The diagnosis of biliary stricture is often missed or delayed because of its indolent course, with up to 20% of patients presenting with subtle clinical manifestations 1 year after the initial injury. Up to 30% of patients with nonmalignant strictures may have a protracted, complicated course necessitating intensive multidisciplinary management with its attendant significant health care costs [8]. Clinically, benign biliary stricture can present with a wide array of manifestations, ranging from being completely asymptomatic to showing overt clinical and laboratory evidence of biliary obstruction. Clinical manifestation may also depend on the underlying cause of biliary stricture and its location. Typically, the symptoms are related to obstructive jaundice with elevated levels of bilirubin and liver enzymes (alkaline phosphatase and γglutamyl transferase) with or without cholangitis. Chronic low-grade biliary obstruction can lead to recurrent cholangitis, stone formation, and even cirrhosis and end-stage liver disease [8].

Diagnostic Approach
Biliary strictures are usually accompanied by upstream ductal dilatation. Ultrasound is a sensitive tool for detecting intrahepatic biliary ductal dilatation and is thus generally the first choice screening exam for the evaluation of biliary obstruction. While the accuracy of ultrasound in the detection of biliary dilatation is greater than 90%, its accuracy in the detection of the underlying cause is lower, varying from 30 to 70% [30].

Multiphase contrast-enhanced CT can be useful for this purpose. The typical imaging clues which help delineate malignant strictures on CT include biliary hyperenhancement, wall thickness greater than 1.5 mm, irregular asymmetric wall thickening with shouldered margins, and long segment strictures. Conversely benign lesions tend to demonstrate smooth, regular, short-segmental narrowing.31 CT also provides the benefit of detecting metastatic lesions in the case of malignancy as well as detecting the underlying cause of obstruction and any associated complications.

MRCP is a highly accurate imaging modality that has been widely adopted in the evaluation of biliary obstruction, with a reported diagnostic sensitivity of up to 98%. However, the sensitivity of MRCP for the differentiation of benign from malignant strictures is weaker, ranging from 30 to 98%. Importantly, MRCP is especially useful and often diagnostic in the evaluation of PSC, iatrogenic bowel injuries, and anastomotic strictures without the need for direct tissue sampling.

Another valuable imaging modality is endoscopic ultrasound (EUS) with or without endoscopic retrograde cholangiopancreatography (ERCP), which has demonstrated up to 97% sensitivity and 88% specificity in differentiating benign from malignant strictures. EUS provides the added benefit of allowing for tissue sampling with cytologic brushings or fine needle aspiration; further interventions including balloon angioplasty or stent insertion can also be performed concomitantly.

Intraductal Endoscopic Ultrasound (IDUS) is a newer technique which utilizes a high-frequency, wire-guided ultrasound probe that is inserted into the extrahepatic bile ducts during ERCP. IDUS with ERCP has shown the ability to diagnose biliary strictures caused by malignant tumors which were not visible on CT. ERCP/IDUS may have superior diagnostic accuracy than MDCT or EUS alone. The drawback of ERCP with IDUS/EUS is its requirement for an invasive endoscopic procedure with risks such as biliary or bowel perforation [9].

Biopsy and cytology of bile ducts and bile samples, as well as a frozen section diagnosis of the marginal bile duct from a malignancy, are the depressed pathological specimens for general pathologists. In addition, the pathological diagnosis is also possibly influenced by the radiological findings and the clinical diagnosis [10].

Treatment Options
There is no agreed standardised management for BBS but endoscopic management is preferred to surgical management in the first instance, Endoscopically BBS are typically managed by ERCP with sphincterotomy, balloon dilatation (BD) and/or stent placement [11].

Prophylactic administration of intravenous antibiotics covering the Gram-negative bacteria Enterococcus and Pseudomonas are recommended for patients with hilar strictures, liver transplantation, and PSC, due to the potential for complex or multiple strictures complicating these conditions [4].

Surgical drainage is the definitive therapy for BBS with high long-term success rates, although surgical morbidity can be substantial[12] Surgical approaches differ case by case, but include; repair of the biliary anastomosis, conversion of a duct to duct anastomosis to an hepaticojejunostomy or ultimately retransplantation [11]. Cholangiojejunostomy is the most widely used surgical procedure for biliary stricture caused by various abnormalities. However, postoperative complications of this surgery are gradually highlighted with its extensive clinical application, especially complications of reflux cholangitis, anastomotic stoma stricture and intrahepatic lithiasis [13].

Percutaneous transhepatic biliary drainage (PTBD) is usually reserved for long complex strictures or disconnected bile ducts that cannot be traversed by an ERCP approach or patients who have undergone Roux-en-Y reconstruction [11].

Treatment of recurrent BBS is similar to the management of primary BBS, however given the recent adoption of FCSEMS as a primary modality for BBS management, consideration can be made to treating patients with a FCSEMS or giving the patient a longer than previous trial with multiple plastic stents before considering referral for surgical biliary reconstruction [11].

Novel techniques, including magnetic compression anastomosis, intraductal radiofrequency ablation, and biodegradable stents, may be useful for selected BBS cases refractory to endoscopic or percutaneous methods [4].