|Year : 2016 | Volume
| Issue : 1 | Page : 23-29
Sonographic measurement of fasting gallbladder volume in healthy adults in North-West, Nigeria
Nura Idris, SK Idris, MK Saleh, MA Suwaid, AM Tabari, K Isyaku, SA Abubakar, A Ismail, MA Yahuza, NA Kabo
Department of Radiology, Aminu Kano Teaching Hospital, Kano, Nigeria
|Date of Web Publication||12-Feb-2016|
Department of Radiology, Aminu Kano Teaching Hospital, Kano
Source of Support: None, Conflict of Interest: None
Background: Quantitative assessment of gallbladder volume (GBV) is an important tool for evaluating many pathologic conditions affecting the gallbladder (GB). Therefore, there is need to establish a baseline sonographic normogram of GBV in our locality for early detection and follow-up of subjects that may develop GB diseases. Objective: To determine the mean and range of fasting GBV and to assess the relationship between GBV and age, sex, and body mass index (BMI). Methodology: The study was a cross-sectional prospective study conducted at the Aminu Kano Teaching Hospital, Kano, North-Western Nigeria. Four hundred healthy adults aged 18–60 years were recruited for the study. Subjects were scanned using Esaote MyLab 40 (Italy) ultrasound and a 3.5 MHz curvilinear transducer after 6–8 h fasting. Scanning was done in supine and right anterior oblique positions. The length, height and width of the GB were obtained and the volume (cm 3) calculated using the ellipsoid formula. The height and weight of the subjects were measured and their respective BMI calculated. Results: There were 238 males (59.5%) and 162 (40.5%) females, with an age range between 18 and 60 years and mean age of 35.6 years (±12.9). The mean fasting GBV was 24.2 cm 3 (±8.4 cm 3), with a volume range of 11.1–50.9 cm 3. The mean BMI was 23.75 Kg/m 2 (±8.25). GBV was found to be significantly larger in males compared to females (P = 0.043); larger in older individuals (P = 0.000); and larger in those with higher BMI (P = 0.000). Conclusion: The study has established a mean fasting GBV of 24.2 cm 3 among healthy adults in Kano, North-Western Nigeria. This mean showed positive correlation and variation with age, sex and BMI. The values obtained in this study are comparable with values from other geo-political zones in Nigeria and other parts of the world.
Keywords: Gallbladder, sonography, volume
|How to cite this article:|
Idris N, Idris S K, Saleh M K, Suwaid M A, Tabari A M, Isyaku K, Abubakar S A, Ismail A, Yahuza M A, Kabo N A. Sonographic measurement of fasting gallbladder volume in healthy adults in North-West, Nigeria. Niger J Basic Clin Sci 2016;13:23-9
|How to cite this URL:|
Idris N, Idris S K, Saleh M K, Suwaid M A, Tabari A M, Isyaku K, Abubakar S A, Ismail A, Yahuza M A, Kabo N A. Sonographic measurement of fasting gallbladder volume in healthy adults in North-West, Nigeria. Niger J Basic Clin Sci [serial online] 2016 [cited 2019 Oct 23];13:23-9. Available from: http://www.njbcs.net/text.asp?2016/13/1/23/174595
| Introduction|| |
The gallbladder (GB) is an important part of the digestive system that appears as a pear-shaped sac that connects the common bile duct via the cystic duct. It is a vital organ that plays a crucial role in the digestive process through the secretion of bile. In normal individuals, bile flows into the GB when the sphincter of Oddi is closed. It stores, concentrates and periodically empties bile for the normal digestive process of fat. Bile salts reduce surface tension and in conjunction with phospholipids and monoglycerides, are responsible for the emulsification of fat preparatory to its digestion and absorption in the small intestine.
Determination of GB volume (GBV) is clinically important due to notable variation in GB size/volume in certain disease conditions and physiological states. This variation in volume could predispose to stone formation especially in subjects with larger fasting GBV. Abnormal GBV and emptying have been reported in diabetics.
