Rectal Artery Embolization for the Treatment of Hemorrhoidal Disease

Abstract

The term “hemorrhoid” is commonly invoked to characterize the pathologic process of symptomatic hemorrhoidal disease instead of the normal anatomic structure. While often treated with conservative measures, rectal artery embolization offers a minimally invasive alternative for patients with persistent or severe symptoms. This technique involves blocking the blood supply to the hemorrhoids using embolic agents, reducing blood flow, and alleviating symptoms. This review explores the clinical evaluation, techniques, and outcomes associated with rectal artery embolization for the treatment of hemorrhoidal disease. A discussion of the pathophysiology of hemorrhoids, the anatomy of rectal arteries, and the embolization procedure is provided in detail. Additionally, the safety and efficacy of the technique, including potential complications and outcomes, are reviewed.

Hemorrhoids are arteriovenous vascular plexuses that cover the anal canal and distal rectum. They become symptomatic in cases of inflammation, prolapse, thrombosis, enlargement, or displacement. ¹ The most common symptom of hemorrhoidal disease is chronic rectal bleeding, typically after defecation. One-third of Americans are found to have hemorrhoidal disease during screening colonoscopy. ² Although there is no recent national data on the prevalence of hemorrhoidal disease, various epidemiological studies estimate the prevalence rate to be between 4 and 40%. ^{3 4}

Hemorrhoids can be classified as internal or external based on their location. Internal hemorrhoids are located above the dentate (pectinate) line and are covered by columnar epithelium, similar to that of the intestine. In contrast, external hemorrhoids are located below the dentate line and are covered by squamous epithelium, like the skin. ⁵ Hemorrhoids that originate both above and below the dentate line are classified as mixed hemorrhoids. According to Goligher's classification, internal hemorrhoids are divided into four grades based on their appearance and degree of prolapse ( Fig. 1 ): grade I, bleeding without prolapse; grade II, prolapse during straining that retracts spontaneously; grade III, prolapse during straining that requires manual repositioning; and grade IV, irreducible prolapse that remains outside the anal canal. ^{6 7}

Fig. 1.

Grading of internal hemorrhoids (in blue). ( a ) Grade I. Hemorrhoids are enlarged but remain within the anal canal (asterisk). They may cause bleeding but do not prolapse outside the anal opening. ( b ) Grade II. Hemorrhoids prolapse out of the anal canal during straining or defecation but spontaneously retract back inside. ( c ) Grade III. Hemorrhoids prolapse out of the anal canal during defecation and require manual reduction to be repositioned inside. ( d ) Grade IV. Hemorrhoids are irreducibly prolapsed, meaning they always remain outside the anal canal and cannot be pushed back in manually. This grade can be associated with significant discomfort and complications.

Treatment options for hemorrhoids include conservative, office-based, and surgical therapies. Conservative therapies are the first-line treatment and include consuming a high-fiber diet, drinking adequate water, taking sitz baths, and using laxatives, topical treatments, and phlebotonics. Office-based therapies are considered when grades I to III hemorrhoids do not respond to conservative treatments. Infrared coagulation, band ligation, and sclerotherapy are effective office-based options with few complications, though they have a high recurrence rate. Despite significant advancements in nonsurgical methods, surgical treatments remain the most effective and are recommended for recurrent, external, mixed, and high-grade internal hemorrhoids (grades III and IV). Common surgical methods include hemorrhoidectomy, hemorrhoidopexy, and Doppler-guided hemorrhoidal artery ligation (DG-HAL). ^{8 9}

In 1995, DG-HAL was first introduced for the treatment of grade II–III internal hemorrhoids. This technique reduces blood flow and bleeding by ligating the terminal branches of the superior rectal artery (SRA). ¹⁰ Later, the “emborrhoid technique” was developed, which involves placing coils in the same arterial branches through the endovascular route instead of performing endorectal artery ligation. ¹¹

In this review, a discussion of the clinical evaluation and indications for rectal artery embolization for the treatment of chronic hemorrhoidal disease is presented along with a description of the pathophysiology of hemorrhoidal disease, as well as the relevant anatomy of rectal arteries and its variants. The embolization procedure and techniques are described in detail, including complications, clinical outcomes, and postprocedural follow-up.

