Diagnostic analysis of urinalysis

Urinalysis is one of our most important clinical diagnostic tools. The following questions are designed to facilitate self-assessment of your interpretation of routine urinalysis of several patients admitted to the Veterinary Teaching Hospital, University of Minnesota. When choosing your answer, remember to distinguish between observations and interpretations, and to consider the best answer in terms of probabilities rather than possibilities.

Further information about techniques and interpretations of urinalysis may be obtained from the recently published book entitled, "Urinalysis: A Clinical Guide To Compassionate Patient Care". This textbook, authored by myself and Dr. Jerry B. Stevens, was made possible by an educational grant from Bayer. For further information on how a veterinarian may obtain a copy while supplies last, contact Bayer Animal Health, Shawnee Mission, KS; (800) 633-3796, option 4.

• 1. Consider the following results obtained by analysis of a voided urine sample obtained by cystocentesis from a 6-year-old neutered male Great Dane.

Color = Light yellow

Protein = 4+

Turbidity = Clear

RBC = 0 - 1/hpf (high power field)

Specific gravity = 1.032

WBC = 0 - 1 / hpf

PH = 6.5

Casts = Occasional hyaline/hpf

Glucose = Negative

Epithelial cells = Occasional

Acetone = Negative

Bacteria = None

Bilirubin = Negative

Crystals = None

Occult blood = Negative

The most probable interpretation of the results of this urinalysis is that the patient:

a. Is normal

b. Has generalized glomerular disease (i.e., glomerular proteinuria).

c. Has generalized tubular disease (i.e., tubular proteinuria).

d. Has an inflammatory process somewhere along the urinary tract (i.e. post-glomerular proteinuria).

e. Has findings indicative of congestive heart failure or fever (i.e., pre-glomerular proteinuria).

The most probable answer to question 1 = option b.

Comments about answers:

a. Proteinuria of this magnitude is definitely not normal.

b. Marked proteinuria in the absence of significant numbers of red blood cells and white cells is the hallmark of generalized glomerular disease.

c. Proteinuria of this magnitude would not be expected as a result of primary tubular disease.

d. Absence of significant numbers of red blood cells and white cells eliminates the likelihood of an inflammatory response.

e. Proteinuria of this magnitude would not be expected as a result of pre-glomerular causes.

• 2. Consider the following results obtained by analysis of a fresh urine sample obtained by cystocentesis from a 5-year-old spayed female Miniature Schnauzer.

Color = Yellow

Protein = 3+

Turbidity = Cloudy

RBC = Numerous/hpf

Specific gravity = 1.014

WBC = Numerous/hpf

PH=. 8.0

Casts = None

Glucose = Negative

Epithelial cells = Many

Acetone = Negative

Bacteria = Numerous cocci

Bilirubin = Negative

Crystals = Moderate struvite

Occult blood = 4+

The best interpretation of the results of this urinalysis is that the patient:

a. Has an inflammatory process somewhere along the urinary tract caused by bacterial infection.

b. Has an inflammatory process somewhere along the genitourinary tract caused by bacterial infection.

c. Has an inflammatory process somewhere along the urinary tract caused or complicated by bacterial infection.

d. Has struvite uroliths associated with urinary tract infection.

e. Has pyelonephritis resulting in impaired ability of the kidneys to concentrate urine.

The most probable answer to question 2 = option c.

Comments about answers:

a. The combination of significant numbers of RBC, WBC and protein indicate inflammation. Detection of bacteria indicate the inflammation is associated with infection. However, these results do not permit differentiation between bacterial infection as a cause or complication of urinary tract inflammation. Most bacterial urinary tract infections develop secondary to underlying abnormalities in host defense mechanisms.

b. Although this answer is not totally incorrect, to conclude that the genital tract is definitely involved in a sample obtained by cystocentesis is an overstatement.

c. In light of the preceding comments for options a and b, this appears to be the best interpretation.

d. d. Although magnesium ammonium phosphate uroliths may be present, struvite crystalluria is not by itself a reliable index of their occurrence.

e. Although these findings are consistent with bacterial infection of the kidneys associated with impaired urine concentration, further diagnostic investigation would be required to verify or exclude this interpretation.

• 3. Consider the following results obtained by analysis of a urine sample collected by cystocentesis from a 7-year-old spayed female Malamute.

Color = Pink

Protein = 3+

Turbidity = Slightly turbid

RBC = >100/hpf

Specific gravity = 1.035

WBC = 0 to 1/hpf

PH = 7

Casts = None

Glucose = Negative

Epithelial cells = Occasional

Acetone = Negative

Bacteria = None

Occult blood = 3+

Crystals = Occasional struvite

The best interpretation of the results of this urinalysis is that the patient has:

a. An inflammatory disease of the urinary tract

b. Pyelonephritis

c. Hematuria induced by struvite uroliths

d. A hemorrhagic lesion of the urinary tract excluding the urethra.

e. Iatrogenic hematuria induced by trauma during cystocentesis.

The best answer to question 3 = option e.

