Pelvic abscesses

A pelvic abscess most commonly follows acute appendicitis, or gynaecological infections or procedures. It can also occur as a complication of Crohn's disease, and diverticulitis or following abdominal surgery. An abscess contains infected pus or fluid, and is walled off by inflammatory tissue. A pelvic abscess may grow quite large before making a patient ill, or causing obvious signs, and so may be easily missed.

• In males the abscess is usually located between the bladder and the rectum.

• In females the abscess usually lies between the uterus and the posterior fornix of the vagina, and the rectum posteriorly.

• A tubo-ovarian abscess is one type of pelvic abscess which is found in women of reproductive age, and may be a complication of pelvic inflammatory disease.¹ In this case it is an inflammatory mass which involves the ovary and Fallopian tube.

How common is a pelvic abscess? (Epidemiology)

• Uncommon.

• Predisposing factors include Crohn's disease, diabetes mellitus, immunodeficiency and pregnancy. In Crohn's disease, abscesses may occur either spontaneously or as a complication of surgery.²

Symptoms of pelvic abscess (presentation)

• Systemic features of toxicity: fever, malaise, anorexia, nausea, vomiting, pyrexia.

• Local effects: eg, pain, deep tenderness in one or both lower quadrants, diarrhoea, tenesmus, mucous discharge per rectum, urinary frequency, dysuria, vaginal bleeding or discharge.

• Rectal or vaginal examination: may reveal tenderness of the pelvic peritoneum and bulging of the anterior rectal wall.

• Partial obstruction of the small intestine: this may sometimes occur.

Differential diagnosis

• Pelvic inflammatory disease.

• Appendicitis.

• Diverticular disease.

• Generalised peritonitis - eg, from a perforated peptic ulcer.

• Sepsis following termination of pregnancy or miscarriage.

Diagnosing pelvic abscess (investigations)

• FBC; ESR; CRP.¹

• Ultrasound.

• CT/MRI scanning may be more effective at identifying the origin of the abscess.³⁴

Treatment for pelvic abscess

• Arrange urgent admission to hospital.

• Management is usually by drainage of the abscess along with antibiotic treatment. Antibiotics used alone are occasionally effective for very early, small abscesses.

• Antibiotic choice is guided by the likely cause and local resistance patterns and guidelines, but usually needs to be broad-spectrum until the pathogens are determined.

• Image-guided pelvic abscess drainage has high clinical success and low complication rates. The only factor affecting the clinical success rate is the presence of fistula.⁵ Procedures used for drainage of the abscess include:

  • Ultrasound-guided aspiration and drainage: usually the abscess would be rectally drained in men, and in females it would be drained vaginally.^{6 7}

  • CT-guided aspiration and drainage. Percutaneous drainage often uses a trans-gluteal approach.⁸

  • Endoscopic ultrasound-guided drainage (EUS-guided drainage). Evidence supporting this as an effective, minimally invasive option is growing.^{9 10}

  • Laparotomy or laparoscopy with drainage of abscess may be required in some cases.

• An abscess which is enlarging suprapubically needs draining urgently.

• In females the abscess is more difficult to diagnose if coils of bowel lie between the abscess and the posterior fornix and it may have to be drained suprapubically.

• Abscess drainage with adjuvant thrombolytic treatment, such as tissue plasminogen activator (tPA), has been used to aid drainage.^{11 12}

• Definitive surgery may be required after initial drainage for some causes of pelvic abscess, such as appendicectomy for abscesses due to appendicitis, or salpingo-oophorectomy for tubo-ovarian abscess.

Prognosis and complications¹³

The prognosis will depend on the aetiology of the abscess, underlying well-being of the patient and the speed of diagnosis and effective management. An abscess may sometimes drain spontaneously into the rectum.

The prognosis is poor with regards to future fertility problems in women of the reproductive age group who have had a pelvic abscess. This is because complications of a pelvic abscess include ectopic pregnancy and subfertility due to severe damage to the fallopian tube, ciliary epithelium and ovary. Chronic pelvic pain has been observed in around 33% of patients, related to scarring and adhesions.