Psoas abscess - not as rare as we think?

OBJECTIVE: Iliopsoas abscess (IPA) is a rare condition with a reported worldwide incidence of 12 new cases per year with primary abscesses now predominating. The presentation is often vague and the diagnosis not considered.
METHOD: The medical records of 15 consecutive patients presenting to our hospital in a 3-year period with IPA were reviewed. Demographic data, presenting features, predisposing factors and the investigations performed were recorded. Abscesses were classified as primary or secondary and the treatment provided and eventual outcomes were analysed.
RESULTS: Fifteen patients (eight males) were included. Nine patients were pyrexial on admission, 14 were anaemic and all had raised inflammatory markers. Only five patients presented with the classical triad of pain, fever and limp. The median time to diagnosis was 3 days with a median hospital stay of 27 days (range 7-243 days). Fourteen patients were diagnosed by computed tomographic scan. Three patients were treated with antibiotics alone whilst 11 received percutaneous drainage (PCD) as well. Of these, five had recurrence following initial drainage, needing further PCD procedures but none needed open drainage. Only one patient underwent open drainage initially. The mortality rate was 20%.
CONCLUSION: The incidence of IPA is probably under-reported. The vague presentation leads to delays in diagnosis and increases morbidity and a high index of suspicion is the key to early diagnosis. Percutaneous drainage with antibiotics is the first line of treatment although recurrence rate is high. Open drainage allows simultaneous treatment of underlying pathology in secondary abscesses.