explore a radiomics-clinical model for predicting the response to initial superselective arterial embolization (SAE) in renal angiomyolipoma (RAML).

Materials and methods

A total of 78 patients with RAML were retrospectively enrolled. Clinical data were recorded and evaluated. Radiomic features were extracted from preoperative contrast-enhanced CT (CECT). Least absolute shrinkage and selection operator (LASSO) and intra- and inter-class correlation coefficients (ICCs) were used in feature selection. Logistic regression analysis was performed to develop the radiomics, clinical, and combined models where the fivefold cross-validation method was used. The predictive performance and calibration were evaluated by the receiver operating characteristic (ROC) curve and calibration curve. Decision curve analysis (DCA) was used to measure clinical usefulness.

Results

The tumor shrinkage rate was 29.7% in total, and both fat and angiomyogenic components were significantly reduced. In the radiomics model, 12 significant features were selected. In the clinical model, maximum diameter (p = 0.001), angiomyogenic tissue ratio (p = 0.032), aneurysms (p = 0.048), and post-SAE time (p = 0.002) were significantly associated with greater volume reduction after SAE. Because of the severe linear dependence between radiomics signature and some clinical parameters, the combined model eventually included Rad-score, aneurysm, and post-SAE time. The radiomics-clinical model showed better discrimination (mean AUC = 0.83) than the radiomics model (mean AUC = 0.60) and the clinical model (mean AUC = 0.82). Calibration curve and DCA showed the goodness of fit and clinical usefulness of the radiomics-clinical model.

Conclusions

The radiomics-clinical model incorporating radiomics features and clinical parameters can potentially predict the positive response to initial SAE in RAML and provide support for clinical treatment decisions.

Safety, Efficacy, and Predictors for Late Reintervention After Embolization of Renal Angiomyolipomas – Embolization renal angiomyolipoma

Purpose To retrospectively analyze the procedural and long-term clinical outcome of the selective embolization of renal angiomyolipoma. In addition, potential predictive factors for higher risk of late re-intervention were analyzed.

Methods Retrospective monocentric study, including 34 consecutive patients, analyzing the safety, efficiency, and long-term clinical outcome of catheter-directed embolization of renal AML. Additionally, the difference in postembolization renal function between patients embolized in the acute and in the elective setting was analyzed. Secondly, we also evaluated whether volume/diameter of the AML and presence of intralesional aneurysms are risk factors for late re-intervention.

Results Embolization of renal AML was performed to control volume (n = 21; 62 %) or to stop spontaneous hemorrhage (n = 13; 38 %) with angiographic success in all cases but was associated with renal abscess (n = 1) and pulmonary embolism (n = 1) without a significant difference in renal function before and after embolization (P = 0.513). Volume/diameter (P = 0.276/P = 0.21) and presence of aneurysms before embolization (P = 0.37) are not predictive for a higher risk of late re-intervention.

Conclusion Catheter-directed embolization is a safe and effective treatment modality for asymptomatic and bleeding renal AML, without a negative impact on renal function. Initial mass volume/diameter or presence/absence of intralesional aneurysms does not seem to be predictive for late re-intervention.

Key Points:

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Selective Arterial Embolization of Renal Angiomyolipomas with a N-Butyl Cyanoacrylate-Lipiodol Mixture: Efficacy, Safety, Short- and Mid-Term Outcomes

Selective arterial embolization (SAE) for renal angiomyolipoma (rAML) is effective to treat or prevent bleeding. We report our experience using a cyanoacrylate–Lipiodol mixture. We performed a single-center retrospective review of all rAMLs embolized with cyanoacrylate glue between July 2014 and June 2020. Demographics, tuberous sclerosis complex (TSC) status, clinical presentation, angiography features, and follow-up data were recorded. Pre- and post-procedure rAML sizes and volumes were estimated from computed tomography (CT) or magnetic resonance imaging (MRI) studies. Kidney function was assessed before and after the procedure. We identified 24 patients (22 females and 2 males, mean age 51 years) treated for 27 AMLs, either prophylactically (n = 20) or as an emergency (n = 4). Technical success was achieved for 25/27 AMLs; two patients, each with a single AML, required nephrectomy and repeated embolization, respectively. Major complications occurred in three patients and minor complications such as postembolization syndrome in 15 patients. AML volume reduction after embolization was 55.1% after a mean follow-up of 15 months (range, 1–72 months). Factors associated with greater volume reduction were a smaller percentage of fat (p = 0.001), larger initial rAML volume (p = 0.014), and longer follow-up (p = 0.0001). The mean creatinine level did not change after SAE. Embolization of rAMLs with a mixture of cyanoacrylate and Lipiodol is feasible, safe, and effective in significantly decreasing tumor volume.

