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Priapism: a case study and review.

INTRODUCTION

Priapism is defined as a persistent erection of the penis that continues more than four hours beyond, or is unrelated to, sexual stimulation (1). The term is derived from Priapus, the Greek God of fertility. It typically involves only the corpora cavernosa and resulting in dorsal penile erection with the corpus spongiosum and glans penis remain soft and uninvolved (2). However, cases of priapism with involvement of the corpus spongiosum and sparing of the cavernosal spaces have been reported. It is relatively uncommon disorder with an incident rate of 0.5-0.9 cases per 100,000 person-years (1). Even though priapism may occur at all ages, priapism in children is extremely rare and is most commonly related to underlying conditions such as malignancy and haematological diseases (1).

Priapism is categorised to three different subtypes which are ischaemic (veno-occlusive, low flow) priapism, non-ischaemic (arterial, high flow) priapism, and stuttering (intermittent) priapism. Ischaemic priapism is the most common form of priapism which accounts for 95% of all priapism cases. It is usually painful and rigid erection, characterised by little or no cavernous blood flow resulting in abnormal (dark red) cavernous blood gases (hypoxia, hypercapnia, and acidosis) (3). Therefore, ischaemic priapism is considered a medical emergency. On the other hand, non-ischaemic priapism is caused by unregulated cavernous arterial inflow. This unregulated flow results in a persistent erection, usually neither fully rigid nor painful, and has been proposed to occur via a mechanism that involves stimulation of endothelial nitric oxide synthase by the turbulent blood flow (1). Unlike ischaemic priapism, the cavernous blood gases in non-ischaemic priapism are not hypoxic, hypercapnic, or acidotic. Lastly, stuttering priapism is described as repeated form of ischaemic priapism in which painful erections occur frequently with intervening periods of detumescence (diminution of the erection) (3). This type of priapism is uncommon and poorly understood.

CASE PRESENTATION

A forty year old Caucasian male presented to the Emergency Department (ED) at Dunedin Public Hospital with priapism. He suffers from complete paraplegia at T12 level from a motor vehicle accident in 1994. After the accident, he develops difficulty passing urine due to urethral false passage or stricture. Initially, a suprapubic catheter was installed as an ongoing treatment together with urethral dilation. The suprapubic catheter was later removed after successful self-catheterisations. He also has a history of bladder stones. Initial physical examination suggested ischaemic priapism. There was no sign of pelvic, penile, or perineal trauma. Prior to the episode, the patient took neither any drugs nor any alcoholic drinks. Blood samples were sent to the laboratory for cavernous blood gases, full blood count, and renal function tests.

The cavernous blood gases (Table 1) showed hypoxia, hypercapnia, and acidosis which confirmed the diagnosis of ischaemic priapism. All routine haematology results were within the respective reference ranges with the exception of the total white blood cell count (12.2 x [10.sup.9]/L [4.0 - 11.0 x [10.sup.9]/L]) and neutrophils (9.8 x [10.sup.9]/L [1.9 - 7.5 x [10.sup.9]/L]), which suggested the present of inflammation or infection. There was no sign of haematological abnormalities such as a haemoglobinopathy or leukaemia. In addition, renal function tests were also within the reference range limits.

Detumescence was achieved by cavernosal irrigation with 0.90% w/v saline, followed by insertion of cavernospongious shunt under general anaesthesia. The patient was discharged the following day with 1000 mg paracetamol, 500 mg amoxicillin and 125 mg clavulanic acid.

DISCUSSION

In general, priapism can be considered as an imbalance between arterial inflow and outflow which disturbs regulatory control in erectile function. The imbalance of arterial inflow and outflow may be caused by disturbances in the mechanism controlling penile detumescence and the maintenance of penile flaccidity due to excess release of contractile neurotransmitter, malfunction of the intrinsic detumescence mechanism, obstruction of draining venules, or prolonged relaxation of intracavernosal smooth muscle (4). The aetiology of priapism is mainly categorised to primary (idiopathic) and secondary to other conditions or diseases. However, it is more appropriate to discuss the aetiology of priapism according to its specific subtypes.

