Page 111 - Remedial Andrology

Aspiration of blood from the corpora cavernosa usually reveals dark ischaemic blood (Table 33) (LE: 2b). Blood
gas analysis is essential to differentiate between ischaemic and non-ischaemic priapism (Table 34). Further
laboratory testing should be directed by the history, clinical examination and laboratory findings. These may
include specific tests (e.g., haemoglobin electrophoresis) for diagnosis of SCD or other haemoglobinopathies.

9.1.2.4 Penile imaging
Colour Doppler US of the penis and perineum is recommended after clinical diagnosis and can differentiate
ischaemic from non-ischaemic priapism as an alternative or adjunct to blood gas analysis [1245, 1272-1274]
(LE: 2b). Colour Doppler US can identify the presence of the fistula as a blush with 100% sensitivity and 73%
specificity [1274].

Ultrasound scanning of the penis should be performed before corporal blood aspiration in ischaemic
priapism to prevent aberrant blood flow which can mimic a non-ischaemic picture or reperfusion picture after
intervention for low-flow priapism [1275].

Following Colour Doppler US there will be an absence of blood flow in the cavernosal arteries in ischaemic
priapism. Return of the cavernous artery waveform indicates successful detumescence [1243, 1274, 1276].
After aspiration, reactive hyperaemia may develop with a high arterial flow proximally that may be misleading
and result in the diagnosis of non-ischaemic priapism.

Penile MRI can be used in the diagnostic evaluation of priapism and may be helpful in selected cases of
ischaemic priapism to assess the viability of the corpora cavernosa and the presence of penile fibrosis. In
particular, in cases of refractory priapism or delayed presentation (> 48 hours), smooth muscle viability can
be indirectly assessed. In a prospective study of 38 patients with ischaemic priapism, the sensitivity of MRI in
predicting non-viable smooth muscle was 100%, when correlated with corpus cavernosum biopsies [1275]. In
this study, all patients with viable smooth muscle on MRI maintained erectile function on clinical follow-up with
the non-viable group being offered an early prosthesis.

Table 34: Key findings in priapism (adapted from Broderick et al. [1243])

Ischaemic priapism Non-ischaemic priapism
Corpora cavernosa fully rigid Typically Seldom
Penile pain Typically Seldom
Abnormal penile blood gas Typically Seldom
Haematological abnormalities Sometimes Seldom
Recent intracavernosal injection Sometimes Sometimes
Perineal trauma Seldom Typically

Table 35: Typical blood gas values (adapted from Broderick et al. [1243])

Source pO (mmHg) pCO (mmHg) pH
2
2
Normal arterial blood (room air) > 90 < 40 7.40
(similar values are found in arterial priapism)
Normal mixed venous blood (room air) 40 50 7.35
Ischaemic priapism (first corporal aspirate) < 30 > 60 < 7.25

9.1.2.5 Recommendations for the diagnosis of ischaemic priapism

Recommendations Strength rating
Take a comprehensive history to establish the diagnosis which can help to determine the Strong
priapism subtype.
Include a physical examination of the genitalia, perineum and abdomen in the diagnostic Strong
evaluation.
For laboratory testing, include complete blood count, white blood cell count with blood cell Strong
differential, platelet count and coagulation profile. Direct further laboratory testing should
be performed depending upon history and clinical and laboratory findings. In children with
priapism, perform a complete evaluation of all possible causes.

110 SEXUAL AND REPRODUCTIVE HEALTH - MARCH 2021