Clinical Chemistry - Urine Phase Contrast

Hey, here's Natasha again:]

I’m here to talk about urine phase contrast.

The purpose of performing urine phase contrast is mainly to differentiate isomorphic red blood cells and dysmorphic red blood cells present in the urine. Apart from that, if there are presence of white blood cells, microorganisms, epithelial cells, casts or/and crystals, they will be noted as well.

Isomorphic red blood cells, can suggest urological diseases which are non-glomerular origin. They appear bright and circular in shape. Isomorphic red blood cells still retain the haemoglobin whereas dysmorphic red blood cells have lost the haemoglobin.

Dysmorphic red blood cells, however, can suggest diseases of glomerular origin such as glomerulonephritis, etc. Dysmorphic red blood cells may appear circular or slight difference in shape and also appear as dark, thick rings.

The presence of microorganisms can indicate urinary tract infection (UTI). They may appear cocci or bacilli in shape, singly, pairs or in chains.

Crystals can be found in urine specimens that are super saturated with a crystalline compound and the formation of crystals are pH dependent. Thus a change in urine pH may cause crystal precipitation. For example, calcium oxalate maybe found in deposit of both acid/alkali urine. It may be regarded as a normal constituent of urine or may indicate renal calculi, renal disease or glycol poisoning.

The type of microscope used is the urine phase contrast microscopy. As compared to normal microscopy, the optical components of this microscope are able to change the different phases of structures into differences in light intensity.

Normal microscopy is when there is no optical contrast technique is employed. It uses transmitted light to view a specimen that contains natural contrast/colour or is stained.

The type of counting chamber used is Med-Fuchs Rosenthal counting chamber. This counting chamber is a little different from the counting chamber that we get to use in school during MCT practicals. It only consists of 16 big squares with 16 smaller squares in each of the big square. Any adjacent four squares can be used to count the isomorphic and/or dysmorphic red blood cells.

For urine phase contrast, fresh first morning mid-stream urine is collected and spin down at 2000 rpm for 10mins. The supernatant is then discarded (most of the time the cell pellet is not as visible, thus usually ¾ of the urine is discarded). The remaining urine containing the cells is then mixed well and pipetted onto the counting chamber. It is then viewed under the microscope.




Drawings are not drawn to scale.



In this picture, WBCs are the larger cells with granules inside. Isomorphic RBCs are bright ones and smaller in size than WBC. Dysmorphic RBCs are the dark, ring-shaped cells.
Picture is taken from http://lab-qa.org/u_atlas/sem01_22.htm



Med-Fuchs Rosenthal Counting Chamber. Click to have a better view:] Picture is taken from http://www.hausserscientific.com/FuchsRosenthalDirect.htm