Efficacy and safety of prophylactic superselective embolization for angiomyolipoma at the renal hilum

Objective

This study investigated the efficacy and safety of superselective transcatheter arterial embolization for angiomyolipoma at the renal hilum.

Methods

Between August 2012 and January 2015, 13 patients with 16 angiomyolipomas at the renal hilum underwent initial, prophylactic, superselective transcatheter arterial embolization. The patients were followed by computed tomography or magnetic resonance imaging, and volume-reduction ratios after embolization were measured.

Results

The mean or median post-embolization volume reduction ratios were 23% (follow-up duration, 1–2 months), 55% (3–6 months), 55% (7–12 months), 66% (1–2 years), 67% (2–3 years), and 54% (>3 years). After initial embolization, none of the 16 tumors bled or required surgery; two (13%) tumors recurred; and three (19%) tumors received repeat embolization. Estimated glomerular filtration rates were not decreased at medians of 7 days (near the time of discharge) and 39 days (first clinical follow-up) post-procedure, compared with baseline. Except for post-embolization syndrome, no procedure-related complications occurred.

Conclusions

Superselective embolization for renal hilar angiomyolipoma is safe and kidney-preserving, with good tumor volume reduction and bleeding prevention.

Radiologic and clinical results of transarterial ethanol embolization for renal angiomyolipoma

OBJECTIVE

We sought to determine the efficacy and safety of selective arterial embolization for renal angiomyolipoma (AML) using ethanol alone or ethanol with additional embolic materials and to analyze the factors influencing safety and efficacy.

METHODS

One hundred nineteen AMLs treated with embolization were included retrospectively during a 15-year period. Technical, radiologic, and clinical success were recorded and risk factor analysis was performed. Complications on follow-up images, post-embolization syndrome (PES), major complications, and changes in renal function were also evaluated.

RESULTS

Technical success was achieved in 106 of 119 tumors. Tumor size significantly decreased after treatment (reduction rate: 55%). Significant risk factors for tumor reduction included tumor enhancement on preprocedural CT and residual tumor staining. Radiologic success was achieved in 114 of 119 tumors (risk factor: residual tumor staining), and clinical success was achieved in 22 of 23 patients. Complications on follow-up images occurred in 40 of 119 tumors, and PES occurred in 53 of 104 patients. No major complications occurred. There were no cases of renal function impairment.

CONCLUSION

Selective transarterial embolization using ethanol alone or ethanol with additional embolic materials reduced AML size, alleviated symptoms, and can be performed safely without permanent impairment.

KEY POINTS

• Percutaneous transarterial ethanol embolization reduces AML size and alleviates symptoms. • Embolization can be performed safely without permanent impairment of renal function.

FairEmbo Concept for Arterial Embolizations: In Vivo Feasibility and Safety Study with Suture-Based Microparticles Compared with Microspheres

PURPOSE

Microspheres are effective embolic agents, especially for the management of bleeding and oncologic lesions. The first FairEmbo study reported the effectiveness of embolization using suture fragments. The effectiveness and safety of arterial embolization with suture-based microparticles (SBM) were assessed in a swine model.

MATERIALS AND METHODS

In this ethical-approved animal study, a polar artery in each kidney was embolized in four swine: one side with hand-cut non-absorbable SBM (Flexocrin 2®) and the contralateral side with Embozene® 900 for comparison. Swine were followed for 3 months (M3) to evaluate the effectiveness and the safety of SBM. Follow-up protocol included clinical monitoring, computed tomography (CT) control and digital subtraction angiography (DSA), followed by histological analyses. The SBM confection parameters were evaluated by automatic microscopic sizer. RStudio software and Mann-Whitney test (significance at P < 0.05) were used for statistics.

