AIM: To detect the presence of RBC’s, WBC’s, casts, yeast cells, crystals, bacteria in urine deposits as an aid in the diagnosis of urinary tract infections (UTI’s).
TECHNIQUE: The technique used in urine microscopy is called wet mounting/preparation.
MATERIAL/APPARATUS: Urine specimen, microscope, glass slide, cover slip, test tube, test tube rack, discard jar, grease pencil, centrifuge.
- Describe the appearance of the urine specimen first by reporting its colour (e.g. pale yellow, yellow, and amber, bloody or smoky brown) and turbidity (i.e. whether it is clear or cloudy).
- Transfer about 10 ml of the urine specimen into clean test tube. In cases of many urine specimens, label the test tubes using grease pencil to avoid any chaos that might emanate in the course of the analysis.
- Place the test tube (s) containing the urine specimen into the centrifuge machine and centrifuge at 400 rpm for 5 minutes. This is done in order to sediment the cells and other materials/particles sought for in the urine specimen.
RPM means “Revolutions per Minute”.
- Pour the supernatant of the test tube content after centrifuging, into a discard jar. This is done by completely inverting/holding the test tube at an angle of 90o over the discard jar to get rid of the supernatant.
- Remix the sediment remaining in the test tube by tapping the bottom of the test tube on the desk or with your hand. Be careful to avoid generation of aerosol.
- Transfer a drop of the mixed sediment onto a clean glass slide and cover with a cover slip.
- Examine the prepared slide under the microscope using ×10 and ×40 objective lens. Make sure the condenser iris of the microscope is closed sufficiently in order to get a good contrast while viewing the fields of the slide
NOTE: Make sure that the contents of the centrifuge machine (test tubes) are balanced i.e. only even numbers of test tubes are to be allowed in the centrifuge, in order to avoid breakage of the centrifuge and subsequent damage to the centrifuge machine. Odd numbers of test tubes should not be allowed in the centrifuge before its operation.
REPORTING OF THE RESULT:
Report the appearance of the urine specimen examined. Presence of any of the following: WBC’s, RBC’s, casts, crystals, yeast cells, bacteria e.t.c. is reported using + sign depending on the number or amount found. Their absence is reported as “nil”.
Urine is H2O containing the H2O – soluble waste products removed from the blood stream through the kidney. Bacteriological examination of urine is done when the signs and symptoms of an infection or disease points to UTI’s, hypertension, and renal insufficiency. It should be done in persons with suspected systemic infection or fever of an unknown origin, and it is also desirable for women in the first trimester of pregnancy.
DEFINITIONS OF SOME TERMS ASSOCIATED WITH URINE ANALYSIS
Bacteriuria: This is the presence of bacteria in urine.
Cystitis: This is the infection of the urinary bladder.
Haematuria: This is the presence of blood in urine.
Pyuria: This is the presence of pus cells (dead WBC’s) in urine.
Pyelonephritis: This is the infection of the kidney.
Urethritis: This is the infection of the anterior urinary tract.
Dysuria: This is the pain experienced on passing urine.
Polyuria: This is an increase in the volume of urine.
Oliguria: This is a decrease in the volume of urine.
Anuria: This is a cessation of urine flow.
Hypersthenuic urine: Urine with a high specific gravity.
Hyposthenuic urine: Urine with a low specific gravity.
Isosthenuic urine: Urine with a normal specific gravity.