Safety and Efficiency of Prostatic Abscess Transgluteal Drainage: A Case Report and Review of the Literature

Prostatic abscess (PA) is an uncommon disorder that mainly affects diabetic and immunocompromised patients. It requires a high index of suspicion for diagnosis since it can clinically mimic acute prostatitis. Historically, transurethral drainage along with antimicrobial therapy has been the gold standard therapy. However, advances in imaging modalities have shifted the management of PA to less invasive approaches. Here, we present a case of a large PA drained by the percutaneous transgluteal approach. This access route is a safe, effective, and well tolerated alternative for PA drainage, done under local anesthesia and providing a relatively cleaner approach than transrectal or transperineal drainage, allowing easier and better catheter fixation as well. This article illustrates the different steps of the procedure and reviews the literature on PA management.


Introduction
In contemporary practice, prostatic abscesses (PAs) are rare due to the widespread use of broad-spectrum antimicrobial therapy. Most cases of PA result from complications of acute bacterial prostatitis that were inadequately treated [1]. They are most often seen in patients with diabetes mellitus, immunosuppression, on chronic dialysis, or those who have chronic indwelling catheters [2]. The signs and symptoms of PA can mimic those of bacterial prostatitis, frequently leading to a delayed diagnosis. Treatment consists of pus drainage and urinary diversion (Foley catheter/suprapubic catheter), along with appropriate antibiotic administration [3].

Case Presentation
A 96-year-old male nonsmoker with hypertension, a complete bundle branch block treated with a pacemaker, chronic atrial fibrillation, benign prostatic hyperplasia, and recurrent urinary tract infections, presented to our emergency department with a 1-month history of lower urinary tract symptoms (abnormal frequency and dysuria), along with dyspnea and general status alteration. As reported by his family, the patient was having intermittent episodes of lowgrade fever during the last month.
Upon arrival, vital signs showed a temperature of 38.3 °C, heart rate of 98 beats per min, blood pressure of 110/70 mm Hg and respiratory rate of 24 breaths per min. The patient appeared clinically ill. Physical examination included a digital rectal examination (DRE), which revealed a large and painful prostate, with an area of fluctuation lateralized to the left side. Initial laboratory tests were consistent with urinary tract infection and acute kidney injury, with blood tests revealing a white blood cell (WBC) count of 15,800/ mm 3 (79% neutrophils), creatinine level of 3.66 mg/dl, urea of 112 mg/dl, and C-reactive protein level of 261. Urine analysis showed numerous WBCs, 8-10 red blood cells, and numerous bacteria. Urine and blood cultures were taken. Initial medical management consisted of intravenous fluids and broad-spectrum antibiotics (imipenem). A Foley catheter was inserted for urinary diversion and accurate urine output monitoring; it was subsequently replaced 48 h after antibiotic initiation.
Pelvic ultrasound revealed a 5.7 × 5.2 × 5 cm hypoechoic and heterogeneous collection in the left central and peripheral zone of the prostate, displacing the prostatic urethra to the right, suggestive of a PA (Fig. 1).
A noninjected computed tomography (CT) scan of the pelvis was performed to evaluate the extension of the abscess to adjacent organs. It was concordant to the ultrasound, showing a left paramedian intraprostatic collection measuring 64 × 54 × 50 mm, with no evidence of extraprostatic extension (Fig. 2).
Given the size of the PA and the patient's condition, percutaneous CT-guided drainage was performed through a left transgluteal approach in the right lateral decubitus position ( Fig. 3). The traditional Seldinger technique was done with an 18-gauge long-sheathed needle inserted into the collection and subsequent spontaneous drainage of thick purulent material (40 cm 3 ) that was sent for culture (Fig. 4). The needle was inserted through a small window to avoid rectal or sciatic nerve injury. Even though we were close to the sciatic nerve, it was clearly identified and avoided. A 0.035-in. stiff guidewire was then coiled within the collection through the sheath followed by insertion of a 10 French pigtail catheter over the guidewire with all of its side holes within the collection. The drain was fixed to the skin and kept inside the prostatic collection for continuous drainage (Figs. 5, 6). The whole procedure was done under local anesthesia and was very well tolerated by the patient.
Following drain insertion, the patient's condition improved, and he subsequently became clinically and hemodynamically stable as the sepsis resolved in the following days. His creatinine level also progressively returned to the normal range.
Both urine and purulent fluid cultures grew multisensible Escherichia coli. Therefore, the patient was shifted to third-generation cephalosporin (Ceftriaxone). The catheter was flushed twice daily with 10 ml normal saline. It drained an additional 50 ml pus during the next 72 h. After ensuring complete resolution of the collection on a control pelvic ultrasound (Fig. 7), the pigtail catheter was removed. The patient was discharged home after a full antibiotics course of 4 weeks and a negative control urine culture.

