Gallstone disease (cholelithiasis) is a very common hepatobiliary disorder amongst the world and one of the most common conditions that leads to surgical interventions, morbidity as well as increased health-care utilization [1]. The incidence of gallstones has significantly increased over the last few decades, related more to the increase in obesity, less physical activity and more metabolic disorders [2]. As obesity has been found to be an independent risk factor for gallstone formation in epidemiological studies, excessive body fat increases the risk of cholesterol supersaturation of bile, decreased mobility of the gall bladder, and chronic low-grade inflammation [3,4]. A person who is obese can then have much higher risk for symptomatic gallstones, along with complications of gallstones like cholecystitis, pancreatitis and biliary obstruction [5].

However, ultrasonography is the initial imaging modality of choice in the diagnosis of gallstone disease due to its wide availability, radiation-free nature, low cost and ease of use [6]. In the general population, sensitivities and specificities above 90% have been reported with conventional transabdominal ultrasound [7]. In obese patients, its diagnostic value could not be comparable because the quantity of the subcutaneous adipose tissue could lower the acoustic windows as well as the sound travels through the deep location of the gallbladder, the attenuation of ultrasound beams, and the interference from bowel gas, all of which impede the diagnosis [8,9]. This technical difficulty can result in various problems in visualisation of the gallbladder and occasional false-negative results, which can result in a delayed diagnosis and treatment [10].

These challenges have been addressed, to a certain degree, in obese people through recent technological developments and changed scanning strategies [11]. The studies of the last few years have consistently showed that optimised ultrasound techniques, such as scanner positioning, intercostal scanning, compression of the probe, optimisation of gain and depth settings and the use of high performance transducers, can enable better images and an improved diagnostic outcome in difficult-to-image patients [12,13]. Using more advanced probes, Heinitz et al. found that obesity had a negative impact on the quality of the ultrasound assessment and probe type remarkable in the depiction of anatomy in higher BMI patients [13]. In a similar fashion, sensitivity has improved in morbidly obese people for gallbladder disease using endoscopic and laparoscopic ultrasound [14,15].

Ultrasound imaging is not just limited to the gallbladder when it comes to being impaired by obesity—it also makes it difficult to evaluate the liver, pancreas and abdominal vasculature [16]. Thus, radiologists and sonographers are increasingly being encouraged to tailor imaging protocols for optimal diagnostic accuracy or predictability based upon other aspects of the patient's anatomy, or body habitus. Despite these advances, few regional reports have been available of the effectiveness of optimized methods of detecting gallstones for obese individuals, especially those in South Asian countries where obesity is rapidly associated with a high prevalence of gallstones [18].

With the increasing prevalence of obesity and gallstone disease, the need for better diagnostic accuracy of ultrasonography in obese individuals is of clinical significance. Early detection and proper diagnosis can minimize unnecessary surgery and complications, and can guide timely surgical intervention [19]. Thus, the present study investigated the usefulness and efficacy of these ultrasound techniques in obese cases when compared to standard ultrasound techniques, and determined their effect on gallstone detection and gallbladder visualization.

The present descriptive cross sectional comparative study was carried out in the department of Radiology, under the supervision of the Department of Headquarter Teaching Hospital, Mirpur, Azad Jammu and Kashmir in collaboration with the College of Mohtarma Benazir Bhutto, Shaheed Medical College, Mirpur, from July 2024 – November 2024. This study compared the ultrasound performance of optimized ultrasound techniques and conventional ultrasound techniques in detecting gallstones in obese humans. Ethical approval was given by the Institutional ethical review committee of the affiliated medical institution before data collection. All participants signed informed consent forms after receiving information on the aims, benefits and possible research risks and confidentiality of all patient data was respected along the entire research journey, according to the principles outlined in the Declaration of Helsinki.

Obesity patients with a body mass index (BMI) ≥30 kg/m² who presented with the clinical suspicion of gallstone disease were included through non-probability with consecutive sampling technique, a total of 97 patients with obesity. Randomly selected patients from the outpatient and inpatient departments referred for abdominal ultrasonography were recruited, irrespective of their gender, age ≥ 18 years. To minimize confounding factors that may affect the image visualization of the gallbladder, potential participants with past history of cholecystectomy, hepatobiliary malignancy, severe ascites, pregnancy or severely compromised general health were excluded. Demographic data such as age, gender, BMI (Body Mass Index), presenting symptoms and clinical history were documented on a standard proforma developed for this study.

Experienced radiologists using the standardized scanning protocol with a Toshiba Xario ultrasound machine, equipped with a curvilinear 2-5 MHz transducer performed all the ultrasound examination of patients. Patients were examined in a conventional ultrasound examination in the supine position after an overnight fast and deep breathing procedure at the start. Optimized ultrasound techniques were then utilized in the same patients such as using the "up to" and "up-right" position, intercostal position, graded probe compression, and gains and depths to enhance acoustic penetration and gallbladder visualization. Standard and optimized scanning parameters were evaluated and documented in regard to the presence of gallstones, the appearance of the gallbladder wall, posterior acoustic shadowing and overall image quality. Diagnostic improvement was evaluated by comparing the quality of visualization and the detection rate of the gallstone by the two methods.

The data collected were entered and analyzed with the computer program statistical package for social sciences (SPSS) version 26. Data numerics like Age and BMI were reported as mean ± SD and qualitative data like outcome of visualization or gallstone detection were frequencies and percentages. Chi square was used for categorical variables to compare the diagnostic performance of the standard and optimized ultrasound techniques. A p value < 0.05 was interpreted as being statistically significant. When appropriate, results were tabulated and presented in charts to aid comparison and interpretation of results.

In all, there were 97 obese subjects with suspected gallstone disease recruited. The mean age of the participants was 44.8 ± 11.6 years (range: 21-69 years). Among the study population, 61 (62.9%) were females and 36 (37.1%) were males. The mean body mass index (BMI) was 33.7 ± 3.4 kg/m². The majority of the patients were presenting with right upper quadrant abdominal pain, dyspepsia, nausea or fat intolerance.

In 61 (62.9%) patients, a conventional ultrasound examination was obtained which showed appropriate visualization of the gallbladder, and in 86 (88.7%) patients, appropriate visualization of the gallbladder was obtained using optimized ultrasound examination. In standard ultrasound, the poor visualization, which was caused by excessive adipose tissue and bowel gas interference, was noted in 36 (37.1%) of the patients, but the significance was reduced with the use of optimized ultrasound scanning technique to 11 (11.3%) patients. In optimized ultrasound methods, gallbladder visualization was improved and the differences among groups were statistically significant (p < 0.001).

Table 1: Demographic and Clinical Characteristics of Participants

When performing standard ultrasound examination, gallstones were detected in 54 (55.7%) patients, and when using optimized ultrasound examination, they were detected in 68 (70.1%) patients. Patient repositioning, probe compression and intercostal scanning all proved useful in the application of optimization strategies, and came with an additional 14 accurately diagnosed cases of gallstones. A difference in the detection rate of gallstones between the two ultrasound methods (standard vs optimized) was statistically significant (p = 0.018).

Table 2. Comparison of Standard and Optimized Ultrasound Techniques

The left lateral decubitus position improved visualization of gallbladder in 29 (29.9%) patients, intercostal scanning improved visualization in 24 (24.7%) patients and graded compression of the probe reduced bowel gas interference in 21 (21.6%) patients. There were 18 cases (18.6%) in which the image became clearer when a gain and depth adjustment was used. Several optimization approaches combined resulted in optimum diagnostic improvement in the patient group with BMI > 35 kg/m².

Table 3. Effectiveness of Individual Optimization Techniques

Standard ultrasound use in obese individuals was calculated as 79.4% sensitive and optimized ultrasound techniques had a sensitivity of 94,1%. The same was found for the image quality score which was significantly better for optimized scans than for conventional scans (p < 0.001). The prevalence of gallstones was higher in female compared with male patients, but this was not statistically significant (p = 0.072).

The data shows that optimized ultrasound techniques contribute to a significant improvement in the accuracy of visualization and diagnostics of gallstones in obese people, and minimizes the risk of false negative examination, ultimately enabling more efficient radiological examination.

