An apparatus for accessing a body lumen includes a tubular member including a proximal end, a distal end sized for introduction into a body lumen, and a passage extending along a steerable distal portion of the tubular member. The passage includes a first region extending substantially parallel to a center of modulus of the distal portion and a second region offset from the center of modulus. A steering element is disposed through the passage extending along the distal portion that includes a proximal end disposed adjacent the tubular member proximal end, and a distal end fixed to the tubular member distal end beyond the distal portion. A steering adjustment member is slidable within the passage for selectively directing a portion of the steering element between the first and second regions to vary the steerability of the distal portion.