West African Journal of Radiology

ORIGINAL ARTICLE
Year
: 2019  |  Volume : 26  |  Issue : 1  |  Page : 9--14

Cavernosal artery peak systolic velocity among normal adults in Abuja, Nigeria: A Baseline parameter for sonographic diagnosis of vasculogenic erectile dysfunction


Joshua Oluwafemi Aiyekomogbon1, Oseremen I Aisuodionoe-Shadrach2,  
1 Department of Radiology, Federal Medical Centre, University of Abuja, Abuja, Nigeria
2 Division of Urology, Department of Surgery, University of Abuja Teaching Hospital, University of Abuja, Abuja, Nigeria

Correspondence Address:
Dr. Joshua Oluwafemi Aiyekomogbon
Department of Radiology, Federal Medical Centre, University of Abuja, Abuja
Nigeria

Abstract

Background: Erectile dysfunction is consistent inability to achieve and maintain erection of sufficient rigidity for satisfactory sexual performance. It is well known that the hemodynamic function of the penis correlates well with the peak systolic velocity (PSV) of the cavernosal artery (CA) which is the most reliable, sensitive, and objective parameter used in evaluating the state of the erectile tissues of the penis. This study was aimed at establishing the normal CA PSV in this environment, as it may differ from the values among Americans, Caucasians, and Asians. Materials and Methods: The study was conducted between July 2015 and January 2017, at the Department of Radiology, Federal Medical Centre, Abuja. Twenty-nine consecutive patients referred by the urologist to the radiology department of the aforementioned institution for penile ultrasound were evaluated using triplex Doppler sonography with high-frequency linear array transducer. The penile scan was done before and after intracavernosal injection of 10–20 μg prostaglandin E1. The waveforms of CAs were obtained alternately using the angle of inclination ≤60°, and the PSV of the CA was documented at 5-min interval, from 5 to 40 min. Results: PSV of CA varied between 26 and 104.4 cm/s (mean: 46.72 ± 16.21) among the entire research participants. No significant discrepancy was noted between PSV of the right and left cavernosal arteries. The PSV had a strong positive relationship with age (P = 0.002), with the highest values found among those ≤30 years. Conclusion: The mean PSV of cavernosal arteries established in this study is not significantly different from the values obtained among Americans, Caucasians, and Asians, indicating that racial difference has no effect on this important sonographic variable.



How to cite this article:
Aiyekomogbon JO, Aisuodionoe-Shadrach OI. Cavernosal artery peak systolic velocity among normal adults in Abuja, Nigeria: A Baseline parameter for sonographic diagnosis of vasculogenic erectile dysfunction.West Afr J Radiol 2019;26:9-14


How to cite this URL:
Aiyekomogbon JO, Aisuodionoe-Shadrach OI. Cavernosal artery peak systolic velocity among normal adults in Abuja, Nigeria: A Baseline parameter for sonographic diagnosis of vasculogenic erectile dysfunction. West Afr J Radiol [serial online] 2019 [cited 2019 Mar 23 ];26:9-14
Available from: http://www.wajradiology.org/text.asp?2019/26/1/9/248952


Full Text



 Introduction



Erectile dysfunction (ED) is defined as a consistent inability to achieve and maintain erection of sufficient rigidity for satisfactory sexual performance.[1],[2] A complex mechanism is required to attain penile erection, and it involves synchronous and coordinated interaction of nervous, arterial, venous, and sinusoidal systems. A disruption of any of these components usually results in ED.[2]

There are three corporal bodies in the penis; two dorsally placed corpora cavernosa (CC) and a single ventrally placed corpus spongiosum (CS), which contains the urethra [Figure 1]. The three are enclosed in a bulk fascia, and the two CC are enclosed by tunica albuginea. The two CC are separated by a septum which has fenestrations that allow communication between the corpora bodies. The arterial supply of the penis is from the internal pudendal arteries (IPA), which are anterior branches of the internal iliac arteries.[3] Each IPA gives off the penile artery proper which branches into a cavernosal artery (CA) and a dorsal artery (DA) at the base of the penis. The CA primarily supplies the CC, while DA supplies the skin and the glans penis. The venous drainage of the CC is by emissary veins, which drain into the dorsal, crural, and cavernosal veins.[3],[4]{Figure 1}

