Pelvic Abscess

Etiology

The pelvic abscess is a frequent complication of an infection of the lower genital tract, including pelvic inflammatory disease. Other causes subsumed in the etiology of pelvic abscess are operative procedures like hysterectomy, laparotomies, caesarian sections, and induced abortion. Cancers of pelvic organs, trauma to the genital tract, Crohn disease complications, and diverticulitis are other significant causes.[6] In Crohn disease, the pelvic abscess may occur spontaneously and secondary to the surgery.[7] In females, it usually lies between the uterus, posterior fornix, and the rectum, which sometimes drains automatically into the rectum.

The risk factor for the pelvic abscess is the same as that of pelvic inflammatory disease like multiple sexual partners, sexually transmitted infection, intrauterine device, diabetes, low immune system.  Other recognizable risk factors that have been studied in developing post-surgical abscess classify as preoperative, intraoperative, and postoperative causes.

The preoperative risk factors involved in pelvic abscess formation are untreated pelvic inflammatory disease, hydrosalpinx, endometrioma, uncontrolled blood sugar with HbA1c greater than 6.5, renal comorbidities, obesity with BMI over 30, congenital anomalies of the genital tract. Asymptomatic bacterial vaginosis is also a known documented risk factor for postsurgical vaginal cuff cellulitis and abscess formation.[8]

The perioperative risk factors include intraoperative blood loss of over 500ml, prolonged surgical procedure exceeding 140 minutes, patients undergoing extensive surgeries like para-aortic lymphadenectomy, pelvic lymphadenectomy, pelvic exenteration for pelvic malignancies.

The postoperative risk factors include uncontrolled blood sugar over 200 mg in the first 48 hours, and prolonged preoperative hospital stay also increases the incidences of surgical site infections and pelvic abscess formation. Postoperative hematoma is also one of the critical causes of pelvic abscess.

Epidemiology

In reproductive age women, pelvic abscess most frequently present as the progression of the end-stage of pelvic inflammatory disease, involving Fallopian tube, ovary, and adjacent pelvic organs.[4][9] One-third of the women who have hospitalized with the pelvic inflammatory disease found to have a tubo-ovarian abscess. Notice that all the cases of abscess are not associated with pelvic inflammatory disease. The incidence of pelvic abscess is less than 1% in a patient undergoing obstetric and gynecological surgeries.

Pathophysiology

The pelvic abscess is a circumscribed collection of infected exudate. It is formed by liquefaction necrosis. It develops due to an imbalance between host defense mechanisms and insufficient antibiotic coverage in the setting of bacterial inoculum of high virulence. The necrotic tissues are built up around the infective exudate, which formed a thick fibrous wall. If the pus does not drain, it will localize the microbes as well as toxins which could be detrimental to the host and make it more difficult for antimicrobial agents to penetrate the fibrous inflammatory capsule and act on it. The enzymatic degradation of immunoglobulins and local release of complements occurs, which results in persistent pus formation.

In young women, pelvic abscess occurs as one of the complications of pelvic inflammatory disease. It starts as an ascending infection from the vagina, cervix and spreads to the uterus, fallopian tube, ovary, and peritoneum.  It causes endothelial damage and edema of the fallopian tube and consequently leads to tubal blockage. Notably, it generally occurs in the follicular phase of the menstrual cycle. Likewise, high estrogen and cervical ectopy help link Neisseria Gonorrhea and chlamydia to the genital tract, which is one of the most common causes of Pelvic inflammatory disease and its complication.

In postoperative patients, the theory is that blood loss, serous fluid, lymphatic debris, necrotic tissue, and fibrillar hemostats cumulates in the lower pelvic area and vaginal vault. It results in the formation of a simple collection of fluid. The fluid accumulation eventually becomes infected via skin contamination and vaginal opening and results in pelvic abscess formation. The pathogenic organism ascends from the vagina, endocervix, and via skin to the surgical site, including vaginal vault and abdominal incision.

