Abdominal actinomycosis.

Abdominal actinomycosis has been recognised for over 150 years yet remains largely unknown to most clinicians. It's varied presentations are usually considered to represent malignancy rather than an infective process - and was once described as 'the most misdiagnosed disease'. Actinomyces are gram positive bacilli of the Actinomycetales genus, and A. israelii is responsible for the majority of human disease. They are normal commensal inhabitants of the human bronchial and gastrointestinal tracts and seem to only cause pathological infection after preceding mucosal breakdown. Patients who have undergone appendicectomy, have had a missed perforated appendicitis or women with a history of intrauterine contraceptive device use are at an increased risk. Florid abscess formation with fistulation, abundant granulation and dense surrounding fibrosis are common. Diagnosis prior to, or even during, surgery is rare and the findings are usually mistaken for acute inflammatory pathologies or malignancy. The treatment of choice is prolonged antibiotic therapy, usually with penicillin to which the organisms remain exquisitely sensitive, although delayed recurrence is possible. This review outlines the historical background of actinomyceal infection and considers the epidemiology, pathophysiology and clinical features of abdominal actinomycosis.