Which condition is often associated with the presence of pus in the urine?

The condition associated with the presence of pus in the urine is pyuria. Pyuria is specifically defined as the presence of white blood cells, or pus, in the urine, which is indicative of inflammation or infection within the urinary tract. This response typically occurs as a result of various underlying conditions, including urinary tract infections.

In the context of the other conditions, cystitis refers to inflammation of the bladder, which can result in urinary symptoms, but it is not synonymous with the presence of pus specifically. Pyelonephritis is an infection of the kidneys and can cause pyuria, but it is a broader condition and not solely defined by the presence of pus. Nephrotic syndrome involves the loss of proteins in urine and can lead to various urinary symptoms, but it isn't primarily characterized by the presence of pus. Thus, pyuria is the most precise term to describe the presence of pus in urine, making it the correct answer.