Pathophysiology

Hemorrhoids are clusters of vascular structures, consisting of small arteries and veins, that are attached to the wall of the anal canal. Internal hemorrhoidal disease is characterized by hypertrophy of the hemorrhoidal vascular plexus, leading to an increase in arterioles, venous lakes, and arteriovenous shunts. This results in elevated blood flow to the arteries supplying the hemorrhoids, causing congestive symptoms, and, over time, prolapse accompanied by bleeding. ¹¹ Transperitoneal Doppler ultrasound findings have confirmed greater degrees of vascular hypertrophy and an increased number of arteries in patients with high-grade internal hemorrhoidal disease. ¹²

The physiopathology of hemorrhoidal disease remains controversial, but it is believed to be multifactorial. Factors such as sliding anal cushions, disruption of stromal scaffolding, hyperperfusion and enlargement of the hemorrhoidal plexus, increased anal pressure, rectal redundancy, and local inflammation all significantly contribute to the development and complications of the disease. ¹³

Various risk factors have been identified as potential contributors to the development of hemorrhoids, including conditions associated with elevated intra-abdominal pressure, such as constipation, straining, and certain exercises like cycling and weightlifting. Conversely, a lack of exercise, low-fiber diets, and insufficient fluid intake can increase the risk of hemorrhoids by leading to constipation. Pregnancy and abdominal obesity also raise the risk of hemorrhoidal disease by causing constipation and venous congestion. ^{2 14} Aging is another risk factor, as it increases the ratio of connective tissue to muscle, leading to the prolapse of hemorrhoidal tissue. ^{15 16}

Conventional Rectal Arterial Anatomy

According to earlier anatomical studies, SRA is the primary source of blood supply to the hemorrhoidal plexuses, while the middle rectal artery (MRA) and inferior rectal artery (IRA) are less commonly involved. ¹⁷ The SRA is the terminal branch of the inferior mesenteric artery (IMA) and provides the main blood supply to the rectum. It usually follows the downward course of the IMA along the posterior side of the sigmoid colon, reaching the posterior aspect of the upper rectum. At around the level of the third sacral vertebra (S3), ∼12 cm above the pectinate line, it splits into right and left branches. On average, four branches of the SRA give rise to feeder arteries within the rectal wall. The distal branches of the SRA enter the bowel wall ∼4 cm above the pectinate line, subdividing into smaller vessels that form a plexus around the corpus cavernosum recti (CCR) and supply the hemorrhoidal plexuses at the anorectal junction through the submucosal layer ^{18 19 20 21 22} ( Figs. 2 and 3 ).

Fig. 2.

Type 1 arterial hemorrhoid revascularization. ( a ) Frontal digital subtraction angiogram (DSA) demonstrates a dominant right superior rectal artery (SRA) anterior branch with an accessory posterior trunk (arrow). ( b ) The frontal DSA image shows the codominant right (previously embolized) and left branches (arrow) of the SRA.

Fig. 3.

Arterial hemorrhoid vascularization. The frontal digital subtraction angiogram image shows a right hypertrophic superior rectal artery (arrowhead), with reflux in an enlarged middle rectal artery (arrow).