When the penis is flaccid, there is a high resistance of arterial blood flow into it.[4],[5] Erection starts when an autonomic neurogenic impulse relaxes the cavernosal arterioles and sinusoidal spaces, resulting in increased arterial inflow to the penis as cavernous arteries dilate. This is accompanied by relaxation of the smooth muscle of the CC with expansion and elongation of the cavernous sinusoids as they fill with blood. The venules and emissary veins are compressed against the taut tunica albuginea which ultimately decreases, stops, and even reverses the venous flow.[5] This veno-occlusive mechanism maintains sinusoidal distension and rigid erection. A defect in these mechanisms leads to vasculogenic ED.[5] In the flaccid phase, monophasic waveforms are recognized in the CA with a low-velocity and high-resistance flow [Figure 2]. After the onset of erection, there is increased systole and diastole, corresponding to the beginning of the filling phase. When the intracavernosal pressure (ICP) begins to rise, a dicrotic notch appears at the end of systole, and progressively decreased diastole is observed. As the ICP equals the systemic diastolic pressure, the end-diastolic velocity disappears. Diastole is later reversed due to the increased ICP above it, reflecting the full-erection phase [Figure 3], [Figure 4], [Figure 5], [Figure 6].[6]{Figure 2}{Figure 3}{Figure 4}{Figure 5}{Figure 6}

Following intracavernosal injection (ICI) of active pharmacologic agents such as prostaglandin E1 (PGE1) or papaverine, a peak systolic velocity (PSV) ≥25 cm/s was said to be normal.[1],[2] There may be racial variations, and existing values in the literatures are values obtained among Americans, Caucasians, and Asians.[1],[2],[3],[4],[5],[6] These may differ from the values among Africans; hence, the need to establish a normal value in this environment. Establishing a normal value of the PSV of the CA is also imperative as it is the basis for diagnosing venogenic and arteriogenic erectile dysfunctions, as the treatment options for each of these entities differ.

 Materials and Methods



This study was conducted within 18 months spanning from July 2015 to January 2017, at the Department of Radiology, Federal Medical Centre, Abuja, Nigeria. Out of the patients referred to the Radiology Department for penile Doppler ultrasound (PDU), on the basis of clinical suspicion of ED, twenty-nine of them had normal response to PGE1 stimulation with PSV ≥25 cm/s which connotes normalcy. These twenty-nine normal patients were then enrolled into the study, using triplex Doppler sonography. Cigarette smoking was discontinued, for smokers among the cohort 72 h before the study as smoking causes penile vasospasm and increased sympathetic nervous system tone thus affecting penile erection.[7] The technique of the procedure was explained in detail to the participants at recruitment and before the examination on the booked date. A proper drug history (antihypertensive and antiepileptic) and cardiac status were also inquired before the study. Patients with sickle cell disease, uncontrolled diabetes, and systemic hypertension were excluded from the study as these diseases are known risk factors for arteriogenic ED.[8] After obtaining a signed informed consent, they were evaluated with color Doppler ultrasound machine (Mindray DC 7 2014, China) using high-frequency wideband (5.0–12.5 MHz) linear array transducer in a quiet and comfortable room to ensure privacy and patients' cooperation. The study was performed with patients in the supine position, and penis in normal anatomical position, lying on the anterior abdominal wall. Following application of coupling gel to the ventral surface of the penis, transverse and longitudinal scan of the penis was done before and after injection of PGE1. Preinjection assessment involved panoramic assessment of the echo pattern of the penis in flaccid state for the presence of plaques, fibrosis, or tunica albuginea defect/fracture. The spectral waveform with PSV measurement was also documented [Figure 1] and [Figure 2].

