Urethral diverticula are a relatively common finding among women with chronic genitourinary conditions, such as recurrent infections, postvoid dribbling, and dyspareunia. The level of awareness of the disorder and the practitioner's desire to make the diagnosis are reported to have the most direct influence on the incidence of urethral diverticulum. This statement reflects both the difficulty of the diagnosis and the varying levels of awareness of the disorder throughout the medical community. Recently, increased awareness and discussion of urethral diverticula have allowed the diagnosis to be made more frequently and with less delay than in the past.
History of the Procedure
In 1805, William Hey first described a female with suburethral diverticulum in the medical literature; however, he claimed to have first observed and treated this lesion about 20 years earlier. In the first half of the 20th century, only 17 cases were reported, and, as a result, the condition was assumed to be quite rare. Reports of cases, including a large series from Johns Hopkins Hospital, dating from 1950-1970 have revealed that suburethral diverticula in fact are not rare. Increased awareness of the diagnosis and increased interest in female urology and urogynecology have led to the publication of many reports and review articles in recent years.
In 1875, Lawson Tait was the first to suggest surgical excision as treatment for these lesions. In 1938, Johnson reported on 5 patients treated with complete excision of the diverticular sac. In 1962, Tancer and Hyman described surgical treatment by partial ablation in a small series of 11 patients. Subsequently, the lead author has reported successful treatment of many additional patients with no occurrences of postoperative urethrovaginal fistulas. In 1970, Spence and Duckett pioneered a marsupialization procedure for distally occurring diverticula.  These 3 operations continue to be the mainstays of surgical therapy today.
In 1956, Davis and Cian introduced positive-pressure urethrography, which was a major advance in the diagnostic tools and preoperative evaluation of urethral diverticula.  In 1973, Jack Robertson published a landmark article on gynecologic urethroscopy using carbon dioxide gas as a distension media.  He described visualization of the diverticular orifice using this technique. Subsequently, ultrasound and magnetic resonance imaging (MRI) have been added to the diagnostic armamentarium.
The definition of a diverticulum according to Dorland's Medical Dictionary is "a pouch or sac occurring normally or created by herniation of the lining mucous membrane through a defect in the muscular coat of a tubular organ." Because the etiology of suburethral diverticula is uncertain, whether or not this disorder is the result of a true herniation of urethral mucosa or some other pathologic process is equally unclear. In fact, the favored theory describing the genesis of urethral diverticula, ie, rupture of an obstructed infected paraurethral gland back into the urethra, does not fit the definition of a true diverticulum.
A urethral diverticulum can be described as an outpouching of tissue from the urethra into the urethrovaginal potential space. The lining of the diverticulum most commonly is identical to the urethral mucosa. Most urethral diverticula are believed to be derived from dilated paraurethral ducts or glands.
The frequency with which this disorder occurs is difficult to estimate due to the high probability of a substantial number of missed or misdiagnosed cases in any given population. In addition, research has demonstrated a sizable pool of asymptomatic women with demonstrable diverticula. In one study, asymptomatic women with cervical cancer were studied with positive-pressure urethrography. A prevalence of urethral diverticula of 3% was reported in this group. Many of these diverticula were small, ranging in size from 2-16 millimeters in diameter. Based on these findings, the smallest of these diverticula conceivably may have represented filling of large, but otherwise normal, paraurethral glands.
Another series identified diverticula in 4.7% of 129 asymptomatic women. Other sources reveal an incidence of 2-5% in a referral population of women with genitourinary ailments. Finally, prevalence rates of 16% and 40% have been reported in female patients with recurrent urinary tract infections (UTIs).
In one publication, a referral practice in urology and urogynecology reviewed a database consisting of almost 2000 patients seen over an 8-year period. Seventy-nine patients (4%) were identified with a periurethral mass. Most patients (91%) were referred due to persistent irritative lower urinary tract symptoms or incontinence with the mass discovered during the subsequent evaluation. Only 7 patients (9%) were referred specifically for a mass. The diagnosis of urethral diverticulum was made in 84% of the cases. Notably 4 patients (6%) were diagnosed with an associated malignancy. Other diagnoses included fibromuscular tissue mass (7%), leiomyomata (5%), ectopic ureterocele (2.5%), vaginal squamous cell carcinoma (2.5%), and 1 patient had an infected granuloma. 
Urethral diverticula are much more common in females than in males. The rare cases reported in males generally have been associated with lower urinary tract congenital anomalies or surgical trauma. In a series of 108 female patients from the Mayo Clinic, the age range was reported as 10-76 years, with the disorder observed most commonly in women aged 30-50 years.