The IRA typically originates from the internal pudendal artery (IPA) within the ischiorectal fossa, which itself arises from the internal iliac artery (IIA) in most individuals. It then divides into branches that supply the external and internal anal sphincters, eventually extending to the subcutaneous and submucosal tissues of the anal canal. These branches connect with those from the opposite side and may also connect with branches of the MRA. The IRA also supplies the external hemorrhoids and the levator ani muscle. ^{23 24}

While the anatomy of the SRA and IRA is generally consistent, the MRA's anatomy varies significantly between individuals. ²¹ Recent anatomical studies show that the most common origins of the MRA are the IPA, inferior gluteal artery, and gluteal-pudendal trunk. Other potential sources include the IIA, inferior vesical artery, obturator artery, and prostatic artery. In most cases, MRAs are found unilaterally. ^{23 24 25} The MRA follows a complex path from the pelvic sidewall, passing through the pelvic nerve plexus and parietal pelvic fascia before reaching the mesorectum. One to three MRA branches penetrate the mesorectum from the lateral, ventrolateral, and dorsolateral sides, in that order of prevalence. ²³ Connections between the MRA and the SRA or IMA were commonly observed. ²⁵

Classification of Rectal Arteries and Variants

Panneau et al ²⁶ described three patterns of hemorrhoidal arterial vascularization ( Fig. 4 ). Type 1 is the most common type, and it is characterized by hypertrophy of at least one SRA without MRA hypertrophy. Type 1 includes numerous variants with the most frequently demonstrating a common trunk of the SRA that splits into two anterior branches and a smaller posterior trunk, followed by equal dominance of the anterior arteries and posterior trunk and less frequently, a unilateral SRA dominance without hypertrophy of the MRA on the opposite side ²⁷

Fig. 4.

Illustrations of the the types of arterial vascularization of hemorrhoids: (a) type 1, bilateral hypertrophy of the superior rectal artery (SRA) without hypertrophy of the middle rectal artery (MRA); type 2, hypertrophy of a unilateral SRA and hypertrophy of the contralateral MRA; and type 3, bilateral hypertrophy of the MRA without hypertrophy of the SRA.

Type 2 hemorrhoid vascularization involves unilateral hypertrophy of the SRA and MRA on opposite sides ( Fig. 5 ). It is important to assess the dominance of the MRA in this case. MRA branches arise from the anterior trunk of the IIA, supplying the distal rectum and connecting with the SRA and IRA. These anastomoses allow for catheterization of the MRA from the SRA, and vice versa, especially when significant anastomosis is present. Catheterizing the IIA is crucial for accurately assessing the dominance of the SRA and MRA, which guides treatment decisions. ²⁸

Fig. 5.

Digital subtraction angiogram (DSA) detailing the corpus cavernosum recti (CCR) complex. ( a ). Frontal DSA image shows type 2 arterial hemorrhoid vascularization with a right hypertrophic superior rectal artery (arrowhead), with reflux into an enlarged middle rectal artery (arrow). ( b ) The CCR is a complex vascular structure that is made up of a dense network of arteriovenous anastomoses. The multiple arteriovenous shunts within the hemorrhoids at the anorectal junction (arrows) form a cushion that plays a role in bowel continence.

Type 3 and the least frequent hemorrhoidal vascularization is characterized by hypertrophy of the MRA on both sides without SRA hypertrophy. Like type 2, assessing MRA dominance is critical. During high-pressure angiography using a power injector, MRA enlargement can be seen when contrast reflux from the MRA washes out the contrast in the SRA, making it less visible ( Fig. 6 ).

Fig. 6.

( a ) CT angiography for a vascular checkup before embolization in an 83-year-old woman. Concordant axial CT angiogram and ( b ) superior rectal artery (SRA) arteriogram show hypertrophy of the left SRA and a blush (arrow) feeding the corpus cavernosum recti (CCR) (arrowhead).

Additional, less common anatomical variants have also been observed, which may complicate the task of optimal embolization. ²⁶ In one common variant, the SRA is small in diameter but opacifies a larger MRA on the same side due to an anastomosis between these two arteries. The MRA then becomes responsible for supplying the CCR and can cause symptoms, requiring embolization. This embolization can be performed immediately after catheterizing the MRA through the anastomosis. In cases where there are two MRA anastomoses at the hemorrhoidal pad level, the CCR is supplied by bilateral MRAs. By embolizing a single MRA, the pathological condition can be effectively treated. However, after embolization, there is a risk of arteriovenous fistula formation, which allows early venous drainage after arterial opacification. ²⁶ In rare cases, the IRA may become hypertrophied and feed the CCR. This should be considered in patients whose bleeding symptoms persist after complete embolization of the SRA and MRA. Due to the risk of ischemia, IRA embolization is challenging and should be carefully evaluated.

