Penile Injection and Aspiration

Anatomy and Physiology

The key anatomy is for penile injection and aspiration is basic penile anatomy. This starts superficially with the skin and dartos fascia. Beneath the dartos is the superficial dorsal vein. Deep to that is Bucks fascia that surrounds 3 cylindrical structures and the dorsal neurovascular bundle. The three cylinders within the penis are a paired corpora cavernosa, which lies superiorly and laterally to the final cylinder, the corpora spongiosum. These cylinders perform vastly different functions. The corpora spongiosum surrounds and supports the urethra and prevents occlusion of the urethra during erection. The paired corpora cavernosa are the cylinders that fill with blood during erection, causing the rigidity of the penis. This rigidity is imparted by a tough covering called the tunica albuginea and the blood contained within these cylinders. The cylinders of the corpora are connected by fenestrations that allow blood to flow freely between the cylinders. 

Normal erection physiology begins with sexual stimulation, which causes relaxation of smooth muscles of the corpora via parasympathetic signals causing an increase in nitric oxide (NO) to cyclic guanosine monophosphate (cGMP) ratio. The arterial system dilates, increasing blood flow into the corpora while also decreasing outflow by compression of the subtunical venous plexus and the emissary veins. When the penis reaches its erect state, the pressure is around 100 mmHg. Detumescence begins with a decrease in the NO/cGMP ratio stimulating contraction of smooth muscle, in turn triggering a decrease in pressure. This is likely due to decreased obstruction of venous outflow and reduction of the arterial flow back to baseline.[5][6]

Ischemic priapism is limited oxygenated blood inflow and deoxygenated blood outflow. This is believed to originate from the dysregulation of NO/cGMP, leading to decreased venous return. There is stasis of blood within the corpora, which becomes thick and coagulates, preventing further venous outflow. This stasis causes endothelial and smooth muscle damage, further preventing venous outflow and leading to fibrosis.[7] 

Non-ischemic priapism is often secondary to trauma resulting in injury to the arterial system. This injury causes unopposed arterial flow into the corpora but unrestricted venous outflow. Treatment involves observation, embolization, or surgical ligation.[8]

Indications

Penile injection and aspiration are indicated if a patient is experiencing ischemic priapism for less than 72 hours, and the erection has not resolved with other less invasive techniques. If the patient has surpassed the 72-hour mark, the chances of organic erections in the future are virtually none, and he can be treated conservatively, controlling his pain.[9]

Contraindications

An ischemic priapism time of greater than 72 hours is a contraindication as injection and aspiration preserve erectile function, and patients with an erection of greater than 72 hours will not achieve erections organically.[9] Other than the duration of ischemic priapism, no contraindications exist for performing penile injection and aspiration, as this is a medical emergency.

Equipment

• Antimicrobial prep 
• Fenestrated drape
• Sterile gloves
• Anesthetic: plain lidocaine with syringe and needle for injection 
• Large bore butterfly needle 
• Blood gas syringe 
• Saline flushes 
• Empty 20 mL to 30 mL syringe
• Phenylephrine solution: concentration 100 micrograms to 500 micrograms per mL 
• Dressings: gauze and self-adherent wrap

Personnel

Penile injection and aspiration are generally performed in the emergency department by the emergency department physician or the urologist on call. No other assistants are typically required but can provide assistance if needed.

Preparation

A thorough history and physical examination are paramount prior to performing this procedure as these will generally elucidate the cause of priapism, allowing proper recommendations and long-term treatment. The clinician must discuss how long the erection has been present as well as associated penile pain. The physician needs to learn if this has happened to the patient previously. One also needs to determine if there has been recent trauma. Determining medication and recreational drug use is also important. A history of blood abnormalities or cancers, including leukemia, should be discussed.

The physical exam includes the abdomen but primarily should focus on the genitalia. It also must involve the evaluation of blood pressure, as treatment can cause dangerous elevations of blood pressure. The rigidity of the penis and glans needs to be noted. The tenderness of the penis to palpation requires assessment. If phallus is rigid and tender, this suggests ischemic priapism, where semi-rigid and less tender phallus palpation is suggestive of non-ischemic (high flow) priapism.

