If you have an erection lasting more than four hours, you need emergency care. The emergency room doctor will determine whether you have ischemic priapism or nonischemic priapism. This is necessary because the treatment for each is different, and treatment for ischemic priapism needs to be done as soon as possible.

Medical history and exam

To determine what type of priapism you have, your doctor will ask questions and examine your genitals, abdomen, groin and perineum. He or she might be able to determine what type of priapism you have based on whether you're experiencing pain and the rigidity of the penis. This exam might also reveal the presence of a tumor or signs of trauma.

Diagnosis tests

Diagnostic tests might be needed to determine what type of priapism you have. Additional tests might identify the cause of priapism. In an emergency room setting, your treatment will likely begin before all test results are received. Diagnostic tests can include:

  • Blood gas measurement. In this test, a tiny needle is inserted into your penis to remove a sample of blood. If the blood is black — deprived of oxygen — the condition is most likely ischemic priapism. If it's bright red, the priapism is more likely nonischemic. A lab test measuring the amounts of certain gases in the blood can confirm the type of priapism.
  • Blood tests. Your blood can be tested to measure the number of red blood cells and platelets present. Results might show evidence of diseases, such as sickle cell anemia, other blood disorders or certain cancers.
  • Ultrasound. You might have Doppler ultrasonography, a noninvasive test that can be used to estimate your blood flow through blood vessels by bouncing high-frequency sound waves (ultrasound) off circulating red blood cells. This test can be used to measure blood flow within your penis that would suggest ischemic or nonischemic priapism. The exam might also reveal an injury or abnormality that might be an underlying cause.
  • Toxicology test. Your doctor might order a urine test to screen for drugs that might be the cause of priapism.