Preprocedural Evaluation

Choosing between minimally invasive treatments and surgical procedures for hemorrhoid management can be complex. Guidelines from different professional societies indicate that there is considerable overlap in the criteria for these options, underscoring the nuanced nature of the decision-making process. ²⁹ Important factors to take into consideration include but are not limited to hemorrhoid symptomatology and the dominance of pain and bleeding; hemorrhoids' size, position, and severity; patient preferences; and certain clinical contraindications for each particular treatment options such as anticoagulation state, inflammatory conditions affecting the anorectal region, and patient preference. ³⁰ Overall, patients are assessed using the hemorrhoidal bleeding score and a visual analog scale (VAS) for symptoms, and minimally invasive treatments are offered to patients with grade I to III and chronic symptoms, and patients with grade IV can be considered for rectal artery embolization if other invasive procedures are contraindicated.

Major contraindications for hemorrhoidal embolization include anorectal cancer and general contraindications for conventional therapeutic and diagnostic angiography. The existing evidence does not suggest routine preprocedural imaging in all patients. Some studies have suggested a preprocedural CT angiography may be helpful in patients with metabolic risk factors as they may have considerable atherosclerosis; patients with portal hypertension as varicose rectal veins due to portal hypertension may be implicated in hemorrhoidal bleeding, ³¹ and in patients in which anatomic anomalies or vascular lesions are suspected. ³²

Embolization Procedure

Conventionally, transfemoral access is used for this procedure, and most of the available literature have used the transfemoral route. This approach may be associated with higher rates of access site complications compared with the radial artery approach. ³³

After obtaining access, the IMA is selected using a reverse curve catheter. cone beam CT also be useful in identifying and catheterizing any target arteries. This is done to identify any hypertrophic arteries and optimal targets for superselective catheterization. The goal is to identify and catheterize all involved SRA branches using a microcatheter. The microcatheter is advanced as distally as possible and contrast injection is used to opacify the CCR. Isosorbide dinitrate should be held available in case of vasospasm.

The two main agents reported for this technique are coils and particles. Coils are favored for their ability to occlude proximally and reduce bowel ischemia risk. ³⁴ A sample case of coils embolization of MRA and SRA anastomosis is shown in Fig. 7 . It is important to note that coils alone may not ensure complete devascularization due to distal anastomoses with MRA and IRA, leading to potential recanalization. ¹ To address this, and to increase the rate of complete embolization in more distally located vessels, combining coils with polyvinyl alcohol (PVA) particles was introduced in 2016, providing more distal embolization closer to the hemorrhoidal plexus and targeting anastomotic branches. In this method, particles are injected first to achieve embolization of the distal SRA and near the CCR, after which coils are placed more proximally. ³⁵

Fig. 7.

Anastomosis between the superior rectal arteries (SRA) and middle rectal artery (MRA) in a 54-year-old woman. ( a ) Frontal digital subtraction angiography (DSA) shows a large right MRA (arrow) after injection of contrast material into the SRA, which is connected to the MRA via an anastomosis. In this case, the corpus cavernosum recti is vascularized by the SRA. ( b ) The coils were placed across the anastomosis (arrow).

