Nomogram of Common Bile Duct Diameter in Children from a Tertiary Care Center in Central India: A Cross-sectional Observational Study

ABSTRACT

Background:

Normal common bile duct (CBD) diameter measurements are essential to distinguish from pathological conditions. The size criteria used for adults do not apply to children. There are differences among studies reported from various geographic regions. There is a lack of literature, particularly from India.

Methods:

A cross-sectional observational study was conducted at a tertiary care center in Central India. A sample size of 96 was calculated using a sample size formula to estimate the population mean. Children aged from newborns to 15 years old with no hepatobiliary pathology who required ultrasonography were included. The GE Logiq S8 ultrasound machine (GE Healthcare, Wauwatosa, WI, USA) was used to measure CBD diameter.

Results:

A total of 131 children were included, with a mean age of 6.05 ± 3.75 years (range: 1 month–14 years). The children were divided into three age groups: under 1 year (n = 13; CBD diameter: 1.01 ± 0.36), 1–10 years (n = 89; CBD diameter: 2.36 ± 0.94), and over 10 years (n = 19; CBD diameter: 2.77 ± 0.87). There is a significant difference in CBD diameters among the age groups (P < 0.001), with no significant difference between the 1–10 years and over 10 years groups (P = 0.07). In addition, there is a correlation between liver span and CBD diameter (P < 0.001).

Conclusion:

The mean CBD diameter in children showed a positive correlation with age and liver span. This data can serve as a reference standard for CBD diameter in children, especially in Central India. It may aid in distinguishing pathologically dilated CBD.

INTRODUCTION

Surgical jaundice in children encompasses a range of conditions that include congenital disorders such as biliary atresia, choledochal cyst, inspissated bile duct syndrome, and others. In older children, pathologies such as stones can cause common bile duct (CBD) obstruction and jaundice. Many of these conditions can be easily identified with ultrasonography (USG), which detects dilated CBD, a critical marker for further investigation.[1]

Normative data on CBD diameter are available from adult literature,[2] but due to anatomical and developmental differences, they are not applicable to the pediatric population. Only a few studies have investigated normal pediatric CBD diameters, and none are from India.[3] Even among those reported studies, there was considerable variation, probably due to geographical differences that might reflect body habitus, nutritional status, and genetic factors across populations.

Our study aims to address this gap by measuring CBD diameter in healthy children from a cohort in central India to develop a nomogram. This nomogram could serve as a reference for identifying abnormal CBD dilation and could be valuable for pediatricians, pediatric surgeons, and pediatric radiologists in decision-making.

METHODS

Study design

A cross-sectional observational study was conducted from March 2023 to February 2024 at a tertiary care center in Central India (IHEC-LOP/2023/IL094).

Sample size

The required sample size was calculated to be 96 cases, assuming to estimate the mean CBD diameter with a 95% confidence interval (CI) of ±0.2 mm (standard deviation [SD] = 0.99) using the formula . Where n is the required sample size, Z is the standard deviate at 95% CI (1.96), SD is the SD, and E is the margin of error (0.2 mm).

Inclusion/exclusion

This study included all children from newborn to 15 years old who presented to the pediatric surgery department and required abdominal USG. Children with hepatobiliary pathology or where the CBD was not clearly visualized were excluded.

Machinery

CBD was measured using a GE Logiq S8 ultrasound machine (GE Healthcare, Wauwatosa, WI, USA). Both linear (high frequency) and curvilinear (low frequency) transducers were used, depending on the patient’s age, sex, and body habitus.

Measurement taken

Measurements were taken by two dedicated radiologists to reduce interobserver variation. The child’s age, sex, CBD diameter, gall bladder status (such as contracted or distended), and liver size were recorded. All children were examined in a fasting state of at least 4 h, except for those unable to fast that long, and were assessed in both supine and left lateral decubitus positions using intercostal and subcostal approaches. The CBD was examined in its entire length from the cystic duct to the pancreas, and the maximum anteroposterior diameter, measured between inner mucosal borders, was recorded.

Statistical methods

The statistical analysis was conducted using R Studio (version 4.5.1; RStudio, PBC, Boston, MA, USA). Descriptive analyses were presented as mean ± SD, median with interquartile ranges, and percentiles. The Spearman correlation test was used to assess monotonic relationships. Differences between age groups were analyzed using ANOVA, followed by the post hoc Tukey’s HSD test. A student’s t-test was employed to compare CBD diameters between male and female children.

RESULTS

Out of 191 patients, 164 children did not have any hepatobiliary pathology. After reviewing the liver function tests and other investigations following USG, the remaining children were excluded as per the exclusion criteria. CBD was detectable in most children; those in whom CBD was not visualized were previously excluded. The gallbladder was distended in 131 children, but 33 children had contracted gallbladders, probably due to inadequate fasting, and were excluded from the analysis.

Of the 131 children, 84 were males and 47 were females. The mean age of the children was 6.05 ± 3.75 years (range: 1 month–14 years). The mean CBD diameter was 2.31 mm ± 0.99 mm (range: 0.5 mm–6.8 mm), and the mean craniocaudal liver span was 10.93 ± 2.08 cm (range: 4.7 cm–15.4 cm).

