Renal Arteriovenous Shunts: Clinical Features, Imaging Appearance, and Transcatheter Embolization Based on Angioarchitecture

Safety and Efficacy of Endovascular Treatment for Congenital Renal Arteriovenous Fistulas

BACKGROUND

Congenital renal arteriovenous fistulas (AVFs) represent an uncommon disease, but are clinically relevant as burdened with risk of severe complications.

METHODS

All cases of congenital AVFs treated over the last 10 years were identified on a prospectively maintained database. Treatment strategies and outcomes were investigated according to STROBE guidelines. A comprehensive literature review was also performed using to investigate the results of endovascular strategies in this setting.

RESULTS

Among 163 renal lesions embolizations, 6 cases of unilateral type 2 AVFs (4 women; median age 53 years, range 41-75). Indication for treatment was growing lesions (2, 33.3%), lumbar/abdominal pain (3, 50%) or haematuria (1, 16.6%) All patients underwent embolization of feeding (n = 4, 66.7%) or segmental arteries (n = 2, 33.3%) with 1 or more embolic agents. Clinical success was 100%. No systemic or renal complications were detected. No reinterventions were required. The 6-month follow-up CTA showed obliteration of the AVF in all cases. A comprehensive literature review identified 72 relevant cases (70.8% symptomatic) Coils (n = 25, 34.6%) or an association of several embolic agents (n = 30, 41.6%) were the most used overall clinical success rate ranged between 88% and 100%. No migration of the embolic agent no recurrences were reported in most of series and no impact on renal function was described in any case.

CONCLUSION

Despite surgical approaches may be required in selected cases, endovascular embolization represents a valid option in treatment of renal AVFs with low risk of complications and satisfactory mid-term results.

A Huge High-Flow Aneurysmal Renal Arteriovenous Malformation Treated With Endovascular Transcatheter Embolization

Renal arteriovenous anomalies are uncommon. They are characterized by an abnormal vascular connection that usually bypasses the capillary bed. Most are acquired arteriovenous fistulas (AVF) while the rest are congenital or idiopathic arteriovenous malformations (AVM). AVF are usually caused by renal interventions, trauma, or neoplastic processes. They can lead to hypertension, heart failure, hematuria, and renal insufficiency. A 69-year-old woman presented with arrhythmia, tachycardia, mild ankle edema, and increasing fatigue. Right kidney color Doppler ultrasound confirmed the presence of a huge AVM with a blood flow of 9 L/minute and a dilated, 35 mm in diameter, right renal vein. Two months later, an attempt to embolize the AVM failed as the Amplatzer™ Vascular Plug II (Abbott Laboratories, Chicago, Illinois, United States) migrated to the pulmonary circulation and was later removed. Complete embolization was achieved by implanting two Amplatzer Vascular Plug IIs, various embolization coils, histoacryl glue, and lipiodol. Control angiography revealed significant stenosis in the right subclavian artery endovascular access, which was managed with BeGraft (Bentley InnoMed GmbH, Hechingen, Germany) and Zilver (Cook Group Incorporated, Bloomington, Indiana, United States) stents. The patient was discharged on the third postoperative day, all her symptoms resolved, and she reported eventual recovery. Three months later, the patient was operated on due to a 40x58 mm pseudoaneurysm at the right femoral access site. Thus, renal AVMs should be included as a potential alternative diagnosis for various symptoms such as hematuria and hypertension resistant to medication. Endovascular embolization is a less-invasive, safer, and more effective option than open surgery but has a risk of complications. Success requires fully occluding the shunted vessel, preventing embolic material migration, and preserving normal arterial branches. It depends on selecting adequate techniques and embolic materials individually, based on etiology and precise vascular anatomy assessment.

Transarterial Embolization of Renal Arteriovenous Malformations: Treatment Outcomes According to Angiographic Classification

PURPOSE

To assess the different adjunctive catheter techniques required to achieve complete occlusion of renal arteriovenous malformations (rAVMs) of different angioarchitectural types.

MATERIALS AND METHODS

Overall, data on 18 patients with rAVM (Type 1, n = 7; Type 2, n = 2; Type 3, n = 9; mean age, 53.8 years) who underwent 25 procedures between 2011 and 2022 were reviewed. The clinical presentations, endovascular techniques, arteriovenous malformation (AVM) occlusion rate, adverse events (including the incidence of renal infarction), and clinical symptoms and outcomes (including recurrence/increase of AVM) were analyzed according to the Cho-Do angioarchitectural classification. Posttreatment renal infarction was classified as no infarction, small infarction (<12.5%), medium infarction (12.5%-25%), and large infarction (>25%) using contrast-enhanced computed tomography or magnetic resonance imaging.

RESULTS

Hematuria and heart failure were presenting symptoms in 10 and 2 patients, respectively. The embolic materials used were as follows: Type 1 rAVM, coils alone or with n-butyl-2-cyanoacrylate (nBCA); Type 2 rAVM, nBCA alone or with coils; and Type 3 rAVMs, nBCA alone. Fourteen patients underwent adjunctive catheter techniques, including flow control with a balloon catheter and multiple microcatheter placement, alone or in combination. Immediate postprocedural angiography revealed complete occlusion in 15 patients (83%) and marked regression of rAVM in 3 (17%). Small asymptomatic renal infarctions were observed in 6 patients with Type 3 rAVMs without any decrease in renal function. No major adverse events were observed. All symptomatic patients experienced symptom resolution. Recurrence/increase of rAVM was not observed during the mean 32-month follow-up period (range, 2-120 months).

CONCLUSIONS

Transarterial embolization using adjunctive catheter techniques according to angioarchitectural types can be an effective treatment for rAVMs.

Post-traumatic renal arteriovenous malformation failed endovascular embolization

Renal arteriovenous malformations (AVMs) are abnormal connections between the renal arteries and venous system. Arteriovenous fistulas account for 70%-80% of renal arteriovenous abnormalities, often resulting from iatrogenic injuries. While most renal AVMs are asymptomatic, hematuria is a common symptom caused by AVM rupture into the renal calyces. Angiography is the gold standard for diagnosis, but noninvasive imaging techniques like ultrasound, computed tomography, or magnetic resonance imaging are commonly used for initial evaluation. Most renal AVMs are managed conservatively. Symptomatic patients typically undergo endovascular embolization, the preferred treatment, while surgery is reserved for unstable patients or those with complex vascular anatomy. We present a case of a 32-year-old man with renal AVMs following a motor vehicle accident. The patient initially received unsuccessful endovascular embolization but achieved successful treatment through open fistula ligation. This case highlights the challenges in managing renal AVMs and the importance of considering alternative interventions when initial treatments prove ineffective.

