How can I differentiate between ischemic and non-ischemic priapism during a clinical evaluation?

To differentiate ischemic from non-ischemic priapism during clinical evaluation, key features include the duration, pain, rigidity, and diagnostic tests.

• Ischemic priapism typically presents as a painful, rigid erection lasting more than 4 hours, often with a history of sudden onset and no recent sexual stimulation. The corpora cavernosa are fully rigid, and the glans penis is usually soft or less rigid. This condition is a urological emergency due to the risk of tissue ischemia and necrosis ¹.
• Non-ischemic priapism usually follows trauma and presents as a painless or less painful, partially rigid erection. The erection is often less rigid than ischemic priapism and may have a history of perineal or penile trauma. It is not an emergency as it involves unregulated arterial inflow without ischemia ¹.
• Diagnostic evaluation includes corporal blood gas analysis obtained via aspiration. In ischemic priapism, blood is dark, hypoxic, acidotic, and hypercarbic (low pO2, high pCO2, low pH), reflecting trapped deoxygenated blood. In non-ischemic priapism, blood gas values are similar to arterial blood (normal pO2, pCO2, and pH) due to unregulated arterial inflow (Bivalacqua et al., 2022).
• Additional investigations such as colour Doppler ultrasound can help differentiate by showing little or no blood flow in ischemic priapism versus high flow in non-ischemic priapism (Bivalacqua et al., 2022).

Summary: Painful, rigid, prolonged erection with hypoxic corporal blood gas indicates ischemic priapism requiring urgent intervention, whereas painless, less rigid erection with normal arterial blood gas and often post-trauma suggests non-ischemic priapism, which is less urgent ¹ (Bivalacqua et al., 2022).