What stage of pneumonia involves filled alveoli with PMNs and RBCs?

The stage of pneumonia characterized by filled alveoli with polymorphonuclear leukocytes (PMNs) and red blood cells (RBCs) is known as red hepatization. This stage occurs when the inflammatory response is well established and the lungs exhibit consolidation, where the alveoli become filled with exudate, primarily consisting of cells and fluid due to the body's immune response to the infection.

During red hepatization, the alveoli take on a liver-like appearance, which is where the term "hepatization" is derived. This stage is typically observed a few days after the onset of pneumonia and signifies that the body is actively fighting the infection. The presence of fibrinous exudate, PMNs, and RBCs not only reflects the vigorous immune reaction but also shows the extent of the inflammatory process in the lung tissue.

Understanding this stage is important in the context of pneumonia progression and the effectiveness of the body's immune response, which can vary depending on various factors such as the patient's overall health and any underlying conditions.