Urine 1 Flashcards
Functions of the Kidney
- Eliminates of metabolic wastes from the body
- Maintains normal levels of body electrolytes and essential organic molecules (i.e. homeostasis)
- Produces important hormones
Urinary Tract Anatomy
Kidney
Ureter
Urinary bladder
Urethra
• Glomerular filtration
• Filtration of blood occurs at the glomerulus
• Driven by high blood pressure
• Permitted by semipermeable capillary membrane
allows passage of water and dissolved solutes of low molecular weight
Reabsorption (of the kidneys)
o The majority of small molecules in the glomerular filtrate are reabsorbed before they exit the body in urine
o ~ 90% of filtered molecules are reabsorbed in the renal tubule
Excretion (of the kidneys)
o Some molecules are excreted into the glomerular filtrate as it moves through the renal tubule
Voided Sample of urine
- Collect urine as animal urinates
- Contaminated by bacteria
- Preprandial (before meal)
a. Most concentrated
b. Not affected by eating or exercise - Midstream sample is the cleanest
Manual Express of urine
- Mainly used in cats and small dogs
- Must never exert too much pressure – bladder can be ruptured
- Never should be used with an animal with urinary tract obstruction
- Urine may contain RBC – bladder can be damaged during compression
Specimen Collection of urine
A. Voided Sample
B. Manual Express
C. Catheterization
D. Cystocentesis
Catheterization of urine
- One preferred method – sterile if done correctly
- Insert catheter into bladder via urethra
- Sterile catheter/sterile gloves
- Avoid trauma to urethral mucosa
- RBC common
Cystocentesis of urine
- Dogs/cats sterile collection
- Insert sterile needle directly into bladder through abdominal wall
- Surgical prep – remove as much urine as possible to avoid leakage through the needle hole
Biochemical Analysis of Urine
- Chemical substances excreted in urine can be measured
- Chemical assays are made using a dipstick w/ individual test pads for each chemical
- Deviations from normal expected levels can be an indication of disease
pH of urine
pH
• Measure of H+ concentration in urine
• Abnormally low pH associated w/ hypoventilation, starvation, prolonged vomiting and diarrhea
• Abnormally high pH associated w/ hyperventilation, bacterial UTI, postprandial urine sample
• May be falsely increased if urine is left out at room temperature for a long time before analysis
Urine is typically acidic or alkaline
pH < 7 in carnivores
pH > 7 in herbivores
Protein in urine
• A small amount of protein is excreted by an animal on a normal basis- Usually not detectable
• Method of urine collection affects protein level in urine
• Proteinuria usually indicates disease of the urinary system
o kidney damage (usu. glomerulus), urinary tract inflammation
• Falsely increased if urine has prolonged contact w/ the test pad on dipstick
Glucose in urine
• Not normally detected in urine
• Glucosuria occurs when blood glucose is
170-180 mg/dl in dog
260-310 mg/dl in cat
• Conditions associated w/ glucosuria include
o diabetes mellitus, stress/excitement, high carbohydrate meal
• May be falsely decreased in refrigerated urine
Ketones
• Ketone group-containing acids that result from fat breakdown
• Not normally detected in urine
• Ketonuria occurs when fat is metabolized for energy when carbohydrates are not available
o diabetes mellitus, pregnancy toxemia/ketosis, starvation/fasting
Bile pigments
- Chemicals derived from the breakdown of hemoglobin:
- Bilirubin
- Urobilinogen
- Bilirubinuria can be due to
- RBC destruction, hepatocellular damage,bile duct obstruction
- Small quantities of bilirubin can be detected in normal dogs
- Bilirubin is unstable in urine samples
Blood
- Red blood cells (RBC’s) and hemoglobin are detected by the same pad
- Hematuria can be due to
- bacterial UTI, urolithiasis, interstitial cystitis, neoplasia, renal disease, trauma
- Color of urine can be abnormal w/ hematuriaà wine, brown, cloudy red
- Abnormal urine color may disappear after centrifugation
Hemoglobin
- Hemoglobin is not normally present in urine
- Hemoglobinuria occurs w/ massive RBC destruction à autoimmune hemolytic anemia, blood transfusion incompatibility
- Color of urine containing hemoglobin can be abnormalà wine, brown, cloudy red
- The color of the sample doesn’t change after centrifugation
Myoglobin
- Oxygen-carrying molecule found in muscle that is similar to hemoglobin
- Detected by the blood test pad as hemoglobin and gives urine a dark brown to black color
- Myoglobinuria observed when significant muscle damage occurs- exertional rhabdomyolysis, trauma, toxicity
Nitrite
- Produced by bacteria from nitrate in urine
- Increased levels are supposed to indicate a bacterial UTI
- Not a reliable test in dogs and cats
Leukocytes
(i.e. White Blood Cells)
• Pyuria is indicative of infammation in the urinary tract
• Possible causes include- bacterial UTI, urolithiasis
• Test pad is not very sensitive in dogs, not reliable in cats
Urinary Sediment Analysis
- Performed as part of complete urinalysis procedure
- Detects abnormalities not seen on gross or biochemical analysis
- Confirms results of biochemical analysis
Urine collected for sediment analysis should be…
- Fresh sample
- Concentrated urine sample
- Collected by cystocentesis
Hyaline cast
o Rectangular, clear retractile, with of renal tubule, parallel sides, rounded ends
o Inflammation in the renal tubules
o Consists of precipitated protein
o Finding 0-2/LPF may be normal
Cellular casts
o incorporation of WBC’s, RBC’s, renal tubular epithelial cells into precipitated protein matrix
o most likely indicate inflammation in the renal tubule
o Red blood cells= stuck to the surface of the precipitated protein, parallel sides, and rounded edges.
