Urethral Prolapse

Urethral prolapse is a relatively uncommon urogenital condition characterized by the protrusion of the distal urethral mucosa through the external urethral orifice. It is most frequently observed in male dogs, particularly brachycephalic breeds, and is rarely reported in cats. The prolapsed tissue appears as a congested, edematous, and often hemorrhagic mass at the tip of the penis, which can cause dysuria, hematuria, and excessive licking. The condition is typically classified as either acute or chronic, with acute cases presenting as a sudden, painful swelling, while chronic cases may show recurrent bleeding and mucosal irritation. Surgical intervention is often required to correct the prolapse and prevent recurrence, with techniques including manual reduction, amputation of the prolapsed mucosa, and urethropexy. The condition is distinct from other penile or urethral disorders such as urethral neoplasia, trauma, or urethral prolapse secondary to urolithiasis, and requires careful diagnostic evaluation to rule out underlying causes.

The exact etiology of urethral prolapse is not fully understood, but several factors have been implicated. The most commonly cited cause is increased intra-abdominal pressure, which can result from excessive straining during urination, defecation, or due to conditions such as constipation, diarrhea, or prostatic disease. In brachycephalic breeds, conformational abnormalities, including a short, wide pelvis and a more caudally positioned penis, may predispose to prolapse. Additionally, congenital weakness of the urethral attachments or the suspensory ligament of the penis may contribute. Hormonal influences, particularly hyperestrogenism, have been suggested as a possible factor, although evidence is limited. Trauma to the penis, such as from mating or self-trauma, can also precipitate prolapse. In some cases, no definitive cause is identified, and the condition is considered idiopathic. Underlying urogenital infections or urolithiasis may cause increased straining and secondary prolapse. Iatrogenic causes are rare but can occur following improper catheterization or surgical manipulation.

Urethral prolapse is most commonly reported in male dogs, with a higher incidence in brachycephalic breeds such as English Bulldogs, Boston Terriers, and Pugs. This breed predisposition is likely due to anatomical factors, including a relatively long penile urethra and a more caudally positioned penis, which may increase the risk of mucosal protrusion. The condition is rare in cats and is typically seen in neutered males, possibly due to reduced penile length and altered anatomy. Age of onset is variable, but it is more frequently observed in young adult dogs, with a median age of around 2 to 4 years. There is no clear sex predilection in dogs, as it occurs almost exclusively in males due to the presence of a penis. Working dogs or those with high levels of physical activity may be at increased risk due to trauma or increased abdominal pressure. The overall incidence is low, but it is a recognized clinical entity in small animal practice. In a retrospective study, urethral prolapse accounted for less than 1% of all urogenital surgical cases in dogs.

The pathophysiology of urethral prolapse involves a combination of anatomical and mechanical factors. The distal urethra is normally anchored to the surrounding penile tissue by connective tissue and the urethral attachments. When these attachments are congenitally weak or become stretched, the urethral mucosa can slide distally and protrude through the external urethral orifice. Increased intra-abdominal pressure, such as during straining, forces the bladder and proximal urethra caudally, which can push the distal urethral mucosa outward. The prolapsed mucosa becomes congested and edematous due to venous congestion and impaired lymphatic drainage, leading to a characteristic red, swollen mass. The exposed mucosa is subject to trauma from contact with the environment, self-trauma from licking, and friction, which can cause ulceration, bleeding, and secondary bacterial infection. Chronic prolapse may lead to fibrosis and thickening of the mucosa, making manual reduction more difficult. In severe cases, the prolapsed tissue may become strangulated, leading to ischemia and necrosis. The condition can also cause partial or complete urethral obstruction, resulting in dysuria and potential bladder distension.

