Hepatic technetium‐99m‐mebrofenin iminodiacetate scans and serum γ‐glutamyl transpeptidase levels interpreted in series to differentiate between extrahepatic biliary atresia and neonatal hepatitis

Abstract

Hepatic technetium‐99m‐mebrofenin iminodiacetate (99mTc‐mebrofenin IDA) scans and serum γ‐glutamyl transpeptidase (GGTP) have high sensitivity for extrahepatic biliary atresia (EHBA). This study was based on the hypothesis that the interpretation of results of 99mTc‐mebrofenin IDA scans and serum GGTP levels in series would result in a reduction of the false positivity observed with these tests individually. The aetiology of neonatal cholestasis in 132 study patients was: 25% (33/132) EHBA, 45.5% (60/132) neonatal hepatitis (NH) with an identifiable cause and 19.7% (26/132) idiopathic NH. Of the various clinical, biochemical and imaging parameters that were significantly different between patient groups, sensitivity for EHBA was: serum GGTP ≥ 150 IU 1−1(100%), 99mTc‐mebrofenin IDA scans (100%), pale stools (82.8%) and total serum bilirubin ≥ 12mg d1−1 (66%). However, specificity ranged from 48.5 to 79%. Of the 63 patients who had non‐excreting IDA scans, operative cholangiograms could be avoided on the basis of a specific aetiological diagnosis of NH, made concurrently, in only 9 infants. The rest (54) underwent operative cholangiograms; 21 (39%) of these had patent biliary trees and therefore underwent the procedure unnecessarily. If serum GGTP (<150 IU 1−1) had been used as a screen after IDA scanning in these 54 patients, operative cholangiograms could have been avoided in another 12 patients and thereafter only 9/42 (21%) of the operative cholangiograms would have been considered unnecessary. Conclusion: A diagnostic algorithm is proposed wherein serum GGTP level (at a cut‐off level that maintains 100% sensitivity for EHBA) is used in series with non‐excreting 99mTc‐mebrofenin IDA scans (for patients with no specific aetiological label). This strategy reduces the false positivity of individual tests.