Term
| What are the 3 components of a urinalysis? |
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Definition
1. Chemical analysis
2. Specific gravity
3. Microscopic sediment analysis
All of them are essential and must be interpreted together! |
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Term
| What are 3 types of lab tests that evaluate the urinary tract? Which are routinely used clinically? |
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Definition
1. Urinalysis
2. Serum Chemistry (looks at substances normally eliminated by kidney)
3. Renal function tests (urine concentrating ability following water deprivation, clearance tests)
The latter is not routinely used in practice. |
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Term
| What is the reserve capacity of the kidney? (i.e. how much kidney can you lose before seeing clinical signs?) |
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Definition
| Abnormal blood tests don't occur until 2/3-3/4 of kidney is incapacitated. Urine tests may provide earlier indication of disease. |
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Term
| Can urinalysis alone provide a specific diagnosis? |
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Definition
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Term
| Epithelial cells, WBCs, bacteria....normal to find in a urine sample? |
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Definition
| Yes, if free catch or catheterized. They come from the lower urogenital tract. (Squamous epithelial cells from vagina, prostate; transitional cells from upper urethra/bladder.) |
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Term
| Epithelial cells, WBCs, bacteria, blood...normal to find in a cystocentesis sample? |
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Definition
| Epithelial cells (transitional cells) can be aspirated from mucosal surface, so yes. If WBCs are present they must have originated from the kidney and/or bladder. Any bacteria in cysto indicates infection as kidney/bladder should be sterile. Blood in cysto can be an artifact from puncturing a capillary with cysto needle. |
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Term
| Can a urine sample be left for a few hours to be processed? Why/why not? How should it be stored? |
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Definition
Urinalysis should be performed ASAP (within 1-2 hrs) unless it's refrigerated.
*At room temp, it loses CO2 to environment, resulting in increased pH...which can cause lysis of RBCs, casts, and WBCs, and alter crystal composition.
*Alkaline urine can also cause false-positive dipstick results for protein.
*Bacteria in sample can overgrow (and may metabolize glucose/ketones present, depending on type).
Refrigerate urine if there will be >1-2 delay in processing. Warm to room temp before performing tests. |
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Term
| What are some pretty urine colors you might see, and why? |
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Definition
Pale yellow to amber: normal (depends on concentration)
Pink-reddish: normal in rabbits and some other herbivores (pigments in plants consumed)
Orange-red: blood or free hemoglobin
Red-brown to black: oxidized Hb or myoglobin
Dark yellow: bilirubin
Green: biliverdin (oxidized bilirubin) |
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Term
| Is normal urine clear in all species? |
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Definition
| In most species, yes, but in horses and rabbits may be cloudy due to crystals. |
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Term
| What are some potential sources for urine turbidity? |
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Definition
crystals
mucus
cells
bacteria
casts (rarely enough to cause turbidity alone)
lipid (esp. in cats)
Protein is NOT generally a source of turbidity. |
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Term
| What is normal pH range for carnivore urine (including suckling herbivores)? Adult herbivores? |
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Definition
Carnivores: pH 5.5-7.5
Adult herbivores: pH 7.0-8.5 |
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Term
| What two situations can cause a decrease in urine pH? |
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Definition
1. Acidosis (kidney appropriately dumps H+ in response to acidosis)
2. Paradoxical aciduria associated with hypochloremia. Can happen with vomiting or displaced/torsed abomasum (loss or sequestration of HCl, respectively). Results in alkalosis and dehydration. In response to dehydration (decreased ECF) and angiotensin, kidney reabsorbs water and Na+. To maintain electrical neutrality, HCO3- is absorbed along with Na+, taking it OUT of the urine making urine more acidic. (Normally Cl- would go with Na+ to preserve electrical neutrality, but Cl- is unavailable due to HCl loss/sequestration.) When Cl- and HCO3- are no longer available to go with Na+, Na+ exchanges with H+ (or K+)...resulting in hypokalemia and an even more acid urine. |
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Term
| What 4 physiological (and one lab) situation can cause an increase in urine pH? |
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Definition
1. Alkalosis
2. Bacterial infections w/ urease-producing pathogens (Strep and Proteus, classically)
3. Post-prandial alkaline tide (release of bicarb into ECF is cleared by kidney)
4. Distal renal tubular acidosis (diseased tubular cells can't secrete H+ into urine due to carbonic anhydrase deficiency, so secrete K+ instead, resulting in hypokalemia).
