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. In this case it is an inflammatory mass which involves the ovary and Fallopian tube^{1 2} .

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 surgery³ .

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.

Investigations

• FBC: raised white cell count often but not invariably¹ .

• Ultrasound.

• CT/MRI scanning may be more effective at identifying the origin of the abscess⁴ .

Management

• 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 fistula⁵ . 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 approach⁸ .

  • 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

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.