Embolization Therapy: Principles and Clinical Applications, 1 Ed.

Priapism

Daniel Do • Marcelo Guimaraes

Priapism is defined as the state of tumescence in the absence of sexual stimulation persisting beyond 4 hours and can be divided into ischemic or low-flow and nonischemic or high-flow classifications.1Overall incidence of priapism is reported to be low within the general population (0.5 to 0.9 cases per 100,000 person-years).24 Resolution of priapism while preserving erectile function remains the goal of treatment strategies.1

Ischemic priapism, also known as veno-occlusive priapism, represents approximately 95% of cases.5 This stems from persisting cavernosal smooth muscle relaxation with resultant failure of contraction, which in turn causes compartment syndrome, increasing intracavernosal anoxia, and acidosis. Immediate treatment is required as tissue damage may begin in as little as 12 hours from onset.6 Most patients suffering from ischemic priapism for duration greater than 24 hours experience complete erectile dysfunction.7 Treatment includes pain control, intracavernosal injection of a sympathomimetic drug, aspiration of the corpora, and surgical shunting; endovascular intervention typically has no significant role in treating low-flow priapism. Sickle cell disease represents the most common cause of ischemic priapism in childhood and is found in 63% of cases. In adults, 23% of cases are attributable to sickle cell disease, with a reported lifetime probability of development in 29% to 42% of patients.4,5,8,9 Given this, concomitant workup and treatment of underlying hematologic blood dyscrasias are often performed on presentation. As endovascular embolic therapy has a limited role in the treatment of ischemic priapism, this chapter will primarily focus on nonischemic priapism.

Nonischemic priapism, also known as arterial priapism, was first described by Burt et al.10 in 1960 and represents a relatively rare phenomenon. It is most commonly a result of perineal or penile trauma, which results in an abnormal fistulous communication typically involving the cavernosal artery and adjacent penile sinusoidal spaces.5,11 Additional causes related to metastatic disease and intracavernosal injections have been reported,12,13 with spontaneous resolution rates of up to 62%.1 High-flow priapism is not considered a urologic emergency as there is maintained arterial inflow through the fistula, allowing oxygenation of the cavernous tissue. Although not at risk for ischemic damage, long-term sequelae may occur from possible structural damage secondary to the increased and persistent arterial inflow.1315 Treatment strategies for managing nonischemic priapism include watchful waiting, application of ice packs, ultrasound-guided compression, surgical intervention, endovascular introduction of methylene blue, and endovascular embolization.14,16,17

Endovascular techniques have been described using both temporary and permanent embolic agents, including autologous blood clot and gelfoam as well as microcoils, acrylic glue, and particles, respectively.1,4,18,19Endovascular intervention, first reported by Wear et al.19 in 1977, is considered the standard of care beyond conservative treatment, with reported success rates approaching 90%. The risk of erectile dysfunction has been reported to be as low as 5% with use of temporary embolic agents.1

Surgical options including shunting, penile exploration, and direct arterial fistulous ligation are considered a last resort treatment strategy.1 Overall success rate of 20% for shunt surgery and 63% for ligation surgery have been reported.1,13

CLINICAL APPLICATIONS

Correct identification of priapism classification is critical as endovascular management plays a role only in cases of nonischemic priapism. A typical clinical history for nonischemic priapism includes an episode of trauma followed by a nonpainful, partially rigid erection. The onset of priapism may be delayed up to 2 to 3 weeks and can be secondary to arterial spasm or ischemia.4 Physical examination will confirm a partially tumescent corpora carvernosa, and routine laboratory testing is performed to exclude anemia and possible hematologic abnormalities, none of which would be expected with nonischemic priapism.4 Acquisition of cavernous blood gas analysis should reflect arterial blood color and normal levels of pO2, pC02, and pH.

Color duplex ultrasonography of both the penis and perineum is recommended. Visualization of normal or increased blood flow velocities within the cavernosal arteries confirms a diagnosis of nonischemic priapism.16,20Additionally, size of the cavernosal artery may demonstrate enlargement greater than reported upper normal limits of 0.7 mm.21 Direct visualization of the causative fistula and/or pseudoaneurysm is often encountered and can assist in localization and preprocedural planning.1,4,20,22 Initial treatment strategy can encompass observation in conjunction with ice packs and site-specific perineal compression. Spontaneous resolution of nonischemic priapism has been reported in up to 62% of cases.1 However, observation alone can pose a theoretical risk of secondary tissue fibrosis due to excessive, constant arterial inflow resulting in erectile dysfunction.1315,23 Timing of definitive therapy remains institution and patient dependent.

