The significance of microabscesses in liver transplant biopsies: A clinicopathological study

Parenchymal microabscesses (MA) in liver transplant biopsies are frequently associated with cytomegalovirus (CMV) infection. However, other potential causes of MA have not been fully investigated. We studied additional etiolo gies for MA via histological evaluation and clinicopathological correlation . Three hundred seventy-two liver transplant biopsies from 97 patients (fro m 1991 to 1997) were reviewed and stained immunohistochemically for CMV. Nu merous histological features were evaluated including size and number of MA , lobular and portal inflammation, and cholestasis. Medical records were re viewed for radiographic, laboratory, and other clinical data from the time of biopsy. The chi(2) or Fisher's Exact test and ANOVA with adjusted multip le comparisons were used to determine statistical significance. Sixty-two o f 372 biopsies (17%) from 43 patients contained MA. Biopsies were obtained between 4 days and 2.3 years posttransplant (median, 14 days). Nineteen per cent of biopsies had CMV infection at the time of biopsy; 27% were associat ed with other bacterial, viral, or fungal infections; 10% had graft ischemi a; 15% had biliary obstruction/cholangitis; 3% had a combination of ischemi a and sepsis; and no explanation was found in 26% of biopsies. Numerous MA within a biopsy (>9) correlated with CMV infection (P < .005); no other his tological features, including size of MA, correlated with the etiology of M A. Overall, 43 of 97 (44%) liver transplantation patients at our institutio n had biopsies demonstrating MA at some point in their posttransplantation course. CMV infection appears responsible for only a minority of cases. MA, although nonspecific, are an important histological finding in numerous co nditions that may have a significant impact on both graft survival and over all patient morbidity.