Radiological investigation of the GB and biliary tract in both healthy and diseased subjects has evolved from cholecystography to more modern imaging modalities such as dynamic ultrasonography, dynamic cholescintigraphy, computed tomography scan, magnetic resonance cholangiopancreatography and endoscopic retrograde cholangiopancreatography. However, these imaging modalities have become less popular due to the use of ionizing radiation and contrast media. For these reasons, the sonographic method has been accepted and used with increasing frequency as an important investigative tool for monitoring changes in GBV. Ultrasonography is particularly useful because it is easy to use, cheap, widely available.
There is an increase in GB size/volume with age and increase in body surface area, whether this could represent risk factors for the occurrence of gallstone remains uncertain. The risk factors for increased fasting GBV and the consequent higher tendency for gallstone formation, like diabetes and sickle cell disease, are emerging as a major health problem in Africa, including Nigeria. Hence, the need to establish a baseline sonographic normogram in this region for early detection and follow-up of subjects that may develop GB disease.
The study was carried out in Aminu Kano Teaching Hospital (AKTH) a tertiary hospital that serves a population of over 20 million people mainly from the states of Kano, Jigawa and Katsina, all in the North-Western region of Nigeria.
| Methodology|| |
This was a cross-sectional study involving healthy adults conducted at the ultrasound clinic of AKTH, Nigeria within a period of 1 year. Ethical approval was obtained from the Ethical Committee before the commencement of the study.
The heights and weights of the subjects were measured using standard anthropometric technique. Height was recorded in meters and weight in kilograms.
The body mass index (BMI) was obtained using the formula; weight/height 2 (Kg/m 2).
Subjects had abdominal ultrasound following a 6–8 h fasting to ensure satisfactory GB distension and to reduce the amount of gastric and intestinal gas.
Subjects were scanned using Esaote MyLab 40 (Italy) coupled with curvilinear 3.5 MHz transducer. The scanning was done in supine and right anterior oblique position after the application of the adequate amount of coupling gel over the GB region in the right hypochondrium.
Measurement of GB indices was done on each subject with the subject in the supine position, and transducer placed over the right hypochondrial area, in the midclavicular line and angled cephalad in both longitudinal and transverse planes. Compliance with fasting was also assessed (stomach and duodenal regions were thoroughly scanned to check for food residue or fluid). After visualisation of the maximal GB longitudinal outline, the length was measured on arrested respiration. Subsequently, the probe was rotated through 90° to obtain the maximal transverse dimensions i.e., the width and height, with calipers crossing each other at 90° [Figure 1],[Figure 2],[Figure 3],[Figure 4].
|Figure 1: A line drawing showing a longitudinal section of the gallbladder|
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|Figure 2: A line drawing showing a transverse section of the gallbladder|
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|Figure 3: Longitudinal ultrasounds scan of right hypochondrium showing site of measurement of gallbladder length|
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|Figure 4: Transverse ultrasound scan of the right hypochondrium showing sites of measurement gallbladder width and height|
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Since the shape of the GB was considered as an ellipse, the volume of the GB in cm 3 was calculated from the ellipsoid formula; thus:
Volume of gallbladder (V) = Length (L) × Width (W) × Height (H) × π/6
V = L × W × H × 0.52,
Statistical analysis of the data was done with the aid of computer-based Statistical Package for Social Sciences SPSS (version 16.0) for windows.
| Results|| |
A total of 400 consecutive adults were studied, comprising of 238 (59%) males and 162 (40.5%) females with a ratio M:F = 1:1.5 [Figure 5].
[Table 1] shows the age of the subjects which ranged from 18 to 60 years with a mean age of 35.6 (±12.9) years. The mean age for the males was 37.6 (±13) years, and that for the females was 32.8 ± 12.3. The age parameter was unevenly distributed with the majority of the subjects falling in the age group of 21–30 years [Figure 6].
|Figure 6: Histogram showing frequency of distribution in the various age groups|
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[Table 2] depicts volume of the GB, which ranges between 11.07 cm 3 and 50.98 cm 3, with a mean volume of 24.2 cm 3 (±8.4 cm 3). [Figure 7] depicts a bar chart showing group GBV and a number of respondents, with the majority of respondents 98 (24%) showing a GBV ranging from 15 to 18.99 cm 3.