Compound and dynamic mixture of pathogenic and nonpathogenic bacteria ascend from the vagina comprises anaerobic facultative gram-negative and gram-positive bacteria. As a result of an imbalance of the pathogenic and nonpathogenic bacteria, the sterile tissue gets infected and evolves in a pelvic abscess. Infection is usually polymicrobial, with the predominance of anaerobic bacteria. The bacteria involved are Escherichia coli, Bacteroides fragilis, Bacteroides, Peptostreptococcus,  aerobic Streptococcus, and Peptococcus.[10]

History and Physical

The clinical presentation of the pelvic abscess is highly variable. Patients may present with a high-grade fever, general malaise, nausea, vomiting, tachycardia, lower abdominal pain, vaginal discharge, vaginal bleeding, retention of urine, and change in bowel habit. Leukocytosis with a left shift along with elevated erythrocyte sedimentation rate and high C-reactive protein is present in blood workup.[3] Ectopic pregnancy should always be ruled out on a urine pregnancy test. A diagnosis is conventionally made based on the presence of fever and palpable mass or fullness. In 1983 a study conducted by Landers and Sweet demonstrated that 35% of women with abscess present afebrile, while 23% had normal leucocyte count. In the same study, they reported that 50% of the patients with tubo-ovarian abscess present with fever, 28% with nausea, and 21% with vaginal bleeding.[10]

The complete physical exam includes a thorough abdominal, vaginal, and rectal examination. Superficial or deep abdominal tenderness on abdominal palpation may be indicative of peritonitis. The comprehensive vaginal examination consists of the bimanual and speculum exam. The bimanual vaginal exam should assess the size of the uterus, mobility, consistency, and adnexa. Usually, the cervical motion tender is present, the uterus is tender, boggy, and most likely pushed anteriorly.[9] An abscess can be unilocular or multilocular. It can be palpable as a well-defined fluctuant mass, and it can also be less distinct and presents as a fullness on the bimanual vaginal exam. On the rectal exam, tenderness and bulging of the anterior rectal wall may be present.

Evaluation

Different imaging techniques are the most effective way to determine the size and location of an abscess. Pelvic ultrasound is the first method of choice to evaluate a pelvic mass in the women of reproductive age group. It can help in differentiating between the fluid-filled lesion and the solid lesion. It is a relatively easy and inexpensive method of imaging with no ionizing radiation. On ultrasound, an abscess appears a collection of pus with different sizes of delicate internal echoes. Transvaginal ultrasound is always superior to transabdominal ultrasound.[11] Multilocular abscess on imaging is likely to represent multiple inflamed tissue adherent to each other and a small collection of pus, mostly seen in a tubo-ovarian abscess. Unilocular abscess probably appears as an actual localized mass on imaging.

Ultrasound is still the safe and first method of choice in women of reproductive age group and tubo-ovarian abscess. A study conducted by Hiller et al. demonstrates that the majority of cases are multilocular 85%, and 73% had internal fluid echos, 95% has thick enhancing uniform abscess wall. Other common findings demonstrated were mesosalpinx 91% and infiltration into fat. A less common finding on CT was bowel thickening and infiltration of the uterosacral ligament.[12]

Other radiological techniques used in diagnosis include computed tomography and magnetic resonance. Computed tomography (CT) and magnetic resonance imaging (MRI) are cross-sectional imaging methods often used in postoperative patients with suspected abscess. In postoperative patients, the ultrasound is less likely to locate the pelvic abscess because of the collection of postoperative air, open surgical wounds, and abundant gas.[13] CT scan with oral and intravenous (IV) contrast enhances the diagnostic accuracy. Oral contrast opacifies the bowel loop, while IV contrast enhances the vascularity of the mass and opacifies the urinary tract in the contrast CT scan. The pelvic abscess exhibits as a hypodense collection with peripheral round or oval intensification on CT scan. CT scan has slightly better sensitivity and specificity than ultrasound.  In the review of a few studies in the past, it has demonstrated that sensitivity to detect abscess was 78% to 100 % compared to ultrasound has the sensitivity of 75 to 82% and CT scan with the specificity of 100 vs. 92 % for an ultrasound.[14][15][16] Furthermore, the MRI is usually recommended to clarify or supplement ultrasound findings as it does not determine the origin of the mass and the extent of the disease. It does not provide any additional information.[17]

Moreover, other investigations include complete blood count, blood culture, exudate culture and sensitivity, wet mount test of vaginal discharge, and a urine pregnancy test to rule out an intrauterine and ectopic pregnancy.

Treatment / Management

All the patients with suspicion of pelvic abscess and diagnosis should be admitted to the hospital regardless of the size of the pelvic abscess. All patients should be monitored closely for sepsis and rupture. The initial approach to the treatment is Broad-spectrum antibiotics. A multilocular abscess usually represents tubo-ovarian abscess and substantially respond well to Antibiotic treatment alone.

Conservative Management

The ideal candidates for conservative management alone are women with no sign of sepsis and rupture, hemodynamically stable and, pelvic abscess greater than 8 cm on imaging. In a study by Granberg et al. in 2009 stated that 25% of the patient fails to respond to conservative treatment.[4] A localized unilocular abscess more likely referred to postsurgical complications and generally requires surgical drainage.