RESULTS

The average size of SBM was 1002 μm (SD = 258). All targets were effectively embolized by SBM with an angiogram defect estimated at 45.6% (95% CI [35.9-55.2]), compared to 40.5% (95% CI [30.6-55.5]) for Embozene® group (P = 0.342). The average duration of SBM embolization procedure was significantly increased compared to Embozene® embolization (1202 s versus 222 s, P = 0.029). There were no statistical differences in M3 DSA and CT for SBM and Embozene®, with persistence of partial arterial occlusion and atrophic embolized area. No postoperative complications were observed on clinical and CT controls.

CONCLUSION

This experimental study suggests that embolization with SBM is feasible, safe and effective in short- and medium-term follow-up as compared to microspheres.

Renal function, complications, and outcomes of a reduction in tumor size after transarterial embolization for renal angiomyolipomas: a meta-analysis

OBJECTIVE

The present study aimed to evaluate renal function, complications, and changes in tumor size after transarterial embolization for patients with renal angiomyolipomas.

METHODS

We performed a meta-analysis of transarterial embolization in patients with renal angiomyolipomas from January 1994 to April 2018. Endpoints of interest were the estimated glomerular filtration rate, serum creatinine levels, blood urea nitrogen levels, complications, and reduction of tumors.

RESULTS

A total of 30 studies comprising 653 patients were included. A total of 32.0% of patients were treated by urgent transarterial embolization for spontaneous ruptured renal angiomyolipomas. Other patients sought to relieve symptoms or received embolism prophylactically. The estimated glomerular filtration rate showed no significant difference between before and after embolization. In 363 patients with data on complications, post-embolization syndrome occurred most frequently (54.0%). Only 16 (4.4%) patients had major complications. The diameter of sporadic angiomyolipomas was reduced by a mean of 2.09 cm (95% confidence interval [CI], 0.73-3.45 cm; I2 = 29.3%) and they were reduced in size by 30.0% (95% CI, 16.0%-44.0%; I2 = 27.9%).

CONCLUSIONS

Transarterial embolization of renal angiomyolipomas affects renal function preservation, with a low complication rate. Transarterial embolization is useful for sporadic and tuberous sclerosis complex-related angiomyolipomas.

Use of a mixture of Lipiodol and Cyanoacrylate in percutaneous embolization treatment of symptomatic renal Angiomyolipomas: Our experience

Purpose of this report is to describe safety and effectiveness of selective artery embolization in the treatment of bleeding angiomyolipomas (AMLs) of the kidney using a mixture of Lipiodol and Cyanoacrylate. Two patients with bleeding AMLs underwent to superselective embolization of the lesions using microcatheter and Lipiodol mixed with Cyanoacrylate in the ratio 3:1. Primary bleeding control rate was 100% with no major complications. Follow-up CT (mean time 18 months) demonstrated a significant reduction in size (about 50%) of the lesions. In conclusion, selective artery embolization with Lipiodol and Cyanoacrylate appear to be safe and effective in the treatment of bleeding AMLs.

Tuberous sclerosis complex: new insights into clinical and therapeutic approach

Tuberous sclerosis complex (TSC) is a complex disease with many different clinical manifestations. Despite the common opinion that TSC is a rare condition, with a mean incidence of 1/6000 live births and a prevalence of 1/20,000, it is increasingly evident that in reality this is not true. Its clinical sequelae span a range of multiple organ systems, in particular the central nervous system, kidneys, skin and lungs. The management of TSC patients is heavily burdensome in terms of time and healthcare costs both for the families and for the healthcare system. Management options include conservative approaches, surgery, pharmacotherapy with mammalian target of rapamycin inhibitors and recently proposed options such as therapy with anti-EGFR antibody and ultrasound-guided percutaneous microwaves. So far, however, no systematically accepted strategy has been found that is both clinically and economically efficient. Thus, decisions are tailored to patients' characteristics, resource availability and clinical and technical expertise of each single center. This paper reviews the pathophysiology and the clinical (diagnostic-therapeutic) management of TSC.