Discussion
PAs are rare, and their incidence has decreased due to the widespread use of broad-spectrum antimicrobial therapy. Most cases of PA result from complications of acute bacterial prostatitis [1].
Before significant advances in antibiotics, most cases of PA were caused by Neisseria gonorrhea, with mortality rates reaching 30%. Currently, Enterobacteriaceae are the dominant causative organisms, mainly E. coli. Other gramnegative rods have also been implicated [1]. Two pathologic mechanisms have been suggested as the etiologies of PAs: urinary reflux from the urethra toward the prostatic acini or hematogenous dissemination from a septic focus [2].
Predisposing factors for PA formation include diabetes mellitus, liver cirrhosis, immunosuppression, chronic indwelling catheters, and chronic dialysis [2]. A high index of suspicion is required in these patients because rapid progression to septic shock might occur [1].
The signs and symptoms of PA are nonspecific and can mimic those of bacterial prostatitis, frequently leading to a delayed diagnosis. It should be suspected in high-risk patients with fever and lower urinary tract symptoms that do not improve after 48 h of antibiotics [2]. The most typical sign is a severely tender prostate with an area of fluctuation on DRE. Patients can also present with acute urinary retention in 33% of cases [1].
Transrectal ultrasound (TRUS) is the diagnostic method of choice. It usually shows one or multiple hypoechoic areas containing pus but underestimates the real extension of the abscess. A CT scan of the pelvis can detect the periprostatic extension of the abscess, particularly to the ischiorectal fossa and perineum. Little data are available to support the use of magnetic resonance imaging in PA [1].
Once the diagnosis of PA is made, resuscitation measures should be started including oxygen, intravenous fluids, and broad-spectrum antibiotics. The available literature contains many reports describing the management of PAs, but there  are no standardized guidelines due to the rarity of this urological disease [1].
The treatment of a PA depends on its size and shape. Monofocal abscesses < 1 cm in diameter can be treated conservatively with broad-spectrum parenteral antibiotics alone [3]. Failure to respond quickly to antibiotics with no signs of clinical improvement requires drainage of the abscess with or without urinary diversion [1]. Multifocal abscesses or abscesses > 1 cm in diameter should be evacuated [3]. There are multiple methods for drainage (e.g., transurethral, transrectal, or transperineal), each of which has its advantages and disadvantages [2].
Minimally invasive procedures such as TRUS-guided aspiration or transperineal ultrasound-guided aspiration are currently considered the standard procedure for the drainage of PAs as they are easy to perform, have low morbidity, and  can be repeated in case of failure or incomplete drainage [1]. The disadvantages of the transrectal route include the possibility of incomplete drainage due to the limitation of the size of the puncture needle, risk of rectal bleeding, risk of exacerbation of infection due to fecal bacteria, and difficulty maintaining the catheter in place (which is usually preferable in the case of large abscesses); whereas the transperineal approach is a relatively painful procedure, usually done under general anesthesia, with the risk of nerve damage and sexual dysfunction [2].
Transurethral drainage, which was previously the first choice of therapy by urologists to treat PAs, is currently reserved for persistent abscesses that recur despite minimally invasive treatment [1]. In the case of multifocal and/or large (> 3 cm) abscesses, a high success rate of transurethral drainage has been reported and therefore should be considered [2]. It consists of opening the cavity of the abscess and removing the pus-filled vesicle with a resectoscope. The disadvantages of this access include high-risk anesthesia, the possibility of inducing bacteremia or sepsis, and sexual dysfunction [3].
In our patient, we drained a large PA with another minimally invasive method, namely the percutaneous transgluteal approach. Multiple cases of deep pelvic abscesses drained through this approach were reported [4], but we did not encounter such a method of evacuating a PA in our review of the available English literature.
The transgluteal approach requires a precise anatomic understanding of the pelvis. The ideal approach for transgluteal access is to insert the catheter under CT guidance, as close to the sacrum as possible at the level of the sacrospinous ligament, to avoid any injury to the sciatic nerve and rectum [4].
Using the transgluteal approach, a high-risk surgery was avoided in this elderly, critically ill patient with multiple comorbidities (indication for transurethral drainage in PA > 3 cm). Furthermore, this technique used a relatively clean route, thus preventing possible exacerbation of infection compared to other techniques. We believe that this access route is a safe, effective, and well tolerated alternative for the drainage of PAs, requiring only local anesthesia. In the case of transrectal access, there is potential for subsequent infection of the periprostatic tissues with fecal bacteria, in addition to the possibility of urethral injury and rectovesical fistula formation if the indwelling catheter is left in place for a long period of time [3]. The transperineal approach has the disadvantages of being more irritating compared with other techniques and taking twice as much time [5].
Although pain has been cited as a common side effect of the transgluteal technique [4], our patient tolerated the procedure and the catheter very well. Other complications include hemorrhage, nerve injury, and catheter malposition [4], which are common to all of the minimally invasive techniques. Pseudoaneurysm of the inferior gluteal artery has also been described [6].

Conclusion
Minimally invasive procedures are currently used for PA drainage. The percutaneous transgluteal route described in this report is a safe, effective, and well-tolerated alternative for PA drainage done under local anesthesia and offers a sterile approach with adequate catheter positioning and fixation.
Author contributions The manuscript has been read and approved by all of the authors, the requirements for authorship have been met, and each author believes that the manuscript represents honest work. Funding None.

Data availability
The authors confirm that the data supporting the findings of this study are available within the article.

Conflict of interest The authors have no conflicts of interest to declare.
Ethical approval Ethical approval was not required for this case report.

Consent for publication A signed patient consent form was obtained.
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