Discussion

Priapism is defined as an unwanted, prolonged penile erection or clitoral swelling3 lasting for more than 6 hours, in the absence of sexual desire or stimulation.1 It is a rare complication after surgery, with only a few case reports available.3–7 Priapism is classified into high flow (non-ischaemic) and low flow (ischaemic), based on the blood flow in the penis (table 1).1

High-flow priapism results from extensive arterial inflow due to injury of the corporal bodies creating an arteriosinusoidal fistula8 between the cavernous artery and the lacunar spaces of the CC.9 This injury results from direct trauma to the penis or perineum and usually cause the erection to be semirigid and painless compared with the low-flow state. In high-flow priapism, the penis is well oxygenated with blood gas values similar to arterial blood and can be confirmed by penile colour Doppler ultrasonography.9 Initial therapy consists of watchful waiting, mechanical compression, ice packing, aspiration of the cavernous bodies and irrigation with alfa-adrenoreceptor.11 12 If spontaneous detumescence fails, arterial embolisation of the cavernosa artery or internal pudendal artery should be considered.3 Paradoxically, epidural analgesia can be the cause or treatment of this condition.13

Low-flow or veno-occlusive priapism is by far the most common form, especially in paediatric populations.9 It results from blocking venous outflow and red blood cell stasis or sludging in haematological diseases.9 Frequent causes are use of medication (eg, antipsychotics, anaesthesia and epidural analgesia), haematological diseases (most common Sickle cell disease, leukaemia) and neurological disorders in paediatric population (eg, spinal cord injury, transverse myelitis and cerebrovascular disease). Pain originates from tissue ischaemia and smooth muscle hypoxia. Histopathological changes occur initially with interstitial oedema (up to 12 hours) resulting in endothelial thrombocytic adherence (by 24 hours) and finally lead to cell necrosis with or without fibrosis and calcifications (48 hours).1 14 Prompt diagnosis and treatment of this urological emergency is imperative. Failing to do so, causes irreversible damage with fibrosis and loss of penile tissue resulting in possible erectile dysfunction and impotence.9 Treatment encompasses conservative management, such as exercise, ice and ejaculation preceding surgical intervention. Surgery is aimed at restoring arterial inflow and increasing venous outflow of the cavernosal bodies. Primarily, intervention involves intracavernosal blood aspiration and warm saline irrigation with local sympathomimetic drugs.1 Aspiration and irrigation is successful in 77% of the cases.15 If there is no improvement, then shunt therapy should be considered, which has an overall success rate of approximately 75%.16 Surgery consists of shunting the distal glans into the CC, using either a surgical blade (Ebbehoj procedure17) or a biopsy needle (Winter procedure18). If this procedure is unsuccessful, cavernosphenous19 or open proximal cavernospongiosum4 shunting should be considered.

In our case, we suggest that in this case persistent erection was secondary to low-flow stat. Moreover, we can only speculate about the factors responsible for the priapism. It was most likely caused by either general or epidural anaesthesia or by a vicious circle that was initiated by the anaesthesia and a persisting erectile state causing permanent damage to the cavernous bodies. Absence of direct trauma, pain and a full erection hinted a state of low flow. To our knowledge, the patient did not have any haematological diseases. Several case reports indicate that surgery can be a primary cause for priapism4–7; however, we regarded it as less likely, given the location of the operation field relative to normal erectile physiology. Failed conservative treatment and discontinuation of the thoracic epidural analgesia suggested another culprit. We suspect propofol (2,6-diisopropylphenol), which was used during induction and surgery, based on the clinical presentation and available literature.20–22 Unfortunately, the exact mechanism of propofol-induced and epidural analgesia priapism remains poorly understood.23 An autonomic imbalance between blockage of sympathetic or parasympathetic neuronal centres, responsible for physiological erections, underlies this pathophysiology.24 The anaesthetic effect of propofol might block the sympathetic vasoconstrictor action or enhance the parasympathetic vasodilatory action causing priapism. Propofol is also known to influence the nitric oxide-mediated smooth muscle relaxation, modulate on GABA-A and adrenal steroidogenesis which contributes to the physiology of an erection.25 26

A total of 1662 mg of propofol administered by pump was used during the surgery. Additionally, intravenous 2.765 mg remifentanyl, 60 mg ropivacaine and 15 µg sufentanil were administered via the epidural space. Postoperative epidural settings were 16 mg ropivacaine and 4 µg sufentanil hourly.

This case gave rise to staff education concerning priapism, facilitating prompt identification of this rare complication. This case outcome underscores the importance of early diagnosis in the face of preventing permanent damage. Patients may feel embarrassed and hesitant to report penile complains toward opposite gender medical professionals, and they could be afraid of stigmatisation.

We presented a case of a postoperative patient with low-flow priapism. We failed prompt identification and diagnosis, which resulted in emergency interventions with mediocre effect. Due to the delay in treatment, erectile dysfunction ensued and penis prosthesis was considered, although the patient decided against prosthesis hence the erectile dysfunction was manageable with medication.