Tris-acryl gelatin particles (TAGp) have also been used, with optimal sizes ranging from 500 to 1,200 μm depending on desired outcomes. A recent study showed no significant difference in clinical success between using particles with coils versus coils alone, with both achieving a 100% technical success rate and no major complications. ³⁶ Gelfoam has also shown similar efficacy to particles in SRA embolization. ³⁷

Complications and Postprocedural Follow-up

While no major complications have been reported, including sphincter dysfunction, anal canal stenosis, anorectal ischemia, and necrosis, rare cases of arterial thrombosis have been reported including external hemorrhoid thrombosis the day after embolization (which was managed conservatively with topical medication) ³⁸ as well as thrombosis in the right common femoral artery. ³⁸ Several studies reported minor complications after the procedure, including fever, pain, transient rise of hepatic enzymes, tenesmus, rebleeding, nausea, and vomiting ^{39 40 41} that usually resolves with supportive care. In a study assessing the safety of SRA embolization with particles, tenesmus after the procedure has been reported, and more than half experienced minor complications, such as small superficial (45%) and rectosigmoid junction (7%) ulcerations, and small fibrotic scar tissue (2%) leading to scarring and anal stenosis. Unlike other complications, rectosigmoid junction ulcerations required treatment with mesalazine enemas and were considered a result of nontarget embolization. Additionally, some patients experienced low-pressure residual bleeding after the procedure, lasting up to 1 month due to the discharge of hemorrhoidal tissue. ³⁶ Very few patients experienced puncture site complications (e.g., hematoma, ecchymosis, and radial artery pseudoaneurysm) as reported in other studies. ^{38 42}

After the embolization, patients are followed up to evaluate their symptom changes and to detect and treat any complications or recurrences. The follow-up period after embolization varies from a few hours to 18 months. ⁴¹ During the follow-up period, treatment efficacy was assessed by clinical success rate, which is defined by symptom resolution, patient satisfaction, improved quality of life, and postprocedural scores, such as VAS Goligher grade, and bleeding score. Otherwise, it will be considered a procedure failure, and we should look for embolization of residual arteries. ^{11 26 33} Rebleeding is the main cause of clinical failure and may indicate a recurrence.

Outcomes

Most of the reported literature for SRA embolization comes from case series and case reports, but they have shown SRA embolization to be safe and effective with favorable technical and clinical success rates. ^{34 35 39 43 44 45} A 2022 meta-analysis of 13 studies, including 381 patients, showed that rectal artery embolization was associated with improvements in bleeding scores, the VAS for pain, and quality of life. ⁴⁶ The analysis showed a pooled technical success rate, defined as the complete occlusion of the feeding arterial branches to the hemorrhoidal plexus, of 99% (95% CI: 94–100%), a pooled clinical success, generally defined as an improvement of at least two points in bleeding or symptomatic reductions of hematochezia or discomfort, of 82% (95% CI: 73–89%), and no reported major complications. Interestingly, there was an increase in the grade of internal hemorrhoids, but the clinical significance was uncertain. In another systematic review and meta-analysis published in 2021, fourteen studies with 362 patients undergoing catheter-directed hemorrhoidal dearterialization were identified, and the analysis found a significant decrease in the bleeding scores with no bowel ischemia, necrosis, or anorectal complications. ⁴⁷ The study also found a significant decrease in the average rebleeding rate in the coils and particles group when compared with the coils-only group in subgroup analysis (10.05 vs. 21.5%; p  < 0.0001). A recent 2023 retrospective cohort study from a multidisciplinary outpatient interventional center ²⁹ comprising 134 patients who underwent embolization with spherical particles and microcoils found a high technical success rate of 99% with a clinical success, defined as improvement in hemorrhoid-related symptoms without requiring additional therapy, of 93% at 1-month follow-up and only 10 patients requiring repeat embolization. The study found significant improvements in all mean outcomes at 1 month, including hemorrhoid symptoms score, hemorrhoid-related pain, quality of life, bleeding scores, and mean hemorrhoid grade, with no severe adverse events. Another meta-analysis published in 2024 consisting of 15 studies found a high technical success rate in most studies (72–100%) with the majority reporting no major or immediate postprocedural complications. ⁴¹ There was significant heterogeneity in inclusion criteria, exclusion criteria, and procedure details, with the majority of studies (73.3%) using a transfemoral approach and coils (60%) as a primary embolic agent, followed by a combination of coils and particles in 26.6% of studies, and 6.6% with particles alone.

