All cases of NiP from a single tertiary andrology centre were retrospectively identified from electronic hospital records between January 2007 and December 2021. Diagnosis of NiP was made following a relevant clinical history of preceding trauma and with a corporal blood gas showing bright red blood and raised oxygen tension (pO2 > 90 mm Hg, pCO2 < 40 mm Hg, pH 7.40) 15. CDUS was conducted by a uroradiologist within 48 hours of presentation with diagnosis of NiP made by presence of intracorporal AVF(s) and characteristic low resistance waveforms (low resistive index (RI), high peak systolic (PSV) typically >50cm/sec and end diastolic velocities (EDV) typically >20cm/sec and mean velocity (MV) >6.5cm/sec in the affected cavernosal artery(s)16,17. Patients were counseled on the treatment options, and a conservative approach with compression and ice pack application is attempted for up to two weeks. If unsuccessful, catheter angiography and embolization was performed within one month of initial presentation. Inclusion and exclusion criteria are specified in table 1.
CDUS was carried out with a 12-18 MHz linear probe on an Acuson 500 (Siemens, Germany). Waveforms were measured in the cavernosal arteries at the most proximal point in the crura; both left and right (and any accessory cavernosal arteries) were sampled. Measurement was carried out over at least three cardiac cycles according to good sonographic practice and in all cases, angle correction was applied18. In cases of unilateral AVF, the trace from the cavernosal artery in the affected side was used. In cases of bilateral AVFs, the side with the highest velocity value was used for analysis.
CDUS protocol and analysis:
CDUS waveforms were analysed and Peak systolic velocity (PSV), End Diastolic Velocity (EDV) and Resistive Index (RI) measured from the velocity trace and Mean Velocity (MV) was calculated. MV is calculated by integrating the velocity trace with respect to time and describes the velocity of blood in an artery throughout the cardiac cycle, and the authors have published prior data to show how MV can help differentiate between ischemic and non-ischemic priapism even when PSV is raised17. MV was calculated by transferring waveforms to a 1mm square digital grid and calculated using the equation below:
MV = (Integral above the baseline - integral below the baseline in mm2)/
(length cardiac cycle in mm) x (number of mm squares for a height of 100cm/s)
Angiography technique:
Informed written consent was gained from all patients. Angiography was carried out under local anaesthetic via unilateral common femoral or radial artery access. Subselective catheterisation of the anterior trunk of the internal iliac artery was performed with 2.7fr microcatheter (Progreat®, Terumo, Japan). Angiography was performed at the distal Internal Pudendal Artery (IPA) and the vessels supplying the AVF identified. Nitroglycerin aliquots of 100-200micrograms were used to prevent arterial spasm. Embolization was performed until no further contrast blush was observed and thrombosis of the AVF was observed on intraoperative ultrasound.
Follow-up:
Clinical success was defined as a flaccid penis at rest. Examination and follow-up unstimulated CDUS was carried out at 1 week, 1 month, and 4-24 months after return to flaccid state. If recurrent AVF was confirmed on follow-up CDUS , further embolization was performed. Current guidelines on priapism do not explicitly define a follow up period but in this institution’s experience such patients benefit from a close regular follow up with interventional radiology and andrology for at least 12 months after NiP occurred.
A resting flaccid penis CDUS trace was considered abnormal when a low resistance waveform pattern was detected, defined by: EDV above 5cm/sec, MV above 4cm/sec in the affected cavernosal artery19. EF was tested by 30 point International Index of Erectile function domain A questions (IIEF-EF) and patient subjective reports of EF in andrology clinic. ED was diagnosed if a patient scored less or equal to 25 on the EF domain A of the IIEF-EF questionnaire20.
Statistical tests:
Descriptive statistics were reported and data were tested for normal distribution using quantile-quantileplots.
Non-parametric tests were used to test the relationship between specific clinical, technical and outcome variables: age of patient, duration of priapism, number of AVFs, number of treatment episodes required, and ultrasound variables of PSV, EDV, RI and MV. A P value less than 5% was considered statistically significant. SPSS® statistical package version 22 (IBM Corp, Armonk, NY, USA) was used for statistical analysis.
Ethical consideration:
After discussion with the local research department, formal ethical committee approval of this retrospective audit of anonymized patient data was not considered necessary.
Conflicts of Interest:
None of the authors have any conflicts of interest to declare