Ischaemic priapism can be caused by many factors as shown in Table 2. Sickle cell disease is the most common cause of ischaemic priapism. It accounts for 23% of adult cases and 63% of childhood cases (1). In patient with sickle cell disease, the prevalence of priapism is up to 3.6% in patients < 18 years old, increasing up to 42% in patients [greater than or equal to] 18 years old (1). The dysfunctional nitric oxide synthase and Rho-associated protein kinase (ROCK) signalling, and increased oxidative stress associated with NADPH oxidase mediated signalling are thought to be the mechanisms of sickle cell disease associated priapism (1). The second most common causes of ischaemic priapism are the intracavernosal injection of a vasoactive erectile agent and alcohol or drugs abuse. In contrast, nonischaemic priapism is mostly associated with antecedent trauma such as blunt perineal, pelvic, or penile trauma. In a rare case, Fabry's disease can also cause non-ischaemic priapism due to unregulated high arterial inflow (5). The causes of stuttering priapism are usually idiopathic and in rare cases, a neurological disorder. In addition, a very rare condition called partial priapism or idiopathic partial thrombosis of penis can be caused by bicycle riding, trauma, drug usage, sexual intercourse, haematological diseases and [alpha]-blockers (1). It is a subtype of priapism limited to the crura of the penis.

The differential diagnosis of priapism can be done by physical examination, laboratory testing, and/or penile imaging. Ischaemic priapism is a compartment syndrome. The corpora cavernosa are rigid and tender, but the glans penis is soft. The patient usually complains of pain. Conversely, in non-ischaemic priapism, the corpora cavernosa are tumescent (beginning to swell or erect) but not fully rigid. The physical examination usually reveals pelvic, penile, or perineal trauma. In stuttering priapism, the erection is painful and the penis is rigid as in ischaemic priapism. The duration however, is usually shorter. Between erections, the penis is usually normal, but fibrosis can be found in some cases (1). The key findings in priapism is summarised in Table 3. During physical examination, it is important to take notes on important points such as duration of erection, degree of pain, previous episodes of priapism and treatments, current erectile function, medication including recreational drugs, history of pelvic, genital, or perineal trauma, and history of haematological abnormalities (e.g. sickle cell disease, leukaemia) (2,3).

Laboratory testing should include full blood count (followed by haemoglobin electrophoresis if a haemoglobinopathy is suspected), coagulation profile, cavernous blood gases, and urine toxicology (1,3). Cavernous blood gases are essential tests to distinguish between ischaemic and non-ischaemic priapism. Typical cavernous blood gas values in priapism are shown in Table 4. In addition, colour Doppler ultrasonography of the penis and perineum can be performed as an alternative to cavernous blood gases. Penile arteriography can also be done to show the lack of blood flowing the cavernous artery in ischaemic priapism. It can also identify the presence and site of cavernous artery fistula (ruptured helicine artery) in nonischaemic priapism (3).

In general, the aim of priapism treatment is to return the penis to a flaccid and non-painful state, and therefore to avoid permanent damage to the corpora cavernosa (corporal fibrosis) and/or erectile dysfunction. However, conditions such as persistent penile oedema, ecchymosis, and partial erections can occur and mimic unresolved priapism (3). Acute ischaemic priapism is considered a medical emergency and therefore requires rapid intervention. In ischaemic priapism beyond 12 hours, corporal specimens show interstitial oedema, progressing to destruction of sinusoidal endothelium, exposure of the basement membrane, and thrombocyte adherence at 24 hours (1). At 48 hours, there is evidence of thrombi found in the sinusoidal spaces and smooth muscle necrosis with fibroblastlike cell transformation (1). Studies show that treatment beyond 48-72 hours may help to relieve erection and pain but have minimum benefit in preventing erectile dysfunction. The ischaemic priapism treatment is sequential. It should move on to the next stage if the last treatment fails (Table 5). In patients with underlying condition, it is vital that the treatment of ischaemic priapism is provided concurrently with appropriate treatment for the underlying disease.

On the other hand, treatment of non-ischaemic priapism is not an emergency. It should start with conventional treatment such as applying ice to the perineum or site-specific perineal compression. It is followed by selective arterial embolisation, preferably using absorbable materials such as autologous blood clot and gelatin sponges, which are non-permanent (3). Surgical therapy is rarely performed unless there are contraindications for selective embolisation or embolisation failure.

Finally, the main goal in the management of stuttering priapism is to prevent the future episodes. It includes alpha-adrenergic agonists (pseudoephedrine) and hormonal therapy (GnRH, digoxin, and baclofen) (1,3). It is important to remember that hormonal agents interfere with normal sexual maturation and therefore should not be used in children who have not achieved full sexual maturation (3). Intracavernosal injection of phenylephrine should be considered in patients who either fail or reject the systemic treatment.

CONCLUSIONS

Priapism is a rare condition which can potentially develop to a medical emergency depending on its subtypes. While some aspects of priapism are still lacking, a better understanding of the pathophysiology, diagnosis, and treatment will benefit the patient's outcome. Therefore, guidelines on the assessment and management of priapism need to be followed consistently.

Christian Christian

Southern Community Laboratories, Dunedin

AUTHOR INFORMATION

Christian Christian, BMLSc MNZIMLS, Medical Laboratory Scientist

Biochemistry Department, Southern Community Laboratories, PO Box 6064,Dunedin, 9016.

