Pitfalls in the diagnosis of gallbladder disease in clinically severe obesity.

Background: Cholelithiasis affects 10-20% of the USA population, with higher incidence in certain ethnic groups. Obesity is associated with an increase in gallstone formation, reported in up to 45% of morbidly obese patients. Ultrasound is the best diagnostic tool, although its accuracy is less in this particular population. This paper discusses false negative sonographic findings in morbid obesity.

Methods: Retrospective review of 5257 patients submitted to bariatric surgery. Cholecystectomy had previously been performed in 16%. Gallbladder ultrasound was obtained in the remaining group, and cholecystectomy was done based on this information and/or intraoperative observations. Radiology results and surgical findings were correlated with pathology reports. Misread films were reviewed by a radiologist blind to these reports.

Results: The series consisted of 88% females. Mean age, weight and percentage overweight were 37 years, 125 kg and 105%, respectively. Cholecystectomy was performed in 3084 patients (59%). Discrepancies between radiological and pathological findings were found in 35 cases (1.1%). Five correct diagnosis of lithiasis also had gallbladder hydrops. Four 'inconclusive' and 20 'negative' studies showed definitive pathology. In six cases of 'non/poor visualization', lithiasis was encountered.

Conclusions: Preoperative gallbladder ultrasound is mandatory in bariatric surgery. Results are accurate and false-negative reports rare if sonographers and radiologists are experienced. Non/poor visualization is usually due to technical problems or gallbladder pathology, not due to the patient's size. False-negative results are commonly caused by soft stones, microlithiasis or polypoid cholesterolosis. Single calculus impacted in the cystic duct can produce hydrops, resulting in a negative sonogram.