Variant arterial anatomy related to Prostate Artery Embolisation (PAE)

S Nirmalarajan1 & G Schlaphoff2

1Medical Imaging Department, Prince of Wales Hospital, Randwick, NSW, Australia2Department of Interventional Radiology, Liverpool Hospital, Liverpool, NSW Australia

No conflicts of interest or financial disclosures.

1. To provide a comprehensive review of variant arterial anatomy related to PAE, within the framework of an established angiographic classification system.

2. To compare the reported incidence of arterial variants with findings from a case series of PAE at a single Australian institution with illustrative examples.

3. To describe the impact of variant arterial anatomy on PAE technique and outcomes.

Learning Objectives

Background• PAE is emerging as an effective treatment option for benign prostatic hyperplasia (BPH).

• Accurate identification of the prostate arteries, variant anatomy and intra/extra-prostatic anastomoses is crucial for improvingtechnical success and preventing non-target embolisation.

The IIA branching pattern is highly variable; however, it usually bifurcates into an anterior divisionand a posterior division.

Yamaki et al (1998) classified the IIA anatomy into 4 groups according to the pattern of branching of the:

– superior gluteal artery (S)

– inferior gluteal artery (I)

– internal pudendal artery (P)

OVERVIEW

INTERNAL ILIAC ARTERY (IIA) ANATOMY

Group A: Posterior division IIA:• formed by the superior gluteal

artery Anterior division IIA:• formed by the gluteopudendal

trunk, which gives rise to the inferior gluteal and internal pudendal arteries

Group B: Posterior division IIA:• formed by the gluteal trunk,

which gives rise to the superior and inferior gluteal arteries

Anterior division IIA:• formed by the internal pudendal

artery

Group C: Trifurcation of the IIA gives rise to the superior gluteal, inferior gluteal and internal pudendal arteries

Group D: Posterior division IIA:• formed by the common trunk for

superior gluteal and internal pudendal arteries

Anterior division IIA:• formed by the inferior gluteal

artery

S

IP

Group A

SI

P

Group B

SIPGroup C

SP

I

Group D

• The origin of the prostate artery is highly variable and there is a lack of uniformity in the reported nomenclature.

• Typically, the prostate gland is supplied by two branches:

• Central (anterolateral) branch

• Supplies the central zone and median lobe

• Capsular (posterolateral) branch

• Supplies the peripheral zone

• These branches usually arise from a single common trunk. Occasionally, they may have independent origins (dual arterial supply).

• Intraprostatic anastomoses (ipsilateral or contralateral) are common. Extra-prostatic anastomoses with arteries supplying the bladder, rectum or penis are variably present.

(de Assis et al, 2015; Carnavale et al, 2017)

PROSTATE ARTERY ANATOMY

Background

Classification Description

Type I Origin from anterior division of IIA in a common trunk with the superior vesical artery (SVA)

Type II Origin from anterior division of IIA, inferiorly to SVA

Type III Origin from obturator artery

Type IV Origin from internal pudendal artery

Type V Less common origins

The classification system proposed by de Assis et al (2015), provides a standardised framework for categorising prostate artery origin into 5 types:

Digital Subtraction Angiographic anatomy was retrospectively reviewed in 101 PAE procedures performed at a single Australian institution (Liverpool Hospital, Sydney) between 2015 and 2018.

PAE was performed in patients with BPH and lower urinary tract symptoms (LUTS) following clinical assessment in a multi-disciplinary team with Urology and Interventional Radiology, and pre-procedure CTA and MRI. Intra-procedural Cone-beam CT was used in every case. Each patient was followed up in the Liverpool Hospital Interventional Radiology clinic.

Procedure detailsMETHOD

A total of 202 pelvic sides were reviewed. For each pelvic side:

The IIA branching pattern was classified into 4 groups according to the classification system described by Yamaki et al (1998)

Dual prostate artery supply was defined as independent origins of the peripheral and central branches from a single side. In these cases, the prostate artery origin was classified according to the origin of the main central branch.

The prostate artery origin was classified into 5 types according to the classification system described by de Assis et al (2015)

The incidence of each anatomic type (IIA branching pattern; prostate artery origin) and the incidence of dual supply was calculated as a percentage and compared with available literature.

Clinical findingsIIA Branching

patternStudy Result Yamaki et al

(1998)(review of 645 cadaveric

pelvic sides)

Bilhim et al (2011)

(review of 42 pelvic side angiograms)

Group A 178/202 88.1% 79.5% 61.9%

Group B 21/202 10.4% 15% 31%

Group C 3/202 1.5% 5.3% 7.1%

Group D 0/202 0% 0.2% 0%

IVA/Prostate artery origin Study Result de Assis et al (2015) Bilhim et al (2012)

Type I 42/202 20.8% 28.7% 20.1%

Type II 47/202 23.8% 14.7% 17.8%

Type III 36/202 17.8% 18.9% 12.6%

Type IV 66/202 32.7% 31.1% 34.1%

Type V 7/202 3.5% 5.6% 15.4%

Dual supply from a single pelvic side

25 out of 202 pelvic sides 12.4%

Not visualised on DSA (due to atherosclerotic disease)

4 out of 202 pelvic sides 2.0%

SGA

IGA

IPA

Obt

GPT

PA

SGA

IGA

Gluteal trunk

IPA

VPT

SVA

PA

Trifurcation

SGA

IGA

IPA

Obt

PA

• The posterior division of the IIA is formed by the superior gluteal artery (SGA)

• The anterior division of the IIA is formed by the gluteopudendal trunk (GPT).

• In this case, the gluteopudendal trunk trifurcates into the inferior gluteal (IGA), internal pudendal(IPA) and obturator (Obt) arteries.

• PA = Prostate artery

GROUP A (88%)

• The posterior division of the IIA is formed by the gluteal trunk which gives rise to the superior and inferior gluteal arteries.

• The anterior division of the IIA is formed by the internal pudendal artery.

• In this case, there is a common vesicoprostatic trunk (VPT) arising from the anterior division, which gives rise to the superior vesical artery and prostate artery.

GROUP B (10%)

• The IIA trifurcates into the superior gluteal, inferior gluteal and internal pudendalarteries.

• In this case, there is a quadrification of the IIA, as the obturator artery arises from the same origin. Note, the obturator origin is not included in the Yamaki et al classification system.

GROUP C (2%)

Group A88%

Group B10%

Group C2%

IIA branching pattern

SGAIGA

IPA

PA

SVA

Obt

SGA

IGA

Gluteal trunk

IPA

VPT

SVA

PA

IGA

IPA

PA

Obt

SGA

IGA

IPA

Obt

PA

Type I21%

Type II24%

Type III18%

Type IV33%

Type V4%

Prostate artery origin The prostate artery arises from the obturator artery.

TYPE III (18%)

TYPE IV (33%)

The prostate artery arises from the internal pudendal artery.Most common type of origin.

The prostate artery arises from the anterior division of the IIA inferior and separate to the origin of the SVA.

In this case, the anterior division of the IIA is formed by the gluteopudendal trunk which trifurcates into the inferior gluteal, internal pudendal and obturatorarteries.

TYPE II (24%)

PA

PA

PA

PA

The prostate artery arises from the anterior division of the IIA in a common vesicoprostatic trunk with the superior vesical artery (SVA).

TYPE I (21%)

Prostate artery supplied by the inferior mesenteric artery

(IMA)

Type V (less common origins)

Prostate artery arising from the superior gluteal artery (posterior division IIA)

TYPE V

Common origin (trifurcation) of the internal pudendal,

obturator and prostatic arteries

TYPE V

Prostate artery origin from an aberrant obturator

artery, which arises from the external iliac artery (EIA).

TYPE V TYPE V

SGA

IGA

IPA

PA

SGA

IGA

IPA

Gluteal trunk

PA

Obt

Trifurcation

EIA

Aberrant Obt

PA

PA

IMA supply

Intra/extra-prostatic anastomosesIntraprostatic anastomosis

• Left prostate arteriogram demonstrates filling of the dorsal penile artery, due to the presence of an extra-prostatic anastomosis.

• The penile anastomosis was protected with coil occlusion. Subsequent left prostate lobe arteriogram demonstrates improved enhancement of the intraprostatic branches.

Intra and extraprostatic anastomosis

• DSA and intraprocedural cone beam CT after selective left prostate artery catheterisation demonstrates the central and capsular branches of the prostate artery.

• The central branch typically demonstrates a more horizontal course, whilst the capsular branch usually runs more vertically.

• Multiple ipsilateral intraprostaticanastomoses are commonly present between the central and capsular branches.

Extraprostatic anastomosis

• Right prostate lobe arteriogram through the microcatheterdemonstrates an intraprostatic shunt and contralateral filling of the left prostate artery (solid arrow).

• There is also an extra-prostatic anastomosis with filling of the dorsal penile artery (dashed arrow).

• Coil occlusion of the extraprostaticanastomoses was performed prior to PAE.

Prostate artery branches

PA

Central

Capsular

Left prostate arteriogram demonstrates opacification of the right prostate gland and the right capsular and central branches, illustrating the presence of intra-prostatic anastomoses.

• Accurate identification of the prostate artery is critical for successful PAE.

• The observed incidence of IIA branching patterns and prostate artery origins was found to be similar to the reported incidence in previous studies.

• An awareness of less common (Type V) prostate artery origins and an understanding of intra/extra-prostatic anastomosis improves technical success, reduces the chance of revascularisation and minimises non-target embolisation.

Conclusion

References

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• Bilhim T, Pisco JM, Tinto HR, Fernandes L, Pinheiro LC, Furtado A, et al. Prostatic arterial supply: anatomic and imaging findings relevant for selective arterial embolization. Journal of Vascular and Interventional Radiology. 2012;23(11):1403-15.

• Carnevale FC, Soares GR, de Assis AM, Moreira AM, Harward SH, Cerri GG. Anatomical Variants in Prostate Artery Embolization: A Pictorial Essay. CardioVascular and Interventional Radiology. 2017:1-17.

• de Assis AM, Moreira AM, de Paula Rodrigues VC, Harward SH, Antunes AA, Srougi M, et al. Pelvic arterial anatomy relevant to prostatic artery embolisation and proposal for angiographic classification. Cardiovascular and interventional radiology. 2015;38(4):855-61.

• Yamaki K-I, Saga T, Doi Y, Aida K, Yoshizuka M. A statistical study of the branching of the human internal iliac artery. The Kurume medical journal. 1998;45(4):333-40.