Embolisation of a high - flow renal arteriovenous fistula with the use of simultaneous transvenous and transarterial approach and balloon-assisted coil embolization

BACKGROUND

Renal arteriovenous fistula (RAVF) is a rare vascular malformation, which can be asymptomatic or may cause hemorrhage, hypokalaemic hypertension, heart failure and hematuria. Endovascular embolization is a minimally invasive method which can preserve renal parenchyma. In our case, balloon assisted coil embolization with simultaneous transvenous and transarterial approach was used. A remodelling balloon, which is routinely used in neurovascular procedures, was chosen in order to eliminate the risk of coil migration and preserve feeding artery and renal parenchyma.

CASE PRESENTATION

We present a case of successful balloon - assisted coil embolization of a high flow renal arteriovenous fistula in a 25-year-old male patient via simultaneous transarterial and transvenous approach with preservation of the feeding artery.

CONCLUSION

Endovascular embolisation is a safe and effective treatment of RAVFs with low risk of complications. Simultaneous transarterial and transvenous coil deployment with the use of a flow control balloon catheter can eliminate the risk of coil migration and coil protrusion into the parent artery with permanent RAVF occlusion and renal parenchyma preservation.

Acute Abdominal Pain Without Gross Hematuria as an Atypical Initial Presentation of Renal Arteriovenous Malformation

Congenital renal arteriovenous malformations (AVMs) occasionally manifest with recurrent gross hematuria, typically in young populations. Acute abdominal pain without previous episodes of gross hematuria in young women is frequently considered a diagnosis related to obstetric and gynecological conditions or acute appendicitis, excluding the possibility of clot retention, which is more commonly associated with the elderly. A 36-year-old woman with no history of gross hematuria presented with acute lower abdominal pain. Adnexal torsion was initially considered based on her symptoms and ultrasonography findings. However, contrast-enhanced computed tomography (CT) revealed clot retention and delayed contrast excretion in the right kidney. After bladder irrigation, she returned complaining of right flank pain. Subsequent plain CT revealed contrast pooling in the right kidney and hydronephrosis. In addition to these findings, small vessels in the right renal hilum were found to be prominent in the arterial phase on the first contrast-enhanced CT. Finally, angiography of renal arteries confirmed the diagnosis of a congenital cirsoid-type renal AVM, which was successfully treated with ethanol embolization. This case highlights the importance of understanding an atypical presentation of renal AVMs, which is acute abdominal pain, even in the absence of prior gross hematuria and the characteristic CT findings. Early diagnosis of renal AVMs is crucial for preventing potentially serious complications, including repeated clot retention and life-threatening rupture. The diverse clinical manifestations and images of renal AVMs should be recognized to facilitate prompt and accurate diagnosis.

Management of Renal Artery Aneurysms and an Arteriovenous Shunt in a Hemophilic Patient: A Case Report

This case report details the management of a 66-year-old male with hemophilia A (HA) who presented with recurrent hematuria, and was found to have renal artery aneurysms and was subsequently diagnosed with a renal arteriovenous (AV) shunt. While the primary focus centers on the successful endovascular coil embolization of renal artery aneurysms, the concomitant presence of the AV shunt accentuates the significance of this case. Imaging techniques were crucial in the discovery of renal aneurysms and the diagnosis of the AV shunt malformation of the renal artery. This included an ultrasound, CT-angiography and digital subtraction angiography. The treatment approach employed prioritized endovascular coil embolization for its efficacy and reduced morbidity. Following the initial successful embolization, the identification of the AV shunt during subsequent embolization led to its targeted treatment. The case was also complicated by acute prostatitis that was treated medically. The patient's HA required careful administration of coagulation factor replacement therapy to control bleeding throughout the process. This case highlights the importance of reporting on the management of rare and complex pathologies to better understand and guide future treatments, especially involving this rare combination of renal AV shunts and hemophilia A.

Renal Arteriovenous (AV) Fistula after High-Grade Blunt Renal Trauma Caused by Traffic Accidents

PURPOSE

To report a series of three patients with traumatic renal AV fistulas after blunt renal laceration.

METHODS

We retrospectively analyzed the renal trauma cases treated in the Department of Urology of Salzburg University Clinic during a time period of 10 years concerning traumatic AV fistula formation and other clinical parameters.

RESULTS

In total, 3 cases of traumatic AV fistula formation were identified in 106 blunt renal trauma patients (2.8%), with a mean age of 39 (17-56) years. All renal traumas were classified as American Association for the Surgery of Trauma (AAST) grade IV. Two patients were primarily treated with ureteral stent; one was managed conservatively. All AV fistulas were diagnosed after a mean time of 7 (1-13) days. Two patients were symptomatic with gross hematuria, and the mean time between trauma and onset of symptoms was 11 (9-13) days. All cases were managed via coil embolization after a mean of 10 (8-13) days. Two patients received a second intervention after a mean of 18 (11-25) days. The mean AV fistula size was 18.7 (12-24) mm. Mean hemoglobin loss was 3.6 g/dL. One patient received one erythrocyte concentrate. Discharge was after a mean time of 13.3 (7-12) days, with the mean time of intensive care treatment being 2.3 (1-3) days.

CONCLUSIONS

Traumatic renal AV fistula is a rare but severe complication associated with higher-grade renal trauma. It can become evident through hematuria or blood loss several days after the initial trauma. The availability of coil embolization in a trauma center can help kidney preservation management.

Physiological role of hydrogen sulfide in the kidney and its therapeutic implications for kidney diseases

For over three centuries, hydrogen sulfide (H2S) has been known as a toxic and deadly gas at high concentrations, with a distinctive smell of rotten eggs. However, studies over the past two decades have shown that H2S has risen above its historically notorious label and has now received significant scientific attention as an endogenously produced gaseous signaling molecule that participates in cellular homeostasis and influences a myriad of physiological and pathological processes at low concentrations. Its endogenous production is enzymatically regulated, and when dysregulated, contributes to pathogenesis of renal diseases. In addition, exogenous H2S administration has been reported to exhibit important therapeutic characteristics that target multiple molecular pathways in common renal pathologies in which reduced levels of renal and plasma H2S were observed. This review highlights functional anatomy of the kidney and renal production of H2S. The review also discusses current understanding of H2S in renal physiology and seeks to lay the foundation as a new targeted therapeutic agent for renal pathologies such as hypertensive nephropathy, diabetic kidney disease and water balance disorders.