Once diagnosed, a combination of parental antibiotics should be started to treat the mixed aerobic and anaerobic microbes. The gold standard antibiotics regimen is the combination of clindamycin or metronidazole with an aminoglycoside, penicillin, or third-generation cephalosporins. Aztreonam is a substitute for aminoglycoside in patients with renal impairment. Other antibiotics with high therapeutic efficacy that may be options as a single agent include extended-spectrum antibiotics (cefoxitin, cefotetan, cefotaxime, ceftizoxime), beta-lactamase inhibitors (ticarcillin-clavulanate and carbapenems, meropenem, ertapenem,)extended-spectrum penicillin (piperacillin-tazobactam).[3][18][19] Parental antibiotics should continue for 24 to 48 hours after the patient becomes afebrile and subsequently be switch to oral antibiotics. The ideal duration of antibiotics has not been rigorously studied. A vaginal cuff abscess is a likely complication of a post-hysterectomy infection that satisfactorily responds to dilatation and drainage of the vaginal cuff.

Surgical Management and Drainage of a Pelvic Abscess

Recent evidence suggests that it is acceptable and beneficial for the patient to perform primary surgical drainage along with appropriate antibiotic coverage. It decreases the length of stay of hospitalization and improves fertility outcomes. A study by Perez and medina reported that surgical drainage is needed if the size of the abscess is over 8 cm or failure to respond to adequate antibiotic treatment in 2 to 3 days.[20] The criteria for failure of treatment include; increase in leucocyte count, tense and tender abdomen, despite the antibiotic therapy there is no reduction in the size of the abscess, new onset of fever, and increase in the size of the abscess.

Different techniques are available for surgical drainage of the pelvic abscess, but in the past, the preferred approach was laparotomy. Many gynecologists still prefer this surgical route for the removal and drainage of the surgical abscess. Most of the gynecologist employs vertical incision in need for the proper visualization of abdomen and pelvis. Following steps should be done in the removal and surgical drainage of the abscess:

• Always confirm the diagnosis first with the appropriate backup.
• Cultures are obtained upon entering into the peritoneal cavity and abscess itself.
• Surgically remove the abscess as much as possible if the abscess is in the ovary, an adnexectomy is likely necessary.
• Always irrigate the peritoneal cavity with normal saline to lessen the burden of infection.
• All the tissues removed sent for culture and histopathology.
• Leave in the closed suction drain until the output from the drain is minimal, and the patient improves clinically.

Now the laparoscopic approach is being used for the drainage. The laparoscopic approach is being used more successfully in a patient with no exhibition of the rupture of an abscess. The choice between laparotomy and laparoscopy depends upon the determination and skill of the surgeon.  However, the CT, MRI, or U/S guided drainage with antibiotics is the procedure of choice and has a success rate of 80% to 90%.[21][22] A study conducted by Perez and Medina, states that these techniques have several advantages over laparoscopy, it requires no anesthesia, less morbidity, decreases the length of stay in hospital.[23][24] CT-guided transgluteal percutaneous drainage is a safe procedure, especially for deep abscess of postsurgical type. It is a successful procedure where the anterior approach to the pus collection is not feasible.[25] Endoscopic ultrasound (ESU)-guided drainage is another safe and effective method of draining in the pelvic abscess, which is not manageable to percutaneous drainage.[6][26] Some of the recent studies have shown the effectiveness and safe use of intracavitary tissue plasminogen activator (tPA) for refractory and complicated abscess.[27][28] Rupture of the pelvic abscess is always a life-threatening emergency in such patients immediate fluid resuscitation, and surgery required with antibiotics therapy.(A1)

Differential Diagnosis

Differentials diagnosis of the pelvic abscess includes:

• Pelvic inflammatory disease
• Ectopic pregnancy
• Sepsis following miscarriage 
• Appendicitis
• Renal colic
• Bowel obstruction
• Obturator hernia

Prognosis

The prognosis for the patients with a localized abscess is good; it usually depends on the timely diagnosis, prompt management, and etiology of the collection of pus. The prognosis is poor with regards to infertility in women of the reproductive age group who have had a pelvic abscess.[9]

Complications

The complication of a pelvic abscess includes ectopic pregnancy, the scar tissue from the previous inflammation and infection prevents the fertilized ovum to implant in the uterus and results in ectopic pregnancy.

Infertility is another prevalent complication, adhesion as a result of abscess and inflammation causes severe damages the fallopian tube and ciliary epithelium and ovary and results in infertility.[29] Chronic pelvic pain has seen in one-third of the patients, and pain is related to scarring and adhesions from the previous abscess and infection.[9][30]