A pelvic abscess most commonly follows acute appendicitis, or gynaecological infections or procedures.

• In males the abscess is located between the bladder and the rectum.
• In females the abscess lies between the uterus and the posterior fornix of the vagina, and the rectum posteriorly.
• A pelvic abscess may grow quite large without making a patient very ill, or causing obvious signs, and so may be easily missed.

Epidemiology

• Uncommon.
• Predisposing factors include Crohn's disease, diabetes mellitus, immunodeficiency and pregnancy.

Presentation

• Systemic features of toxicity: fever, malaise, anorexia, nausea, vomiting, pyrexia.
• Local effects, e.g. pain, deep tenderness in one or both lower quadrants, diarrhoea, mucous discharge per rectum, urinary frequency, dysuria.
• Rectal or vaginal examination may reveal tenderness of the pelvic peritoneum and bulging of the anterior rectal wall.
• There may be partial obstruction of the small intestine.

Differential diagnosis

• Pelvic inflammatory disease.
• Appendicitis.
• Diverticulitis.
• Generalised peritonitis, e.g. from a perforated peptic ulcer.
• Septic abortion.

Investigations

• FBC: leukocytosis.
• Sigmoidoscopy.
• Barium enema.
• Ultrasound.
• CT/MRI scanning may be more effective at identifying the origin of the abscess.¹

Management

• Arrange urgent admission to hospital (same day).
• Management is usually by drainage of the abscess along with antibiotic treatment. Antibiotics used alone are occasionally effective for very early, small abscesses.
• Surgical procedures include laparotomy or laparoscopy with drainage of abscess.
• If there are no signs that the infection is spreading upwards into the peritoneal cavity, an operation is not urgent. Antibiotics are given as for peritonitis (cephalosporin or gentamicin, plus metronidazole or clindamycin) with close monitoring of the patient's temperature and the mass. The abscess should then be drained as soon as it is 'ripe'.
• An abscess which is enlarging suprapubically needs draining urgently.
• A pelvic abscess following a septic abortion or puerperal sepsis may be caused by anaerobes, and so be particularly serious and likely to spread. The abscess should be drained early.
• Ultrasound-guided aspiration and drainage: the abscess should be rectally drained in men, and in females it should be drained vaginally.² This is preferable to laparotomy, but this may be necessary.
• In females the abscess is more difficult to diagnose if coils of gut lie between the abscess and the posterior fornix and it may have to be drained suprapubically.
• Percutaneous abscess drainage is performed using CT or sonographic guidance.³

Prognosis

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

Document references

1. Kalish GM, Patel MD, Gunn ML, et al; Computed tomographic and magnetic resonance features of gynecologic abnormalities Ultrasound Q. 2007 Sep;23(3):167-75. [abstract]
2. Saokar A, Arellano RS, Gervais DA, et al; Transvaginal drainage of pelvic fluid collections: results, expectations, and AJR Am J Roentgenol. 2008 Nov;191(5):1352-8. [abstract]
3. Harisinghani MG, Gervais DA, Hahn PF, et al; CT-guided transgluteal drainage of deep pelvic abscesses: indications, technique, Radiographics. 2002 Nov-Dec;22(6):1353-67. [abstract]

Internet and further reading

• Wheeless CR et al; Incision and Drainage of Pelvic Abscess via the Vaginal Route, Atlas of Pelvic Surgery
• Mudgil SM; Pelvic Inflammatory Disease/Tubo-ovarian Abscess, e-Medicine, Aug 2009

Acknowledgements