Postembolization Intratumoral Chronic Bleeding, without the Classic CT Feature of Active Extravasation, in Tuberous Sclerosis Complex-Related Renal Angiomyolipoma: Two Case Reports

Two patients with tuberous sclerosis complex each had multiple bilateral renal angiomyolipomas. After undergoing embolization for a ruptured angiomyolipoma, patient 1 experienced long-lasting abdominal fullness; contrast-enhanced computed tomography (CECT) revealed a large chronic hematoma without contrast extravasation. Patient 2 underwent embolization for the largest right renal angiomyolipoma which contained a chronic hematoma. 2 weeks later, the symptom of abdominal fullness presented, and CECT revealed that the preexisting hematoma had enlarged without contrast extravasation. In both cases, a second embolization of the angiomyolipomas resulted in shrinking of the intratumoral hematomas and alleviation of the associated symptoms. Therefore, chronic postembolization intratumoral bleeding from renal angiomyolipoma may present as a persistently large or growing hematoma with an associated symptom of abdominal fullness but without the typical CECT feature of active extravasation.

Are We Overtreating Renal Angiomyolipoma: A Review of the Literature and Assessment of Contemporary Management and Follow-Up Strategies

Renal angiomyolipoma (AML) are benign tumours composed of fat, muscle, and disorganised blood vessels. Historic treatment algorithms for sporadic AML based on size fail to consider additional risk factors such as tumour vascularity and pseudoaneurysm formation. As AML is now predominantly incidental, rupture is rare and its mortality low. The recent publication of the largest longitudinal series to date also suggest that growth is uncommon, challenging existing surveillance paradigms. The evidence assessing treatment strategies in AML are reviewed, with particular emphasis on incidental sporadic AML. The relative merits of various AML treatments are discussed, and areas of clinical uncertainty highlighted.

Evaluation of split renal function before and after renal arterial embolization for angiomyolipoma using absolute ethanol

PURPOSE

Transcatheter arterial embolization (TAE) with absolute ethanol is widely accepted as a therapeutic procedure for renal angiomyolipoma (AML). We aim to evaluate the split renal function before and after AE for renal AML by using 99m-technetium (99mTc)-mercaptoacetyltriglycine 3 (MAG3) renography.

METHODS

This study was approved by the Institutional Review Board. The study population comprised 11 renal AML patients (three males, eight females, age 55.1 ± 13.8 years, AML in eight right and three left kidneys) who received unilateral renal TAE with absolute ethanol from April 2002 to January 2013. Blood renal function (i.e. serum creatinine and estimated glomerular filtration rate [eGFR] and split effective renal plasma flow [ERPF]) calculated on 99mTc-MAG3 renography was compared before and within 1 week after renal AE. Statistical analysis was calculated using Wilcoxon signed-ranked test.

RESULTS

TAE for renal AML was technically successful in all patients. Serum creatinine and eGFR did not change before and after TAE. ERPF on the embolized kidney did not change before (127.3 ± 60.8 ml/min) and after (127.6 ± 47.4 ml/min) TAE (p = 0.9726). ERPF on the nonembolized kidney showed a statistically significant increase before (152.5 ± 46.8 ml/min) and within 1 week after (169.1 ± 41.5 ml/min) TAE (p = 0.0093 and p < 0.05, respectively).

CONCLUSION

TAE for renal AML may not induce renal dysfunction on the embolized kidney and may immediately increase the renal blood flow of the nonembolized kidney.

Preparation and evaluation of biocompatible long-term radiopaque microspheres based on polyvinyl alcohol and lipiodol for embolization

