pISSN 1598-298X / eISSN 2384-0749 J Vet Clin 34(3) : 218-221 (2017) http://dx.doi.org/10.17555/jvc.2017.06.34.3.218

Idiopathic Ischemic Priapism in a Shih Tzu

Jiyoung Park, Sung Ah An, Seong Mok Jeong and Kyoung won Seo1 College of Veterinary Medicine, Chungnam National University, Deajeon 34134, Republic of Korea

(Received: January 09, 2017 / Accepted: March 08, 2017)

Abstract : A 14-year-old castrated Shih Tzu weighing 5.4 kg presented with painful penile erection and dysuria that had been ongoing for 2 days. Treatment with salbutamol and gabapentin was initiated, but after 24 hours, the dog had not responded, so it was decided to proceed with penile amputation. The patient went into cardiac arrest during the surgery and died, despite attempted cardiopulmonary resuscitation. During the surgery, the penis was found to have an enlarged, tortuous, purple blood vessel located dorso-caudally to the bulbus glandis. A hemi-circular fibrous mass was found inside the vessel on histopathological examination; this mass may have induced the ischemic priapism by occluding the vein. This report describes a rare case of ischemic priapism in dogs. Key wards : persistent erection, ischemic priapism, dog.

Introduction mildly depressed but in a favorable condition. After analgesic medication (tramadol 3 mg/kg, IV) was Priapism is a penile erection that persists more than 4 administered, screening tests, including blood examinations hours without sexual interest or stimulation, which causes (complete blood count [CBC], and serum chemistry tests for discomfort and difficult urination (5,7,16). The incidence in electrolyte, C-reactive protein [CRP], and D-dimer levels), human medicine ranges from 0.5 to 1.5 cases per 100,000 abdominal radiography, ultrasonography, and urinalysis, were person-years and it occurs in all age groups from newborns performed. A serum biochemistry profile revealed increased to the elderly (16,18). Priapism can be categorized into three alkaline phosphatase (ALKP) (1756 U/L, reference range 23- subtypes in people: ischemic (> 95%, low flow, veno-occlu- 212) and alanine aminotransferase (ALT) (193 U/L, reference sive), non-ischemic (high flow, arterial), and stuttering (inter- range 10-100) levels. Mildly elevated CRP (10 mg/L, refer- mittent or recurrent ischemic) (2,16,18). The ischemic type is ence range 0-7) was also detected. There were no specific caused by venous congestion and increased blood viscosity, findings on the radiographs. Ultrasonography of the bilater- while the non-ischemic type is caused by increased arterial ally enlarged bulbus glandis showed hypoechoic echogenic- flow through the corpus cavernosum (7). The former is often ity but no specific etiologic factors such as neoplasia or other related to sickle cell disease, neoplasia, spinal cord injury, obstructions. With a tentative diagnosis of idiopathic priapism, vasoactive drugs, anesthesia, or idiopathic conditions; the lat- medical treatment with salbutamol (0.05 mg/kg, PO, bid) and ter is often caused by blunt perineal trauma, vasoactive drugs, gabapentin (10 mg/kg, PO, bid) was initiated. The exposed or neurological conditions (7,16). penis was also kept moist and an Elizabethan collar was put Priapism is very uncommon in dogs and cats (11,13), so the in place. However, there was no response to the medication incidence in domestic animals has not been determined (15). and the condition of the penile tip worsened over the next 24 This report describes a case of ischemic priapism in a dog. hours (Fig 1). Penile amputation with urethrostomy was scheduled as the salvage treatment. Case Under general anesthesia, the penis was bluntly dissected after preputial incision. When the bulbus glandis was exposed, A 14-year-old castrated Shih Tzu weighing 5.4 kg presented an enlarged, tortuous, purple-to-charcoal-colored blood ves- with an enlarged, edematous, persistently erect penis, and sel emerged (Fig 2). This vessel, suspected to be the dorsal anorexia, vomiting, and dysuria that had been ongoing for penile vein, ran from the dorso-caudal level of the bulbus two days. The owner stated that the dog had not suffered any glandis toward the penile root. The vein disappeared abruptly trauma. At the time of presentation, the patient had an at the caudal penile root. Just before penile amputation, car- exposed penis projecting out of the prepuce, with a firm and diac arrest occurred and the patient died despite attempted enlarged bulbus glandis. The distal tip of the penis was con- cardiopulmonary resuscitation. The owner declined a full gested and swollen. The patient exhibited discomfort and necropsy, so the vascular abnormality was the only tissue pain on palpation around the erect penis; otherwise, he was sample obtained. When the sample was examined histopathologically (IDEXX, 1Corresponding author. CA, USA), there was a hemi-circular mass (> 1 mm in diam- E-mail : [email protected] eter) on the wall of the blood vessel (Fig 3). The mass was