Email: christian.christian@sclabs.co.nz.

REFERENCES

(1.) Salonia A, Eardley I, Giuliano F, Moncada I, Hatzimouratidis K. Guidelines on priapism. European Association of Urology 2015. http://uroweb.org.

(2.) Cherian J, Rao AR, Thwaini A, Kapasi F, Shergill IS, Samman R.. Medical and surgical management of priapism. Postgrad Med J 2006; 82: 89-94.

(3.) Montague D, Jarow J, Broderick GA, Dmochowski RR, Heaton JP, Lue TF, et al. Priapism, guideline on the management of priapism. American Urological Association 2003. www.auanet.org/education/guidelines/priapism.cfm.

(4.) van der Horst C, Stuebinger H, Seif C, Melchior D, Martinez-Portillo FJ, Juenemann KD. Priapism--etiology, pathophysiology and management. Int Braz J Urol 2003; 29: 391-400.

(5.) Liguori G, Bucci S, Benvenato S, Trombetta C, Belgrano E. Priapism: pathophysiology and management. J Androl Sci 2009; 16: 13-20.
Table 1. Cavernous blood gases. Specimen type: cavernous
blood. Oxygen therapy (L/min): on air.

                           Result   Reference range

Blood pH                    6.99       7.35-7.45
pC[O.sub.2] (mmHg)           85          35-45
[p.sub.O](mmHg)              12          30-40
HC[O.sub.3] (mmol/L)        19.2       22.0-32.0
Base excess (mmol/L)       -19.2       -2.0-2.0
[O.sub.2] Saturation (%)     12           --
Lactate (mmol/L)            13.7        0.5-2.2

Table 2. Aetiology of ischaemic priapism (references 1 and 3)

* Idiopathic

* Haematological abnormalities (sickle cell disease,
thalassemia, leukaemia)

* Drugs (vasoactive agents, antidepressants, anticoagulant,
recreational drugs, alcohol)

* Toxin-mediated infections (scorpion sting, spider bite, rabies)

* Metabolic disorder (Fabry's disease, amyloidosis)

* Neurogenic disorders (syphilis, spinal cord injury, brain
tumour)

* Neoplasms (metastatic or regional infiltration)

Table 3. Key findings in the evaluation of priapism (references
1 and 3)

                                                      Ischaemic
                                                      priapism

Corpora cavernosa fully rigid                         Usually
Corpora cavernosa tumescence without full rigidity    Seldom
Penile pain                                           Usually
Abnormal cavernous blood gases                        Usually
Haematological abnormalities                          Usually
Recent intracavernosal injection                      Sometimes
Perineal trauma                                       Seldom

                                                     Non-ischaemic
                                                       priapism

Corpora cavernosa fully rigid                         Seldom
Corpora cavernosa tumescence without full rigidity    Usually
Penile pain                                           Seldom
Abnormal cavernous blood gases                        Seldom
Haematological abnormalities                          Seldom
Recent intracavernosal injection                      Sometimes
Perineal trauma                                       Usually

Table 4. Typical blood gas values in priapism (references 1 and
3)

Source                                    p[O.sub.2]    pC[O.sub.2]
                                            (mmHg)         (mmHg)

Normal mixed venous blood (room air)--
similar to normal flaccid penis               40             50
Ischaemic priapism (cavernous blood)          <30           >60
Normal arterial blood (room air)--            >90           <40
similar to non-ischaemic priapism

Source                                     pH

Normal mixed venous blood (room air)--
similar to normal flaccid penis           7.35
Ischaemic priapism (cavernous blood)      <7.25
Normal arterial blood (room air)--        7.40
similar to non-ischaemic priapism

Table 5. Treatment of ischaemic priapism (references 1 and 3)

1. Preliminary treatment

* Local anaesthesia of the penis

* Insertion of wide bore butterfly (16-18G)

* Aspiration cavernosal blood until bright red arterial blood
obtained

2. Cavernosal irrigation

* Irrigation with 0.90% w/v saline solution

3. Intracavernosal treatment

* Injection of sympathomimetic drugs (phenylephrine)

4. Surgical treatment

* Surgical shunting

** Distal shunts (Winter, Ebbehoj, and Al-Ghorab procedures)

** Cavernospongious (corporospongiosal) shunt

** Cavernosaphenous (corporosaphenous) shunt

* Primary penile implantation for priapism >36 hours
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Title Annotation:CASE STUDY
Author:Christian, Christian
Publication:New Zealand Journal of Medical Laboratory Science
Article Type:Clinical report
Date:Apr 1, 2017
Words:2088
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