o White blood cells = infections
o Precipitated protein plus Whatever cell is present at time cast are forming
Waxy cast
o severe degeneration of the rental tubules
o wider, most sever, squared off ends, opaque, cracks in the sides
Fatty cast
o Precipitated protein d fat- lipid droplets, st. stephens cross (4 dots)
o Normal in cats
o Seen in catheterization (from lubricant)
o Can attach itself to a hyaline cast present in the urine
Crystals
o Form when the constituent minerals are present in the urine
o Presence in urine may be considered normal or abnormal
Whether a certain type of crystal forms depends on:
the concentration of the constituent minerals in the urine
the pH of the urine
the temperature of the urine
Microorganisms in urine
Normal urine is free of microbes
Contamination can occur when collecting voided urine samples
Bacteria and yeast most often seen
Bacteria present in great #’s w/ UTI
Miscellaneous
Mucus threads Spermatozoa Fat droplets Plant fiber, pollen Starch granules Parasite eggs
Red Blood Cells (RBC’s)/Erythrocytes
o Indicated bleeding from somewhere in the urinary tract
o Bacterial UTI, urolithiasis, interstitial cystitis, urolithiasis
• Small ruffled circles- start crenation. Clear or slightly more yellow. No nucleus,polka dot/foamy
• Caused by: Inflammation, trauma, catherizeting, cytsto,
• Smallest cell seen in the urine
White Blood Cells (WBC’s)/ Leukocytes
o Indicate inflammation of the urinary tract
o Bacterial UTI, urolithiasis , neoplasia
o granular on the inside, regular around the edge
o Inflammation, bacteria (lots of WBC), normal for occasionally WBC
Bacteria
- Environment mental contamination= no accompanying WBC
- Gram negative rods- easy to get fecal contamination into the urethra (naturally found in GI)
- Gram positive cocci- from skin
Epithelial Cells
Squamous>Transitional>Renal tubular
• Squamous
• Transitional
• Renal Tubular
Renal Tubular
o found in renal tubule
- line the renal tubules. Small. Round. Large nucleus compared to cytoplasm
Squamous
o found in the distal urethra, vulva, vagina, prepuce
- fried egg, largest cell. Line the urethra and bottom portion of the bladder. Common.
Transitional
o found in renal pelvis, ureter, urinary bladder, proximal urethra
round. Large nucleus. Line the bladder and ureter. Stretch Flat and bounce back. Clumps.
Casts
o Cylindrical structures made of precipitated protein that assume the shape of the renal tubular lumen where they form
o May be indicative of renal disease
o Least severe< Hyaline
Granular cast
o All represent different stages of degeneration of a cellular cast
o degenerate as sits in real tubules
o granular= can’t tell which cell
Uroliths
A. Calculi (stones) composed of various minerals
B. After surgical removal, uroliths are often sent to outside labs for analysis
Common types of Uroliths
Triple phosphate
Urate
Oxalate
Cystine
Triple phosphate
– most common in both dogs and cats
a. Salts of magnesium, ammonium, calcium, and phosphate
b. Radioopaque, hard, white or yellow
c. Common in alkaline urine
Urate
a. Composed of ammonium urate
b. Radioluscent, yellow, brittle
c. Common in Dalmatians (uric acid)
Can be brittle, don’t’ palpate to hard can break
Oxalate
a. Composed of calcium oxalate
b. Radioopaque, hard
c. Sharp protrusions, can severely traumatize the bladder
Cystine
a. Composed of amino acid cystine
b. Yellow, smooth
c. Radioluscent, easily pulverized
Palpate
Struvite crystals
triple phosphate/MAP-magnesium ammonium phosphate
Most common
Prism/Rectangle/ coffin lid
Favor neutral to alkaline urine
can be normal in dog urine
Can from when sitting at room temperature
Bacteria can promote struvite crystals
Calcium oxalate dihydrate crystals
Neutral to slightly alkaline– but prefer acidic
Envelopes
Can from when sitting at room temperature
Can form into stones
Seen in miniature schnauzers
Calcium oxalate monohydrate crystals
Forms in a toxic situation - Ethylene glycol toxicity
o Six sides crystals/picket fence
Flat, oval, sharp
Calcium carbonate
Found in normal horse, rabbit, GP, goat
Usually have a lot of mucus in urine too
Look like air bubbles, but with color—yellow brown
Variably sized spheroids
Amorphous crystals
haven’t grown to be a big crystal
• Look like sand- fine granules
• Could lead to other crystals
• no specific clinical interpretation
Billirubin crystal
conjugated bilirubin
normal in dogs, more in more concentrated urine
Needle/hay like crystals. Sharp, pointed, slender
Attached to a fat cell, look like flashlight
Seen in high concentrated urine
no specific clinical interpretation
precipitate onto other formed elements
abnormal in feline, equine, bovine, or camelid urine
Ammonium urate/biruate crystal
Potatoes that have sit out to long. May or may not have Round with torn like projections Alkaline Urate uroliths portal vascular anomalies Dalmatians and Bulldogs
