Prostatic Artery Embolization (PAE)

Abstract

Benign prostatic hyperplasia (BPH) is a common condition affecting the majority of men over 60 years of age. BPH incidence increases with age and often leads to lower urinary tract symptoms including frequency, urgency, and straining. In patients that do not respond to pharmacological therapy, options include transurethral procedures such as transurethral resection (TURP) or photovaporization, surgical prostatectomy, and prostate artery embolization (PAE).

The goal of PAE is to occlude arterial supply to the prostate by selective catheterization and subsequent embolization, most commonly with spherical tris-acryl gelatin microspheres. Over weeks to months, reduced blood flow leads to necrosis of prostatic adenomatous tissue, resulting in reduction of prostate size and decreased urethral impingement, eventually allowing for long-term resolution of symptoms in a majority of patients. Advantages of this technique compared with the standard surgical option, TURP, include faster recovery times, fewer side effects, and lower complication rates with near equal efficacy.

Overview

Background

The prostate is a gland located in the pelvis underneath the bladder. It wraps circumferentially around the urethra and secretes seminal fluid made within its tissues. Benign prostatic hyperplasia (BPH) is an increase in the size of the prostate on a cellular level. Proliferation of the cells that either make up the stromal tissue supporting the prostate’s glandular units or contribute to the epithelial lining of these units can occur with increasing age, causing a rise in overall prostate volume. Given the anatomical position of the prostate, growing adenomatous tissue can result in urethral compression and eventual interference in urinary or ejaculatory functions. This can lead to multiple lower urinary tract symptoms (LUTS) including frequency, hesitancy, urgency, nocturia, and interrupted stream.¹ BPH increases in prevalence with age, affecting a majority of men over 60 years old, but a specific inciting event for these prostatic changes has not been identified.²

Focused History of Patient

The patient in this case was a 63-year-old male with an enlarged prostate and a 3-year history of progressive urinary hesitancy and urgency, as well as worsening hematuria. To treat this, a prostatic artery embolization (PAE) was performed.

Physical Exam

During the history and physical, it is important to exclude malignant, infectious, neurologic, or other obstructive causes for symptoms the patient is experiencing. Patient-reported outcomes can be measured by having patients fill out an International Prostate Symptom Score (IPSS) questionnaire. This survey can be used to follow disease progression or treatment response, and can serve as a subjective measurement of a patient’s symptoms prior to and after PAE.² A digital rectal exam can be useful for grading prostate size and excluding malignancy or prostatitis. Decisions on PAE candidacy can also be influenced by findings on imaging, including prostate volume, or specific measurements related to urinary symptoms, such as peak urinary flow or postvoid residual.³ Urinalysis, serum creatinine, and prostate-specific antigen levels are typical laboratory tests used to distinguish between LUTS. In addition to physical exam, patients should obtain a consultation by a urologist and possibly undergo cystoscopy and urodynamic testing for direct visual evaluation of the gland to rule out malignancy in cases of bloody urine and to establish baseline bladder function.

Imaging

Upon initial evaluation, the patient may require imaging, such as trans-rectal ultrasound or magnetic resonance (MR) imaging, to define the gland size, morphology (such as the presence of a median lobe), and rule out other causes of LUTS. Prostatic vasculature is extremely variable with numerous possibilities for origin of the prostate’s arteries.⁴ Unfortunately, conventional CT and MR lack the resolution to reliably define prostatic vascular anatomy. Thus, digital subtraction angiography (DSA) is used for visualization of vasculature. Cone beam CT angiography is also commonly used in PAE, with recommendation that it be utilized in addition to DSA to improve identification of the prostatic arteries.⁵ Lastly, internal iliac arteriograms from before and after injection of embolizing agents can be compared to ensure occlusion of prostatic blood supply.

Natural History

If BPH goes untreated, continued enlargement of the prostate can occur with the potential for complete blockage of the urethra. Any LUTS the patient is experiencing are likely to be exacerbated. Escalation of incontinence or significant blood loss due to hematuria may have an even greater impact on the quality of life for a patient.

Continued prostate growth may eventually lead to sequelae affecting the bladder and kidney. With stasis of urine within the bladder, patients are at increased risk of urinary tract infections and pyelonephritis. Urinary retention, the most common BPH complication requiring hospitalization, with the need for emergent treatment is also possible. Bladder calculi and detrusor muscular dysfunction can occur over time. Renal consequences include hydronephrosis and renal insufficiency associated with either acute kidney injury or chronic kidney disease.^6,7

Options for Treatment

Approved pharmacologic therapy for BPH treatment includes α-adrenergic blockers, 5α-reductase inhibitors, and phosphodiesterase type 5 inhibitors, which work to control symptoms or decrease prostate volume.

If medications fail or if patients present with severe LUTS initially, multiple transurethral surgical options exist. Transurethral resection of the prostate (TURP) is currently the most common, involving endoscopic cautery and removal of prostate tissue. Transurethral incision of the prostate (TUIP) is similar, but is performed without removal of prostatic tissue. For very significant prostatic enlargement, complete excision with prostatectomy is an option.

