Flow dynamics in the liver is altered in different hepatobiliary and cardiac pathologies, causing changes in hepatic vasculatures sizes and flow pattern changes which can be assessed by ultrasound (USG) study. Before one can use these measurements and observations to diagnose pathologies, a clear grasp of normality is crucial.

In the field of pediatrics, this is particularly challenging as the normal range of measurements may change with age, weight, height, gender and race of children.

Taking hepatic veno-occlusive disease as an example, current literature is conflicting regarding whether sonographic findings show consistent association with the disease. Sonographic findings therefore now have limited role in contributing to the diagnosis.

This may be related to the lack of a robust age corrected normal range of measurement for reference.

Existing literature shows that the normal portal vein diameter varies with age, weight and height and possibly gender. Literature for normal measurements of hepatic vein and hepatic artery in children is lacking.

In this study, the investigators aim to conduct a prospective, cross-section observational study to establish the normal measurements ranges of hepatic vein, hepatic artery and portal vein in healthy children in the investigators' locality.

Flow patterns, including qualitative assessment and quantitative measurements of resistive index and flow velocities will also be assessed.

These age corrected normal measurements will be very helpful in the diagnosis and follow-up of hepatobiliary and cardiac pathologies associated with alterations in dynamics of hepatic circulation.

Trial Objectives and Purpose:

1. To establish normal limits of diameter of hepatic vein, hepatic artery and portal vein according to age, weight, height and gender.
2. To establish normal waveform pattern in ultrasound Doppler assessment of hepatic vein, hepatic artery and portal vein. (Qualitative analysis)
3. To establish normal limits of flow parameters assessed by ultrasound Doppler in hepatic vein, hepatic artery and portal vein according to age, weight, height and gender.

Trial Design:

A prospective cross-section observational study.

Recruitment of study subjects:

Patients attending Hong Kong Children's Hospital for clinically indicated USG examination will be invited to participate in this study under specific inclusion and exclusion criteria.

Treatment of subjects:

Recruited subjects will proceed to the clinically indicated USG study they are referred for first. After the clinically indicated USG study is completed, additional USG & Doppler assessment of hepatic vasculatures will be performed, taking an additional 5 - 10 minutes.

All examinations will be done using a Philips EPIQ 5G ultrasound machine. Curvilinear or linear probe will be used depending on subjects' physique. Size measurements, qualitative and quantitative Doppler assessment of hepatic vein, hepatic artery and portal vein will be made and recorded.

Statistical method to be employed:

Continuous variables will be tested for normality by Shapiro-Wilk's test. Simple statistics including mean and standard deviations (+/- 2 SD) will be used to determine normal ranges for age.

Comparisons will be done by student's t-test. Relations between height, weight and gender with vessels diameter will be tested by Pearson correlation.

Linear multiple regression analysis will be utilized with vessels diameter as the dependent variable.

Number of subject to be enrolled (observation study): 300

Rationale:

Sample size = (Standard normal variate)2 X (Standard deviation)2 / Presicion2 Sample size = 1.962 X 22 / 12 Sample size = 15.37

Standard normal variate = 1.96 at 5% Type I error Standard deviation = up to 2mm (from prior study of portal vein diameter) Precision = 1mm

In view of aim of determining age corrected normal range of vessels diameter in children, a much bigger sample size will be obtained to improve accuracy.

Target to include 300 children in this study.

Age groups:

Around 30 cases for each of the following age groups:

1. 0 - 1 years old
2. 1 - 2 years old
3. 2 - 4 years old
4. 4 - 6 years old
5. 6 - 8 years old
6. 8 - 10 years old
7. 10 - 12 years old
8. 12 - 14 years old
9. 14 - 16 years old
10. 16- 18 years old

Inclusion Criteria:

1. Patient < / = 18 years of age.
2. No history of hepatobiliary nor cardiac pathology as checked with record in ePR. Verbal confirmation will be done with patient or parent / legal guardian.
3. Attending USG study other than that of the hepatobiliary system. (ie. Patients attending for thyroid USG, urinary system USG, musculoskeletal system USG etc.)

Exclusion Criteria:

1. Patient > 18 years of age
2. Known history of hepatobiliary or cardiac pathology.
3. Unstable patients.
4. Intolerance of USG examination
5. Uncooperative patients.
6. Patient requiring sedation for USG study.

Patients attending Hong Kong Children's Hospital for clinically indicated USG examination will be invited to participate in this study.