Under aseptic technique, 10–20 μg of PGE1 was injected to one of the CCs laterally at the distal two-third of the penis with a 30G needle. The variation in the doses of PGE1 was based on the patient's age; smaller doses were used for the young and higher doses for the elderly.[1]

Owing to the variation in the PSV of the CA at different locations across the penile shaft, PSV being higher proximally, CA was consistently interrogated for spectral waveform assessment and PSV measurements at the junction of the proximal third and distal two-third of the penile shaft.[1],[3] When visualization of the CA was optimal, the waveforms were obtained alternately using an angle of inclination ≤60°. Immediately after ICI, the spectral waveform and peak systolic velocities (PSV) of the cavernosal arteries were documented at 5-min interval, from 5 to 40 min, as shown in [Figure 3], [Figure 4], [Figure 5], [Figure 6]. The PSV of CA was determined electronically with the software package of the ultrasound machine.

The patients were kept in the departmental observation room for 3 h after the procedure to check for the possibility of complication such as priapism, and the urologist was informed of that possibility, but none had this complication. Furthermore, none of the patients had hematoma at the injection site, and no ecchymosis was observed in any of them.

Ethical consideration

Approval for the study was obtained from the Ethical and Research Committee of Federal Medical Centre, Abuja. Anonymity was maintained on all the information obtained from the patients, and the patients had the choice to deny consent or opt out of the study at any stage without necessarily affecting the quality of care obtained in the hospital.

Data analysis

The results were reported as mean ± standard deviation (SD). The collected data were analyzed using Statistical Package for Social Science (IBM) version 23, Chicago, IL, USA. Analyses tests used in this study were independent samples t-test, paired samples t-test, ANOVA, and Pearson's correlation. The paired samples t-test was used to compare data obtained from the right and left cavernosal arteries, while ANOVA was used to evaluate the differences between age groups, and the Pearson correlation was used to evaluate the correlation between numeric variables. All tests of significance were two-tailed, and P < 0.05 was considered statistically significant.

 Results



Twenty-nine patients used for this study ranged between 30 and 65 years (mean age, 41.81 ± 7.64 years). One was in his third decade; two were in their fourth decade; ten in fifth decade; thirteen in sixth decade; and three in seventh decade [Table 1]. Based on previous research works, CA PSV ≥25 cm/s were considered normal and that formed the basis of normalcy in our study.[1],[2] The mean PSV of CA on the right and left sides, respectively, was 47.32 ± 17.58 cm/s and 46.11 ± 15.00 cm/s. Paired samples correlation and paired samples test showed no significant differences between the PSV of the right and left CA, as shown in [Table 2] (P = 0.436). Hence, the PSV of the right and left cavernosal arteries was analyzed together.{Table 1}{Table 2}

Following ICI of PGE1, PSV varied between 35.4 cm/s and 72.2 cm/s among the participants (mean: 46.7 ± 16.2); between 35.4 cm/s and 68.2 cm/s on the right (mean: 47.3 ± 17.6); and between 35.4 cm/s and 76.1 cm/s on the left (mean: 46.1 ± 15.0) [Table 1]. The PSV of the participants had a strong positive relationship with age, P = 0.002 [Table 3]. The graphical representation of the relationship between age and PSV of the entire participants is shown in [Figure 7]. The highest CA PSV was found in those ≤30 years.{Table 3}{Figure 7}

None of the patients had priapism following ICI of PGE1. The longest duration of erection was 2 h, found in one patient who later reverted back to flaccid state at home. There were no anatomical penile arterial variants seen among the research participants.

