[Reference values in abdominal ultrasound - liver and liver vessels]

Reference values for B-mode abdominal ultrasound are being controversially discussed due to the limited data in the literature. A systematic survey of data published so far is presented for liver and hepatic vessels.

A literature search for reference values in the abdomen from 1970 to 2010 in healthy subjects 18 years of age and older was carried out. In accord with the determination of reference intervals for laboratory values, reference values are generally determined with the aid of 95 % reference intervals and the associated 90 % confidence intervals. Evaluated parameters were the size and volume of the liver, the portal vein diameter and cross-section and the diameters of the hepatic veins.

Liver size is usually determined by its longitudinal diameter in the midclavicular line. Although not sufficiently evaluated, < 16 cm can be used as a reference value. Numerous methods, which are not comparable, have been described for the determination of liver volume. For the portal vein diameter, refererence intervals could be deduced from 6 studies. Data from 4 studies on the liver veins differ depending on the exact localisation of measurement.

Normal values are helpful in delineating numerous pathological changes in the respective organs. Unfortunately, data are scarce and the examination technique, so far, has not been standardised sufficiently to compare data. A multicentre trial is required to standardise examination techniques and improve the quality of the results.