[Table 3] shows the mean of GBV in the various age groups. The maximum mean GBV of 26.25 cm 3 (±8.62 cm 3) was recorded in the age group of 41–50 years while the minimum mean volume of 19.96 cm 3 (±5.18 cm 3) was noted in the age group 20 and below. The maximum (upper value) of 51.33 cm 3 was also observed in the age group 51–60 years. Hence, there is significant correlation between GBV and age with P = 0.000 using Fisher's exact test.
The mean value for males is 24.87 cm 3 (range = 12.27–51.35 cm 3) and that for females is 23.21 cm 3 (range = 11.07–49.24 cm 3).
[Table 4] shows cross tabulation of GBV groups against sex. The minimum GBV group of 11–14.99 cm 3 was noted in 18 (7.6%) males and 16 (9.9%) females, whereas the maximum volume of 47–50.99 cm 3 was observed in 12 (5.0%) males and 2 (1.2%) females. There is positive correlation between GBV and sex, being larger in males than females (Student's “t”-test two-tailed significant P = 0.046 [Table 5].
[Table 6] depicts cross tabulation of BMI against GBV. There were 292 subjects with mean BMI of 23.75 (±8.25) - (normal range [World Health Organisation] - 18.5–24.99 Kg/m 2) whereas 108 subjects showed mean BMI of 25.99 (±8.89) and had higher values. The smaller GBV of 15–18.99 cm 3 was recorded among 24% of subjects with normal BMI and 15% of those with larger BMI. Larger GBV of 43–46.99 cm 3 was noted in 0.68% of normal BMI subjects and 6.48% of larger BMI subjects. Hence, there is a positive association between GBV and BMI (P = 0.006).
| Discussion|| |
Ultrasonography is the most promising method of GBV estimation allowing both GB visualisation and measurement of its kinetics. The assessment of GBV is based upon its visualisation and application of a method used for the GBV calculation. These methods can either be dependent on GB shape like the ellipsoid method or independent of GB shape such as sum-of-cylinder method. Several studies validating the ultrasonography methods for GBV estimation have been described.
Ultrasound is an important investigative tool for quick, simple, non-invasive and safe evaluation of the GBV., The location, shape and volume of GB can all be easily assessed with ultrasound. Determination of GBV is clinically important due to notable variation in GB size/volume associated with certain disease conditions and physiological states. This variation in volume could predispose to stone formation especially in subjects with larger fasting GBV.
The GBV in this study was calculated using the ellipsoid formula. This is currently the simplest and most widely accepted method for clinical practice as proposed by Dodds et al. The sum of cylinder method is moderately cumbersome and time-consuming for routine clinical use.
A total of 400 subjects were studied comprising of 238 (59.5%) males and 162 (40.5%) females with a mean age of 35.6 (±12.9) years, and range of 18–60 years. The highest frequency of 121 subjects was observed in the 21–30 years age group. This is presumably because a large number of the volunteers were students. In addition, it reflects the nature of our national demographic structures. The results of Nigeria Demographic and Health Survey 2008 showed that the household population has a greater number of younger people than older people. The broad base of the population pyramid indicates that Nigeria's population is young.
The sex and age distribution of subjects in a pilot study by Ugwu et al. on quantification of GBV to establish baseline contraction indices of 50 healthy Nigerian adults comprising of 29 males and 21 females with age range 18–62 years is similar to that in this study.
Palasciano et al. studied 1246 (60%) males and 830 (40%) females in a cohort study in Italy, with age range 30–69 years and the mean age of 50 years. While Olokoba et al. studied 200 subjects in a comparative study in Ilorin with age and sex matched control having a mean age of 52.9 (±10.7) years and age range of 25–75 years. The sex distribution of subjects studied by Palasciano et al. is similar to the index study while the mean age of both Olokoba et al. and Palasciano et al. are higher than the presented study. This is likely due to the difference in the study design. The mean and age range by Donald et al. in his study of 30 healthy volunteers (15 men, 15 women; mean age, 33 years [range, 22–65 years]) is similar to the current study.
