Both percutaneous transhepatic biliary drainage (PTBD) and endoscopic retrograde
      cholangiography (ERC) are accepted approaches in the management of patients with malignant
      obstruction at the biliary hilum. In routine clinical practice, ERC is generally favored on
      the basis of: 1) high technical and clinical success rates for other (non-hilar) indications;
      2) the perceived safety of ERC relative to PTBD; 3) the perceived ability to perform more
      comprehensive tissue sampling at the time of ERC compared to PTBD; 4) the avoidance of
      external tubes which are often needed for PTBD; and 5) because patients with suspected
      malignant hilar obstruction (MHO) typically present to and are managed by
      gastroenterologists. However: 1) observational data suggest that PTBD is superior for
      achieving complete drainage of MHO1 and some guidelines recommend the percutaneous approach
      over ERC for Bismuth type 3 & 4 hilar strictures; 2) the generally quoted risks of PTBD are
      based on outdated studies and may be exaggerated; and 3) endoscopic diagnosis of
      indeterminate biliary strictures remains suboptimal despite the use of cholangioscopy and
      multi-modal sampling.

      Although many patients who undergo initial ERC require subsequent PTBD for adequate drainage,
      no randomized trials comparing the two modalities for suspected MHO have been published. The
      main hypothesis is that even though PTBD will be more effective than ERC for decompression of
      suspected MHO, this advantage will be offset by the favorable safety profile and superior
      diagnostic capability of ERC. If, however, PTBD is found to be substantially superior (by a
      pre-specified margin) in terms of drainage, or if the potential advantages of ERC are not
      realized, then the existing clinical approach to MHO must be reappraised. Moreover,
      identifying patient and stricture characteristics that predict response to PTBD or ERC may be
      important for informing clinical decision-making and guidelines.