Delayed diagnosis of pyogenic liver abscess remains a challenging problem in the emergency department because of the associated high morbidity and mortality. Objective: To evaluate the sensitivity of ultrasono-graphy in the diagnosis of pyogenic liver abscess in patients presenting to the emergency department and the factors that may influence this sensitivity. Methods: A retrospective study was conducted in patients diagnosed with pyogenic liver abscess in the emergency department (ED) of a tertiary care teaching hospital for a period of 5 years. Between May 2001 and April 2006, 268 patients diagnosed with pyogenic liver abscess were evaluated by ultrasonography and/or CT scanning. The age, sex, clinical presentation, location and number of abscesses and the underlying disease of these two groups were compared. Results: Of the 268 patients admitted via the ED who were discharged or died with a diagnosis of pyogenic liver abscess, there was a predominance of men (M/F173/95) and the mean age was 57.6 years (range 17-90). 38 had false negative findings on ultrasonography (sensitivity 85.8%) and required abdominal CT scanning for definitive diagnosis. In the other 230 cases, ultrasonography alone was sufficient for diagnosis. Location of the abscess in segments 4 and 5 of the liver raised the sensitivity of ultrasound for diagnosis, while location in segment 8 was most associated with delayed diagnosis by ultrasonography. Right costal angle knocking pain was significant for pyogenic liver abscess even if ultrasound was negative. Conclusions: The size and location of the liver abscess and the underlying comorbid diseases may affect the diagnostic sensitivity of ultrasound for pyogenic liver abscess in clinical practice. A high index of suspicion should be maintained in patients with diabetes mellitus, previous biliary tract intervention or gastrointestinal malignancy. Follow-up CT scanning is recommended if right flank knocking pain is present, even if ultrasonography is non-revealing. A diagnostic protocol for liver abscess may be feasible in the future.
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