Recent advances in the management of priapism

Clinical history

Ischaemic priapism often presents well beyond the four-hour time frame commonly used as the time interval in international guidelines whereby smooth muscle necrosis within the corpus cavernosum commences⁵.

Non-ischaemic priapism can have a preceding history of blunt or penetrating perineal or genital trauma, which may have occurred several weeks before the onset of priapism. Penile discomfort rather than severe penile pain is often reported by patients; however, accurately distinguishing this condition from ischaemic priapism, which requires prompt intervention, is imperative.

Radiological imaging in priapism

Assessment of blood flow within cavernosal arteries and the corpus cavernosum to distinguish ischaemic from non-ischaemic priapism subtypes can be performed using colour penile Doppler ultrasonography. Impaired blood flow of the distal corpus cavernosum and reduced or absent perfusion within the cavernosal arteries is seen in ischaemic priapism cases on colour penile Doppler imaging. However, if blood has already been aspirated from the corpora, interpreting penile Doppler studies can be problematic because of the development of abnormal aberrant blood flow in sections of the corpus cavernosum⁶. In non-ischaemic priapism, the Doppler studies will demonstrate a high velocity throughout the corpus cavernosum and often the demonstration of a fistula. A recent study interpreting the Doppler waveforms shows that the interpretation is often difficult once interventions have been undertaken⁷.

Blood gas analysis

A more reliable investigation to distinguish between ischaemic and non-ischaemic priapism is to aspirate blood from the corpus cavernosum for blood gas analysis prior to any other intervention⁸. This will confirm blood with a low pO₂ and acidosis if the diagnosis is ischaemic priapism or a normal pO₂ and normal pH in cases of non-ischaemic priapism (Table 2).

i) Aspiration and instillation of α agonists into the corpus cavernosum

Following a penile block, if aspiration of ischaemic blood fails to resolve the priapism, instillation of α-adrenergic agonists (usually 200 μg of phenylephrine repeated to a maximum of 1,500 μg) is the next step. Both aspiration and injection of α-agonists is performed via a large bore needle (19G) inserted through the glans penis and into the corpora or directly into the penile shaft at the 2 or 10 o’clock positions to avoid injuring the neurovascular bundles. This manoeuvre aims to increase the smooth muscle tone of the corpora cavernosa and promote detumescence.

Alternative α-adrenergic agonists include metaraminol and adrenaline. High-dose phenylephrine has also been successfully utilised in small case series⁹, although in refractory cases it is unlikely to be successful owing to the development of irreversible smooth muscle dysfunction^5,10. Ischaemic blood aspiration alone may remedy the ischaemic priapism in up to-one third of cases; therefore, it should always be the first approach before administering phenylephrine because of the impairment of smooth muscle contraction by the development of an ischaemic microenvironment^11,12. Phenylephrine injection should be performed with continuous monitoring of blood pressure, especially in patients with pre-existing hypertension, as it may potentially precipitate a cardiovascular event.

Priapism episodes lasting more than 24 to 36 hours are less likely to respond to corporal blood aspiration and instillation of α-adrenergic agonists because of the presence of irreversible smooth muscle damage. However, it is essential to perform the above manoeuvres in all patients presenting with ischaemic priapism irrespective of the time of presentation. This is because the absolute time point at which permanent smooth muscle damage occurs is not clear, although hypoxia, glucopenia, and acidosis usually develop within six hours of the commencement of ischaemic priapism.

If ischaemic priapism is reversed within 24 hours, there is usually a recovery of erectile function in approximately 50% of patients, while a duration of more than 36 hours of the priapism episode is invariably associated with a degree of corporal fibrosis and erectile dysfunction¹³. The outcomes in the time period of 24 to 36 hours are variable and governed by the degree of ischaemia and the amount of reversible smooth muscle function if penile detumescence is achieved.

Both in vitro and in vivo studies have shown that hypoxia and glucopenia may function as independent factors causing cavernosal smooth muscle dysfunction and that irreversible histopathological alterations are caused by the combination of acidosis, glucopenia, and hypoxia that last for more than four hours⁵.

Histologically, as priapism continues, the corpus cavernosum undergoes progressive changes. In cases where priapism is of a short duration (less than 12 hours), the tissue consists of minor endothelial defects with occasional lymphocytic infiltration but the smooth muscle cells remain intact. It is only after 12 to 14 hours of ischaemic priapism that the trabecular smooth muscle cells show the beginning of focal cytoplasmic transformation, with the perinuclear cytoplasm, endoplasmic reticulum, ribosomes, and Golgi apparatus exhibiting an increase in size. In the time period of 24 to 48 hours, there is widespread endothelial destruction and exposure of the basement membrane. In addition to this, the smooth muscle cells undergo transformation as well as necrosis. Persistent blood stasis for over two days is related to the infiltration of the trabecular tissue with inflammatory cells and the smooth muscle cells undergoing necrosis or phenotypically changing into fibroblast-like cells¹⁴.

