Confounding factors in ultrasound liver elastography. Part 2. Distortion of measurement results due to the characteristics of the state of the body and external influences

Abstract

The purpose of the study was to analyze the external influences and characteristics of the state of the organism being examined, which affect the results of ultrasonic elastography of the liver. Internal confounding factors include: inflammation and some other, besides fibrosis, liver pathology: amyloidosis, hemochromatosis, toxic hepatitis, lymphoma, cysts, tumors, veno-occlusive liver disease, as well as the degree of hydration, circulatory failure, renal failure, obesity, ascites, pregnancy, biliary hypertension and other less significant factors. External confounding factors are: food, alcohol; smoking and pharmaceutical preparations. The elastographic index of liver fibrosis is affected by the severity of its inflammation. Active hepatitis with a fivefold or more increase in aspartic aminotransferase and/or alanine aminotransferase overestimates the results of liver stiffness and does not enable a reliable investigation. With obstructive jaundice, in the absence of significant initial liver damage, Young’s modulus usually increases twofold to threefold. After biliary decompression by percutaneous bile duct drainage, Young’s modulus decreases. The presence of confounding factors should be indicated in the study protocol.

Keywords

• ultrasound
• shear wave elastography
• liver fibrosis
• stiffness
• young’s modulus
• liver