The aim of this work was to develop long-term radiopaque microspheres (LRMs) by entrapping lipiodol in biocompatible polyvinyl alcohol with multiple emulsions chemical crosslinking method. The high content of lipiodol (0.366 g/mL) was hardly released from LRMs in vitro and the radiopacity could maintain at least 3 months after subcutaneous injection in mice without weakening. A series of tests was performed to evaluate the feasibility of LRMs for embolization. LRMs were proved to be smooth, spherical, and well dispersed with diameter range of 100–1200 μm. Young's modulus of LRMs was 55.39 ± 9.10 kPa and LRMs could be easily delivered through catheter without aggregating or clogging. No toxicity of LRMs was found to mouse L929 fibroblasts cells and only moderate inflammatory in surrounding tissue of mice was found after subcutaneous injection of LRMs. After LRMs were embolized in renal artery of a rabbit, the distribution and radiopacity of LRMs in vivo were easily detectable by X-ray fluoroscopy and computed tomography (CT) imaging, respectively. More accurate distribution of LRMs in embolized kidney and vessels could be detected by high-revolution visualization of micro-CT ex vivo. In conclusion, the LRMs were proved to be biocompatible and provide long-term radiopacity with good physical and mechanical properties for embolization.

C-arm cone-beam computed tomography in interventional oncology: technical aspects and clinical applications

C-arm cone-beam computed tomography (CBCT) is a new imaging technology integrated in modern angiographic systems. Due to its ability to obtain cross-sectional imaging and the possibility to use dedicated planning and navigation software, it provides an informed platform for interventional oncology procedures. In this paper, we highlight the technical aspects and clinical applications of CBCT imaging and navigation in the most common loco-regional oncological treatments.

Role of embolization in the treatment of renal masses

Renal arterial embolization (RAE) performed for the treatment of renal masses has been proven to be a safe and effective technique, with several decades of experience. RAE is well tolerated with few complications, particularly if the time interval from embolization to surgery is reduced to less than 48 hours. Review of the literature suggests that RAE is also extremely effective for palliation of symptoms in the setting of nonoperative advanced stage renal cell carcinoma. In addition, this technique plays a large role in the management of angiomyolipomas that are symptomatic or at risk of spontaneous rupture. To date, RAE has not been evaluated in a randomized controlled setting, which has contributed to its underutilization. All of these potential benefits warrant the need for prospective studies for further validation.

Long-term results of preventive embolization of renal angiomyolipomas: evaluation of predictive factors of volume decrease

OBJECTIVES

To evaluate the efficacy of selective arterial embolization (SAE) of angiomyolipomas based on the percentage volume reduction after embolization and to identify predictive factors of volume decrease.

METHODS

Patients receiving prophylactic SAE of renal angiomyolipomas were included retrospectively over 3 years. The volume change after SAE and haemorrhagic or surgical events were recorded. Initial tumour volume, percentage tumour fat content, mean tumour density, embolic agent used, number of angiomyolipomas and tuberous sclerosis disease were evaluated as predictive factors of volume decrease.

RESULTS

A total of 19 patients with 39 angiomyolipomas were included with median follow-up of 28 months (interquartile range 21-37 months). All treatments were technically successful (92% primary and 8% secondary). No distal bleeding or any increase in size or surgical nephrectomy after SAE was recorded. Mean volume reduction was 72% (±24%). Volumes before SAE (R(2) = 0.276; p = 0.001), percentage fat content (R(2) = 0.612; p < 0.0001) and mean angiomyolipoma density (R(2) = 0.536; p < 0.0001) were identified as predictive factors of volume decrease. In multivariate regression, only percentage fat content influenced volume decreases.

CONCLUSIONS

SAE is an efficient treatment for angiomyolipoma devascularisation and volume reduction. A significant reduction of volume is modulated by the initial volume and tissue composition of the tumour.

KEY POINTS

• Selective arterial embolization is effective for angiomyolipoma devascularisation and volume reduction • Volume reduction depends of initial volume and tissue composition of the tumour • Selective arterial embolization is a low radiation treatment.

Renoduodenal fistula after transcatheter embolization of renal angiomyolipoma

Transcatheter embolization of renal angiomyolipomas is a routinely performed, nephron-sparing procedure with a favorable safety profile. Complications from this procedure are typically minor in severity, with postembolization syndrome the most common minor complication. Abscess formation is a recognized but uncommon major complication of this procedure and is presumably due to superinfection of the infarcted tissue after arterial embolization. In this case report, we describe the formation of a renoduodenal fistula after embolization of an angiomyolipoma, complicated by intracranial abscess formation and requiring multiple percutaneous drainage procedures and eventual partial nephrectomy.