Urine microscopy

Once this dipstick check has been carried out, a microscopic examination is the next step using urine sediment. To do this, the urine sample is centrifuged (spun) to concentrate the substances in it at the bottom of a tube. The fluid at the top of the tube is then disposed of and the drops of fluid remaining are examined under a microscope and the following will be noted on your urine sample report:

Red blood cells (RBCs)

Normally, a few RBCs are present in urine. Inflammation, injury, or disease in the kidneys or elsewhere in the urinary tract, for example in the bladder or urethra, can cause RBCs to leak out of the blood vessels into the urine. However, RBCs can also be due to blood from haemorrhoids or menstruation, kidney, bladder or urethral cancers, enlargement of the prostrate in men; kidney stones and certain blood diseases such as sickle cell anaemia.

White blood cells (WBCs or leukocytes)

The number of WBCs in urine is normally low. When the number is high, it indicates an infection or inflammation somewhere in the urinary tract due to the immune system response.The agreed total number of leukocytes to be present in a millilitre of urine to establish the baseline for infection remains unchanged since the work of C Dukes in 1928. He proposed a threshold of less than 10 wbc/per millilitre of urine as the upper limit of normal white blood cell excretion in the urine. Above that limit and the sample may be positive for infection.

Also note that White Blood Cell or Leukocytes can also indicate chronic kidney inflammation caused by a kidney stone, a tumour of the kidneys, bladder or urethra, infections such as chlamydia or other sexually transmitted diseases and fungal infections such as Thrush.

Epithelial cells

Epithelial cells can be either squamous, originating from the vagina, urethra or genital skin, urothelial, that is cells from the bladder wall and finally renal tubular originating from the kidneys.When analysing the sample, significant epithelial cells may lead to further analysis to identify their type. Squamous epithelial cells originate from the urethra or vagina and are commonly found in urine samples due to transfer whilst providing the sample – these are often reported as a contaminate in the sample without specific analysis of the actual type of epithelial cell. However, it’s the presence of urothelial epithelial cells that would indicate a urinary tract infection. Or, if many renal (kidney) epithelial cells are discovered in urinalysis, then it could indicate a viral infection or problem with the kidneys.


Casts are particles that are formed from protein secreted by kidney cells. Under the microscope, they often look like a sausage shape because of the way they form and in healthy people they appear nearly clear. This type of cast is called a ‘hyaline’ cast. When an infection is present in the kidney, other things such as RBCs or WBCs can become trapped in the protein as the cast is formed. When this happens, the cast is identified by the substances inside it, for example as a red blood cell cast or white blood cell cast. Different types of casts are associated with different kidney diseases and the type of casts found in the urine may give clues as to which is affecting the kidney. Normally, healthy people may have a few casts. After strenuous exercise, more casts may be detected. Cellular casts, such as RBC and WBC casts, indicate a kidney disorder.


Urine contains many dissolved substances (solutes) – waste chemicals that your body needs to eliminate after filtration through the kidneys.These can form crystals and they may group together to form kidney “stones”. These stones can become lodged in the kidney itself or in the ureters – tubes that pass the urine from kidney to the bladder – causing extreme pain. Medications, drugs, and x-ray dye can also crystallize in urine.

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