The unequal distribution of sex noted in this study may have stemmed from the fact that women found pregnant, and those on oral contraceptive pills were excluded from the study. So also student sex ratio in Kano shows more male than female.
The mean fasting GBV in this study (24.2 cm 3) is comparable with the findings of Olokoba et al.,, in their comparative study in 2006 on 100 type 2 diabetic patients and 100 age and sex matched healthy controls in Ilorin, Nigeria. The healthy controls had a mean GBV of 24.3 (±12.8) cm 3. This study also agrees with the findings of Pallota et al. in their study on 150 healthy volunteers in Italy, which shows a mean fasting GBV of 23.8 cm 3 (±12.5). This is in consonant with the index study. The mean volume of fasting GB reported by Keshavarzian et al. in Baltimore, USA of 24.9 ± 2.7 cm 3 is also similar to this study. Findings from this study are however in contrast to findings of Kishk et al. who recorded higher mean GBV of 28.2 cm 3 in a study comprising of 20 healthy controls in Egypt and those of Huang et al. with a mean GBV of 26.3 cm 3 in a study of 10 healthy volunteers. The slightly higher mean GBV recorded, could be as a result of the small sample sizes in those studies. The correlation of GBV from this study with those recorded for studies with larger sample sizes suggest that fasting GBV shows no significant variation between ethnic groups, countries and possibly races.
Caroli-Bosc et al. in a study in France found age to be correlated with GBV. They reported statistically significant increased GBV in subjects of 50 years and above (P = 0.001). This agrees with the findings in this study, where fasting GBV was noted to be maximum at age 50–60 years. There is significantly positive (two-sided significance P = 0.000) correlation between this age and GBV established in this study. This is also similar to the findings of Palasciano et al. in a sonographic population study among Italians who found that GBV significantly increased with age in healthy non-obese males (P < 0.01).
The increased fasting GBV at higher age brackets is thought to be due to hypocontractility of the GB with consequent decrease in GB contraction index. This could be attributed to ageing which leads to replacement of normal muscle fibers with fibrous tissue, or differences in hormonal and neurological profiles between the young and the elderly.
Caroli-Bosc et al. could not establish any significant correlation between sex and GBV, however this is contrary to the findings of Chapman et al. who found a significantly larger GBV in males. The present study also found males to have a significantly larger fasting GBV than females (Student's “t”-test two-tailed significant, P = 0.0462). The findings of Donald et al. that male subjects had significantly higher fasting GBVs than female subjects did (P = 0.02), further corroborates this observation.
Sari et al. reported a positive correlation between fasting GBV and BMI P < 0.05. This is also in agreement with findings in this study, regarding the relationship between fasting GBV and BMI (P = 0.006). A positive and statistically significant relationship was found between GB volume and BMI in both sexes., A similar observation was made by Donald et al. i.e. BMI showed a significant positive (one-tailed significance, 0.001) correlation with fasting GBV (r = 0.55). Body habitus is known to alter GB dynamics, with both obese and non-obese (higher BMI) people having significantly greater fasting GBV and residual GBV values with slower GB emptying rates than normal-sized individuals. This could possibly explain the reason for the above finding.
The pathogenesis of gallbladder disease involves numerous mechanisms which are present in subjects with high BMI. These include excess hepatic secretion of cholesterol and subsequent supersaturation of bile, inflammation and fatty infiltration of the GB, (cholecystosteatosis) and blunted gallbladder contractility. The resultant GB hypo-motility leads to increased fasting and residual volumes, as well as decreased fractional emptying of the GB and stasis which predispose to gallstones formation. The relative risk of gallstone formation appears to rise as body weight increases and this positive correlation with increasing BMI is more pronounced when BMI exceeds 30 kg/m 2. There is increased fasting GB volume and reduced GB emptying in patients with gallstone, and this is thought to be due to impaired GB motility, but whether this is a primary or secondary abnormality remains to be determined. Even though subjects found to have gallstone were excluded from the study. This is a potential area for further study.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6]