The children were divided into three groups: infants (<1 year, n = 13), children aged one to 10 years (n = 89), and children over 10 years old (n = 29). The details of age-specific CBD measurements are shown in Table 1.

Table 1.

Descriptive statistics for common bile duct diameter

Age group	Sample size (n)	Mean±SD (mm)	Range (mm)	5th percentile	50th percentile	95th percentile
<1 year	13	1.01±0.36	0.5–1.5	0.56	1.00	1.50
1–10 years	89	2.36±0.94	0.6–6.8	1.14	2.30	3.92
>10 years	29	2.77±0.87	1.5–4.8	1.60	2.60	4.36
Overall	131	2.51±0.84	1.0–4.6	0.75	2.30	4.00

SD: Standard deviation

The Spearman’s correlation test was performed to assess the relationship between CBD diameter and age, which showed a statistically significant relationship (rho = 0.46, P < 0.001). A linear regression model indicated that age can be a predictor of CBD diameter (P < 0.001), with the equation: CBD diameter in mm = 1.606+ (0.117 × Age in years). A scatter plot showing the relationship between age and CBD diameter is presented in Figure 1.

Figure 1.

Scatter plot of age versus common bile duct. CBD: Common bile duct

An ANOVA test indicated a significant difference in CBD diameters between age groups (F^[2128] =18.07, P < 0.001). Post hoc Tukey’s HSD tests revealed a significant difference between the <1-year age group and both the 1–10-year and more than 10-year groups (P < 0.001 for both). However, the difference between the 1–10-year and more than 10-year groups is not statistically significant, with a P = 0.07.

As an incidental finding, we found a significant correlation between liver span and CBD diameter (rho = 0.47, P < 0.001). There was no statistically significant difference in CBD diameters between genders (t = −0.33, df = 116.78, P = 0.74).

DISCUSSION

Measuring CBD diameter in children can help identify choledochal cysts and distinguish biliary dilatation caused by sludge or stones. Although many studies exist for adults, normal CBD measurements in children are not well defined. Only a few studies have assessed normal CBD sizes in children using magnetic resonance imaging,[4,5] USG,[1,6,7,8] and cholangiography[9,10] (intravenous or ERCP-guided). A key issue is the large variation in the average diameters reported across these studies. Most of these studies are from the USA and China, with none from India.[3]

The mean diameter of the CBD in our study is 2.31 ± 0.99 mm. Hernanz-Schulman et al.[6] reported a mean diameter of 1.27 ± 0.67 mm. Kocaoglu et al.[5] reported a mean of 3.1 mm. Lindholm et al.[7] reported a mean diameter of 2.4 mm.

The studies classified age groups differently. We considered three age groups based on the physiological growth spurts in children: infancy (birth to 1 year), 1–10 years, and more than 10 years (pubertal growth spurt). Lindholm et al.[7] uses a similar classification.

Our mean CBD diameter in infants under 1 year old was 1.01 ± 0.36 mm, with a maximum of 1.5 mm. Gwal et al.[4] reported a mean of 2.1 ± 0.5 mm and a range of 1.1–3.2 mm; Hernanz-Schulman et al.[6] reported a mean of 0.74 ± 0.4 mm; Lindholm et al.[7] reported a mean of 1.24 ± 0.54 mm; and Zhang et al.[1] reported a mean of 1.15 ± 0.53 mm.

We found a significant correlation between age and CBD diameter, with a rho = 0.46 and P < 0.001. Similar findings were reported by Gwal et al.,[4] Hernanz-Schulman et al.,[6] Lindholm et al.,[7] Witcombe and Cremin,[10] and Zhang et al.[1] Kocaoglu et al.[5] did not report any correlation, likely because their study included children aged 5–17. Although we did not evaluate this directly, most of these studies did not show any correlation with the child’s sex, weight, or height. We identified a new correlation suggesting that CBD diameter may be related to liver span, with a rho of 0.47 and P < 0.0001. Additionally, we observed no significant difference in CBD diameter between children aged 1 and 10 years and those older than 10 years. This may be due to studying only children up to 15 years old, possibly excluding those undergoing pubertal growth spurts, which can continue until age 18.

The strengths of this study are its cross-sectional design, which reduces recall bias often seen in retrospective studies; most of the reported studies were retrospective, except for Zhang et al.[1] and Hernanz-Schulman et al.[6] It is likely the first study from India to report these findings. The study identified a correlation with liver span and found no size difference between age groups 1 and 10 years and those over 10 years (up to 15 years). The limitations are of age restriction to <15 years, and the absence of secondary tests to confirm the CBD diameter. Motivated by these points, we plan to expand this research to include older age groups up to 18-year-old patients and encourage others to publish results in this underrepresented area.

CONCLUSION

This study established a nomogram for CBD diameter in a cohort of children from Central India. Our analysis showed a positive correlation between age and CBD diameter (P < 0.001) and between liver span and CBD diameter (P < 0.001). This study also found no correlation between the age groups 1–10 years and 10–15 years (P = 0.07). These data provide a valuable reference tool for identifying pathologically dilated CBD in children.

Conflicts of interest

There are no conflicts of interest.

Funding Statement

Nil.