Several intrinsic and extrinsic factors predispose to urethral prolapse. Intrinsic factors include breed-related anatomical variations, such as a relatively long penile urethra and a more caudally positioned penis in brachycephalic breeds, which increase the mobility of the distal urethra. Congenital weakness of the urethral attachments or the suspensory ligament of the penis may also be a factor. Hormonal imbalances, particularly hyperestrogenism, have been suggested to cause relaxation of the urethral tissues, although this is not well-documented. Age is a predisposing factor, with young adult dogs being more commonly affected, possibly due to higher levels of sexual activity and increased abdominal pressure during mating. Extrinsic factors include any condition that causes increased intra-abdominal pressure, such as chronic constipation, diarrhea, prostatic disease, or urethral obstruction. Trauma to the penis, either from external injury or self-trauma, can also precipitate prolapse. Prior urogenital surgery or catheterization may weaken the urethral attachments. Obesity may increase abdominal pressure and contribute to the condition. Additionally, excessive physical activity or strenuous exercise can increase intra-abdominal pressure and predispose to prolapse.

The clinical signs of urethral prolapse are typically localized to the urogenital tract. The most common presenting complaint is a visible mass at the tip of the penis, which is often described as a red, cherry-like swelling. This mass may be painful, and the dog may exhibit excessive licking of the area. Hematuria, either at the beginning or end of urination, is frequently observed due to trauma to the prolapsed mucosa. Dysuria, or difficulty urinating, may occur if the prolapse is large enough to partially obstruct the urethral lumen. In some cases, the dog may strain to urinate, and the urine stream may be altered or split. The prolapsed tissue may become ulcerated or necrotic, leading to a foul odor or purulent discharge. Systemic signs are uncommon but may include lethargy or fever if secondary infection occurs. In chronic cases, the prolapse may be reducible manually but recurs. Physical examination reveals a congested, edematous, and sometimes hemorrhagic mass protruding from the external urethral orifice. The mass may be covered with a fibrinous exudate or have areas of necrosis. Palpation of the penis may elicit pain, and the dog may resent manipulation.

Differential diagnoses for a mass at the tip of the penis in a male dog include: 1) Urethral neoplasia (e.g., transitional cell carcinoma, squamous cell carcinoma) - typically occurs in older dogs, may be firm, irregular, and invasive; cytology or biopsy is diagnostic. 2) Penile trauma - history of trauma, presence of lacerations or hematoma, and absence of a distinct mucosal prolapse. 3) Penile hematoma - swelling due to blood accumulation, often following trauma or mating, may be fluctuant and painful. 4) Urethral prolapse secondary to urolithiasis - presence of urinary calculi, which can cause straining and secondary prolapse; imaging and urinalysis are helpful. 5) Transmissible venereal tumor (TVT) - typically a cauliflower-like mass on the penis, sexually transmitted, cytology shows characteristic cells. 6) Penile papilloma - benign viral-induced growth, usually multiple, and may be pedunculated. 7) Foreign body - such as a grass awn or hair, causing localized inflammation and swelling. 8) Paraphimosis - inability to retract the penis into the prepuce, resulting in swelling and congestion, but the entire penis is involved, not just the urethral mucosa. 9) Urethral fistula - an abnormal communication between the urethra and skin, often due to trauma or infection, presenting with urine leakage. 10) Balanoposthitis - inflammation of the glans penis and prepuce, which may cause swelling and discharge, but the urethral orifice is not specifically prolapsed.

The diagnostic approach for suspected urethral prolapse begins with a thorough history and physical examination. The presence of a characteristic red, congested mass at the tip of the penis is highly suggestive. Gentle manipulation may allow temporary reduction, but the prolapse often recurs. To confirm the diagnosis and rule out other conditions, the following steps are recommended: 1) Perform a complete physical examination, including assessment of the penis and prepuce, and note any signs of trauma, neoplasia, or infection. 2) Obtain a urine sample via cystocentesis for urinalysis and culture to rule out urinary tract infection or urolithiasis. 3) Perform diagnostic imaging, including abdominal radiographs and ultrasonography, to evaluate the bladder, prostate, and urethra for underlying causes such as calculi, prostatic disease, or masses. 4) If neoplasia is suspected, fine-needle aspiration or biopsy of the mass is indicated. 5) In cases of recurrent prolapse or if manual reduction is unsuccessful, surgical exploration may be necessary to assess the extent of the prolapse and the integrity of the urethral attachments. 6) Preoperative blood work, including complete blood count, serum biochemistry, and coagulation profile, is recommended to assess overall health and surgical risk. 7) If the prolapse is associated with excessive straining, further investigation into gastrointestinal or urinary causes is warranted.

