Presence of RBC in urine is known as

The correct option is Hematuria.

To understand why this is the correct answer, let's break down the medical terminology and explore the meaning of each option provided:
1. Hematuria: This term is derived from two Greek words: "hema" (meaning blood) and "ouron" (meaning urine). In medical terminology, the suffix "-uria" refers to the presence of a substance in urine. Therefore, hematuria literally translates to the presence of blood, specifically red blood cells (RBCs), in the urine.
2. Proteinuria: The suffix "-uria" combined with "protein" represents the abnormal presence of proteins (such as albumin) in the urine, which typically indicates a kidney filtration issue rather than RBCs.
3. Urolithiasis: This term refers to the formation or presence of stony concretions (calculi or kidney stones) anywhere in the urinary tract.
4. Nephritis: The suffix "-itis" denotes inflammation. Nephritis is the inflammation of the kidneys, which can cause hematuria but is not the term for the presence of RBCs in urine itself.

Thus, the presence of red blood cells (RBC) in urine is clinically defined as Hematuria.