Renal arteriovenous malformation causing hematuria: Case report and review of the literature

RATIONALE

Renal arteriovenous malformations are rare vascular morphological anomalies that can be classified as congenital, idiopathic and acquired, of which congenital renal arteriovenous malformations are the most common. This disease is a rare cause of hematuria. In this case report, we report the diagnosis and treatment of a patient with renal arteriovenous malformation. We also review the symptoms, diagnosis and treatment of renal arteriovenous malformations in the published literature.

PATIENT CONCERNS

A 35-year-old female patient presented to a local hospital with right-sided lumbar abdominal pain with hematuria for 2 days. Physical examination showed percussion pain in the right renal area. Laboratory tests such as routine blood and blood biochemistry did not show any significant abnormalities when the patient entered the hospital. Considering the patient's medical history, a urological computed tomography scan showed blood accumulation in the right renal pelvis, upper middle ureter and bladder. Subsequently, routine blood tests showed that the patient's red blood cells and hemoglobin continued to decrease. An emergency renal arteriogram was performed, which showed a tortuous right upper renal pole branch artery and multiple thickened veins communicating with it.

DIAGNOSIS

This patient was diagnosed with cirsoid renal arteriovenous malformation.

INTERVENTIONS

Renal artery embolization was performed immediately after the renal arteriogram was performed on the patient.

OUTCOMES

On review of the angiogram, the tortuous right upper renal pole branch artery was found to be obstructed, and the thickened vein disappeared, and the renal vein was normally visualized in due course. On the third postoperative day, the patient was free of hematuria. Physical examination showed no percussion pain in the renal area. The patient healed and was discharged. A 1-year follow-up was performed and the patient gave feedback that she no longer had symptoms such as back pain and hematuria in her daily life.

LESSONS

This case illustrates that early use of vascular interventions is an important method for the diagnosis and treatment of cirsoid renal arteriovenous malformations.

Complications after Nephron-sparing Interventions for Renal Tumors: Imaging Findings and Management

The two primary nephron-sparing interventions for treating renal masses such as renal cell carcinoma are surgical partial nephrectomy (PN) and image-guided percutaneous thermal ablation. Nephron-sparing surgery, such as PN, has been the standard of care for treating many localized renal masses. Although uncommon, complications resulting from PN can range from asymptomatic and mild to symptomatic and life-threatening. These complications include vascular injuries such as hematoma, pseudoaneurysm, arteriovenous fistula, and/or renal ischemia; injury to the collecting system causing urinary leak; infection; and tumor recurrence. The incidence of complications after any nephron-sparing surgery depends on many factors, such as the proximity of the tumor to blood vessels or the collecting system, the skill or experience of the surgeon, and patient-specific factors. More recently, image-guided percutaneous renal ablation has emerged as a safe and effective treatment option for small renal tumors, with comparable oncologic outcomes to those of PN and a low incidence of major complications. Radiologists must be familiar with the imaging findings encountered after these surgical and image-guided procedures, especially those indicative of complications. The authors review cross-sectional imaging characteristics of complications after PN and image-guided thermal ablation of kidney tumors and highlight the respective management strategies, ranging from clinical observation to interventions such as angioembolization or repeat surgery. Work of the U.S. Government published under an exclusive license with the RSNA. Online supplemental material and the slide presentation from the RSNA Annual Meeting are available for this article. Quiz questions for this article are available in the Online Learning Center. See the invited commentary by Chung and Raman in this issue.

An Update of Treatment of Pancreatic Arteriovenous Malformations

Pancreatic arteriovenous malformation is a rare entity (0.9%). There are about 200 articles available in PubMed. This review article includes 86 published articles, with 117 cases published after 2000. The median age at diagnosis was 51, and most of the patients were male (87.0%). The symptoms included pain, bleeding, pancreatitis, ulcers in the duodenum or stomach, varix formation, jaundice, and ascites. The diagnostic modalities were angiography, contrast-enhanced CT, MRI, and/or Ultra Sound. The most common treatments were surgery and embolization. The clinical success rate of embolization reported was 57.7%. The tailored embolization based on each agio-architecture had a clinical success rate of 80%. If embolic therapy is ineffective, surgical intervention should be considered.

Case report: Asymptomatic renal arteriovenous fistula requiring endovascular embolization in a living donor transplanted kidney more than 15-years after last protocol biopsy

Here we present the case of an HLA-identical living-donor kidney transplant recipient, who was incidentally found to have a large complex renal arteriovenous fistula (RAVF) in their transplanted kidney that had been present for nearly 6 years but was previously misinterpreted as being part of a collection of cysts. This patient had undergone 7 protocol biopsies of the transplanted kidney, the last of which had been performed approximately 16 years prior, representing the longest interval between most recent biopsy renal allograft to RAVF diagnosis in the literature date. This report reviews the etiology and principles of management for RAVF.

Usefulness of preoperative simulation with patient-specific hollow vascular models for high-flow renal arteriovenous fistula embolization using a preloading coil-in-plug technique

The development of three-dimensional printers has facilitated the creation of patient-specific hollow vessel models. Preoperative simulations using these types of models have improved our ability to select appropriate devices and embolic materials before performing complex endovascular procedures. This report describes 2 cases of high-flow renal arteriovenous fistulas (r-AVFs) that were successfully treated via short-segment embolization using the preloading coil-in-plug (p-CIP) technique. To our knowledge, this is the first report of r-AVF being treated using the p-CIP technique. Our findings demonstrate that preoperative simulation has the potential to improve the safety and reliability of complex vascular embolization procedures.

Embolisation of an aneurysmal high-flow renal arteriovenous fistula in a paediatric patient: simultaneous arterial and venous approach

BACKGROUND

A large aneurysmal renal arteriovenous fistula (AVF) can cause hypokalaemic hypertension due to activation of renin-aldosterone system due to steal effect from renal parenchyma. In comparison to nephrectomy, endovascular embolisation of renal AVF is minimally invasive and can be nephron sparing, thus preserving renal function. However, such embolisation is technically challenging and can be associated with high risk of embolic migration.

