Clinical History
A 42-year-old male patient presented with a four-day history of painless priapism, two weeks after a penile trauma with urethral bleeding. There was no previous urogenital surgery nor any other significant medical history. Blood tests revealed a decreased haematocrit level (19.2%) and anaemia (haemoglobin, 63 g/L), without leukocytosis.
Imaging Findings
Sonography of the penis showed a polyloculated heterogeneous lesion in the right corpus cavernosum with a largest hypoechoic locule of 28 mm (Fig 1a, b). Colour-coded and spectral Doppler sonograms showed arterial flow within the cavity with a "to and thro" pattern ("Yin and Yang sign") and a dilated feeding artery (Fig 1c, d). The tunica albuginea was intact (Fig 1a). The left corpus cavernosum, the corpus spongiosum and the testicles were unremarkable. After unsuccessful conservative treatment by compression over several days, digital substraction arteriography was performed showing a cavernous pseudoaneurysm with direct arteriovenous shunting (Fig 2a, b, c). Successful Gelfoam® (absorbable gelatin sponge) embolization was performed in the same session (Fig 2d).
Discussion
Priapism is an uncommon medical condition defined as a pathologically prolonged erection of the penis [1, 2]. There are two types of priapism: low-flow and high-flow priapism.
Low-flow priapism, also known as ischaemic priapism, is the more frequent type in which venous outflow of the corpora cavernosa is obstructed, leading to a decreased or absent blood flow in the corpora cavernosa with rigidity and pain. Low-flow priapism is a medical emergency carrying a risk of permanent erectile dysfunction and rarely penile gangrene [2]. Causes of low-flow priapism include haematologic disorders such as sickle cell anaemia and leukaemia, as well as several medications [1, 2].
High-flow priapism, also named nonischaemic priapism, is the subtype that is illustrated in our patient. It usually occurs after penile or perineal trauma causing laceration of the cavernosal artery. Secondary helical arteries lose their regulatory function and arterial blood is bypassed directly from the cavernosal artery into the corpus cavernosum's sinusoidal spaces, frequently in association with the formation of a pseudoaneurym [1, 3, 4]. The venous outflow is preserved with a much lower risk of ischaemia compared to low-flow priapism. In high-flow priapism, the erection is typically painless and the diagnosis may be delayed.
Physical examination is unable to differentiate between the two types of priapism. Cavernous blood gas analysis and colour triplex sonography are essential in diagnostic workup. Blood gas analysis reveals hypoxemia and hypercapnia in the low-flow type, whereas well-oxygenated arterial blood is obtained in high-flow priapism. Colour triplex sonography may show a decreased or absent blood flow in low-flow priapism and a high normal or high and unregulated flow pattern in high-flow priapism, associated with a cavernous arteriovenous fistula or pseudoaneurysm [1, 4].
Treatment of low-flow (ischaemic) and high-flow (nonischaemic) priapism is largely different. In high-flow priapism, clinical surveillance is considered as a first option. Mechanical compression and supportive medications may be considered. In the case of delayed resolution, superselective embolization of the damaged cavernosal artery is indicated for closure of the arteriovenous fistula and/or pseudoaneurym. Permanent or nonpermanent (absorbable) substances are available. Permanently occlusive substances allow for a higher precision in selective deployment but are associated with a higher risk of erectile dysfunction [4].
Differential Diagnosis List
Traumatic pseudoaneurysm of the right cavernous artery with high-flow priapism
Intracavernosal haematoma
Penile fracture with disruption of the tunica albuginea
Low-flow priapism
Final Diagnosis
Traumatic pseudoaneurysm of the right cavernous artery with high-flow priapism
