The ideal time for urine to be collected is first thing in the morning , when it is most concentrated . Ideally , it should be tested within 1 hour of collection or at least on the day of collection . If a client is unable to drop off the patient ' s urine sample straight away , advise them to keep the sample in the fridge . Common in-house urine tests are dipsticks and specific gravity ( SG ) tests . Urine may also be examined microscopically .
Dipstick tests
Dipsticks measure 10 parameters , which are outlined in Table 2 [ 10 – 15 ] ( page 57 ) with related comments . Some parameters on dipstick tests are not accurate , so the sample may need to be sent to an external laboratory .
How to carry out a dipstick test
• Wear appropriate PPE , such as gloves .
• Invert the urine sample several times .
• Place a drop of urine on to each test pad using a pipette . ( Or the dipstick can be dipped into the patient ' s urine , although there is some thought that the colour from each pad may run into others , causing inaccuracies in reading .)
• Tap off the excess urine and wait for the specified amount of time , then read the results from the bottom to the top and record the data .
Specific gravity tests
SG gives an indication of the concentration of a patient ' s urine . Normal SG in dogs is 1.015 – 1.045 and in cats it is 1.035 – 1.060 . High SG levels may be indicative of dehydration , acute renal failure , shock , diabetes mellitus , fluid loss or urinary crystals [ 16 ] . Low SG levels may indicate chronic renal failure , diabetes insipidus , polydipsia , fluid therapy or corticosteroid therapy [ 16 ] .
How to carry out a specific gravity test
• Wear appropriate PPE , such as gloves .
• Using a couple of drops of distilled water , calibrate the refractometer by turning the screw left or right until it reads 1.000 .
• Wipe away the distilled water from the refractometer .
• Apply 2 – 3 drops of urine on the refractometer . Hold up to the light to read the results , and then record them .
How to examine urine using a microscope
• Wear appropriate PPE , such as gloves . Fill an Eppendorf tube with the patient ' s urine and place it into the centrifuge . ( Make two samples to balance out the centrifuge .) Spin for 5 minutes at 2,000 rpm , then remove the samples and place them upright in a holder .
• Pipette most of the urine on to absorbent material and dispose of it in clinical waste . Leave a few drops at the bottom of the Eppendorf .
• If the VS requests a stained urine slide , add one drop of Sedistain .
• Suspend / mix the sample by flicking it a few times . Pipette one drop of urine on to a microscope slide and place a cover slip on top . ( To avoid bubbles , apply the cover slip at a slight angle .)
• Label all samples with the patient ' s name , surname and the date .
• Set up the microscope ( as described earlier in this article ). Examine the urine for crystals , red or white blood cells , bacteria and tissue cells .
The following are common types of urinary crystals .
• Struvite is shaped like a coffin lid . It is mainly found in alkaline urine [ 17 ] . Low numbers of struvite crystals are normal for some dogs and cats . They can be associated with infection , as well as forming plugs that lodge in the urethra in cats , leading to urinary obstruction [ 18 ] . Excessive numbers can cause urinary stones .
• Calcium oxalate dihydrate crystals are shaped like small squares with an X in the centre . Breeds predisposed to calcium oxalate crystals include the Yorkshire terrier , miniature Schnauzer , miniature poodle , Burmese cat and Himalayan cat [ 17 ] . Calcium oxalate can be found in normal urine , particularly if it is acidic or refrigerated [ 18 ] . According to Hill ' s Pet Nutrition [ 18 ] , International Cat Care notes that toxic loads of calcium oxalate are a sign of antifreeze poisoning .
• Cystine is flat , thin and hexagonal shaped . It is found in acidic urine and is associated with renal tubular dysfunction [ 17 ] .
• Ammonium urate is spindle shaped , thorn-apple shaped or rosette shaped . It is found in acidic and neutral urine . Dalmatians are predisposed to its formation , but in other breeds of dog and in cats it may indicate liver disease or portosystemic shunt [ 17 ] .
• Uric acid varies in shape but is generally diamond shaped . It is found in acidic urine but is rare [ 17 ] .
56 Veterinary Nursing Journal