CASE PRESENTATION

We present a case of successful embolisation of a large aneurysmal renal AVF in a 11-year-old girl. The AVF was initially treated with coil embolization via transarterial route, resulting in partial migration of coil into inferior vena cava. After removal of the migrated coil via transvenous snaring, coils were deployed simultaneously via transarterial and transvenous routes to prevent migration. AVF flow dampened but residual flow persisted at 1 month follow up. A second embolization session with additional coil deployment and N-butyl cyanoacrylate (NBCA) injection resulted in successful occlusion of the AVF. At 3 months follow up, the girl's blood pressure and serum potassium level have normalized without need of antihypertensive agent or potassium supplements.

CONCLUSION

Endovascular embolisation can be an effective nephron sparing treatment for large aneurysmal renal AVF. This is particularly important in paediatric patients as most renal function can be preserved with their expected longer life span. Risk of coil migration can be controlled by simultaneous transarterial and transvenous deployment. Complete occlusion of AVF can be aided by additional use of NBCA.

Recurrent urinary retention due to clots caused by a congenital renal arteriovenous malformation that forms a complex vascular network: Report of two cases

INTRODUCTION

Repeated urinary retention due to clots caused by congenital renal arteriovenous malformation is rare.

CASE PRESENTATION

A 40-year-old woman (case 1) and a 66-year-old man (case 2) experienced recurrent urinary retention due to clots. Neither patient had a history of renal trauma nor was taking any medications. Contrast-enhanced abdominal computed tomography revealed a large hematoma in the renal pelvis and ureter with no masses, stones, or vascular lesions and only dilated blood vessels in the arterial phase in case 1. Angiography of the kidney in both patients revealed an arteriovenous malformation, and embolization of the arteries feeding the arteriovenous malformation was performed. Soon after embolization, hematuria disappeared completely with no recurrence for 5 years in case 1 and 2 years in case 2.

CONCLUSION

Congenital renal arteriovenous malformation should be considered as a cause of recurrent clot retention, and angiographic embolization of the feeding arteries can be an effective treatment.

The Renal Vasculature: What the Radiologist Needs to Know

The physiologic role of the kidneys is dependent on the normal structure and functioning of the renal vasculature. Knowledge and understanding of the embryologic basis of the renal vasculature are necessary for the radiologist. Common anatomic variants involving the renal artery (supernumerary arteries and prehilar branching) and renal vein (supernumerary veins, delayed venous confluence, retroaortic or circumaortic vein) may affect procedures like renal transplantation, percutaneous biopsy, and aortic aneurysm repair. Venous compression syndromes (anterior and posterior nutcracker syndrome) can be symptomatic and can be diagnosed with a combination of radiologic features. Renal artery stenosis is commonly atherosclerotic and is diagnosed with Doppler US, CT angiography, or MR angiography. Fibromuscular dysplasia, the second most common cause of renal artery narrowing, has a characteristic string-of-beads appearance resulting from multifocal stenoses and dilatations. Manifestations of renal vasculitis differ depending on whether the affected vessels are large, medium, or small. Renal vascular injury is graded according to the American Association for the Surgery of Trauma (AAST) renal injury scale, which defines vascular injury and active bleeding in renal injuries. Both renal arteries and veins are affected by primary neoplasms or secondarily by neoplasms from adjacent structures. Differentiation between bland thrombus and tumor thrombus and the extent of involvement dictate management in malignancies, especially renal cell carcinoma. Aneurysms, pseudoaneurysms, arteriovenous malformations, and arteriovenous fistulas can affect renal vessels and can be diagnosed with specific imaging features. The radiologist has a critical role in identification of specific imaging characteristics and establishing the diagnosis in the varied pathologic conditions affecting the renal vasculature, which is critical for directing management. Thus, the renal vasculature should be an integral part of radiologists' checklist. ^©RSNA, 2021.

A large adrenocortical adenoma surrounded with a renal arteriovenous malformation

INTRODUCTION

Large adrenal adenomas are clinically rare. We report a case of a large adrenal adenoma with a renal arteriovenous malformation, mimicking a malignant adrenal tumor in preoperative imaging.

CASE PRESENTATION

A 66-year-old woman presented to a local hospital with abdominal pain. A right adrenal tumor was detected, 66 mm in diameter and surrounded by thick and tortuous vessels. Based on the imaging findings, pheochromocytoma was suspected. However, clinical symptoms and endocrine abnormalities were absent, and radionuclide accumulation in scintigraphy was negative. Laparoscopic right adrenalectomy was performed. Intraoperatively, a notable growth of vessels forming a nidus surrounding the tumor was observed. Pathologically, this was diagnosed as an adrenocortical adenoma in conjunction with a renal arteriovenous malformation.

CONCLUSION

We report a case of a large adrenal tumor surrounded with an arteriovenous malformation. To the best of our knowledge, this is the first reported case of this combination.

Use of a 4 mm Amplatzer Vascular Plug II in the treatment of a renal arteriovenous fistula: a case report

Background

We report the use of a 4 mm vascular Amplatzer for the occlusion of a renal arterovenous fistula between the renal artery, at the hylum trifurcation point, and an aneurismatic vein draining into the main renal vein, where there was no possibility to use any other device from the venous side, because of the diameter and the high flow, neither from the arterious side without sacrificing lobar branches. The device was implanted at the exact point of communication, like a patent foramen ovale occluder, with the distal disc into the artery lumen and the other two proximal discs into the venous side.

Case presentation

A 34-years-old Caucasian woman suffered several episodes of paroxysmal supraventricular tachycardia associated with dyspnoea, after the onset of post-pregnancy hypertension. She underwent CTA, spectral Doppler sonography and angiography which showed a renal arteriovenous fistula (RAVF) between the renal artery, at the hylum trifurcation point, and an extremely ectatic vein draining into the main renal vein of the right kidney.

With both arterial and venous access, the RAVF was selectively embolized using a 4 × 6 mm Amplatzer Vascular Plug II, released into the communication between artery and vein ensuring the patency of vessels involved.

The RAVF was almost completely excluded and the hemodynamic effects associated were also corrected.

Conclusions

The use of this device, though in an alternative way, allowed the exclusion of the high flow A-V fistula without sacrificing any parent renal vessel and preserving the renal function.

