Investigations

1st investigations to order

corpus cavernosum blood sampling

Test
Result
Test

Blood is aspirated from the corpus cavernosum.

In ischaemic priapism, blood is hypoxic and dark in colour (brown or dark red). In non-ischaemic priapism, blood is oxygenated and red.[1][4]

Result

ischaemic priapism: pO₂ <30 mmHg, pCO₂ >60 mmHg, and pH<7.25; non-ischaemic priapism: pO₂ >90 mmHg, pCO₂ <40 mmHg, and pH of 7.40

FBC and differential

Test
Result
Test

Should be ordered as initial test in all patients with priapism.[1][4]

WBC count may be raised, suggesting infection or blood dyscrasia. Anaemia and increased reticulocyte count may be present in patients with sickle cell disease.

Result

variable; may show elevated WBC; decreased platelets; decreased Hb; reticulocyte count may be elevated

Investigations to consider

colour duplex ultrasonography

Test
Result
Test

Not a first-line diagnostic test for priapism, but may be useful to differentiate between ischaemic and non-ischaemic disease in a non-acute setting.[1]

May identify a cavernous artery fistula in a patient suspected to have non-ischaemic priapism.

The study should be performed with the patient placed in lithotomy or frog leg position, to scan the perineum first and then the entire penile shaft.[2]

Result

variable; minimal or absent blood flow is seen in ischaemic priapism; in non-ischaemic priapism, blood flow is normal to high in velocity and there may be anatomical abnormalities, such as cavernous arterial fistula or pseudoaneurysm

MRI

Test
Result
Test

MRI may be considered to evaluate for corporal smooth muscle necrosis in patients with prolonged priapism being considered for penile prosthesis placement.[4] It is unlikely to have a role in the initial diagnosis of priapism.[1]

Result

variable; corporal fibrosis; smooth muscle changes

Hb-solubility testing

Test
Result
Test

In patients in whom sickle cell anaemia is suspected and whose status is unknown, a rapid diagnosis can be achieved using a sickle-solubility test.

The test detects any sickle Hb and so is positive in patients with both sickle cell trait and sickle cell disease.

Subsequent confirmation of status requires Hb electrophoresis.

Result

variable; ≥10% HbS in patients with sickle cell disease

Hb electrophoresis

Test
Result
Test

Confirms sickle cell status if unknown and initial Hb-solubility testing is positive.[1]

Result

variable; indicates the presence of sickle cell disease or trait as well as other haemoglobinopathies

medication/toxicology urine screen

Test
Result
Test

Screening for vasoactive medications, or illegal/illicit drugs, may be appropriate.[1]

Medications implicated include alpha-adrenergic receptor antagonists (prazosin, terazosin, doxazosin, tamsulosin), anti-anxiety agents (hydroxyzine), anticoagulants (heparin, warfarin), antidepressants and antipsychotics (trazodone, bupropion, fluoxetine, sertraline, lithium, clozapine, risperidone, olanzapine, chlorpromazine, thioridazine), and antihypertensives (hydralazine, guanethidine, propranolol).[1][10]

Alcohol and cocaine may predispose to ischaemic priapism.[29][30][31]

Result

positive in the setting of medication/substance intoxication

coagulation profile

Test
Result
Test

May be considered to assess for haematological abnormalities.[4]

Result

variable

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