Establishment of a Sprague-Dawley rat model of hepatolithiasis based on common bile duct catheterization

Figure 5 Fourier transform infrared spectroscopy. A: FT-IR spectrum of clinically confirmed calcium bilirubinate hepatolithiasis specimens. Key absorption bands: Broad peak at 3600-2400 cm^-1 (bound water); 3-peak combination at approximately 1637/1633/1630 cm^-1, approximately 1576 cm^-1, and approximately 1541 cm^-1 (characteristic calcium bilirubinate signature); C-H stretching at 2916/2849 cm^-1 (cholesterol). This spectrum serves as the reference standard confirming the analytical method; B: FT-IR spectrum of bile sediment from the experimental group (LPS-treated rats). The spectrum closely matches the clinical reference (Figure 5A): Broad bound-water absorption at 3600-2400 cm^-1; 3-peak combination near 1633/1630 cm^-1, 1599 cm^-1, and the 1500-1400 cm^-1 region, confirming calcium bilirubinate; C-H stretching at 2917/2849 cm^-1, indicating a minor cholesterol component. Taken together, the sediment is predominantly calcium bilirubinate with a small amount of cholesterol. FT-IR: Fourier transform infrared spectroscopy; LPS: Lipopolysaccharide.