Very rarely, periurethral cystic masses have been reported in newborns. Whether these masses represent a congenital form of urethral diverticulum or some type of genitourinary congenital remnant remains uncertain.
The etiology of urethral diverticulum is uncertain, although several theories exist. In 1890, in England, Routh first proposed the most widely quoted theory. He postulated that obstruction of one or more paraurethral ducts may result in formation of a retention cyst within the paraurethral gland. Later, infection supervenes and results in abscess formation and rupture back into the urethral lumen. Epithelialization of the rupture tract results in formation of the neck of the diverticulum.
Over the years, several findings have lent support to this theory. First, the anatomic location of most urethral diverticula corresponds to the location of the highest density of paraurethral glands. The predominant location of both the paraurethral glands and urethral diverticula is along the dorsolateral aspect of the distal two thirds of the urethra. One review found that 85% of diverticula occurred in the distal two thirds of the urethra. In another more recent series, about 60% of diverticula were located along the middle or distal one third of the urethra, with about 15% in multiple locations. In 4% of cases, the location was unknown. In addition, small dilations of the paraurethral duct and gland system have been observed in females without diverticula.
Another etiologic theory is that of urethral trauma from childbirth, catheterization, urethral dilation, or other surgical injury. Although this mechanism may account for a small number of urethral diverticula, causation is difficult to prove. Also, 15% or more of all urethral diverticula occur in nulliparous females with no known history of urethral trauma.
Some suburethral cysts may be congenital, as evidenced by the fact that they have been reported in newborns. Many of these cysts have epithelial linings, which indicate that they arise from structures that are not the paraurethral glands or ducts. Examples include cloacogenic rests lined with colonic epithelium, Gartner duct cysts, and Müllerian remnants. In the opinion of this author, these cysts should not be classified as urethral diverticula.
Rarely, a diverticulum may be associated with an anomalous accessory urethra. Such diverticula are generally recognized at birth, presenting as a large fluid-filled mass occupying space between the main urethra and the clitoris. The external meatus of the accessory urethra is stenotic and drains poorly, resulting in the accumulation of urine in the diverticular sac. Associated genitourinary anomalies, such as absence of the perineum, absence of the labia minora, a multicystic kidney, and hydronephrosis can be encountered. The enlarged accessory urethra and diverticulum can have phallic appearance and, as such, this congenital abnormality is considered by many experts to be a form of pseudohermaphroditism.
A recently published case report describes the use of urography and genitography to aid in defining the anatomy. At 2 days of age, the stenotic meatus was incised to promote drainage. Definitive surgery was undertaken at 5 months of age including excision of the accessory urethra and diverticulum, and indicated genital reconstruction with attention paid to preserving the clitoris and associated structures.
The pathophysiology of most cases of urethral diverticula appears to revolve around obstruction of and infection within the paraurethral glands. The glands are thought to become enlarged and inflamed, eventually forming a retention cyst and then an abscess, which ruptures back into the urethra. In 1890, Routh first described this pathophysiologic mechanism.
In 1953, Telinde suggested that gonococcal infection in the paraurethral glands was an important initiating factor in the pathogenesis of urethral diverticula. In a subsequent small series in 1975, 10 of 31 patients had proven gonorrhea and another 7 had histories suggestive of gonococcal infection. Bacteruria is a common finding in individuals with urethral diverticula. Typical urinary tract pathogens predominate. Bacteruria and recurrent UTIs are thought to result from bacterial growth in the stagnant urine within the diverticulum and reflux of infected material into the bladder. Little else apparently is known regarding the bacteriology of this disorder.
Urethral diverticula may be associated with variable degrees of peridiverticulitis. Tancer and Ravski state that this may result from recurring infection within the diverticulum.  They argue that signs and symptoms, such as urethral tenderness and dyspareunia, appear or become more severe upon development of peridiverticulitis.
On occasion, severe, recurrent infection in and around the diverticulum may result in rupture through the periurethral connective tissue and into the space between this tissue and the vaginal wall. Leng and McGuire proposed this phenomenon in their description of urethral diverticulum subtypes.  The author has observed this phenomenon on 2 occasions, including 1 case in which the rupture may have occurred at the time of double balloon positive-pressure urethrography.
In 1.5-10% of cases, stones may form within the diverticular sac. Stones may be singular or multiple. Most are calcium oxalate or calcium phosphate stones. Stagnation of urine with crystal formation in the presence of chronic infection probably is the main etiologic factor. Stones are more common in men, especially if some degree of associated obstruction is present.  In rare instances, giant calculi have been reported to occur in urethral diverticula.