To date, there have been only a few randomized clinical trials comparing SRA embolization to surgery. In a 2023 trial, 33 patients with symptomatic grades 2 to 3 hemorrhoidal diseases were randomized to undergo SRA embolization ( n  = 15) or Ferguson closed hemorrhoidectomy ( n  = 14) with the objectives including postprocedural pain, technical success, and clinical success. ⁴⁸ While there were no significant differences in clinical success (i.e., improvement of hemorrhoidal symptoms) between the embolization arm and surgery arm at 6 ( p  = 0.695) and 12 months ( p  = 0.691), the trial found a significantly lower mean pain during first bowel movement after the embolization arm than the surgery arm (0 vs. 6.08 ± 4.41; p  = 0.001) with a significantly lower mean use of pain medication (28.92 doses ± 15.78 vs. 2.4 doses ± 5.21; p  < 0.001). The trial also found a 100% technical success rate for embolization, which was similar to those of other reported series. ^{10 49 50} The study also found a clinical success (i.e., improvement of symptoms) of embolization at 12 months of 61.6%, which was slightly lower than the 72% reported in the literature. ^{34 43} There were no severe adverse events reported in either group. In another study, 72 patients diagnosed with grade II–IV internal hemorrhoids were randomized to undergo upper rectal artery embolization ( n  = 36) versus postpartum hemorrhage operation ( n  = 36) and found a higher total effective rate with lower postoperative symptoms and incidence of complications despite no significant differences in 9-month recurrence rates. ⁵¹

Regarding complications, SRA embolization is generally considered very safe, with rare severe adverse events reported in major studies. In the 2022 meta-analysis, ⁴⁶ post-embolization syndromes (e.g., transient low-pressure bleeding, pain, and tenesmus) were found to be common, but all cases were managed well with analgesics. One study did find a minor complication rate of 54%, and these were attributed to small superficial ulcerations or scarring but resolved within 6 months. This meta-analysis also found a 16% pooled rate of bleeding recurrence. In cases of rebleeding, revascularization was performed via new collateral anastomoses as opposed to recanalizing the previously embolized vessels. In the other meta-analysis, minor complications included post-embolization pain, bleeding, tenesmus, fever, and constipation, which all resolved with conservative management. There was one major complication in a patient who developed thrombosis at the puncture site to access the right common femoral artery 6 hours after the procedure who eventually developed massive hematochezia during surgical thrombectomy and died 1 day later. ⁵² Overall, this study found variable rebleeding rates across the studies, ranging from 0 to 44%.

As mentioned in a meta-analysis, the recurrence rate of bleeding varies between 5.4 and 44%. ⁴⁷ In terms of rebleeding, the MRA is suspected to be the primary cause of rebleeding. Thus, considering routine embolization of the enlarged MRA along with the SRA is recommended. In support of the role of MRA as the culprit in patients with rebleeding, a prospective case series of 25 patients who underwent SRA embolization reported enlarged MRA in 6 patients. ⁴³ A retrospective analysis of 45 patients underwent coil embolization, and MRA was successfully embolized in two patients after clinical failure of the SRA embolization. ⁴⁴ If reflux opacifies a hypertrophic anastomotic MRA, it can be embolized directly through the SRA in case of sizeable anastomosis between them, otherwise catheterizing the IIA should be done. ²⁶ Studying a series of patients with hemorrhoids associated with rectal bleeding has shown that there is a connection between the SRA and IRA, and embolization of both may be necessary. ⁵³

Conclusion

Rectal artery embolization represents a promising advancement in the treatment of hemorrhoidal disease. This technique offers a safe and effective alternative to traditional surgical approaches, especially for patients with high-risk profiles or recurrent disease. Future research can be directed toward optimal patient selection, comparison of different embolic agents, and long-term clinical outcomes. Outcomes research will be of particular importance as the comparative efficacy of minimally invasive image-based techniques needs to be determined relative to surgical options.