Kerley B lines are due to-
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 angles(septal or Kerley B lines). Reference:Davidson's medicine-22nd edition,page no:550.
Carcinoma bronchus
Pulmonary edema
Lung abscess
Pulmonary embolism
Respiratory system