Suprapapillary Metal Stent vs. Routine Transpapillary Drainage in Malignant Hilar Biliary Obstruction (SMART-B Trial)

Malignant hilar biliary obstruction is most commonly associated with perihilar cholangiocarcinoma and represents a complex clinical condition characterized by impaired bile flow at or above the hepatic duct confluence. The resulting cholestasis may lead to progressive hepatic dysfunction, increased risk of infectious complications, and reduced tolerance to systemic or surgical therapies. In selected patients, preoperative biliary drainage is performed to optimize liver function and reduce perioperative risk prior to major hepatectomy.

Percutaneous biliary drainage is widely used in this setting due to its ability to selectively decompress specific hepatic segments, particularly in complex hilar strictures. The conventional approach consists of transpapillary internal-external drainage, in which a catheter is advanced across the obstruction and through the papilla into the duodenum. While effective in achieving biliary decompression, this technique may disrupt the function of the sphincter of Oddi and facilitate duodenobiliary reflux, which has been implicated as a potential mechanism for infectious complications.

Percutaneous suprapapillary drainage with placement of a self-expanding metal stent represents an alternative strategy. By avoiding transpapillary manipulation, this approach preserves sphincter function and may reduce bacterial contamination of the biliary tree. Early clinical data suggest a favorable safety profile, particularly regarding infectious outcomes; however, direct comparisons with conventional transpapillary drainage remain limited, and available studies are constrained by methodological limitations.

An additional area of uncertainty relates to patients with potentially resectable disease. In this subgroup, the choice of drainage technique may influence not only peri-procedural outcomes but also subsequent surgical management. Concerns have been raised regarding the potential impact of metallic stents on operative complexity and resectability, although robust data are lacking.

This randomized clinical trial is designed to compare two percutaneous drainage strategies within a standardized institutional framework. Patients with an indication for percutaneous biliary drainage will be allocated to receive either transpapillary internal-external drainage or suprapapillary drainage with a self-expanding metal stent. The study includes both patients with unresectable disease and those with potentially resectable malignancies, allowing for evaluation across different clinical scenarios.

All procedures will be performed by experienced interventional radiologists using uniform technical protocols, and patients will be managed according to institutional standards of care. Follow-up will include clinical, laboratory, and imaging assessment as appropriate to routine practice.

The study is designed to generate comparative evidence regarding the safety and performance of these two techniques. In addition, a prespecified subgroup analysis will focus on patients with potentially resectable cholangiocarcinoma undergoing preoperative biliary drainage, in order to explore the impact of drainage strategy on subsequent surgical outcomes.

Inclusion criteria

• Age >18 years.
• Malignant proximal biliary obstruction on imaging (magnetic resonance cholangiopancreatography or contrast-enhanced abdominal computed tomography) with histopathological confirmation or high clinical and radiological suspicion.
• Total bilirubin > 3 mg/dL.
• Patients not candidates for potentially curative surgical resection due to locally advanced disease, metastatic disease, or inadequate clinical condition.
• Patients with potentially resectable neoplasms, defined as the possibility of achieving complete resection (R0), who meet at least one of the following criteria:

5.1 Estimated future liver remnant <40%, in whom percutaneous portal vein embolization of the side to be resected will also be indicated after initial drainage.

5.2 Prolonged jaundice with total bilirubin >10 mg/dL for more than 14 days. 5.3 Malnutrition, defined as ≥10% unintentional weight loss or albumin <3 g/dL, presumably attributable to cholestasis.

5.4 Indication for neoadjuvant chemotherapy.

Exclusion criteria

• Tumor with distal extension to the duodenal papilla, precluding suprapapillary drainage.
• Prior biliary drainage procedure, either percutaneous (PTBD) or endoscopic (ERCP).
• Acute cholangitis, clinically defined as fever (axillary temperature >38°C) and leukocytosis (white blood cell count >10,000/mm³).
• Uncorrectable coagulopathy.
• Iodinated contrast allergy not amenable to desensitization.