The presence of red blood cells (RBCs) in a urine test may be a sign of a kidney disease or damage to the genitourinary tract.
The RBCs seen in a urine sample may come from any place of the urinary tract, from the kidneys to the urinary meatus (opening of the urethra).
The presence of blood in the urine (macroscopic hematuria) may be evident causing the urine to turn red or tea-colored. However, sometimes the blood can go unnoticed without being evident.
Therefore, if there are RBCs in the urine when it is examined microscopically is called microscopic hematuria and it is noted to be considered for diagnosis.
The observation of microscopic hematuria can be important in the early diagnosis of kidney disorders, malignancy of the urinary tract and to confirm the presence of renal calculi.
Besides, if under the microscope there are a great number of dysmorphic RBCs (RBCs of different size and shape that have cellular protrusions, or are fragmented) is primarily related to glomerular bleeding (kidney damage). On the other hand, if RBCs are similar in size and shape it suggests a problem in the urinary tract.
This test is performed along with other urine tests. The patient must collect a sample of the urine in a specific container using a special kit. This sample will be sent to the lab for the analysis. The urine should be collected by a clean-catch midstream to avoid bacterial contamination.
To study the presence of RBCs in the urine, it is necessary to obtain previously the urinary sediment. For this matter, the urine sample should be placed at rest for some hours waiting for the different elements of the urine (white and red blood cells, crystals, etc.) precipitate to the bottom. As this process is very slow, the urine is centrifuged for about 5 minutes at 1500 or 2000 revolutions per second to obtain a sample of the sediment in less time.
In women, it is important to avoid the possibility of menstrual contamination. Insertion of a tampon before collecting the sample is recommended to prevent this contamination.
It is considered normal to see an occasional red blood cell (1 or 2 per high-power field) when examining the urine sediment with a high-power magnification.
If there are more than 3 RBCs per high-power field in the microscopic exam, it is indicative of damage to the glomeruli of the kidney or trauma to the vessels surrounding the urinary tract. The number of cells present is indicative of the extent of the damage or injury.
A great number of RBCs in the urine may be a sign of:
Sometimes, there are RBCs in the urine related to external causes or medication: