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wall-thickness was 0.25 ± 0.04cm. In a published study done in Federal Medical Centre Abakaliki, by Ugwu9, the mean gallbladder volume was documented to be 29.29 ± 13.75cm3. This value is not statistically different from the mean in this study and as such one can say there is no local variation in gallbladder volume between the two studies.
Soad et al36 and Ramazan et al26 in separate studies done in Wisconsin and Turkey respectively documented similar mean gallbladder volume of 28.0 ± 12.0cm3 and 28.1 ± 12.3cm3 respectively in their normal control subjects. They were not statistically different from the values in this study. Based on their mean gallbladder volume and the mean volume in this study, there is no significant racial variation in gallbladder volume. However a study of gallbladder volume and emptying in Diabetes Mellitus done in New Delhi by Sharma et al37 found the fasting gallbladder volume in their normal control subjects to be 18.9 ± 11.3cm3. This is quite different statistically from our mean volume in this study. The reason for this variation is not clear; however they assessed only 15 subjects to arrive at that volume. This difference may be due to the small number of subjects that were studied.
Standard textbooks1,2,4,8,11 in ultrasound and anatomy with Caucasian bias suggest average gallbladder length of 7.5cm, transverse and antero-posterior diameter not more than 3cm, wall-thickness, not more than 3mm and a volume of about 30-60cm3. From the mean gallbladder length and volume in this study, there is no significant racial difference in gallbladder dimensions, compared to Caucasian values.
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A study done in Ilorin by Olokoba et al10 to determine the relationship between gallstone disease and gallbladder thickness found the mean gallbladder wall-thickness among their normal control group to be 2.1 ± 1.2mm. This value is not statistically different from 2.5 ± 0.04mm arrived at in this study.
Gallbladder dimensions have been documented by some reports to vary with age, sex, weight, height, body mass index and body surface area24-28.
In the entire gallbladder dimensions in this study, there were no statistically significant influence of gender on the dimensions. The mean gallbladder volume in males was 28.39 ± 12.33cm3, while for females it was 26.37 ± 13.04cm3. There was no statistically significant difference between them (P=0.162). Nieves et al25 in their comparative study of gallbladder volume in Spain also found no influence of sex on gallbladder dimensions. Also the study done locally at Lagos University Teaching Hospital (LUTH) by Ngige et al33 did not show any influence of gender on gallbladder dimensions, which is in agreement of the finding in this study.
There was no influence of age on gallbladder dimensions in this study. However a study done in France by Caroli-Bose et al24 to establish the relationship between gallbladder volume and the demographic parameters among adults also, found gallbladder volume to be positively correlated with age. In their study the gallbladder volume was significantly increased in subjects above 50 years. Though age group 51-60years had the highest mean gallbladder volume in this study, there was no positive correlation between gallbladder volume and age. The reason for this may be racial. A study of the sonographic measurement of normal gallbladder sizes in children by
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Hyun et al38, in South Korea and the study done locally by Ngige et al in LUTH, also show positive relationship between gallbladder volume and age. Because these two studies were done in pediatric age group; the reason for this correlation may be due to the fact that most organs, tend to increase in size during growth phase.
In this study, the height of the subjects did not influence the gallbladder dimensions. Several other studies also support this finding24,25. This is different from the report of Jeong-Hyun et al38, which gave strong correlation between gallbladder length and subject height. The reason for this difference may still be, because their study populations were children.
Weight and body surface area of the subjects in this study independently positively correlate with the width, height and volume of the gallbladder. The weight of the subjects showed statistically significant positive correlation with the gallbladder width and height (r=0.125 and 0.122 respectively) and strong positive correlation with the gallbladder volume (r=0.148). Other studies also report weight of the subject to be positively correlated with the gallbladder volume. Jeong-Hyun et al38 reported the subject weight to positively correlate with the gallbladder volume. Also in the study by Ramazan et al26, the gallbladder volume was positively correlated with the body weight and body mass index.
This study did not show any relationship between body mass index (BMI) and gallbladder length, width, height and volume. BMI is an accurate reflection of the body fat percentage in the majority of the adult population and has been used in the classification of obesity. In this study there was no statistically significant influence of
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obesity on gallbladder volume (p=0.390). This is also supported by work done by Caroli-Bose et al24, which found no positive correlation between gallbladder volume and the body mass index. A local study at Federal Medical Center, Abakaliki by Ugwu9 also did not show any relationship between body mass index and gallbladder volume.
However several other studies in the literature demonstrated greater fasting gallbladder volumes in obese subjects than in the non-obese control group26,28,39. It may be difficult to proffer the reason for this variation. However it has been shown that body mass index does not differentiate between body fat mass and muscle mass. It is possible that body mass index may not be a true reflector of body fat mass in this environment. It is also important to note that in this study the subjects that fall within Grade III obesity have the highest gallbladder wall-thickness, which is significantly different from other BMI grouping. However correlation and regression analysis did not show any positive correlation between gallbladder wall-thickness and the body mass index (r=0.108 at a critical r value of 0.113. figure 8)
The Body Surface Area (BSA) also showed strong positive correlation with the height, width and volume of the gallbladder (p=0.025, 0.027 and 0.012). A similar relationship was also established by the study done locally at Abakaliki by Ugwu9, and several other studies24,38,40.
From this study it was established that there is no significant difference in the mean gallbladder volume and wall-thickness in this environment from the Caucasians values. The pattern of correlation between gallbladder volume and the demographic parameters, however tend to vary among different studies. This study established, body
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surface area and subject weight to significantly positively correlate with the gallbladder volume.
From the regression of gallbladder volume on weight and body surface area (BSA) of the subjects (as shown in figures 13 and 14), a regression equation was derived for the determination of gallbladder volume(GB-V) as follows:
GB-V = 0.1705weight + 16.046 r = 0.1477 GB-V = 10.449BSA + 9.1358 r = 0.1386
These equations will help in quick clinical prediction of the gallbladder volume of a subject and will further help in the sonographic assessment of the gallbladder of a patient.
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