Renal Arteries Revisited: Anatomy, Pathologic Entities, and Implications for Endovascular Management

The renal arteries (RAs) are important vessels that usually arise from the abdominal aorta and supply the kidneys; thus, these arteries play a vital role in physiologic functions such as hemofiltration and blood pressure regulation. An understanding of the basis for embryologic development and the frequently variable anatomy of the RAs is necessary to fully appreciate the range of diseases and the implications for procedural planning. Hemorrhage from an RA is relatively common and is typically traumatic or spontaneous, with the latter form often seen in association with underlying tumors or arteriopathy. Accurate diagnostic evaluation of RA disease due to conditions such as atherosclerosis, fibromuscular dysplasia, vasculitis, aneurysm, arteriovenous shunt, embolic disease, and dissection is dependent on the use of multimodality imaging and is essential for selecting appropriate clinical management, with endovascular therapy having a key role in treatment. Surgical considerations include extra-anatomic renal bypass, which remains an important treatment option even in this era of endovascular therapy, and RA embolization as an adjunct to tumor surgery. A novel area of research interest is the potential role of RA denervation in the management of refractory hypertension. ^©RSNA, 2021.

Congenital renal arteriovenous malformation: a rare cause of visible haematuria

We report a case of renal arteriovenous malformation (AVM) and describe its angioarchitecture and endovascular management. A 28-year-old male patient presented with visible painless haematuria. CT of the abdomen showed a right renal AVM. Digital subtraction angiography of the right renal vessels showed an AVM of middle and lower pole segmental arteries with communication to a large saccular aneurysm, which was arising from the right main renal vein. Complete occlusion of the AVM was done by using glue (a mixture of n-butyl-cyanoacrylate and lipiodol), resulting in nonvisualisation of the aneurysm on angiography. His vital signs were stable during the procedure. Follow-up CT after 12 months showed no residual flow in the aneurysm, normal upper pole renal parenchyma and nonvisualisation of AVM. Early diagnosis of this clinical entity is of paramount importance for proper management as it can cause massive blood loss and rapid clinical deterioration.

Renal artery embolization for spontaneous hemorrhage in patients with acquired cystic kidney disease: A 20-year single-center experience

Objectives

To evaluate the safety and effectiveness of transcatheter arterial embolization for controlling spontaneous hemorrhage in patients with acquired cystic kidney disease (ACKD).

Methods

This retrospective study included 18 patients with ACKD (M:F=13:5; mean age, 56 years) who underwent renal artery embolization to control spontaneous hemorrhage between January 2001 and September 2020. The underlying etiology and clinical presentations were reviewed and previous computed tomography (CT) findings were analyzed. Furthermore, angiographic and embolization details, technical and clinical successes, and complications were assessed.

Results

Subcapsular, perirenal, and pararenal hematomas were observed on CT scans for all patients. Contrast extravasation was observed in 15 / 17 patients (88%) on contrast-enhanced CT scans. Angiography showed active bleeding in 14 patients (78%; contrast extravasation [n=6], pseudoaneurysm [n=3], and both [n=5]), suspicious bleeding in 1 (5%), and no bleeding in 3 (17%). The technical and clinical success rates were 100% and 94% (17/18), respectively. Total and partial embolization was performed in 14 (78%) and 4 (22%) cases, respectively. Subsequent surgical nephrectomy was required for one patient with clinical failure due to recurrent bleeding despite total embolization. Procedure-related complications included mild post-embolization syndrome in one patient and contrast-induced nephropathy in five patients (28%) without long-term complications.

Conclusions

Renal artery embolization is safe and effective for controlling spontaneous renal hemorrhage in patients with ACKD.

Location of embolization affects patency after coil embolization for pulmonary arteriovenous malformations: importance of time-resolved magnetic resonance angiography for diagnosis of patency

OBJECTIVES

This study aimed to assess the diagnostic accuracy of computed tomography (CT) and time-resolved magnetic resonance angiography (TR-MRA) for patency after coil embolization of pulmonary arteriovenous malformations (PAVMs) and identify factors affecting patency.

METHODS

Data from the records of 205 patients with 378 untreated PAVMs were retrospectively analyzed. Differences in proportional reduction of the sac or draining vein on CT between occluded and patent PAVMs were examined, and receiver operating characteristic analysis was performed to assess the accuracy of CT using digital subtraction angiography (DSA) as the definitive diagnostic modality. The accuracy of TR-MRA was also assessed in comparison to DSA. Potential factors affecting patency, including sex, age, number of PAVMs, location of PAVMs, type of PAVM, and location of embolization, were evaluated.

RESULTS

The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy of CT were 82%, 81%, 77%, 85%, and 82%, respectively, when the reduction rate threshold was set to 55%, which led to the highest diagnostic accuracy. The sensitivity, specificity, PPV, NPV, and accuracy of TR-MRA were 89%, 95%, 89%, 95%, and 93%, respectively. On both univariable and multivariable analyses, embolization of the distal position to the last normal branch of the pulmonary artery was a factor that significantly affected the prevention of patency.

CONCLUSIONS

TR-MRA appears to be an appropriate method for follow-up examinations due to its high accuracy for the diagnosis of patency after coil embolization of PAVMs. The location of embolization is a factor affecting patency.

KEY POINTS

• Diagnosis of patency after coil embolization for pulmonary arteriovenous malformations (PAVMs) is important because a patent PAVM can lead to neurologic complications. • The diagnostic accuracies of CT with a cutoff value of 55% and TR-MRA were 82% and 93%, respectively. • The positioning of the coils relative to the sac and the last normal branch of the artery was significant for preventing PAVM patency.

A Case of Arteriovenous Fistula After Kidney Trauma Mimicking Tumor

Renal arteriovenous fistulas are rare complications of kidney injury that are usually caused by penetrating or blunt abdominal trauma, percutaneous or open biopsy, or surgery. We report a case of renal arteriovenous fistula after blunt abdominal trauma of a male patient who had traffic accidents. Computed tomography images show arteriovenous fistula lesion mimicking the tumor of the renal pelvis. Through this case, we present how to identify and avoid being confused in diagnosis as well as introduce its clinical manifestations, imaging, and treatment.

