Predictors of malignancy in patients undergoing surgery for Mirizzi syndrome

Mirizzi syndrome (MS) is a rare cause of biliary obstruction. Historically, malignancy was reported in a subset of MS cases, but previous studies predated modern imaging and routine endoscopic retrograde cholangiopancreatography. This study aimed to determine the prevalence of malignancy in contemporary patients with MS and assess whether modern imaging reliably distinguishes benign from malignant cases.

Adult patients (≥18 years) with gallbladder pathology (International Classification of Diseases code K83.1 or 576.2) at a tertiary referral center (2012-2022) were reviewed. Two independent reviewers confirmed preoperative MS diagnoses. Clinical, radiological, and surgical factors were compared between patients with a final diagnosis of MS and malignancy using Fisher's exact and Wilcoxon rank-sum tests.

Among 7406 patients with gallbladder pathology, 37 (0.5%) had a preoperative MS diagnosis. In 5 cases (13.5%), malignancy was found on final pathology. Patients with malignancy were older (69 vs 60 years; P =.04) and less likely to present with pain (40% vs 96%; P <.01). Time from presentation to surgery was longer in malignant cases (53 vs 18 days; P =.04). Despite a trend toward more imaging (2 vs 3; P =.10), no discrete mass was detected preoperatively. There was no difference in frequency of open (80% malignancy vs 59% MS; P =.61), laparoscopic (20% malignancy vs 41% MS; P =.61), or subtotal cholecystectomy (20% malignancy vs 28% MS; P =.99) during the index operation.

Malignancy is common in patients undergoing surgery for MS. Contemporary diagnostic approaches have a poor sensitivity for detecting malignancy preoperatively. A high index of suspicion should be maintained, particularly in older patients without pain. Early hepatopancreaticobiliary surgeon involvement in this patient population may optimize surgical outcomes.