The present study showed that optimized ultrasound techniques could significantly improve the visualization of the gallbladder and improve gallstone diagnosis compared to conventional ultrasonographic techniques particularly in obese patients. The abdominal wall is a difficult problem in ultrasound studies due to the large amount of adipose tissue which distorts ultrasound waves, inhibits the transmission of sound and affects image resolution, with all of which making accurate diagnosis difficult [19]. Overall, the results of this study are consistent with a body of work indicating that patient body habitus can significantly affect the quality of a sonographic examination [20] and further supports the ability to adapt techniques to enhance examination quality in hard-to-image populations.

Patient repositioning, intercostal scanning, probe compression and optimization of the machine parameters at different levels were potentially more likely to improve diagnostic performances in this study and may explain the higher performances observed with optimized ultrasound technique. These alterations lead to better acoustic window and compassionate the bowel gas interference, improving the visualization of the gallbladder and biliary structures. This is also shown by Heinitz et al. in advanced sonographic methods and high-performance transducers which have a significant effect on the depiction of the anatomy in the obese [21]. Similarly, Karlas et al. reported the benefits of the obesity-specific adjustments in abdominal ultrasonography methods in terms of better image quality, and decreased number of false-negative results [22].

Female predominance of patients with gallstone disease that was observed in the present study is in agreement with other reports. Gallstones formation in women is known to be related to hormonal factors such as the cholesterol supersaturation of bile by estrogen metabolites [23]. Moreover, obesity-related metabolic dysfunction is further associated with the risk to develop gallstones especially in middle aged females [24]. In this study, the mean age distribution is also consistent with the epidemiological data from around the world indicating more gallstones with increasing age, associated with metabolic risk factors [25].

With the enhanced sensitivity obtained by optimized ultrasound techniques, important clinical implications arise. Gallstones are less likely to be delayed in diagnosis, more likely to avoid complications like acute cholecystitis and pancreatitis, and costly precipitating imaging tests like CT scan or magnetic resonance cholangiopancreatography (MRCP) can be avoided with early and accurate diagnosis of gallstones in obese patients [26].

Given the fact that the scanning can be performed with minimal or no cost to health care systems, in particularly resource limited countries, optimized scanning protocols can have a profound impact on patient outcomes without creating an extra financial strain [27].

Recent comparison studies of alternative imaging modalities in the obese population corroborate these results from this study. For biliary disease, in morbidly obese patients, there may be additional benefit from invasive tests (endoscopic ultrasound and laparoscopic ultrasound) which are more sensitive for the diagnosis of biliary disease, though these tests are less widely available, may be more expensive, and carry an added risk of complications. Optimized transabdominal ultrasound, on the contrary, represents a practical, non-invasive and cost-effective technique which could be easily integrated into the available radiological work practise [29].

The present study has few limitations, besides its strengths. The first is that this study was conducted in a small number of patients in a single tertiary care hospital that could restrict the generality of the results. Second, no histopathological confirmation or surgical correlation could be obtained for all patients, and the primary evaluation of the ultrasound was emphasized by the imaging-based criteria. Third, ultrasonography is dependent on the operator and the difference of expertise of the radiologist can affect the diagnostic performance [30]. Further, the present invention did not test for any advanced ultrasound technologies, including harmonic imaging and/or artificial intelligence-based ultrasound imaging analysis.

To further confirm the efficacy of optimized ultrasound techniques in obese patients, future multicenter studies with larger patient numbers are recommended. Advanced imaging technologies, high-frequency probes and AI-assisted ultrasonography systems used in comparative research may further assist in understanding how accuracy can be enhanced in situations with challenging patient populations [31]. In addition, an internationally standardized obesity-specific ultrasound protocol and training guidelines for radiologists and sonographers may assist to create a uniformly and consistently applied imaging method globally.

It was found in the present work that optimized ultrasound technique can provide better visualization of gallbladder and better diagnostic accuracy for detecting gallstones in obese patient population than the conventional ultrasonographic techniques. Patient repositioning, inter-coastal scanning, probe compression and parameter optimization of imaging parameters were effective in reducing this limitation due to significant bowel gas and adipose tissue interference. These changes caused a greater response to chromogenic substance and less misleading apparent “no response” during a sonographic evaluation.