218 Idiopathic Ischemic Priapism in a Shih Tzu 219

Fig 1. A gross image of the penile tip in a Shih Tzu with a pri- apism taken 24 hours after initial presentation. composed of fibrous connective tissue with irregularly dense collagenous fiber and a small number of lymphocytes and macrophages. No neoplastic features were present. Vascular endothelial cells of the vascular tunica intima were also absent, leading examiners to believe that the structure could be a damaged blood vessel. This lesion may have induced the ischemic-type priapism secondary to a veno-occlusive effect.

Discussion Fig 3. Histopathological images of the dorsal penile vein in a The pathogenesis of priapism is generally related to any Shih Tzu with an ischemic priapism. An intravascular hemicir- condition of increased penile arterial flow or decreased venous cular mass (arrowhead) > 1 mm in diameter was identified (A: outflow. Penile vascular damage or obstruction with throm- 40×, green line: 1.45 mm). There was no vascular endothelial boembolism and malignancy, prolonged parasympathetic lining (B: 200×) and the mass was composed of fibrous tissue × stimulation, excessive release of erectile neurotransmitters, or with lymphocytes and macrophages (C: 400 ). The section excessive smooth muscle relaxation may cause either condi- identified with an arrow in image A is magnified in images B tion (1,5,12,15). In a prolonged state of erection, the corpus and C. cavernosum contains stagnant blood with low oxygen and high carbon dioxide levels; the resultant increase in viscosity the main venous outflow track develops and ischemic necro- leads to the impairment of venous return (10). This in turn sis of the penis results (5). Intra-sinusoidal thrombi forma- causes edema, leading to further venous occlusion, and a per- tion and smooth muscle cell necrosis and fibrosis occur in an sistent erection develops. Eventually, irreversible fibrosis in ischemic priapism within 24-48 hours (7,18). In this context,

