<prompt> Kerley B lines are due to-Carcinoma bronchusPulmonary edemaLung abscessPulmonary embolism  <response>: In pulmonary oedema,chest X ray shows increased vascularity of the lung fields,and the right and left pulmonary aeries dilate.Subsequently,interstitial oedema causes thickened interlobular septa and dilated lymphatics.These are evident as horizontal lines in the costophrenic anglesseptal or Kerley B lines. Reference:Davidsons medicine-22nd edition,page no:550. 