A periurethral collection variously described as a pseudocyst [48], pseudo-abscess [32] or a non-communicating diverticulum [49] appears to reflect the same underlying process. Notably, the mechanism underlying pseudo-abscess formation is unknown, with hypothesized etiologies including exaggerated host response, infection, or obstruction of periurethral glands. Historically, pseudo-abscess formation was thought to be secondary to delayed hypersensitivity to the bovine dermal product (collagen) [50]; however, repeated skin tests did not show conversion. Furthermore, pseudo-abscesses have been reported with a variety of different injectable agents [44, 45, 51, 52]; thus pseudo-abscess formation may be related to periurethral application, as opposed to simply the specific material utilized. It is worth noting, that while possible with all periurethral injectables, some agents (not approved for periurethral injection) had an unacceptably high rate of local reaction. For instance, dextranomer hyaluronic acid is an agent particularly associated with granuloma [53, 54] and/or pseudo-abscess formation [55].

Clinically, pseudo-abscesses typically present with a palpable well circumscribed anterior vaginal wall mass and potentially de-novo obstructive or irritative voiding symptoms. The mass is variably tender on examination. Several authors have reported that these collections may be infected [56], although many series note sterile culture results [44, 45]. Pelvic imaging in these cases can be clinically useful in ruling out other pathologies [57].

With regard to management, aspiration alone may lead to recurrence of the pseudo-abscess, whereas transurethral unroofing of these periurethral masses is invariably associated with reoccurrence of their presenting symptom of stress urinary incontinence [44, 45]. In these cases, the periurethral pseudocyst is thick-walled, containing cystic or loculated cavities which may or may not communicate with the urethral lumen. The contained fluid is usually non-odiferous viscous appearing fluid, with negative Gram stains and cultures. With larger cavities—not easily accessible via the urethra or with associated loculations—transvaginal unroofing/excision may be needed. Notably, while concerns regarding chronic inflammation and subsequent dysplastic changes have been noted, no cases have been associated with malignant or pre-malignant changes on evaluations occurring up to 19 months postinjection [58].

Notably, if spontaneous drainage of a pseudo-abscess occurs, alternative clinical presentations may arise. For instance, pseudo-abscess formation and subsequent drainage of the submucosal space into the true urethral lumen is the presumptive mechanism for pseudo-diverticulum formation after bulking injection [49, 59]. Likewise, spontaneous pseudo-abscess drainage has been suggested as a rare cause of urethrovaginal fistula formation [60]. Similar phenomena have also been described without pseudo-abscess formation [21, 47]. In these cases, it is possible that the submucosal injection may reduce blood supply to the thin overlying mucosal, as with presumably any injection into a closed space, leading to erosion and fistula formation [21, 47].

An otherwise healthy female with mixed urinary incontinence opted for primary management of her stress component with an injectable bulking agent; bovine glutaraldehyde-cross-linked collagen. After a negative skin test for bovine collagen allergy, a periurethral injection of a total of 5 cm³ was performed uneventfully. Six weeks later, she complained of terminal dysuria, with her symptoms progressing to obstructive symptoms with straining to void, increasing urethral discomfort and dysuria. Her physical examination demonstrated a large tender, non-expressible periurethral fluctuance. Urinalysis and urine culture were both negative for infection. Imaging demonstrated a large fluid collection periurethrally (Fig. 27.2). Given the size and location, the pseudo-abscess was vaginally drained through an inverted-U incision, taking care to preserve the periurethral fascia (Fig. 27.3a, b). A simple longitudinal incision was made directly into the pseudo-abscess, in order to establish complete drainage. The pseudo-abscess fluid here was typical: non-odiferous viscous toothpaste-appearing fluid compresses adjacent tissues, with negative Gram stains and cultures, even for fastidious organisms. The high pressures on the surrounding tissues are putatively the cause of the urethral pain, and reoccurrence of the pain should precipitate an evaluation for recurrence of the pseudo-abscess.

Urethral prolapse has also been reported in case reports with several agents of both current and historic interest [61–64]. The hypothesized mechanism of this complication includes distal particle migration and/or separation of the supporting periurethral tissue. Treatment is local excision in symptomatic cases. Notably, following local excision, many patients will have recurrent stress incontinence.

An additional late local complication is delayed onset urinary retention. As noted above, persistent urinary retention after urethral bulking injection may develop secondary to overbulking, necessitating aspiration or unroofing, though this is uncommon [44, 45, 65, 66]. However, in the elderly, we have encountered the late development of urinary retention due to progressive loss of detrusor power, without intervening outlet obstruction or other complication of the outlet. These rare patients require treatment as clinically indicated for their detrusor failure and the bulking agent itself does not require other management.

One final local sequela to consider after periurethral bulking injection is that of misdiagnosis of a pelvic mass. In some cases where an accurate history is not available, asymptomatic patients may undergo additional work-up or procedures for a periurethral or bladder mass, which is in fact secondary to their prior urethral bulking procedure. Notably, in this setting, imaging can be definitive and potentially prevent additional interventions in asymptomatic cases [57].