Laboratory findings in urethral prolapse are often nonspecific but may reflect underlying conditions. A complete blood count may show mild leukocytosis if secondary infection is present, but is typically within normal limits. Serum biochemistry is usually unremarkable, although elevations in blood urea nitrogen and creatinine may occur if urethral obstruction leads to post-renal azotemia. Urinalysis may reveal hematuria, proteinuria, and pyuria if secondary infection is present. Urine culture and sensitivity should be performed to identify bacterial pathogens and guide antimicrobial therapy. Coagulation profile (PT/aPTT) is recommended preoperatively to rule out bleeding disorders, especially if surgical intervention is planned. Inflammatory biomarkers such as C-reactive protein (CRP) may be elevated in cases with significant inflammation or infection. Synovial fluid analysis is not relevant to this condition. If hyperestrogenism is suspected, hormonal assays may be considered, but this is rarely performed in clinical practice.

Imaging plays a crucial role in the diagnostic workup of urethral prolapse, primarily to identify underlying causes and assess the extent of the condition. Abdominal radiographs may reveal uroliths, prostatic enlargement, or other abnormalities. Contrast urethrography or retrograde urethrography can be used to evaluate the urethral lumen and identify any filling defects, strictures, or diverticula. Ultrasonography of the penis and perineal region can assess the soft tissue structures and may help differentiate a prolapsed urethra from other masses. In cases where neoplasia is suspected, advanced imaging such as computed tomography (CT) or magnetic resonance imaging (MRI) may be beneficial to evaluate local invasion and metastasis. However, these modalities are not routinely necessary for the diagnosis of simple urethral prolapse. Urethroscopy can provide direct visualization of the urethral mucosa and allow biopsy if needed. In chronic or recurrent cases, imaging may reveal anatomical abnormalities such as a short urethra or abnormal positioning of the penis.

Cytological and histopathological evaluation is essential to rule out neoplastic processes and confirm the diagnosis of urethral prolapse. Fine-needle aspiration of the prolapsed mass may be performed, but the findings are often nonspecific, showing inflammatory cells, red blood cells, and epithelial cells. Histopathology of the excised tissue is more definitive. In urethral prolapse, histopathological findings typically include hyperplasia of the urethral epithelium, submucosal edema, congestion, and varying degrees of inflammation and fibrosis. There may be areas of ulceration and necrosis. Special stains, such as Masson's trichrome, can highlight fibrosis. If neoplasia is suspected, immunohistochemistry may be performed to differentiate between different tumor types. Surgical biopsy is recommended in cases where the diagnosis is uncertain or if the prolapse is recurrent and atypical.

Treatment of urethral prolapse can be medical or surgical, depending on the severity and chronicity. In mild, acute cases, manual reduction under sedation or anesthesia may be attempted. The prolapsed mucosa is gently replaced into the urethral orifice, and a purse-string suture or temporary indwelling catheter may be placed to maintain reduction. However, recurrence is common, and surgical correction is often required. Surgical options include: 1) Amputation of the prolapsed mucosa: The prolapsed tissue is excised, and the urethral mucosa is sutured to the penile skin or surrounding tissue using absorbable suture material (e.g., 4-0 polydioxanone or polyglactin 910) in a simple interrupted or continuous pattern. This technique is effective but may result in stricture formation if excessive mucosa is removed. 2) Urethropexy: The urethra is sutured to the surrounding penile tissue or the abdominal wall to prevent recurrence. This is often combined with amputation. 3) Resection and anastomosis: In cases of severe prolapse with necrosis, the affected segment of the urethra may be resected and anastomosed. Preoperative stabilization includes management of any underlying urinary tract infection or obstruction. Postoperative care involves pain management, antimicrobial therapy if indicated, and prevention of self-trauma (e.g., Elizabethan collar). The prognosis is generally good, with a low recurrence rate after surgical correction.