5. Storage of urine sample at room temp. results in loss of CO2 into air. |
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Term
| What's the normal pathway of protein through blood/kidney? |
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Definition
| The glomerular capillary excludes large molecules and negatively charged ones, so albumin and large proteins normally don't make it into the filtrate in any significant quantity. Smaller proteins and a teeny bit of albumin might sneak through, but are reabsorbed by tubular epithelial cells. |
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Term
| What are some methods of measuring protein in urine? Which are truly quantitative? |
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Definition
| Dipstick and SSA are crude and semi-quantitative (more reliable for high [2+ or 3+] protein levels). Spectrophotometry (protein:creatinine) is much more sensitive and specific. |
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Term
| Is the dipstick protein test more sensitive for globulins or albumin? How much protein must be present to show up? |
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Definition
| Albumin. Detects >20-30 mg/dl urinary protein. |
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Term
| What is the SSA test? Pros/Cons? |
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Definition
| Sulfasalicylic acid (5%) is mixed with an equal volume of urine. SSA precipitates protein: turbidity is proportional to protein concentration. Detects globulins and albumin. Fewer false positives than dipsticks but more false negatives. |
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Term
| What other property of urine should be examined if you see increased total protein (to interpret the significance of increased protein)? |
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Definition
| Urine specific gravity: increased protein is more significant in dilute urine than concentrated urine. |
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Term
| What is a normal protein:creatinine ratio for dogs and cats? What ratio means significant proteinuria? |
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Definition
Normal: <0.2-0.5
Proteinuria: >0.5 |
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Term
| What is physiological proteinuria (aka functional renal proteinuria)? |
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Definition
| Presence of protein in urine as a result of a transient overload of tubular absorptive capacity. Can occur in neonates (due to high levels of colostral proteins), seizure victims, and possible after strenuous exercise (reported in humans, unknown in animals). |
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Term
| What are the 5 basic reasons to find pathological proteinuria (think pre-renal, renal, and post-renal)? |
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Definition
1. Pre-renal: Hemoglobinuria/Myoglobinuria
2. Renal: Glomerular Disease (mod-heavy proteinuria)
3. Renal: Tubulointerstitial Disease (tends to be mild proteinuria)
4. Renal/Post-renal: Inflammation/infection of UT (can include kidney)
5. Renal/Post-renal: Hemorrhage in kidney/UT (RBCs, WBCs, and plasma proteins in urine) |
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Term
| How can you figure out if there'e hemoglobin, myoglobin, or RBCs in urine, and what does each result mean? |
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Definition
Positive heme test must be accompanied by examination of urine sediment.
1. Positive heme, RBCs in urine: hemorrhage in UT (can be due to primary clotting abnormality, or secondary to inflammation, necrosis, trauma, neoplasia).
2. Positive heme, no RBCs in urine:
a. hemoglobinuria (usually due to intravascular hemolysis, which turns serum pink) or could be lysis of RBCs in urine due to alkaline urine
b. myoglobinuria (due to trauma, ischemia, or necrosis of muscle; does not cause serum to change color and is accompanied by increased CK, LDH, and AST levels) |
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Term
| Can unconjugated bilirubin pass through the glomerulus? How about conjugated bilirubin? Are either normally found in urine? (species specific?) |
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Definition
Unconjugated bilirubin cannot because it is bound to albumin or other proteins so is too large. Conjugated bilirubin, which is soluble by itself in blood and therefore isn't protein-bound, can pass through the glomerulus. However, there is usually little conjugated bilirubin in the circulation since it should go straight from the liver into bile...it only escapes into circulation and ends up at the kidney when the amount of bilirubin is too much for the liver to secrete into bile at once.
Most species normally have no detectable bilirubin in urine so any presence is significant. The dog can have 1+ (in concentrated urine) because canine kidneys can catabolize Hb (like the liver) resulting in excretion of conjugated bilirubin in the urine. Bilirubin presence in unconcentrated canine urine is significant, though. |
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Term
| What can cause bilirubinuria? |
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Definition
Hemolysis results in increased unconjugated bilirubin which is conjugated by the liver. Conjugated bilirubin builds up in the liver (rate-limiting step is secretion into bile), leaks into liver interstitium and thence to blood. Buildup of bilirubin in liver can be due to:
a) excess hemolysis (abnormal RBCs)
b) hepatocellular disease
c) bile duct obstruction |
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Term
| What is the renal threshold for filtering blood glucose in normal animals? |
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Definition
Cow: 100 mg/dl
Dog/horse: 180 mg/dl
Cat: 260-310 mg/dl |
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Term
| What are some causes of glucosuria with hyperglycemia? |
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Definition
1. Diabetes mellitus
2. Hyperadrenocorticism
3. Exces dietary carbs
4. Fluid therapy containing Glc
5. Epinephrine secretion (scared cats, pheochromocytoma) |
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Term
| What are some causes of glucosuria without hyperglycemia? |
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Definition
1. Congenital renal disorder (e.g. Fanconi Syndrome)
2. Acute renal failure with tubular lesions
3. False positive (with certain drugs) |
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Term
| Are ketones in urine normal? How can they be detected? What are some causes of this finding? |
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Definition
Not normally present. Can be detected via dipstick or acetest (both detect only acetoacetic acid). Ketonuria caused by negative energy balance and lipolysis, due to:
-Bovine ketosis (hypoglycemia)
-Pregnancy toxemia in ewes
-Diabetes mellitus
-Starvation
-Low carb/high fat diet |
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Term
| Are ketones in urine normal? How can they be detected? What are some causes of this finding? |
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Definition
Not normally present. Can be detected via dipstick or acetest (both detect only acetoacetic acid). Ketonuria caused by negative energy balance and lipolysis, due to:
-Bovine ketosis (hypoglycemia)
