An update on mechanisms and treatment options for priapism.

Priapism is an abnormal prolonged penile erection that persists in the absence of any sexual stimulation. Priapism can be subcategorized into three types: ischaemic (low-flow or veno-occlusive), non-ischaemic (high-flow or arterial) and stuttering priapism. Ischaemic priapism is the most common subtype and is associated with multiple aetiologies, most commonly haemoglobinopathies and antipsychotic medications. The mechanisms underlying stuttering priapism are complex, and involve dysregulation of the nitric oxide signalling pathway, Rho-Rho kinase pathway, adenosine, opiorphins, oxidative stress and androgens. The investigation and management of priapism involve a stepwise approach. A clinical history, examination and a blood-gas analysis from the corpus cavernosum helps to distinguish between ischaemic and non-ischaemic subtypes. Colour Doppler ultrasonography and penile MRI can be used in more complex cases, or those with a delayed presentation. Treatment involves cavernosal blood aspiration followed by instillation of an α-adrenergic receptor agonist such as phenylephrine, proceeding to penile shunt surgery (within the first 24-48 h) if the priapism persists. Insertion of a penile prosthesis is indicated when a shunting procedure or penoscrotal decompression fails, or if a patient presents with a priapism persisting longer than 36-48 h depending on the guidelines used. For non-ischaemic priapism following failed conservative treatment, selective arterial embolization of the arteriocorporal fistula can be performed. The aetiology and pathophysiology of the different priapism subtypes help to determine the management of specific patients.