Pyocystis

Etiology

Pyocytis most likely occurs due to the inability of a defunctionalized bladder to expel the epithelial cells and debris that accumulate in the bladder without the flow of urine.[9] It could also be due to the collection of retrograde prostatic secretions in men and the osmotic transfer of water.[10] When this collection of debris/secretions becomes infected, pyocystis occurs.

In a fully functional bladder, the flow of urine prevents the accumulation of debris and subsequent inflammatory and infective processes occurring. Causative organisms are frequently the same as those that most commonly cause lower urinary tract infections, such as E.coli and other gram-negative bacteria. Other common organisms include P. mirabilis, P. aeuginosa, and Enterococcus.[11][12] Retrograde passage of these organisms along the urethra is the most likely source of infection.[6]

The bladder can become defunctionalized either iatrogenically or physiologically. Physiological defunctioning occurs because of anuria secondary to end-stage renal failure. Iatrogenic defunctioning results from supravesical urinary diversion. Both result in a lack of urine flushing through the bladder, putting the patient at risk of pyocystis.[13][9]

Epidemiology

The incidence of pyocytis rose following the introduction of supravesical urinary diversion procedures in the 1960s. Reported cases prior to this were rare. The incidence of pyocytis in patients with end-stage renal disease is unclear in the published literature, but it is a known complication secondary to anuria in this patient cohort.[9][5]

Pyocystis resulting from iatrogenic bladder defunctioning is more common than from end-stage renal failure.[6] The reported rate of occurrence of pyocytis varies from 7 to 67% in patients who have had a urinary diversion procedure.[11][14][2][15] It has also been observed to be more common in female populations.[16] The reason for this is thought to be the shorter female urethra, similar to how women are more at risk of urinary tract infections.[5] 

Culturing of proteus mirabilis in the urine prior to supravesical diversion has been implicated with higher risks of developing pyocystis.[17][3] Pyocystis develops more often in the first 6 to 12 months following surgery.[17] Some studies have shown that there is a significantly increased risk of developing pyocystis if the patient has had pelvic irradiation.[18][19]

Pyocystis is also described as empyema cystis and vesical empyema, though these terms are infrequently used and often used in older descriptions of the condition.[20][3] Because of this, their contribution to epidemiological literature is limited.

Pathophysiology

The accumulation of cellular debris provides a focus for bacterial infection.[1]  If bacterial infection occurs, pus accumulates due to bacterial cell turnover and the host’s inflammatory response. This collection of pus in the bladder is pyocystis. The collection of infected tissue results in the activation of the body’s immune response leading to pain, fevers, and systemic inflammatory response syndrome in severe cases.[1] 

Much like with an abscess or empyema, the body will struggle to get control of the infection due to the difficulty of getting white cells into the purulent fluid. Therefore to manage pyocystis, the purulent tissue must be drained.

History and Physical

Pyocytis will typically present with suprapubic pain, malodorous discharge from the urethra, and fevers for several days prior to admission.[12] In more severe cases, there may also be other systemic signs of infection, such as loss of appetite, nausea, and vomiting.[12] 

Patients presenting with signs of systemic infection and accompanying risk factors should be investigated and treated for pyocystis. These risk factors include surgical defunctioning of the bladder or end-stage renal failure. Alternatively, patients with pyocystis may present with a low-grade fever and some abdominal or pelvic discomfort and may be systemically well. There is a spectrum of presentations for this condition depending on the severity and duration of infection.[21][22]

On examination of the abdomen, there may be a palpable, tender suprapubic mass and inguinal lymphadenopathy.[22] On inspection of the genitalia, malodorous discharge or frank pus may come from the urethra.[17] The clinician may find tachycardia, hypotension, and pyrexia when taking basic vital signs.[21]

Evaluation

Blood tests often show leukocytosis and a raised C-reactive protein (CRP).[13] Blood cultures should be taken; however, these often do not isolate an organism.[9][21] All patients with a differential of pyocytis should be catheterized. This has dual diagnostic and therapeutic benefits. A sample of the bladder contents should be taken for microbiology, cultures, and sensitivities. Most common organisms isolated are E. coli, Pseudomonas aeruginosa, and Enterococcus faecalis. Proteus mirabilis and Serratia marcescens have also been isolated.[12] However, in immunocompromised patients, less common pathogens may be isolated.[21]

The diagnosis of pyocytis can be aided by using computed tomography (CT) and ultrasound. The benefit of ultrasound is that it is more easily accessed and can be performed at the bedside. Ultrasound will show a thickened bladder wall and a heterogeneous echogenic collection.[13] CT scanning may show a thick-walled bladder containing a collection of fluid.[22] CT scanning with IV contrast is preferred for investigation. However, non-contrast CT will display the same features and is useful in patients with end-stage renal failure.[22][2][9]

Investigation and diagnosis of pyocytis may also include cystoscopy to aid bladder access, evacuate toxic collections, and biopsy thick-walled bladder to exclude malignancy.[4][2]

Treatment / Management

In patients displaying signs of urosepsis, initial treatment should include fluid resuscitation and administration of broad-spectrum IV antibiotics.[21] High-risk patients should be treated with antibiotics that cover opportunistic infections. High-risk patients include those who are receiving dialysis, chemotherapy, IV antibiotics, or who have recently been discharged from the hospital.[1] Some patients may have pre-existing urine cultures; these sensitivities will help guide treatment.(A1)

Immediate catheterization of the patient is important in patients with suspected pyocystis. This has dual therapeutic and diagnostic benefits through drainage of infected tissue and acquiring pus for culture, respectively. Once sensitivities are obtained, the antibiotic choice can be tailored to reflect this.

Following catheterization, bladder irrigation should be used to prevent the re-accumulation of infected debris and to assist in clearing the initial collection. This can be continuous irrigation using a three-way catheter or can be done using frequent bladder washouts. Irrigation should be continued in the community for up to 3 months, several times a week, to attempt to eradicate any infection.[12] Intra-vesical antibiotics have been used to treat pyocytis, typically gentamycin or neomycin. Normal saline is also an option.[23][17][24](A1)

The previous positive urine culture of Proteus mirabilis is a significant risk factor for the development of pyocystis following urinary diversion procedures.[25] Some have argued that patients with positive pre-operative urine culture for Proteus mirabilis should be considered for a cystectomy.[5] Alternatively, in sexually inactive females, the Spence-Allen procedure can be considered to prevent the development of pyocytis.[3][17] This involves the creation of a vesicovaginal fistula to allow continuous drainage of bladder contents through the vagina.[26] (B3)

Cystectomy may be necessary for patients not responding to IV antibiotics and irrigation. The need for cystectomy in patients with pyocytis is reportedly up to 25%.[4][15](B2)

Differential Diagnosis

In females with pyocytis urethral discharge can be accidentally misidentified as vaginal discharge, leading to misdiagnosis.[27]

Prognosis

The prognosis of pyocystis depends on the severity of the infection and systemic involvement. Milder cases may be managed in the community with antibiotics and intermittent bladder irrigation. Severe non-resolving infections require surgical management with either the Spence-Allen procedure or total cystectomy.

The need for a cystectomy in patients diagnosed with pyocytis is reported to be between 18.7% and 25%, however, due to the relative rarity of the condition, the number of cases in the studies was low, and a meta-analysis of a larger patient cohort is required to establish more accurate figures.[4][15]

Complications

Complications of pyocytis include the need for surgical management, including the need for a total cystectomy. Sepsis and the corresponding complication can also occur in patients with pyocystis and can result in death.[12]