A dilated common bile duct (CBD) alone or double duct sign (both CBD and dilated pancreatic duct dilatation) along with elevated liver enzymes is strongly indicative of biliary disease.1,2 Technological advancements and affordability of imaging studies have improved over the years resulting in a higher frequency of incidental findings, including bile duct dilation with or without pancreatic duct dilation in patients who otherwise have no signs or symptoms of pancreaticobiliary disease.2,3 Alteration in bile duct size can occur in many benign and malignant conditions including aging, post-cholecystectomy, stone disease, sphincter of Oddi dysfunction, strictures, chronic pancreatitis, chronic opioid usage and malignancies. Despite comprising the lowest percentage of these etiologies, earlier identification of malignancies can result in a more favorable prognosis. The acceptable normal size of the bile duct varies by age and in the post-surgical state.1,2 When no identifiable cause of dilated ducts is seen on ultrasound (US), CT scan, or magnetic resonance cholangiopancreatography (MRCP), evaluation with endoscopic ultrasound (EUS) may be able to detect occult causes.2,4,5 The decision to proceed with EUS must be carefully considered while keeping in mind the potential risks of the intervention. Although EUS and MRCP have similar sensitivities in detecting choledocholithiasis, EUS has a higher ability to detect small stones.6

There is limited literature on the yield of EUS in unexplained dilated CBD or double duct signs with normal liver enzymes. In this study, we will review a single center’s experience and analyze the yield of EUS in those situations and perform multiple logistic regression analyses to investigate the association of multiple variables and duct dilatation.

A retrospective analysis was conducted from January 2015 to October 2021 on patients that met the following criteria.

A total of 1131 EUS procedures were carried out during this period. A total of 32 (3 %) EUS procedures were indicated for unexplained dilated CBD or double duct sign on imaging with normal liver enzymes. 23 had CBD dilatation alone (72 %), and 9 had a double duct sign (28 %). 20 of the included patients were females (63 %) and 12 were males (37 %), with a mean age of 63.8 ± 17 and 68.2 ± 14 years old, respectively (p = 0.424). 16 of the included patients were white (50 %), 12 Hispanic (38 %), 3 African American (9 %), and 1 Asian (3 %) (Table 1).

EUS performed in those with CBD dilatation alone provided a diagnostic yield of 56 % as follow; no pathology in 10 (44 %), sludge in 9 patients (39 %), CBD stone in 3 (13 %), malignant stricture in 1 (4 %) (Fig. 1). 13 patients in the CBD dilation group underwent ERCP that confirmed the diagnosis.

Logistic regression analyses were used to assess the association between the dependent variable of CBD stone or sludge and collected outcomes. No association was found between the diagnosis of CBD sludge/stone and the patient’s age, gender, or CBD size.

On the other hand, EUS in those with double duct signs showed a diagnostic yield of 55 %; no pathology in 4 (45 %), pancreatic head adenocarcinoma in 3 patients (33 %), Biliary stone in one patient, and malignant CBD stricture in one patient (11 % each) (Fig. 2).

CBD dilation can result from a variety of causes, including sludge, stones, strictures, cholangiocar cinoma, periampullary lesions, sphincter of Oddi dysfunction, chronic pancreatitis, chronic opioid usage, etc.3,5,7 Patients with these pathologies will most likely present with signs or symptoms such as jaundice, abdominal pain, or elevated liver enzymes. 5,7 CBD dilation on imaging and elevated liver enzymes has a high pre-test probability of pathological finding on EUS.5,7–9 Incidentally discovered biliary dilation without clinical, laboratory, or identifiable cause on imagining is considered a benign condition that might not warrant further intervention.3 Supporting literature about the importance of using EUS in these conditions continues to evolve with no clear evidence-based approach to evaluate asymptomatic patients with dilated ducts.3,5,7,10

In a study by Malik et al.7, the role of EUS in asymptomatic biliary dilation was evaluated in 47 patients, out of which only 15 patients had an MRCP. The study population was divided into 2 groups: one with normal liver enzymes (n = 32) and another with abnormal liver enzymes (n = 15). EUS showed low yield (6 %) with only 2 patients out of the 32 in the normal liver enzyme group had identifiable cause on EUS (CBD stone and periampullary diverticulum), with higher EUS yield in the abnormal liver enzyme group (8 patients had identifiable reasons out of the 15 P = 0.001). Rana et al.5 conducted a retrospective study to evaluate the diagnostic accuracy of EUS in patients with unexplained CBD dilatation on MRCP. 40 patients were included, 30 had normal liver function tests, and 10 only out of 30 patients showed identifiable causes on EUS, including CBD stone or chronic pancreatitis (Yield 33.3 %). Bruno et al.11 EUS yield in dilated CBD with the normal liver function was 21 % and can be adjusted to 10.5 % as per the author if we excluded chronic pancreatitis or periampullary diverticulum as a cause for dilatation that does not warrant intervention in asymptomatic patients with normal liver enzymes. Oppong et al.2 had a yield of 20 % (8 patients; 3 biliary stones, 3 biliary polyps, 1 portal vein compression, and 1 sludge (microlithiasis).

The diagnostic yield ranged from 6 % to 33 % in these previously mentioned studies,2,5,7,11 unlike our study that showed a diagnostic yield of 56 % in patients with normal liver enzymes. However, the yield would drop to 17 % if microlithiasis (sludge) was considered as a secondary finding that does not warrant intervention in the setting of normal liver function.

Unexplained CBD dilation on imaging with normal transaminases does warrant further investigation by EUS, which increases the chance to identify etiologies such as choledocholithiasis, biliary stricture, and malignancy. By implementing this practice, besides improving the diagnostic yield of the conditions mentioned above, a negative EUS will reduce the unnecessary use of ERCP. On the other hand, EUS should also be considered in patients with a double duct sign even in the setting of normal imagining and liver enzymes due to the possibility of identifying malignant etiologies.

First is the small sample size and its retrospective nature. Secondly, both EUS and MRCP can miss the diagnosis of papillary stenosis and sphincter of Oddi dysfunction. Lastly, the cost-effectiveness of our approach was not factored in, and this must be evaluated in future studies.

None.