Role of imaging in visceral vascular emergencies

Differential diagnosis in non-traumatic acute abdomen is broad and unrelated diseases may simulate each other from a clinical perspective. Despite the fact that they are not as common, acute abdominal pain due to diseases related to visceral vessels may be life-threating if not detected and treated promptly. Thrombosis, dissection, and aneurysm in the abdominal visceral arteries or thrombosis in visceral veins may cause acute abdominal pain. Imaging with appropriate protocoling plays a fundamental role in both early diagnosis and determination of the treatment approach in these cases where early treatment can be life-saving. Computed tomography (CT) appears to be the most effective modality for the diagnosis as it provides high detail images in a very short time. Patient cooperation is also a less concern as compared to magnetic resonance imaging (MRI). As the imaging findings may sometimes be really subtle, diagnosis may be difficult especially to inexperienced imagers. Correct protocoling is also very critical to detect arterial abnormalities as visceral arterial abnormalities may not be detectable in portal phase only abdominal CT scans. In this article, we aimed to increase awareness among imaging specialists to these not very common causes of acute abdomen.

"Renal emergencies: a comprehensive pictorial review with MR imaging"

Superior soft-tissue contrast and high sensitivity of magnetic resonance imaging (MRI) for detecting and characterizing disease may provide an expanded role in acute abdominal and pelvic imaging. Although MRI has traditionally not been exploited in acute care settings, commonly used in biliary obstruction and during pregnancy, there are several conditions in which MRI can go above and beyond other modalities in diagnosis, characterization, and providing functional and prognostic information. In this manuscript, we highlight how MRI can help in further assessment and characterization of acute renal emergencies. Currently, renal emergencies are predominantly evaluated with ultrasound (US) or computed tomography (CT) scanning. US may be limited by various patient factors and technologist experience while CT imaging with intravenous contrast administration can further compromise renal function. With the advent of rapid, robust non-contrast MRI, and magnetic resonance angiography (MRA) imaging studies with short scan times, free-breathing techniques, and lack of ionization radiation, the utility of MRI for renal evaluation might be superior to CT not only in diagnosing an emergent renal process but also by providing functional and prognostic information. This review outlines the clinical manifestations and the key imaging findings for acute renal processes including acute renal infarction, hemorrhage, and renal obstruction, among other entities, to highlight the added value of MRI in evaluating the finer nuances in acute renal emergencies.

Endovascular Management of Renal Arteriovenous Fistula With Large Aneurysm Masquerading as a Renal Cyst

Large renal aneurysms can masquerade as simple renal cysts on ultrasound, especially if Doppler examination is not routinely done to assess flow characteristics. We present a case report of a 26-year-old male, as a clinical challenge in urology, who had minimal symptoms, yet had an arteriovenous fistula with a large aneurysm which was diagnosed as a parapelvic cyst on ultrasound. Endovascular treatment of the arteriovenous fistula was done using a vascular plug with satisfactory outcomes.

Endovascular catheter arterial embolization effectively treats secondary hypertension and increased plasma B-type natriuretic peptide level accompanied by idiopathic renal arteriovenous fistula

A 65-year-old woman with a history of hypertension and atrial fibrillation was referred to our hospital following detection of microscopic hematuria.

Physical examination showed continuous vascular murmur with the maximum point on the right side of the umbilicus. Contrast-enhanced computed tomography showed a right renal aneurysmal-type arteriovenous fistula. She underwent endovascular catheter arterial embolization. Following this, her blood pressure was virtually normalized, and her levels of plasma BNP were significantly reduced.

We recommend that patients with microscopic hematuria should be auscultated around the navel, because renal AV shunt is treatable; this may facilitate cure of secondary hypertension and cardiac load.

Endovascular Embolization of a Previously Treated Renal Arteriovenous Malformation Presenting With Gross Hematuria

Renal arteriovenous shunts are direct communications between the supplying artery and draining vein without the presence of an intervening capillary bed. They can be traumatic or nontraumatic. Coils can be used for embolization of feeding arteries; however, they do not treat the nidus directly. We report a case in which proximal coil placement in feeding arteries led to recanalization of the renal AV shunt through collaterals, resulting in recurrent hematuria. The case was subsequently managed by embolizing the nidus by N-butyl 2-cyanoacrylate glue.

Successful Double-Catheter Coil Embolization of an Iatrogenic Subclavian Artery to Internal Jugular Vein Fistula After Minimally Invasive Cardiac Surgery

It is essential to establish cardiopulmonary bypass by percutaneous insertion of a large-bore catheter via both the femoral vein and internal jugular vein (IJV) for minimally invasive cardiac surgery (MICS). Complications associated with IJV catheterization during MICS have been reported in the literature; however, vascular injury of the subclavian artery (SCA) is rare. We herein present a rare case in which an iatrogenic arteriovenous fistula (AVF) between the right SCA and IJV after MICS was successfully treated by endovascular coil embolization. A 61-year-old man who had undergone mitral valve repair by MICS 10 months before presentation was referred because of pulsatile cervical bruit and tinnitus. Radiographic examination revealed a right SCA pseudoaneurysm associated with an AVF located between the right common carotid artery and vertebral artery. The AVF was completely occluded with detachable coils using a double-catheter technique to avoid coil migration into the IJV. This technique has been used to treat high-flow or complex AVFs, including pulmonary and renal AVFs. As shown in the present case, it is also useful to treat an iatrogenic AVF between the SCA and IJV.

Renal Arteriovenous Fistula

Teaching Point: Color Doppler ultrasound (US) is useful for screening for renal arteriovenous (AV) shunts, especially following renal biopsy, because of its convenience and minimally invasive nature.

Triple-balloon-assisted n-butyl-2-cyanoacrylate embolization of a cirsoid renal arteriovenous malformation

We report a patient with a cirsoid renal arteriovenous malformation (AVM) causing massive hematuria that was successfully embolized by n-butyl-2-cyanoacrylate under triple-balloon occlusion. Proximal balloons were placed in the renal artery and vein for flow control, and a coaxial microballoon was placed in a feeding artery of the AVM to control the delivery of n-butyl-2-cyanoacrylate. Under triple-balloon occlusion, n-butyl-2-cyanoacrylate embolization achieved complete occlusion of the AVM with no procedure-related complications, such as renal infarction. This triple-balloon-assisted technique enabled us to control blood flow and the delivery of n-butyl-2-cyanoacrylate, allowing complete occlusion of the AVM. This approach may prevent proximal embolization and distal migration of n-butyl-2-cyanoacrylate.

