Performing the Urinalysis Laboratory Procedures Analyzing the Urine

Performing the Urinalysis Laboratory Procedures

Analyzing the Urine Sample o A complete urinalysis usually involves 3 steps. n 1. Checking and recording the physical characteristics of the urine n 2. Performing a chemical analysis using a multi-test dipstick n 3. Centrifuging a small portion of the sample and examining the sediment under a microscope

1. Checking and recording the physical properties of the urine o Physical properties include: n n n Color Transparency Odor Specific gravity Volume

2. Chemical Analysis o Many chemical tests can be performed on a small quantity of urine by using a dipstick o Each pad on dipstick is designed to test for a particular substance in the urine. o When the urine comes in contacts with the reagents, a chemical reaction will cause a color change based on the amount of the substance in the urine. o Color is compared to chart, and approximate amount of substance in urine can be determined

o Several brands of dipstick exist.

Chemical analysis o Certain drugs and medications may interfere with chemical tests. o Be sure to know any medications animal is currently receiving when performing a urinalysis.

Components on the Dipstick o o o o Urine p. H Protein Glucose Ketones Bilirubin Urobilinogen Blood Nitrites

Urine p. H o Number of how acidic or alkaline the urine is o p. H is affected by diet. n Plant diets can cause alkaline urine n High protein diets can cause acidic urine o Small animal p. H is usually acidic n In general dog and cat urine p. H is 6 -7 o Large animal urine is usually alkaline o Other factors may affect urine p. H n Fever n Starvation n Certain drugs

Protein o Healthy animals will usually not have any protein in their urine although in some cases trace amounts can be found in concentrated dog and cat urine. o The urine protein level must be interpreted along with the Urine specific gravity. o Small amounts of protein are more significant in dilute or unconcentrated urine. o Protein may be lost in the urine due to glomerulopathies, inflammation, or hemorrhage.

Glucose o If the sugar in the blood is significantly higher than normal, some excess may be found in the urine. o Normal dog and cat urine should be negative for glucose. o In some cases if the urine is not run immediately, false glucose readings may occur.

Ketones o Ketones are the substances formed in the body during the breakdown of lipids. o Normal pet urine should be negative for ketones o When excess amounts of ketones are formed, their levels rise in the blood and then are released in the urine. o Can cause CNS depression and acidosis o May result in ketonuria caused by: n Starvation n Diabetes

Bilirubin o Pigment made by the liver from dead or dying red blood cells. o Small amounts may sometimes be found in healthy dogs. n Dogs can conjugate bilirubin in their kidneys, so small amount may be insignificant. o Bilirubin found in cat urine is a concern and can be a sign of liver disease, bile duct obstruction, or hemolysis.

Urobilinogen o Compound formed from bilirubin by intestinal tract. o Normal dogs and cats have small amounts of urobilinogen in their urine. o Results from dipstick are not considered very accurate and may be difficult to interpret. o Usually recorded as “normal” or “abnormal”.

Blood o Healthy pets may have a few red blood cells in their urine, but greater than ~5 cells per field may indicate a problem. o Hematuria can be due to a number of causes: n n Trauma Urinary Tract Infection (UTI) Bladder Stones Blood Clotting Problems

Blood cells in the Urine

Nitrites o May be produced by the bacteria present in some infections o Test often shows a “false negative” and is considered inaccurate in pets. o However, if positive, should examine sediment closely for bacteria.

Examining Urine Sediment o After urine sediment is centrifuged (generally about 5 minutes), the top portion of the liquid is poured off and the sediment is resuspended and examined microsopically. o Indications for sediment exam include: n Provides additional information n A form of cytology n Must be interpreted with other clinical data, including physical and chemical composition of the urine.

Urine Sediment Exam Procedure o 1. Collect urine in a clean container o 2. Throughly mix specimen and transfer 3 -5 ml volume to a centrifuge tube o 3. Centrifuge for 3 -5 mins o 4. Pour off supernatant o 5. Leave approximately 0. 5 ml of supernatant o 6. Resuspend urine sediment by tapping tube or flicking it w/ your finger. o 7. Examine a stained or unstained sediment. (Or both!)

Potential Sediment Elements o o o White blood cells Red blood cells Lipid droplets Bacteria Crystal Casts

White blood cells o Larger than normal numbers of white blood cells may indicate inflammation from a bladder or kidney infection.

Lipid Droplets o Are common in the sediment of urine, especially in cats. o Number and size may vary o Should not be confused w/ air bubbles or RBC’s. They will be in focus when other structures are not.

Bacteria o Sediment is examined for presence of bacteria o Small amounts may be due to contamination, large amounts may indicate bladder infection (especially if sample is obtained via cystocentesis). o A urine culture and sensitivity may indicated with large amounts of bacteria.

Crystals o Made up of minerals and can sometimes be found in the urine. o Under certain conditions, crystals can clump together to form bladder stones (uroliths). o The p. H of the urine may influence the type of crystal development o Some animals and species are more predisposed to crystal and stone formation.

Common Crystal Types o Struvite o Calcium Oxalate o Ammonium Urate

Casts (These will be covered in depth in Clin-Path!) o Urine Casts are small cylinder-shaped formations of cells and debris from inside the tubules of the kidneys o Presence and composition of casts can indicate kidney function o Types of casts: n Hyaline n Granular n Waxy n Fatty n Cellular n Mixed n Bile stained

Specific Gravity o Measures the concentrating ability of the kidney. o Done with a refractometer n There may be a spot on the dip-stick for SG, however in animals, these are not valid results.

Specific Gravity “normals” p. 158 Lab bk o “Normal” values in dogs is between 1. 001 -1. 060 o “Normal” values in cats can range from 1. 001 – 1. 080 o There is no set “normal” value in animals, however the following guidelines should be used: n n SG: below 1. 008 is said to indicate dilution (hyposthenuric) SG: 1. 008 -1. 012 is said to be fixed or isosthenuric (same SG as plasma) SG: 1. 013 – 1. 030 is considered normal if no dehydration suspected. SG: above 1. 025 implies renal tubule concentration ( in cats, this can indicate renal disease)