-Pregnancy toxemia in ewes
-Diabetes mellitus
-Starvation
-Low carb/high fat diet |
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Term
| What factors affect specific gravity of urine? |
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Definition
1. Number of particles in solution
2. Size of particles in solution
3. Temperature (fluids are denser when cold)
4. Turbidity of urine (how is this different from #s 1-2?)
5. Presence of pigmented material (e.g. hemoglobin) |
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Term
| Define isosthenuric urine |
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Definition
Solute concentration same as glomerular filtrate:
300 mOsm/kg or SG = 1.008-1.012 |
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Term
| Define hyposthenuric urine |
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Definition
Elimination of excess water, leading to a solute concentration lower than glomerular filtrate.
<300 mOsm/kg or SG <1.008 |
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Term
| Define hypersthenuric urine |
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Definition
Reabsorption of water from filtrate to conserve body water: solute concentration is higher than that of glomerular filtrate.
>300mOsm/kg or SG >1.030-1.035 |
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Term
| What is the normal range for urine specific gravity? |
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Definition
TRICK QUESTION - there is no "normal" range since the body's fluid/electrolyte status should dictate SG. However, if kidneys are doing their job, urine should be concentrated in response to:
-dehydration (via kidney response to ADH)
-hypovolemia (via kidney response to ADH and renin->aldosterone)
-decreased CO (via kidney response to renin->aldosterone) |
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Term
| What is the maximal concentrating ability of different species' kidneys, and the appropriate minimal concentration in the face of dehydration/azotemia? |
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Definition
Cow: max = 1.035; appropriate ≥1.026
Dog: max = 1.065; appropriate ≥1.030
Horse: max = 1.035; appropriate ≥1.030
Cat: max = 1.080; appropriate ≥1.035 |
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Term
| What is one of the first signs of renal tubule disease and at what point is it seen? |
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Definition
| Loss of concentrating ability; seen following destruction of 2/3 of nephrons (due to tubular or interstitial disease). |
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Term
| What kinds of cells might you find in urine sediment and what do they look like? |
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Definition
1. Epithelial
a. squamous: largest cells, nucleus small or not present, thin and irregular (often folded) with angular borders.
b. transitional: smaller than squamous cells, "fried egg" shape with large central nucleus; often in clusters.
c. caudate epithelial cell: "kite-shaped"
2. Leukocytes: smaller than epithelial cells, larger than RBCs; round with granular cytoplasm; nucleus may be degraded
3. Erythrocytes: smaller than WBCs, round or crenated; central pallor with no cytoplasmic structures.
4. Sperm (in intact/recently-castrated males or in females after breeding). |
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Term
| Is it normal to see leukocytes in urine sediment? |
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Definition
Yes, if <3-5/hpf (depending on how collected: slightly more if free catch, none if cysto).
>5-8/hpf indicates inflammation or hemorrhage (may be due to UTI, uroliths, neoplasm, tissue trauma/necrosis. |
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Term
| Is it normal to see erythrocytes in urine sediment? |
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Definition
Yes, if <5/hpf (I think b/c likely to be artifact of urine collection if cysto or catheter)
>5/hpf indicates hemorrhage (may be primary - i.e. clotting abnormality - or secondary to inflammation, neoplasia, necrosis, trauma). |
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Term
| Can you verify a bacterial infection based on presence of bacteria in the urine? Rule it out based on absence of bacteria? |
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Definition
| Suspected bacteria in urine sediment could be real or could be Brownian motion of non-bacterial particles. Verify suspected bacteria (esp. cocci) via Gram staining. If bacteria are present, may be from infection or artifact from stain (Sedistain, e.g.). Absence of bacteria in sediment does not rule out a UTI because >10,000 rods/ml must be present to be visualized (and dilute urine can dilute out the # bacteria present). |
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Term
| What do fat droplets look like in urine? When are you likely to see them? |
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Definition
Vary in size; perfectly round with black border. Can be in different plane of focus since they float to top of water under slide.