Due to the presence of chronic inflammation, mucosal changes within the diverticulum often resemble chronic cystitis. Cystitis glandularis, glandular metaplasia, and focal hyperplasia have been reported. Chronic mucosal injury may cause hyperplastic and neoplastic changes within the diverticulum. Rarely, carcinoma develops within a diverticulum. These cases represent 5% of all urethral carcinomas. For unknown reasons, carcinomas appear to be more common in blacks with urethral diverticula. Among diverticulum-associated cancers, about 60% are adenocarcinomas, 30% are transitional cell carcinomas, and 10% are squamous cell cancers. Traditionally, the squamous cell variety was thought to have worse prognosis. More recent information suggests that tumor grade may be more important than cell type as an indicator of prognosis.
In 1998, Leng and McGuire proposed a simple classification system of urethral diverticula partly based on pathophysiologic findings and proposed etiologies.  In their series of patients, they observed some cases in which the mucosal lining of the urethra was observed to be extruding through a defect in the periurethral connective tissue. This finding was at variance with the more typical intraoperative finding of intact periurethral connective tissue surrounding the diverticular sac. They found this subtype to be associated more commonly with previous periurethral surgery. They called this subtype a pseudodiverticulum, although the described lesion closely approximates the medical definition of a true diverticulum.
In the series reported by Leng and McGuire, the pseudodiverticulum often was observed following suture bladder neck suspension procedures. They hypothesized that traction on these sutures during increases in intra-abdominal pressure may have torn the connective tissue, leaving a gaping defect. Most often, this type of lesion had a broad-based ostium, which was easily identifiable on urethroscopy. Also, these patients tended to have fewer chronic lower urinary tract symptoms, with the exception of stress incontinence, which was more common. In this series of 18 patients, 12 had true diverticula, 5 had pseudodiverticula, and 1 patient had both subtypes.
Three cases of urethral diverticulum following synthetic tension-free midurethral sling have recently come to light. [8, 9] These cases were probably related to surgical disruption of the subepithelial connective tissue or erosion of the sling material through this layer. These diverticula have responded to transvaginal diverticulectomy with and without excision of the sling.
The clinical presentation of urethral diverticula varies considerably from patient to patient and also may vary depending on when during the natural history of the disorder the diagnosis is made. Early in the natural history, when the periurethral gland initially becomes infected, the predominant symptoms may be related to urination. At this stage, dysuria, frequency, and postmicturition dribbling may bring the patient to clinical attention. Later, as chronic and recurrent inflammation develops around the diverticulum, low pelvic pain and dyspareunia may be reported as well. Clinical signs such as pyuria, a palpable suburethral mass, suburethral induration, and tenderness may be present. A recent review reported the most common symptoms as follows:
Urinary frequency and urgency (40-100%)
Recurrent UTI (30-50%)
Postmicturition urinary dribbling (10-30%)
Less commonly reported symptoms included stress or urge incontinence, pelvic or suprapubic pain, perineal pain, pelvic pressure, urinary hesitancy, purulent urethral discharge, feeling of incomplete emptying, urinary retention, and isolated terminal dysuria. A recent review of malignancies within urethral diverticula reported a higher incidence of hematuria (49%) and a lower incidence of dyspareunia (5%) in these women.
In a series of 120 patients conducted in Taiwan, 100% of the patients presented with the classic triad of postmicturition dribbling, dyspareunia, and dysuria. The next most common presenting symptoms were incomplete voiding, urgency, and frequency, reported in 38%, 21%, and 18% of the patients, respectively. 
Physical examination findings in cases of urethral diverticulum may be striking, subtle, or completely absent. The appreciated findings may be dictated by the natural history of the disorder and the presence or absence of acute infection. Classic findings include a palpable anterior vaginal wall mass (see the image below) and expression of purulent material from the urethra upon compression. Early series commonly (78%) reported these findings. In more recent series, much lower rates, 2-6%, of this finding have been reported. One factor that may explain these vast differences in physical examination findings is the use of antibiotics early in the disease course and subsequent prevention of abscess formation.
Additionally, changes in reporting habits and increased use of imaging modalities in cases suspected on history alone may be important factors. Still, in a series of 46 consecutive patients, 52% had a palpable mass; however, only 13% had purulent material expressed from the urethra. Of note, 8% of the palpable diverticula contained malignancies, and another 8% contained stones or endometriosis.  Hardness or grittiness within the mass can be appreciated in some cases of diverticula with stones. A palpable anterior vaginal wall mass in the clinical setting of a possible urethral diverticulum raises the index of suspicion for malignancy.