Arteriovenous Fistula-A Rare Complication of IVC Filter Retrieval

Inferior vena cava (IVC) filters are important devices for patients who are at high risk for developing thrombi and pulmonary embolism but have conditions that preclude the use of pharmacologic anticoagulants. IVC filter retrieval has become an important quality initiative backed by Food and Drug Administration guidelines for prompt removal after the filter is no longer indicated. Filter retrieval is a common procedure that usually has very few complications. However, when the filter is tilted or embedded in the caval wall, advanced techniques of retrieval may be necessary. These techniques have a higher rate of success but also a higher risk of complications such as injury to the IVC. Here, we describe a case of IVC filter retrieval resulting in formation of an arteriovenous fistula between the right renal artery and IVC and subsequent successful repair of this fistula using a vascular plug.

Renal arteriovenous malformation: An unusual pathology

Renal arteriovenous malformations are rare renal vascular abnormalities. More commonly, the term refers to the congenital type of malformation. Only a few cases have ever been presented and reported in the literature, mostly with a nidus. We present the clinical, ultrasound and computed tomography findings and discuss the management related to a 63-year-old male with a right congenital renal arteriovenous malformation without a nidus that was successfully managed with coil embolisation. Relevant literature is hereby reviewed to highlight characteristic imaging and appropriate treatment.

Efficacy and Safety of Transvenous Embolization of Type II Renal Arteriovenous Malformations with Coils

PURPOSE

To evaluate the efficacy and safety of transvenous coil embolization of the venous sac for type II renal arteriovenous malformation (AVM).

MATERIALS AND METHODS

A retrospective review was conducted of 8 patients (5 women and 3 men; mean age, 57 years; age range, 41-69 years) who underwent transvenous coil embolization for type II congenital renal AVM at 5 different hospitals between 2012 and 2018. Additional intra-arterial ethanol injection was performed if shunt flow persisted after venous sac coiling. Technical success was defined as complete occlusion of shunt flow with coil embolization. Clinical success was defined as no symptom recurrence during the follow-up period. The renal parenchymal infarction rate was measured on computed tomography (CT), and procedure-related complications were reviewed.

RESULTS

Nine sessions of embolization were performed for 8 patients. The mean venous sac size was 24 mm (range, 10-39 mm), and a mean of 14 micro and/or micro-detachable coils (range, 3-50) were used. The technical success rate was 88% (7 of 8) using coil embolization. One patient (12%) required additional ethanol injection to complete occlusion of the shunt flow and had a less than 10% parenchymal infarction on follow-up CT. No procedure-related complications or recurrences occurred during a mean clinical follow-up period of 20.8 months (range, 4.7-76.6 months).

CONCLUSIONS

Transvenous coil embolization of type II renal AVM showed an 88% technical success rate. One patient (12%) showed less than 10% renal parenchymal infarction after additional ethanol injection. No additional complications or recurrences occurred during the follow-up period.

Transvenous salvage of coil migration with intraprocedural pulmonary circulation protection and successful transvenous coil embolization for the treatment of giant high-flow renal arteriovenous fistula

Transcatheter embolization is a well-established treatment for renal arteriovenous fistula (AVF) in selected cases. Transarterial approach has been the conventional route of access of the AVF. In large arteriovenous shunts, however, transarterial approach inherits the risk of distal migration of embolization material with subsequent pulmonary embolism. We report a case of giant high-flow renal arteriovenous fistula treated with coil embolization. Arterial approach was attempted with double catheter technique, however complicated with coil mass dislodgement. We have retrieved the coil mass via transvenous route with simultaneous pulmonary circulatory protection and subsequent successful transvenous coil embolization with complete obliteration of the AVF was performed.

Simultaneous transarterial and transvenous coil embolization for a large aneurysmal-type renal arteriovenous fistula

A 74-year-old woman underwent abdominal computed tomography for screening, and a right large aneurysmal-type renal arteriovenous fistula (AVF) was found incidentally. The venous sac of the renal arteriovenous fistula was enlarged, and coil embolization was considered. To prevent severe complications such as coil migration, pulmonary embolism, and rupture during procedure, coil embolization was approached via both the feeding artery and the draining vein simultaneously, with balloon occlusion of the feeding artery. It was accomplished successfully, and the patient could discharge without complication.

Long-Term Outcomes of Selective Renal Artery Embolization for Renal Arteriovenous Fistulae with Dilated Venous Sac

PURPOSE

To retrospectively evaluate the role of selective renal artery embolization for renal arteriovenous fistulae (AVFs) with dilated venous sac.

MATERIALS AND METHODS

Between 2002 and 2015, 14 patients (7 men and 7 women; mean age, 60 years) with a single renal AVF with dilated venous sac underwent selective renal artery embolization. Three patients presented with gross hematuria, 4 presented with occult blood in urine, and 1 presented with chronic heart failure. Five patients had a history of renal biopsy or partial nephrectomy. Embolic agents used included pushable fibered coils, detachable microcoils, hydrogel coils, N-butyl 2-cyanoactylate, and/or absolute ethanol. Technical success was defined as complete angiographic occlusion of the renal AVF without visualization of the venous sac. Clinical success was defined as the disappearance of the AVF on ultrasound and contrast-enhanced computed tomography, without any symptoms.

RESULTS

Fifteen sessions of selective renal artery embolization were performed. Technical success was achieved in 13 sessions (86.7%). Clinical success was achieved in 13 patients (92.9%) after a mean follow-up of 48 months (range, 6-155 months). Two major complications occurred-renal vein thrombosis (n = 1) and renovascular hypertension (n = 1)-and were successfully managed with warfarin and an angiotensin-II receptor blocker, respectively. The former patient required re-embolization because of recanalization. No significant changes were observed in the mean serum creatinine level (.86 mg/dL vs .85 mg/dL; P = .67) and the mean estimated glomerular filtration rate (66.0 mL/min/1.73m² vs 67.4 mL/min/1.73m²; P = .4) after 6 months.

CONCLUSIONS

Selective renal artery embolization is a safe and effective treatment for renal AVFs with dilated venous sac.

Varicocele due to renal arteriovenous malformation mimicking a renal tumor: a case report

Background

Renal arteriovenous malformation is an aberrant vascular connection between the renal artery and vein. Acquired renal arteriovenous malformation (arteriovenous fistulae) accounts for approximately 70% of renal arteriovenous abnormalities. Congenital renal arteriovenous malformation, relatively rare, can result in significant hematuria which may require arterial embolization or nephrectomy.