At the molecular level, decreases in phosphodiesterase type 5 (PDE-5) and RhoA/Rho kinase, increased levels of adenosine, and the presence of acidosis, glucopenia, and hypoxia are all likely to contribute to cavernosal smooth muscle dysfunction¹⁵.

ii) Management of priapism using surgical shunts

For those patients in whom corporal blood aspiration and instillation of α-adrenergic agonists are ineffective, surgical shunts are frequently required. The concept of surgically created shunts is to allow the drainage of ischaemic blood from the corpora cavernosa to either the corpus spongiosum or the saphenous vein, although the older shunts (proximal) described are no longer routinely used.

Minimally invasive distal percutaneous shunts such as The Winter and Ebbehoj can be used. The Winter shunt involves the insertion of a large bore needle or a cannula into the glans penis and the distal end of the corpus cavernosum. The Ebbehoj procedure entails a stab incision with a No. 10 scalpel blade into the corpora cavernosa through the glans penis. When percutaneous shunt surgery is unsuccessful, an Al-Ghorab shunt, which is an open corporoglanular shunt involving the excision of a segment of tunica albuginea from the tip of the corpus cavernosum, has been described.

The most recent shunt techniques aim to allow better communication between the distal corpora and glans penis. Described as a T-shunt, the technique involves the insertion of a No. 10 blade through the glans penis into the ipsilateral corpus cavernosum followed by a 90-degree rotation laterally away from the urethra to create a fistula¹⁶. If detumescence is not achieved, the procedure can be redone on the contralateral side (TT shunt technique). In cases where TT shunt has failed, a tunnelling manoeuvre may be attempted; this technique allows the ischaemic blood to be drained from the proximal aspect of the corpora cavernosa. This procedure, also known as the corporal snake manoeuvre, uses a 22 French urethral sound through the previous T-shunt^17,18.

Although early reports demonstrate the safety of a distal shunt coupled with the tunnelling manoeuvre, with resolution achieved in nearly all cases¹⁷, a recent series of 45 patients has shown that the success of the T shunt and tunnelling manoeuvre is dependent on the duration of the priapism¹⁹.

iii) Implantation of a penile prosthesis in acute priapism

If aspiration of ischaemic blood from the corpora cavernosa followed by repeated instillations of α-adrenergic agonists does not induce resolution of the priapism episode, irreversible damage to the smooth muscle is likely to have already occurred. Consequently, efforts to re-oxygenate the corpora with shunt surgery, even though it could resolve the painful priapism episode, will not prevent the onset of refractory erectile dysfunction in the long term, which will ultimately require the implantation of a penile prosthesis²⁰.

Penile prosthesis implantation, which has been the traditional treatment in patients who have developed erectile dysfunction following a prolonged priapism, has now been advocated as an alternative initial management strategy for prolonged ischaemic priapism^21,22.

In fact, urgent penile prosthesis implantation in cases of refractory priapism and cavernosal smooth muscle necrosis reduces the painful priapism occurrence, assures the necessary long-term rigidity required for sexual intercourse, and stops penile shortening and curvature secondary to the development of corporal fibrosis, which would otherwise be unavoidable.

Potential overtreatment of patients with no evidence of necrosis in the cavernosal smooth muscle is one of the risks associated with this approach, and therefore the correct timing of surgery is paramount. Although after 24 to 48 hours of a persistent erection irreversible smooth muscle necrosis has already developed, the use of additional imaging modalities and cavernosal smooth muscle biopsies aid clinicians in the decision of whether or not an early penile prosthesis is suitable or whether a more conservative approach can be used with the hope that there is cavernosal smooth muscle recovery in the long term. In a series of 23 patients, in which the radiological findings have been correlated with biopsies from the corpus cavernosum, gadolinium-enhanced high-definition magnetic resonance imaging (MRI) of the penis demonstrated a sensitivity of 100% when utilised in the detection of necrosis of the cavernosal smooth muscle²³. Therefore, this imaging modality may be extremely useful in supporting the clinical decision to proceed with acute penile prosthesis implantation rather than adopt a conservative policy. Therefore, MRI imaging with diagnostic biopsies aid decision making in these difficult cases.

Implantation of a malleable prosthesis is easier in the early period (first two weeks) of refractory ischaemic priapism, as corporal fibrosis has not been completely established. At a later date, the malleable prosthesis can be exchanged for an inflatable prosthesis, this also allows upsizing of the cylinders²⁴.

In challenging cases where the corpora are severely fibrosed, simultaneous penile prosthesis implantation and corporal reconstruction has been shown to offer satisfactory results. However, patients must be fully counselled and made aware that complication rates are significantly higher in these complex cases because of the severe fibrosis²⁵. Several other techniques have been described (e.g. multiple corporal incisions, corporal excavation, and downsized prosthesis) in order to minimize complications and improve surgical outcomes²⁶.