Normal in cats due to turnover of renal epithelium (containing cytoplasmic liquid). Can be seen in urine of lipemic animals (due to defect in lipid metabolism). |
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Term
| What kind of bacterial growth from a culture of a free-catch sample is most significant? |
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Definition
| High growth of a single type of organism is more likely to be significant. Low growth of a mixture of organisms (esp. those corresponding to normal flora from lower UG tract) is less significant. |
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Term
| Are casts a normal finding in urine sediment? |
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Definition
| NO. Presence of casts indicates either glomerular or tubular damage, usually acute if present in high numbers (but can be either reversible or irreversible). One exception: occasional (1-2 per entire preparation) hyaline casts may be seen in some normal animals. |
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Term
| What types of casts are there, what are they made of, and how are they distinguished? |
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Definition
1. Hyaline: mucoprotein (Tamm-Horsfall protein) alone. Cylindrical, rounded ends, colorless/semitransparent.
2. Cellular: cells embedded in mucoprotein. If RBC cast, yellow-orange-red in color, cylindrical but lumpy. If WBC cast, clear and jumbled/lumpy. If epithelial cell cast, clear but cells can be more orderly (in sheets).
3. Granular cast: mucoproteins, proteins, + debris. Degenerating cellular casts. Look granular.
4. Waxy cast: colorless, dull appearance. Distinct, sharp borders, often with fracture lines.
5. Fatty cast: mucoprotein + fat. Most common in cats b/c epithelial cells contain a lot of lipid. |
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Term
| What is the significance of a hyaline cast? |
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Definition
| Associated with glomerular disease causing renal proteinuria. |
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Term
| What is the significance of an erythrocyte cast? |
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Definition
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Term
| What is the significance of a leukocyte cast? |
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Definition
| Renal inflammation (pyelonephritis) - cast can help distinguish from lower UT inflammation. |
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Term
| What is the significance of an epithelial cell cast? |
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Definition
| Tubular damage (epithelial cells are sloughing). |
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Term
| What is the significance of a waxy cast? |
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Definition
| Chronic disease (waxy casts result from degraded cellular/granular casts). |
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Term
| What is the significance of crystals in the urine? |
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Definition
| Most crystals, in moderate amounts, are not clinically significant in themselves. But if present in amounts large enough to cause calculi, they become significant. |
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Term
| What affects the presence of crystals in a urine sample? |
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Definition
1. Urine pH
2. Solubility and concentration of crystal material
3. Urine temp (crystals may precipitate as urine cools) |
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Term
| Where are struvite crystals most likely to occur? |
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Definition
Neutral or alkaline urine.
Normal in dogs and cats. Sometimes seen in horses. Sometimes in cats with Feline Urologic Syndrome and urethral obstruction. |
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Term
| Where are struvite crystals most likely to occur? |
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Definition
Neutral or alkaline urine.
Normal in dogs and cats. Sometimes seen in horses. Sometimes in cats with Feline Urologic Syndrome and urethral obstruction. |
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Term
| Where are calcium carbonate crystals most likely to occur? |
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Definition
Neutral or alkaline urine.
Horses, rabbits, other herbivores. |
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Term
| Where are calcium oxalate crystals, dihydrate form, most likely to occur? |
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Definition
Neutral or acidic urine.
Normal finding in horses, rabbits (assoc. with ingestion of onions, spinach, rhubarb, other plants). Normal in some dogs and cats dependent on diet. |
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Term
| Where are calcium oxalate crystals, monohydrate form, most likely to occur? |
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Definition
Neutral or acidic urine.
Found in animals following ethylene glycol ingestion. |
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Term
| Where are bilirubin crystals most likely to occur? |
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Definition
| May be normal in canine urine if highly concentrated. in other species, indicates hemolysis or hepatobiliary disease. |
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Term
| Where are ammonium urate/biurate crystals most likely to occur? |
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Definition
Acid, neutral, or alkaline urine.
Can occur in occasional normal animals, and animals with liver disease (e.g. portosystemic shunt): when liver can't metabolize ammonia. |
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Term
| Where are cystine crystals most likely to occur? |
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Definition
Acid urine. Rare.
Congenital cystinuria: predisposes to cystine calculus formation (English bulldogs, dachshunds, Welsh corgis, Newfoundlands). |
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Term
| Where are urate crystals most likely to occur? |
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Definition
Acid urine.
Small numbers may be normal. High levels of urate, ammonium biurate, and other crystals may point to a hereditary defect in purine metabolism (preventing conversion of uric acid to allantoin). Predisposes to urate/calcium oxalte stones (Dalmatians, English Bulldogs). |
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