Laboratory evaluation is required both with a complete blood count (CBC) and a blood gas taken directly from the corpora cavernosa. If the initial aspiration of corpora blood is dark and thick, this suggests ischemia, while brighter red blood suggests non-ischemic priapism. The blood taken from the corpora is the best way to diagnose ischemic vs. non-ischemic priapism. Ischemic priapism will have a pH of less than 7.25, the partial pressure of oxygen (pO2) less than 30 mmHg, and partial pressure of carbon dioxide (pCO2) of greater than 60 mmHg. Non-ischemic priapism will have a pH of 7.4, pO2 greater than 90 mmHg, and a pCO2 of less than 40 mmHg.[10]

No imaging is acutely required, but if malignancy is suspected, a magnetic resonance imaging (MRI) scan is typically the most ideal imaging to evaluate invasion. A penile Doppler can also be used to assess for elevated arterial flow in the setting of high flow priapism.[11]

Technique or Treatment

Prepping and Draping

The entire penis, including the base, is prepped with an antimicrobial solution. At this time, a sterile field is created using towels or drapes.

Procedure

Local anesthesia can be used or foregone entirely. A dorsal penile block is performed using plain lidocaine. A ring block can be performed and/or even superficial skin injection at the projected site of needle insertion. Once the block has completely anesthetized the patient, a large-bore butterfly needle is placed into the corpora cavernosus at a perpendicular angle to the penis at the 2 to 3 o'clock or the 9 to 10 o'clock position near the penile base. Care should be taken not to violate the urethra, the dorsal penile neurovascular bundle, or puncture through to the contralateral corpora cavernosus.

Only one side requires injection and aspiration because the corpora are connected with fenestrations. Limiting the number of punctures to the corpora decreases the risk of penile hematoma. Once the needle has been placed, aspiration can be attempted using a 20 mL to 30 mL syringe. Often aspiration is unsuccessful because the blood has become thick, requiring irrigation with normal saline. This is performed using saline flushes. After saline injection, aspiration is attempted again. This technique can be performed multiple times. If no progress has been made, phenylephrine injection is performed in approximately 200 microgram increments. Vital signs should be checked prior to and after the injection of phenylephrine, along with continual reassessment for symptoms of hypertension. 1000 micrograms is typically the maximum dose of phenylephrine.

After detumescence has occurred, patients should be monitored for the return of the erection and symptoms caused by the phenylephrine injection.

Post-procedure

Gauze and a self-adherent wrap can be placed on the puncture site to help prevent penile hematoma. Patients should be instructed to return if the erection returns.

Complications

Procedure

Pain is commonly associated with this procedure even when an adequate penile block is performed. Phenylephrine is an alpha-adrenergic agonist that can cause headaches, dizziness, blurry vision, hypertension, bradycardia, tachycardia, and irregular cardiac rhythms. Because of these risks, the patient’s vitals need to be closely monitored, and the dosage of phenylephrine should be limited to 1000 micrograms in 1 hour. Recurrence is possible and is an indication that the patient may require a more invasive procedure.

Post-procedure

A penile hematoma can form following puncture of the corpora but can be reduced with an appropriate pressure dressing. The duration of the priapism is directly correlated with future erectile dysfunction due to associated fibrosis. Penile length loss can also occur due to fibrosis.

Clinical Significance

Penile injection and aspiration is a vital procedure in the preservation of penile erectile tissue when patients experience ischemic priapism. These techniques can be performed by physicians who feel comfortable with minimally invasive bedside procedures. 

Enhancing Healthcare Team Outcomes

Prompt diagnosis of priapism allows for the correct treatment. This requires an integrated interprofessional team to communicate effectively and initiate treatment plans in a timely fashion. This will help decrease delay of diagnosis and treatment of priapism, which will improve outcomes and prevent further erectile dysfunction associated with long-standing priapism. With continued erectile function, this decreases further interventions and costs to the healthcare system. Also, knowing when not to perform an intervention decreases the pain and risks to the patient.

An interprofessional team that provides a holistic and integrated approach to priapism can help achieve the best possible outcomes. Treating priapism in a timely manner using injection and aspiration prevents the progression of erectile dysfunction. Therefore, with timely treatment, further intervention for erectile dysfunction can be prevented, improving patient satisfaction and decreasing the risk to the patient.

Collaboration, shared decision making, and communication are key elements for a good outcome. The interprofessional care provided to the patient must use an integrated care pathway combined with an evidence-based approach to planning and evaluation of all joint activities. The earlier signs and symptoms of a complication are identified, the better is the prognosis and outcome of the procedure. [Level 4]