The prognosis for urethral prolapse is generally excellent with appropriate surgical management. The recurrence rate after surgical correction is low, reported to be less than 10% in most studies. Short-term complications include hemorrhage, infection, and urethral stricture, but these are uncommon. Long-term outcomes are favorable, with most dogs returning to normal urinary function. Negative prognostic indicators include underlying conditions such as urolithiasis or neoplasia, which may require additional treatment. Chronic prolapse with fibrosis may be more difficult to manage surgically. Overall, the success rate of surgical treatment is high, and most dogs have a good quality of life postoperatively.

Postoperative follow-up for urethral prolapse is essential to monitor for complications and ensure proper healing. The dog should be re-examined within 7 to 10 days after surgery to assess the surgical site and remove any non-absorbable sutures if used. The owner should be instructed to monitor for signs of dysuria, hematuria, or excessive licking, which may indicate complications. An Elizabethan collar should be worn for at least 7 to 10 days to prevent self-trauma. Restricted activity is recommended for 2 to 4 weeks to allow healing. A recheck examination at 4 weeks postoperatively may include a urinalysis to rule out infection. In cases where underlying conditions were identified, such as urolithiasis, appropriate follow-up imaging or medical management is necessary. Long-term monitoring is generally not required, but owners should be advised to report any recurrence of clinical signs.

Clinical pearls: 1) Always consider urethral prolapse in a young brachycephalic male dog presenting with a penile mass and hematuria. 2) Manual reduction may be attempted but is often unsuccessful; surgical correction is the definitive treatment. 3) When performing amputation, ensure that the urethral mucosa is sutured to the penile skin without tension to prevent stricture. 4) Use fine absorbable suture material (4-0 or 5-0) to minimize tissue reaction. 5) Postoperative use of an Elizabethan collar is crucial to prevent self-trauma. Pitfalls: 1) Failure to identify and treat underlying causes, such as urolithiasis or prostatic disease, may lead to recurrence. 2) Excessive resection of the urethral mucosa can result in stricture formation. 3) Inadequate hemostasis can lead to postoperative hemorrhage. 4) Not performing a biopsy in atypical cases may miss neoplasia. 5) Overlooking the possibility of a foreign body or trauma as the cause of the mass.

Perioperative pharmacological protocols for urethral prolapse surgery are based on Plumb's Veterinary Drug Handbook. Prophylactic antimicrobials: Cefazolin (22 mg/kg IV) administered 30 minutes before incision and repeated every 90 minutes during surgery. Postoperative antimicrobials are not routinely indicated unless infection is present or a urinary catheter is placed. Analgesics: Opioids such as hydromorphone (0.05-0.1 mg/kg IV or IM q4-6h) or buprenorphine (0.01-0.02 mg/kg IV or IM q8-12h) are used for perioperative pain. Nonsteroidal anti-inflammatory drugs (NSAIDs) such as carprofen (2.2 mg/kg PO q12h) or meloxicam (0.1 mg/kg PO q24h) can be used for postoperative pain and inflammation, but should be used with caution in patients with renal or hepatic disease. Local anesthetic blocks, such as a penile block with lidocaine (2 mg/kg) or bupivacaine (1 mg/kg), can provide additional analgesia. Sedatives such as acepromazine (0.02-0.05 mg/kg IV or IM) or dexmedetomidine (1-2 mcg/kg IV) may be used preoperatively. If a urinary catheter is placed, antimicrobial therapy may be indicated based on culture and sensitivity. Chondroprotectants are not relevant to this condition.

The veterinary literature on urethral prolapse is limited to case reports and small case series. A retrospective study by Papazoglou et al. (2001) evaluated 12 dogs with urethral prolapse and found that surgical amputation was successful in all cases, with no recurrence during a follow-up period of 6 to 24 months. Another study by Boothe (1993) described the surgical technique of urethropexy and reported good outcomes. A case series by Tobias and Johnston (2012) in their textbook 'Veterinary Surgery: Small Animal' provides a comprehensive review of the condition and surgical management. There are no prospective randomized controlled trials comparing different surgical techniques. The consensus among experts is that surgical amputation or urethropexy is the treatment of choice, with a low recurrence rate. The use of prophylactic antimicrobials is not well-studied, but is generally recommended based on standard surgical principles. Overall, the evidence supports surgical intervention as the definitive treatment for urethral prolapse.