At times, suburethral tenderness may be the only physical examination finding of note in suspected cases of urethral diverticulum. The differential diagnosis in these instances includes urethral syndrome, acute or chronic urethritis, and interstitial cystitis. In one recent series, suburethral tenderness was present in about 50% of cases, with or without the presence of a palpable mass.
The inability to easily palpate a urethroscope or a similar caliber rigid catheter vaginally along the full length of the urethra has been suggested as an indication of urethral diverticulum. This finding was present in 2 cases of urethral diverticulum and absent in all cases of patients undergoing urethroscopy for other reasons.
The differential diagnosis of an anterior vaginal wall mass includes urethral diverticulum; urethral carcinoma; endometrioma; leiomyomata; Skene gland abscess; Gartner duct cyst; ectopic ureter with ureterocele; and other embryonic remnants, rests, or cysts. Essentially any tissue type can, in rare instances, form a suburethral mass. For example, urethral diverticula with colonic epithelium and Paneth cell metaplasia have been reported. Also, tumors of neuroendocrine origin have been observed in the suburethral region. Rarely, combinations of 2 or more of the above problems may be present. An example of this is carcinoma within a urethral diverticulum. A case of ectopic ureter terminating within a urethral diverticulum also has been reported. 
Include urethral diverticulum in the differential diagnosis in patients reporting recurrent UTIs, stress incontinence or postvoid dribbling, urinary urgency and frequency, dysuria, urethral pain, urinary retention, dyspareunia, hematuria, or purulent urethral discharge.
Treatment of urethral diverticulum is indicated if patients are symptomatic. Small asymptomatic diverticula can be noted in patients' charts and monitored. Indications for future treatment could include the onset of symptoms, hematuria not attributable to another cause, and an increase in size. Following the cases of patients with minimal symptoms may be acceptable because the potential complications from surgical intervention may outweigh the benefits of symptom relief. No studies of expectant management in this setting exist, however. Filling defects within the diverticulum identified on imaging studies may be an indication for surgical treatment, even in the absence of symptoms, because this finding may indicate a malignancy or a stone within the sac.
The female urethra is approximately 4 cm in length. It is embedded in the connective tissue supporting the anterior vagina. The epithelium is stratified squamous in type, which variably becomes transitional as the bladder is approached. The epithelium is arranged into longitudinal folds. At the base of the folds are scattered gland openings along the entire urethral length. These are the openings of the paraurethral glands. Although Regeneri de Graaf first described the openings of the paraurethral glands in 1672, these structures remained poorly characterized until the 20th century. In 1880, Skene detailed the 2 main distal-most ducts and glands, which now commonly are referred to as Skene glands.
In 1948, Huffman published his classic detailed anatomic description of the paraurethral glands.  He performed serial sections in cadaveric specimens and observed the glands to be mostly in relation to the distal two thirds of the urethra. The gland openings primarily were found along the posterior and posterolateral mucosal surfaces. The epithelial lining of these glands was noted to be columnar, and he found that associated inflammation was common.
Many anatomists now regard the paraurethral glands as the homologue to the male prostate gland. In the 1980s, positive histochemical staining of tissue specimens from the paraurethral glands for prostate-specific antigen (PSA) lent support to this concept.
The intrinsic smooth muscle of the urethra is arranged longitudinally and obliquely, with a few circularly arranged fibers. The oblique and circular fibers, in particular, contribute to urethral closure at rest. The striated urethral sphincter is complex, and the configuration of this group of muscles is not universally agreed upon. The bulk of this muscle group is located in the proximal two thirds of the urethra and is composed predominantly of slow-twitch fibers. The pubovisceral portion of the levator ani muscle group, the posterior pubourethral ligaments, and the endopelvic connective tissue that lies between the urethra and the vagina contribute to urethral support and urethral closure during times of increased intra-abdominal pressure. A complete description of extrinsic urethral support and the continence mechanism is beyond the scope of this article.
Contraindications for surgical treatment of urethral diverticula are few and generally involve medical disorders that render surgery of any kind unsafe. In cases of active abscess, definitive surgical treatment probably should be postponed. Temporizing measures include treatment with broad-spectrum, tissue-penetrating antibiotics and drainage either by vaginal incision or by urethral dilation and massage.
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