Teaching Case

69-year-old female with history of cholecystectomy three years ago, after two episodes of cholecystitis, presented to the emergency department with centralised abdominal pain radiating to the back. Initial lipase was 4880 IU/L, AST 184 IU/L, and ALT 65 IU/L.

Axial CT images of the pancreas demonstrates extensive peripancreatic fat stranding with two common bile duct stones (figures 1a, 1b, 1c).

Coronal reconstructed CT images demonstrate prior cholecystectomy clips in the gallbladder fossa (Fig. 3). Figure 2 highlights the two calcified stones in the common bile duct with perienteric inflammatory changes of the duodenum.

Unexpected retained or residual gallstones in the common bile duct (CBD) in patients after cholecystectomy is a rare phenomenon accounting for approximately 2-3% of patients who have undergone cholecystectomy. [2] The size and number of gallstones can put certain patients at a higher risk. Gallbladders that initially contain multiple stones simply have more opportunity to spontaneously secrete a stone and obstruct the CBD. Though not all stones will successfully reach the CBD as they must first pass through the small and tortuous cystic duct, a process that will naturally exclude larger calibre stones. Therefore, it is not surprising that patients who had 3 or more stones, or stones smaller than 7 mm are at significantly higher risk. [1, 3]

Retained stones are primarily diagnosed by imaging, with right upper quadrant ultrasound or abdominal CT. Both imaging techniques are capable of demonstrating a dilated CBD secondary to ductal obstruction, however, there are limitations unique to each modality. The field of view on a RUQ ultrasound examination only visualises a small portion of the proximal CBD. Stones within the distal duct are not directly visualised. With CT, although the entire CBD is imaged, small noncalcified stones may appear isodense to the surrounding CBD. MRCP would be helpful in problem solving in these cases.

Approximately 3-7% of patients with gallstones are complicated by obstructive pancreatitis. [4, 5] Of note is the associated mortality, which has been reported as high as 8%. [7] The presenting symptoms are typically abdominal pain, which overlap with other biliary pathologies. Derangements in lipase and amylase are highly specific. This patient's initial high lipase along with the corresponding CT findings were consistent with acute pancreatitis.

For management of known gallstones in patients without prior cholecystectomy, the National Institute for Health and Care Excellence (NICE) guidelines recommend endoscopic intervention prior to surgery or bile duct exploration during cholecystectomy. However, limited data exists regarding patients with ductal stones after cholecystectomy. There is a total of eight reported patients who experienced symptomatic ductal stone recurrence in the three most recent studies, only one of which required endoscopic stone extraction. [1, 3, 6]

It is possible that CBD stones in postcholecystectomy patients are favourable to spontaneous passage, which was the case in this patient demonstrated by normalisation of her subsequent lipase, AST, and ALT along with concordant endoscopic ultrasound findings.