What does "per lpf" refer to in urine microscopy examination?

In urine microscopy examination, "per lpf" stands for "per low power field." This term is used to standardize the reporting of various findings observed under a microscope, specifically when samples are viewed using a low magnification objective lens.

The correct answer pertains to the number of casts, which are structures that form in the renal tubules from aggregated protein and cells. They can provide significant insight into renal pathology, such as glomerulonephritis or tubular damage. Reporting casts per low power field allows for a consistent framework to determine their prevalence in a given sample, helping in the diagnostic process.

In urine microscopy, while crystals, bacteria, and epithelial cells can also be assessed and reported per low power field, the emphasis on casts as a critical diagnostic feature makes this choice particularly relevant in understanding renal function and potential disorders. Epithelial cells and bacteria typically have different clinical implications compared to casts, which can indicate specific types of kidney injury.