Case presentation

A 64-year-old Asian man presented to the Urology department in our hospital with gradual left scrotal swelling for 2 years. Ultrasound and computed tomography showed an irregular mass in the upper pole of his left kidney. Digital subtraction angiography confirmed cirsoid-type left renal arteriovenous malformation combined with left renal vein ostial stenosis. After digital subtraction angiography and selective segmental renal artery embolization, the varicocele was obviously alleviated.

Conclusions

The etiology diagnosis of varicocele is not always straightforward, and renal arteriovenous malformation should be considered in the differential diagnosis of varicocele and renal mass. Renal arteriovenous malformation is difficult to distinguish from renal tumor according to varicocele and computed tomography presentation, while magnetic resonance imaging and digital subtraction angiography help to make a definite diagnosis and selective renal angiographic embolization is one of the best treatments for renal arteriovenous malformation.

[RENAL ARTERIOVENOUS FISTULA (ANEURYSMAL TYPE) TREATED BY NEPHRECTOMY UNDER BALLOON CATHETER OCCLUSION OF RENAL ARTERY: A CASE REPORT]

A 60-year-old man presented with leg edema and shortness of breath. He was being treated with medication for chronic heart failure for the past 3 years and had been in a traffic accident when he was 13 years old. Computed tomography showed a huge right renal arteriovenous fistula (AVF). The right renal artery measured 16 mm in diameter, the renal aneurysm was observed to be 60 mm, renal vein 87 mm, and the inferior vena cava 60 mm in diameter. His high-output heart failure was attributed to his right renal AVF, for which treatment was deemed necessary. Due to the risk of pulmonary embolism associated with transcatheter arterial embolization, we performed a nephrectomy with temporary interruption of renal blood flow using a balloon catheter. He was observed to be asymptomatic immediately after surgery.

Endovascular Treatment of 12 Cases of Renal Arteriovenous Malformations: The Experience of 1 Center and an Overview of the Literature

Objectives:

Congenital renal arteriovenous malformations (rAVMs) represent rare vascular diseases. The heterogeneous vascular architecture of each rAVM determines the endovascular treatment techniques employed. We reported our experience with the endovascular treatment of a series of rAVMs.

Materials:

This retrospective study consisted of 12 patients with 12 rAVMs who underwent renal arterial embolization (RAE) in our hospital. Embolic materials, including particles, liquid embolic agents (n-butyl 2-cyanoacrylate, Onyx, and ethanol), and coils, were selectively used based on the decisions of interventional radiologists. Technical success was defined as the complete occlusion of the feeding arteries and nidus on postprocedure renal arteriography. Clinical success was defined as the resolution of hematuria or the disappearance of rAVM-relevant symptoms.

Results:

The median follow-up period was 13.5 months (range: 4-72). The technical success based on 12 procedures in 12 patients was 83.3% (10 of 12). In the 2 procedures that technically failed, the existence of multiple fine feeding arteries arising from the proximal portion of different segmental renal arteries explains the incomplete embolization. One of the 2 patients achieved clinical success without additional RAE. The other patient had recurrent hematuria 25 months after initial treatment, which was successfully managed conservatively with hemostatic agents. Thus, the clinical success was 91.7% (11 of 12).

Conclusions:

Renal artery embolization with the selective use of various embolic materials is an effective treatment for patients with rAVMs. The existence of multiple fine feeding vessels arising from the proximal portion of different segmental renal arteries is likely to affect the technical success of treatment.

The smell of renal protection against chronic kidney disease: Hydrogen sulfide offers a potential stinky remedy

Chronic kidney disease (CKD) is a common global health challenge characterized by irreversible pathological processes that reduce kidney function and culminates in development of end-stage renal disease. It is associated with increased morbidity and mortality in addition to increased caregiver burden and higher financial cost. A central player in CKD pathogenesis and progression is renal hypoxia. Renal hypoxia stimulates induction of oxidative and endoplasmic reticulum stress, inflammation and tubulointerstitial fibrosis, which in turn, promote cellular susceptibility and further aggravate hypoxia, thus forming a pathological vicious cycle in CKD progression. Although the importance of CKD is widely appreciated, including improvements in the quality of existing therapies such as dialysis and transplantation, new therapeutic options are limited, as there is still increased morbidity, mortality and poor quality of life among CKD patients. Growing evidence indicates that hydrogen sulfide (H₂S), a small gaseous signaling molecule with an obnoxious smell, accumulates in the renal medulla under hypoxic conditions, and functions as an oxygen sensor that restores oxygen balance and increases medullary flow. Moreover, plasma H₂S level has been recently reported to be markedly reduced in CKD patients and animal models. Also, H₂S has been established to possess potent antioxidant, anti-inflammatory, and anti-fibrotic properties in several experimental models of kidney diseases, suggesting that its supplementation could protect against CKD and retard its progression. The purpose of this review is to discuss current clinical and experimental developments regarding CKD, its pathophysiology, and potential cellular and molecular mechanisms of protection by H₂S in experimental models of CKD.

Transarterial embolisation for congenital renal arteriovenous malformations improves clinical condition even with partial obliteration

AIM

To evaluate the efficacy and safety of transarterial embolisation (TAE), used to treat congenital renal arteriovenous malformations (CRAVMs).

MATERIALS AND METHODS

The medical records were searched retrospectively to identify patients who underwent TAE to treat CRAVM from January 2003 to August 2015. Patient demographics, clinical presentations, and imaging findings were reviewed. TAE outcomes, including complete or partial obliteration, clinical success, complications, renal function changes, and relapse of symptoms or signs after the final TAE, were assessed.

RESULTS

Over the 12-year period, 16 patients (nine male, seven female; median age, 47 years) who underwent 21 TAE procedures to treat 16 CRAVMs were enrolled in the study. The most common clinical presentation was haematuria (81.3%). Thirteen patients (81.3%) had cirsoid and three (18.7%) had aneurysmal CRAVMs. Of the 16 CRAVMs, 11 (68.8%) were peripheral, four (25%) were central, and one (6.3%) was both peripheral and central. The complete obliteration rate was 56.3%. The clinical success rate was 87.5% over a median follow-up period of 398.5 days. Two (9.5%) major complications and 14 (66.7%) minor complications were encountered. No statistically significant change in renal function was evident after TAE.

CONCLUSION

TAE was safe and effective when used to treat CRAVM; the complication profile was acceptable and renal function was preserved. TAE improved the clinical condition of CRAVM patients even when obliteration was only partial.