Which type of drainage is characterized as thick and containing white blood cells?

The type of drainage characterized as thick and containing white blood cells is purulent drainage. Purulent drainage is often associated with infection and indicates the body's immune response to that infection. The presence of white blood cells, particularly neutrophils, in the fluid contributes to its thick texture and cloudy appearance. This type of drainage can vary in color, often appearing yellow, green, or brown, depending on the types of bacteria and the stage of the infection.

In contrast, serous drainage is clear and thin and contains minimal cellular material, primarily composed of serum. Sanguineous drainage is red and consists mainly of blood, while serosanguineous drainage is a mixture of serous and sanguineous fluids and appears pinkish. These types of drainage do not indicate infection in the way that purulent drainage does, making purulent the correct choice for identifying drainage with a significant presence of white blood cells.