TECHNIQUE

Before diagnostic angiography, diagnosis should be confirmed with corporal blood gas analysis and ultrasound. Because the arterial inflow is maintained, there should be adequate time for scheduling and planning before intervention. Foley catheter placement should be considered to improve visualization of the pelvic arteries, especially of the internal pudendal artery (IPA) origin. The IPA is typically the smallest branch of the anterior trunk of the internal iliac artery and is responsible for the external genitalia blood supply. Branches of the IPA include the perineal artery, penile artery, penile bulbar artery, deep penile (cavernous) artery, and the dorsal penile artery (Fig. 52.1). It is important to keep in mind that the right and left sided circulations may communicate through branches at the level of the bulb of the penis and between the obturator and IPA.

Standard femoral artery access and angiographic techniques are used. The angiogram should not be the initial imaging modality, and location of the offending lesion can be ascertained from the diagnostic ultrasound. A contralateral femoral artery puncture is typically performed. Following this, a diagnostic pelvic angiogram (Fig 52.2AC) with selection of the internal iliac artery or its anterior division on the affected side is performed; a Cobra (Cook Medical, Inc., Bloomington, Indiana) or Roberts Uterine Catheter (RUC) (Cook Medical Inc., Bloomington, Indiana) can be used for this angiogram. The Waltman loop technique may be used to form a loop in the 5-Fr diagnostic catheter, which facilitates ipsilateral or contralateral internal iliac arteries catheterization. Interrogation of the unaffected internal iliac artery should be performed to exclude the presence of undetected lesions. Most fistulas will be supplied by the distal IPA. Superselective catheterization of the IPA can be gained through use of standard microcatheter and microwire, introduced coaxially, and advanced just proximal to the fistula.13

The most common abnormal angiographic findings are distal IPA pseudoaneurysm (Fig. 52.2B) or arteriovenous fistula (Fig. 52.3). However, the abnormal contrast blush related a vascular lesion identified at the base of the penis (arrow) should not be confused with a normal blush in the bulb of the corpus spongiosum (Fig. 52.4A,B).

Most lesions involve the distal IPA itself or a distal branch including the common penile artery and the cavernous, dorsal penile, and bulbourethral end arteries.13,24 Successful vascular occlusion has been achieved with various embolic agents including autologous blood clot, gelatin sponge, polyvinyl alcohol (PVA), N-butyl cyanoacrylate (NBCA), and microcoils.1,4,18,25,26 Permanent embolic agents pose a theoretical increased risk of subsequent development of erectile dysfunction, whereas temporary embolic agents pose an increased risk of recurrence.1,14 The ultimate choice of embolic agent should depend on angiographic anatomy, clinical presentation, and operator’s experience. We always discuss with the patient the risks and benefits of the embolic agents and also include the decision about which embolic material will be used.

In our practice, occlusion with small microcoils is expected to be safer than using liquid embolic agents in high-flow arteriovenous fistulas. However, embolic material should be delivered as close to the point of fistulization as possible. In slow-flow arteriovenous fistulas or in pseudoaneurysms, very small gelfoam torpedo(es) pushed through (not injected) a microcatheter may be used. Alternatively, a small microcoil or a very small amount of glue may be used. Glue requires an experienced operator to prepare an adequate glue/Ethiodol concentration (70% glue, 30% Ethiodol) and to have precise delivery. A lower concentration of glue may favor distal nontarget embolization.

COMPLICATIONS

Regarding endovascular treatment of nonischemic priapism, success rates have been reported as high as 80% to 90% with a maximum of three endovascular sessions.13 Reported recurrence rates vary from 7% to 40% without specific mention of embolotherapy used.4,11,15 Erectile dysfunction remains the most significant complication; it has been reported in as many as 39% with the use of permanent embolic agents and in as few as 5% with the use of temporary embolic agents.1 Rare complications of abscess formation within the corpus cavernosum, penile curving, and gluteal ischemia have also been reported.16,18,23

CONCLUSION

In conclusion, embolization is an important tool in the management of high-flow or nonischemic priapism with high success and low complications rates. If technically feasible, preference should be given to temporary embolic agents. On the other hand, permanent embolic agents may be used by experienced interventionists.

TIPS AND TRICKS

• It is crucial that the correct diagnosis of nonischemic priapism be made through careful history, physical examination, cavernous blood gas analysis, and supporting ultrasound findings.

• Misdiagnosis can lead to an unwarranted endovascular procedure in addition to permanent erectile dysfunction if the correct treatment is delayed.

• Ultrasound should be performed in all cases and used to examine the penis, confirming the diagnosis. Examination of the perineum should be performed especially in cases involving saddle injuries as fistulas involving the IPA may be visualized.

• Ultrasound identification of the causative lesion allows for preprocedural angiographic imaging expectations and anticipated contralateral puncture to assist endovascular cannulation.

• Placement of a Foley catheter helps visualize distal pelvic branches

• Perform bilateral internal pudendal arteriograms to understand the vascularization of the external genitalia and penis before embolization is performed.

• On initial endovascular intervention, consider primary use of temporary embolic agents if technically feasible to minimize potential complications involving erectile dysfunction.

• Use of permanent embolic agents may be considered as a primary embolic agent for recurring/persisting lesions and potentially large arteriovenous fistulas.

REFERENCES

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