 Discussion



Grayscale and colour Doppler sonographic penile evaluations are indicated in all cases of ED to establish the diagnosis of vasculogenic ED or ED of morphological origin such as penile fracture or Peyronie's disease.[1],[2],[3],[4] This study was aimed at using triplex Doppler ultrasound technique to establish the normal cavernosal arteries PSV in our environment which may stand as a baseline parameter upon which the diagnosis of vasculogenic ED can be made. From previous studies, PSV of CA <25 cm/s post-ICI of active pharmacologic agent(s) connote arteriogenic ED, while persistent end-diastolic flow >5 cm/s of CA post-ICI and persistent dorsal vein flow are diagnostic of venogenic ED.[1],[5],[8],[9],[10],[11],[12]

PGE1 (Alprostadil), a metabolite of arachidonic acid, a potent smooth muscle relaxant, and a vasodilator with an α-2 adrenergic blocking effect, has the potential of reducing sympathetic overtone in patients with psychogenic erectile dysfunction. This drug was used in the index study because of its efficacy as outlined above and low priapism rates when compared with papaverine.[13] It produces penile erection without the benefit of psychic, or tactile stimuli, and therefore, provides direct test of end-organ integrity which will ultimately offer an etiologic-specific therapy.[13] A modern noninvasive method, oral sildenafil citrate (Viagra) has been used, for PDU evaluation of erectile dysfunction, and the results with this were not statistically different from PGE1 and patients also found this convenient.[14]

Following the injection of PGE1 and / or other vasoactive pharmacologic agents, there is increase arterial flow to the penis to about 25–60 times that of flaccid state during the period of tumescence. At full rigidity, an increase in penile length of 7.5 cm usually requires the entrapment of 80–115 ml of blood. As the penile volume increases to near maximum, the arterial influx declines to keep the penis in the rigid state.[14] The peak velocity at which this occurs is the normal value; this study was aimed at establishing in our centre.

The mean PSV of cavernosal arteries of the participants was 46.72 (SD ± 16.21), with a range between 30.5 and 62.9 cm/s. A value of 30.5 cm/s was, therefore, considered as the lower limit of normal in this study. Golijanin et al.,[1] in the United States of America, found a value of 30–40 cm/s as the normal value of PSV of CA after ICI of vasoactive agent. The findings of Jung et al.[6] in Seoul, Korea also indicated a PSV of >35 cm/s as normal. Barozzi et al.[15] in Italy showed a similar outcome with ours which further affirms that racial differences have no effect on the dynamics of penile vascular flow during full erection. Ghafoori et al.[16] working in Tehran, Iran, with 60 normal patients undergoing Doppler study of the penis found the mean PSV after injection of 60 mg of papaverine to be 47 ± 9.9 cm/s and 46.7 ± 10.7 cm/s on the right and left sides, respectively, when half of the dose was injected separately in each corpus cavernosum. When the entire dose was injected in the right corpus cavernosum, PSV was 47.7 cm/s ± 10.8 and 40.3 ± 9.2 on the right and left sides, respectively, and following the left side injection, PSV was 44.4 ± 7.1 and 51.4± −7.1 cm/s on the right and left sides, respectively. From this study, unilateral injection resulted in discrepancies between the PSV of the right and left CA in favour of side of injection, as against bilateral injection. This observation contrasts previous studies.[9] Nevertheless, in unilateral injection, the observed difference between the PSV of right and left CA was <10 cm/s which is not significant on account of previous researches;[1] hence, the reason for unilateral injection in the index study.

A positive correlation was established between patients' age and PSV of CA in our study. The highest PSV of CA was found in those ≤30 years, and this group had a mean PSV of 72.2 cm/s. This has further affirm previous submissions of other authors which revealed that ED is seen commonly in those above 40 years of age.[2],[5],[9],[10] The advocacy, therefore, is that every patient with ED irrespective of age should have penile sonography done before instituting any form of management as it is noninvasive, nonionizing, and diagnostic. Establishing a specific cause based on the normal range established by this study and those of others is important, particularly in young men, because of the frequency of correctable vascular abnormalities.

None of our patients had penile arterial variants such as communications among the cavernosal, dorsal, and spongiosal arteries, duplication of CA or cross-communication between the right and left cavernosal arteries. Shunt vessels which course from the CS into the corpus cavernosum is another variant, and rarely, collaterals from the urethral arteries may also be seen.[4],[17] These were particularly sought for as they would have been excluded because they are known to affect the results of duplex sonographic evaluation.

