Classification of gallstones using Fourier-transform infrared spectroscopy and photography

Byeong Jo Ha,Sangsoo Park

doi:10.1186/s40824-018-0128-8

Abstract

BackgroundGallstones have conventionally been classified by gross inspection into 4 categories: cholesterol gallstones, black pigment (calcium bilirubinate) gallstones, brown gallstones, and mixed gallstones that contain both cholesterol and calcium bilirubinate. Classification using Fourier-transform infrared (FT-IR) spectroscopy supplements gross inspection; however, the issue of ambiguity in gallstone classification has not been fully addressed to date.MethodsTwenty-six gallstones obtained after surgical gallbladder removal were examined using FT-IR spectroscopy and digital photography, and classified into 6 gallstone groups according to characteristic FT-IR absorption bands.ResultsFT-IR spectra of nine gallstones matched well with that of pure cholesterol, and the gallstones were thus classified as cholesterol stones. Twelve gallstones were classified as calcium bilirubinate stones as they showed characteristic absorption bands of calcium bilirubinate. However, the FT-IR spectra of these gallstones always showed a broad absorption band of bound water at 3600–2400 cm− 1. The other five gallstones were classified as mixed stones with combinations of cholesterol, calcium bilirubinate, and calcium carbonate.ConclusionFT-IR spectroscopy is a powerful and convenient method for gallstone classification. Nevertheless, one should take serious note of the superposition of FT-IR absorption bands of different chemical components of gallstones including that of bound water.

Highlights

Gallstones have conventionally been classified by gross inspection into 4 categories: cholesterol gallstones, black pigment gallstones, brown gallstones, and mixed gallstones that contain both cholesterol and calcium bilirubinate
Gallstones have been divided by gross inspection into 4 categories: cholesterol stones, black pigment stones, brown color stones, and mixed stones that consist of both cholesterol and calcium bilirubinate [2,3,4]
Pure cholesterol gallstones The Fourier-transform infrared (FT-IR) spectrum of a pure cholesterol gallstone as well as the chemical structure of cholesterol is shown in Fig. 1, wherein y axis unit is absorbance and the axis is removed for display

Summary

Introduction

Gallstones have conventionally been classified by gross inspection into 4 categories: cholesterol gallstones, black pigment (calcium bilirubinate) gallstones, brown gallstones, and mixed gallstones that contain both cholesterol and calcium bilirubinate. Gallstones have been divided by gross inspection into 4 categories: cholesterol stones, black pigment (calcium bilirubinate) stones, brown color stones, and mixed stones that consist of both cholesterol and calcium bilirubinate [2,3,4] This classification method is largely dependent upon the external shape and color of gallstones and does not accurately reflect the cases wherein the internal morphology of gallstones is different from the external one. FT-IR is useful when gallstone samples from a large number of patients are examined for purposes of classification and studying the etiology of gallstone formation [5,6,7,8,9] It is well established through these studies that cholesterol, calcium bilirubinate, and calcium carbonate are the three major constituents of gallstones. For detailed examination of gallstone constituents, fluorescence microscopy [13], X-ray diffraction [14,15,16,17], thermogravimetry (TG) and difference scanning calorimetry (DSC) [18], specular reflection spectroscopy [19], scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and

Methods

Results

Discussion

Conclusion