It also underscores the role of using obesity-specific ultrasound protocol for the diagnosis of hepatobiliary disorders in clinical practice, especially in resource-limited healthcare facilities where ultrasonography is still the preferred diagnostic tool to diagnose hepatobiliary disorders. Gallstone identification at an early stage will aid in timely management of gallstones, minimise the risk of possible complications and cost of further imaging investigations. Catherine this is a good study, but further multicenter studies in larger populations are warranted for validation of the results and to explore the use of further innovative imaging techniques to further optimize diagnostic outcomes in among obese individuals.

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12. Gardner MS, Trutescu C, Amianda E, et al. Ultrasound accuracy in obese patients with gallbladder disease. Clin Advisor. 2021;24(7):22-27.
13. Heinitz S, Müller J, Jenderka KV, et al. The application of high-performance ultrasound probes increases anatomic depiction in obese patients. Sci Rep. 2023;13:16297. doi:10.1038/s41598-023-43509-9.
14. gov. Laparoscopic versus transabdominal ultrasound in morbidly obese patients. Identifier NCT00971750. Available from: https://clinicaltrials.gov/ct2/show/NCT00971750
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16. Li B, Tai D, Yan K, et al. Accurate and generalizable quantitative scoring of liver steatosis from ultrasound images via scalable deep learning. arXiv [Preprint]. 2021. doi:10.48550/arXiv.2110.05664.
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18. Khan MA, Ahmed A, Abid K, et al. Rising prevalence of obesity in South Asia and associated hepatobiliary disorders. J Pak Med Assoc. 2021;71(9):2145-2151. doi:10.47391/JPMA.04-685.
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20. Thunnissen FM, Comes DJ, Geenen RWF, et al. Patients with clinically suspected gallstone disease: A more selective ultrasound may improve treatment-related outcomes. J Clin Med. 2023;12(12):4162. doi:10.3390/jcm12124162.
21. Heinitz S, Müller J, Jenderka KV, et al. The application of high-performance ultrasound probes increases anatomic depiction in obese patients. Sci Rep. 2023;13:16297. doi:10.1038/s41598-023-43509-9.
22. Karlas T, Blank V, Müller J, et al. Advances in abdominal ultrasonography in obesity. Ultraschall Med. 2021;42(5):477-486. doi:10.1055/a-1400-5508.
23. Lammert F, Gurusamy K, Ko CW, et al. Nat Rev Dis Primers. 2016;2:16024. doi:10.1038/nrdp.2016.24.
24. Yuan S, Gill D, Giovannucci EL, Larsson SC. Obesity and gallstone disease: Mendelian randomization analysis. Hepatology. 2022;75(5):1237-1245. doi:10.1002/hep.32266.
25. Shabanzadeh DM. New determinants for gallstone disease? Hepatology. 2018;68(1):394-402. doi:10.1002/hep.29734.
26. Lee YT, Chan FKL, Leung WK, et al. Endoscopic ultrasonography in suspected gallstone disease. Gastrointest Endosc. 2020;91(4):876-884. doi:10.1016/j.gie.2019.10.031.
27. Khan MA, Ahmed A, Abid K, et al. Rising prevalence of obesity in South Asia and associated hepatobiliary disorders. J Pak Med Assoc. 2021;71(9):2145-2151. doi:10.47391/JPMA.04-685.
28. Kothari SN, Obinwanne KM, Baker MT, et al. A prospective blinded comparison of laparoscopic ultrasound with transabdominal ultrasound for detection of gallbladder pathology in morbidly obese patients. J Am Coll Surg. 2013;216(6):1057-1062. doi:10.1016/j.jamcollsurg.2013.01.056.
29. Gardner MS, Trutescu C, Amianda E, et al. Ultrasound accuracy in obese patients with gallbladder disease. Clin Advisor. 2021;24(7):22-27.
30. European Society of Radiology (ESR). Recommendations for abdominal ultrasound examination in obese patients. Insights Imaging. 2022;13:88. doi:10.1186/s13244-022-01221-y.
31. Li B, Tai D, Yan K, et al. Accurate and generalizable quantitative scoring of liver steatosis from ultrasound images via scalable deep learning. arXiv [Preprint]. 2021. doi:10.48550/arXiv.2110.05664.