Step 1: The image shows red hepatization of the lung, where the cut surface looks brown-red, firm and airless, resembling liver. Step 2: Red hepatization is a stage of lobar pneumonia, most commonly caused by Streptococcus pneumoniae. Step 3: Lobar pneumonia progresses through congestion, red hepatization (alveoli filled with red cells, neutrophils and fibrin), grey hepatization and resolution. Step 4: The diffuse consolidation of an entire lobe seen here is typical of lobar pneumonia rather than the patchy lesions of bronchopneumonia or any renal condition, so the answer is lobar pneumonia.