I recently had a bronchoscopy. the report stated that my bal "yield"was 50% what does this mean?

Yield: This indicates how sensitive the sampling was. Usually this number varies between 15 and 60%. A higher number means better chances that the results will be helpful in evaluating a patient.

Lavage fluid returnd: BAL stands for "bronchoalveolar lavage". The physician performing the bronchoscopy washed (lavaged) a part your lungs with saline & then sucked the fluid back up to try to capture microorganisms or cells that might be diagnostic. A lavage usually involves a <30 mL of saline at a time. The yield is a piece of technical data: about 50% of the fluid used in the wash was sucked back up. 60% is normal.

Difficult to say: I would need the entire report to see what your results mean.