Fig 2. Surgical images taken during penile amputation in a Shih Tzu with a priapism. Distension of the bulbus glandis with a devi- talized penile tip and distal shaft was noticeable (A). The engorged dorsal vessel of the penis (white arrows) running in the dorsal sur- face of the penile root was apparent (B). 220 Jiyoung Park, Sung Ah An, Seong Mok Jeong and Kyoung won Seo ischemic priapism should be considered an emergency due to tion also provides immediate relief of the compartment syn- the onset of compartment syndrome and immediate therapeu- drome by restoring circulation, relieving pain, and aiding in tic intervention is warranted (2,7,13,16). Non-ischemic pri- detumescence (2). apism is non-emergent and conservative treatment is usually If all of these treatments fail, surgery may be indicated in recommended; ice packs, site-specific compression, and ob- order to preserve the penis. Tunica albuginea incision of the servation can be attempted and further selective arterial bulbus, pars longa incision of the glandis, and exsanguination embolization can be performed (12,16). of stagnant blood and thrombi from the corpus cavernosum In human medicine, there have been extensive studies of cause minimal damage (5,10,11). Unfortunately, priapism in priapism and clear management guidelines are available veterinary patients is usually present for several days before (12,16). Unfortunately, the pathophysiological mechanism of the owners seek help. When priapism has lasted more than priapism in dogs is poorly understood (2,13). Low incidence 24-48 hours in a small animal, causing irreversible penile rates combined with infrequent reports and the paucity of necrosis, penile amputation with urethrostomy is frequently experience make diagnosis difficult, delaying appropriate care. performed (2,7,13). Distinguishing the type of priapism and identifying and treat- Concurrent management of any identified underlying cause ing the underlying cause in a timely manner are imperative (s) should also take place (7). The therapeutic plan is deter- (7). The history and physical examination help clinicians not mined by the primary cause of the priapism, which also only to differentiate between an ischemic and non-ischemic determines the patient’s prognosis (13). The prognosis may priapism, but also to identify the underlying cause. In humans, be either favorable or refractory, otherwise the owner may the ischemic type is often painful, with a rigid penile shaft choose euthanasia in some cases. The duration of the pri- and soft glans, whereas the non-ischemic type is character- apism is the most significant predictor of recovery of normal ized by a partially rigid penis and an absence of pain (2,7, penile erectile function in human medicine; studies to evalu- 14,16). Penile ultrasonography with or without a color Dop- ate the ability of veterinary patients to copulate after recov- pler test may be helpful in detecting any anatomical abnor- ery have not been done (10,16). malities, evidence of trauma, or arterial cavernosal fistula (2,7). The patient in this case had no obvious history of trauma Abdominal and perineal examination is also warranted in and diagnostic examinations showed no evidence of underly- order to identify any evidence of trauma or malignancy (16). ing neurological conditions or malignancy. Although cavern- Priapism in dogs and cats is sometimes idiopathic, but it osal blood gas evaluation and penile necropsy were omitted, can be associated with the following: trauma during mating, ischemic priapism was suspected because of the identifica- neoplasia and metastasis, decreased venous flow after castra- tion of a hemi-circular mass within the dorsal penile vein. An tion, chronic distemper encephalomyelitis, feline infectious inflammatory response at the time of suspected previous vas- peritonitis, neurologic disease (cauda equina syndrome, lum- cular damage may have caused further intravenous fibrous bar stenosis, meningomyelocele, syringomyelia, interverte- mass formation, and this lesion may have ultimately induced bral disk disease, etc.), perineal abscess, thromboembolism, a true veno-occlusive priapism. The patient also showed constipation, urinary tract infection, and phenothiazine tran- severe pain with palpation and did not respond to sympatho- quilizers such as acepromazine and chlorpromazine (1,2,3,5, mimetic medications. 6,7,8,10,15,17). Thromboembolic accidents and spinal inju- There has been a recent report of successful medical man- ries that stimulate the erection center or pelvic nerve are the agement of priapism using a combination of anticholinergic most common causes (8,15). Dogs suffer from both ischemic therapy (atropine, 0.22 mg/kg, IV) and terbutaline (1.25 mg, and non-ischemic priapism, whereas cats may have ischemic PO, bid) in two dogs (1). However, systemic therapy is anec- priapism associated with thrombosis of the penile vessels (2). dotal and especially oral systemic therapy is not indicated to Regardless of the underlying cause, the goal of treatment is treat ischemic priapism in human medicine (9). It could be the restoration of normal circulation in the corpus caverno- considered when other treatment options for ischemic pri- sum and preservation of the penis from severe injury, desic- apism are unacceptable and in cases of non-emergency pri- cation, ischemia, necrosis, or urethral obstruction (8). The apism (7). Initial corporal aspiration and intracavernosal in- initial management of ischemic priapism includes analgesia jection of low dose phenylephrine (1-3 µg/kg) with cardio- and penile lubrication (2). The penis should be kept clean vascular monitoring could have been attempted in this case (7). and further desiccation and self-induced trauma must be pre- The cause of the Shih Tzu’s death was undetermined, but vented (11). The first-line treatment is corporal aspiration there was a reported case of death secondary to massive pul- with or without heparinized saline irrigation (2). Sympatho- monary embolism in a human patient of priapism resulted mimetic agents like phenylephrine, ephedrine, or epineph- from repeated phentolamine and papaverine injection (4). rine may be injected intracavernosally initially or also when This veterinary case emphasizes that, despite its rarity, clini- the aspiration fails (7,14,16). cians should be aware of priapism so that aggressive treat- Aspiration of the corpus cavernosum is both diagnostic and ment may be initiated promptly. therapeutic (12). Cavernous blood gas analysis may be the key to differentiating the type of priapism; results in ischemic Acknowledgement priapism include pH < 7.25, PaO2 < 30 mmHg, and PaCO2 > 60 mmHg, while non-ischemic priapism shows pH of 7.4, This work was supported by research fund of Chungnam

PaO2 > 90 mmHg, and PaCO2 < 40 mmHg (7,14,16). Aspira- National University. Idiopathic Ischemic Priapism in a Shih Tzu 221

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