Characteristics and factors influencing treatment outcome of renal and perinephric abscess--a 5-year experience at a tertiary teaching hospital in Taiwan.

BACKGROUND AND PURPOSE: Diagnosis of renal or perinephric abscess is still a challenge for physicians. This study investigated the effect of location and size of abscess and the time of diagnosis on treatment outcomes.

METHODS: This retrospective analysis enrolled 159 adult patients with renal, perinephric or mixed-type (renal plus perinephric) abscess hospitalized between June 2001 and June 2006. The outcomes of these patients were classified into "poor" and "success" in order to elucidate associated risk factors. 106 patients had clear information of the timing of diagnosis and were categorized into "early" and "delayed" diagnosis groups, depending on whether the diagnosis was made within or after 5 days of admission.

RESULTS: Compared with the early diagnosis group (n = 78), the delayed diagnosis group (n = 28) were older (59.9 +/- 15.9 vs 50.9 +/- 14.9 years, p=0.005) and had less costovertebral angle knocking pain (85.7% vs 51.3%, p=0.021), a higher rate of renal insufficiency (57.1% vs 15.4%, p<0.001) and hospital stay over 22 days (71.4% vs 24.4%, p<0.001). There was no significant difference between these two groups in clinical outcomes. Compared with renal abscess, both perinephric and mixed-type abscess had higher rates of larger abscess (>5 cm in diameter) [84.1% vs 25.6%, p<0.001; and 55.6% vs 25.6%, p=0.012, respectively] and lower rates of Escherichia coli infection (24.4% vs 59.4%, p<0.001; and 26.7% vs 59.4%, p=0.021, respectively). Among all culture-positive patients, the proportion of Klebsiella pneumoniae was 25.6%. Perinephric abscess had higher rates of percutaneous (56.3% vs 31.5%; p=0.005) and surgical drainage (29.2% vs 7.6%; p=0.001) than renal abscess. In multivariate analysis, age > or =65 years (p=0.006; odds ratio [OR], 7.008; 95% confidence interval [CI], 1.75-28.141), thrombocytopenia (p=0.002; OR [95% CI], 10.434 [2.344-46.444]), and abscess without drainage (p=0.001; OR [95% CI], 9.984 [2.640-37.758]) were independent factors for poor outcome (mortality or nephrectomy).

CONCLUSION: Old age, renal insufficiency and lack of costovertebral angle knocking pain may contribute to delayed diagnosis of renal or perinephric abscess, and prolonged hospital stay. The location and size of abscess did not affect clinical outcome in this study, which might be due to adequate abscess drainage. K. pneumoniae is not uncommon in renal or perinephric abscess in Taiwan.