Laser therapies, such as holmium laser ablation or enucleation of the prostate, have recently become more prevalent. Similar therapies include thulium enucleation or photoselective vaporization of the prostate. Numerous other therapies exist, some with less frequent utilization due to lower efficacy and greater recurrence of symptoms, and include transurethral microwave therapy, needle ablation, and urethral stenting or lifting procedures.⁸

Rationale for Treatment

Patients with BPH who are not surgical candidates, who refuse surgery, or who have symptoms refractory to pharmacologic or surgical treatment could likely benefit from PAE. Compared to the aforementioned surgical options, PAE has the advantage of being performed in an outpatient setting where patients are able to ambulate and return home within a few hours after the procedure. PAE is minimally invasive and can be performed using local anesthesia with IV sedation instead of general anesthesia. Additional benefits of PAE include shorter hospital stays, decreased time with indwelling bladder catheters, decreased nocturia, fewer occurrences of postprocedure ejaculatory disorders, decreased blood loss, significant reduction in IPSS scores, and reduced prevalence of LUTS.^1,4,9-10

Special Considerations

Contraindications to PAE include urethral or bladder issues that may affect treatment outcomes, such as bladder atony, neurological disorders affecting the bladder, bladder diverticula or stones that may require surgery, or urinary obstruction due to causes other than BPH. Active urinary tract infections, renal failure, and prostatic malignancy must be ruled out prior to PAE as well. Special consideration should be paid to patients with atherosclerotic or aneurysmatic changes to major vessels or tortuous vessel anatomy leading towards the prostate, as well as to those with allergies to local anesthesia or iodinated contrast.^10-12

Discussion

In the 1970s, PAE was introduced as a method to control hemorrhage after prostatectomy or prostate biopsy.¹³ PAE for the treatment of BPH was first reported in 2000 for a patient with multiple cardiovascular comorbidities who could not undergo surgery.¹⁴ Since then, the rate of the procedure’s application has significantly increased. Currently, short- and long-term outcomes of PAE show low rates of minor complications, rates of less than 1% for major complications, and improvement in quality of life for over 80% of patients. Additionally, total PAE in-hospital costs are significantly less than those for TURP.¹⁵ TURP offers shorter procedure times, but patients do need to receive spinal or general anesthesia for the surgery, which significantly lengthens hospital stays and inflates the cost of the surgery.

Nevertheless, TURP continues to be the gold standard for management of BPH with moderate to severe symptoms. Head-to-head comparison between TURP and PAE has determined that patients experience equivalent improvement in LUTS, similar decreases in IPSS scores, and similar functionality reported in bladder function diaries.^1,4,9 The advantages of TURP include less postoperative pain, greater improvement of bladder outlet obstruction, and greater shrinkage of the prostate.^3,9-10

Limitations of PAE studies include small sample size and limited follow-up times. Considering the novelty of PAE compared to TURP or open prostatectomy, more time is needed to assess the recurrence rate of symptoms for patients in the long-term. Recurrence rates as low as 15% have been cited for PAE, but most studies span 12 months or less.¹⁶ Further research is needed to determine optimal embolization particle size.⁴ Transfemoral versus transradial approaches for access to the prostatic arteries has also been investigated, with both being considered safe for continued use.¹⁷

Meta-analyses have shown similar efficacy amongst TURP and holmium laser enucleation of the prostate, photoselective vaporization of the prostate, and potassium-titanyl-phosphate (KTP) laser vaporization of the prostate, with the minimally-invasive treatments offering the same benefits of decreased hospital times seen with PAE.^18-19 However, true head-to-head studies are lacking and an assumption that PAE would be comparable to these modalities based on review when matched against TURP should not be made.

Studies on other applications of PAE, such as in cancer treatment, are becoming more numerous. PAE will likely continue to grow in popularity as more becomes known about its relative efficacy compared to other BPH treatments.

Equipment

• Embosphere® Microspheres (Merit Medical Systems, South Jordan, UT).
• CONTRA2 (Boston Scientific Corporation, Quincy, MA).
• Fathom® Steerable Guidewires (Boston Scientific Corporation, Quincy, MA).
• Sniper® Balloon Occlusion Microcatheter (Embolx, Inc., Sunnyvale, CA).
• SwiftNINJA® Steerable Microcatheter (Merit Medical Systems, South Jordan, UT).
• Angio-Seal™ Vascular Closure Device (Terumo Medical Corporation, Somerset, NJ).

*Interventional radiologists may use other catheters and wires depending on operator preference and patient access site (radial artery versus femoral artery). This equipment list was optimized by our operator for femoral access cases.

Disclosures

R.R. Ayyagari was a paid consultant for Embolx, Inc., and Merit Medical Systems. The authors have no other potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Statement of Consent

The patient and family referred to in this video article have given their informed consent to be filmed and are aware that information and images will be published online.

Special Acknowledgements

We would like to thank our anonymous patient for his contribution to medical education. We would like to thank the faculty and staff of Yale New Haven Health for their courtesy and expertise during the filming process.