 Conclusion



The mean PSV of cavernosal arteries established in this study is not significantly different from the values obtained among Americans, Caucasians, and Asians, indicating that racial difference may not affect this Doppler parameter. A similar study in other geopolitical zones of the country is recommended as that will authenticate this observation and the assertion made.

Limitations of the study

The small cohort of patients used in this study is a major limitation. This was largely due to general apathy to enrolment into this study. If the study was extended beyond the 18 months of the present study perhaps more patients may have been recruited. A study with larger sample size will be necessary to validate the findings among Nigerians or even Africans. Furthermore, “stopping rules” were not utilized during data collection, and clinical assessment of the participants with the validated and multidimensional international index of erectile function 15 scores was not employed. These are major limitations of the study, and efforts shall be made to accommodate them in future studies.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

References

1Golijanin D, Singer E, Davis R, Bhatt S, Seftel A, Dogra V, et al. Doppler evaluation of erectile dysfunction - Part 1. Int J Impot Res 2007;19:37-42.
2Clifford A, Toppo JN. Role of penile color doppler in the evaluation of erectile dysfunction. Indian J Radiol Imaging 2006;16:891-6.
3Kim SH, Paick JS, Lee SE, Choi BI, Yeon KM, Han MC, et al. Doppler sonography of deep cavernosal artery of the penis: Variation of peak systolic velocity according to sampling location. J Ultrasound Med 1994;13:591-4.
4Pozniak AM, Lee TT. Doppler imaging of the penis. In: Allan P, Dubbins PA, McDicken WN, Pozniac AM, editors. In Clinical Doppler Ultrasound. 2nd ed. Philadelphia, USA: Churchill Livingstone; 2006. p. 251-66.
5Aboseif SR, Lue TF. Hemodynamics of penile erection. Urol Clin North Am 1988;15:1-7.
6Jung DC, Park SY, Lee JY. Penile doppler ultrasonography revisited. Ultrasonography 2018;37:16-24.
7Biebel MG, Burnett AL, Sadeghi-Nejad H. Male sexual function and smoking. Sex Med Rev 2016;4:366-75.
8Lue TF. Erectile dysfunction. N Engl J Med 2000;342:1802-13.
9Benson CB, Vickers MA. Sexual impotence caused by vascular disease: Diagnosis with duplex sonography. AJR Am J Roentgenol 1989;153:1149-53.
10Paushter DM. Role of duplex sonography in the evaluation of sexual impotence. AJR Am J Roentgenol 1989;153:1161-3.
11Quam JP, King BF, James EM, Lewis RW, Brakke DM, Ilstrup DM, et al. Duplex and color doppler sonographic evaluation of vasculogenic impotence. AJR Am J Roentgenol 1989;153:1141-7.
12Meuleman EJ, Bemelmans BL, van Asten WN, Doesburg WH, Skotnicki SH, Debruyne FM, et al. Assessment of penile blood flow by duplex ultrasonography in 44 men with normal erectile potency in different phases of erection. J Urol 1992;147:51-6.
13Porst H. The rationale for prostaglandin E1 in erectile failure: A survey of worldwide experience. J Urol 1996;155:802-15.
14Baçar MM, Batislam E, Altinok D, Yilmaz E, Baçar H. Sildenafil citrate for penile hemodynamic determination: An alternative to intracavernosal agents in doppler ultrasound evaluation of erectile dysfunction. Urology 2001;57:623-6.
15Barozzi L, Pavlica P, Piervitali D. Doppler color ultrasonography of the normal penis. Arch Ital Urol Androl 2000;72:366-70.
16Ghafoori M, Hoseini K, Shakiba M. Comparison of one-side and bilateral intracavernosal papaverine injection on a doppler study of the penis. Int J Impot Res 2009;21:382-6.
17Mancini M, Bartolini M, Maggi M, Innocenti P, Forti G. The presence of arterial anatomical variations can affects the result of duplex sonographic evaluation of penile vessels in impotent patients. J Urol 1996;155:1919-23.