Comments about answers:

a. The paucity of white cells compared to red blood cells is not indicative of an inflammatory response.

b. The findings are not indicative of renal involvement in an inflammatory process.

c. Struvite crystalluria is not a reliable index of magnesium ammonium phosphate uroliths. In addition, most canine struvite uroliths occur as a result of infection with urease-producing bacteria and therefore are associated with an inflammatory response.

d. The urethra cannot be excluded as a source of hemorrhage just because the sample was obtained by catheterization.

e. Trauma to the bladder wall during cystocentesis commonly is associated with hematuria and proteinuria. Proteinuria is primarily caused by loss of plasma proteins with RBC in whole blood. Whereas the sensitivity of diagnostic reagent strips to protein in ~20mg/dl; the normal plasma concentration of protein is 6,000 to 8,000 mg/dl.

• 4. Consider the following results obtained by analysis of a voided urine sample collected from a 5-year-old spayed female mixed Golden Retriever.

Color = yellow

Protein = Neg

Turbidity = cloudy

RBC = Neg

Specific gravity = 1.029

WBC = Neg

PH = 8.0

Casts = Neg

Glucose = Neg

Epithelial cells = Occasional

Acetone = Neg

Bacteria = Many Rods & Cocci

Bilirubin = Neg

Crystals = Many struvite

Occult blood = Neg

The best interpretation of the results of this urinalysis is that:

a. The sample was collected in a nonsterilized container and was analyzed several hours following collection.

b. The patient has bacterial infection of the urinary bladder.

c. The patient has bacterial infection of the kidneys.

d. The patient has bacterial infection of the genital or urinary tract.

e. The patient probably has infection-induced struvite uroliths.

The best answer to question 4 = option a.

Comments about answers:

a. Lack of an inflammatory response suggests that the bacteriuria represents contamination. Detection of rods and cocci also suggest contamination since 75 percent of the bacterial urinary tract infections in dogs are caused by one species of bacteria, while only 18 percent are caused by two species of bacteria. The degree of alkalinity is consistent with analysis of an unpreserved sample many hours following collection. The struvite crystals probably formed in vitro.

b. See comment in option a. It is not possible to localize bacteriuria in voided samples without additional information.

c. See comments in options a and b.

d. See comments options a and b.

e. See comments options a and b.

• 5. Consider the following results obtained by analysis of a voided urine sample from an 8-year-old, spayed female Miniature Dachshund:

Color = Yellow

Protein = 1+

Turbidity = Clear

RBC = 0 - 1/hpf

Specific gravity = 1.050

WBC = 0 - 1/hpf

PH = 6.5

Casts = None

Glucose = Negative

Epithelial cell = Occasional

Acetone = Negative

Bacteria = None

Bilirubin = 1+

Crystals = Few amorphous

Occult blood = Negative

The best interpretation of the results of this urinalysis is that the patient:

a. Has hepatic disease

b. Has an inflammatory disorder of the urinary tract.

c. Is normal

d. Has acute renal failure

e. Has slight injury of the glomeruli adversely affecting their ability to selectively retain plasma proteins in capillary lumens.

The most probable answer to question 5 = option c.

Comments about answers to question 5:

a. Although this interpretation is possible, a mild degree of bilirubinuria in dog urine is often a normal finding. Thus, commonly available tests for bilirubinuria are not reliable as screening tests for abnormalities in bilirubin metabolism in dogs.

b. Proteinuria, RBC and WBC of this magnitude are normal findings, especially in highly concentrated urine.

c. Small quantities of bilirubin are often observed in concentrated urine samples formed by healthy dogs. This phenomenon appears to be related to the fact that their renal tubular epithelial cells can form bilirubin from hemoglobin. Thus, healthy dogs may have mild bilirubinuria even when serum bilirubin concentrations are normal.

d. Concentration of urine to this degree eliminates a diagnosis of primary renal failure.

e. Detection of slight proteinuria in highly concentrated urine is a common finding in healthy dogs.

• 6. Consider the following results obtained by analysis of a urine sample collected by cystocentesis from a 5-year-old neutered male Persian cat:

Color = Yellow

Protein = 1+

Turbidity = Clear

RBC = 5 - 10/hpf

Specific gravity = 1.045

WBC = 0 - 1/hpf

PH = 7.0

Casts = None

Glucose = Negative

Epithelial cells = Occasional

Acetone = Negative

Bacteria = None

Bilirubin = 1 +

Crystals = Few amorphous

Occult blood = Negative

The best interpretation of the results of this urinalysis is that the patient:

a. Has significant bilirubinuria

b. Has inflammatory disease syndrome along the urinary tract.

c. Is normal

d. Has acute renal failure

e. Has lower urinary tract disease

The best answer to question 6 = option a.

Comments about answers:

a. Unlike dogs, bilirubinuria in cats, even when present in small quantities in concentrated urine, is usually indicative of an underlying disorder. Further evaluation of this patient is warranted. In our experience, bilirubinuria in cats has been associated with several disorders including primary hepatic disease, diabetes mellitus, feline infectious peritonitis and feline leukemia-related disorders.

b. The paucity of white cells is not consistent with inflammation.

c. Bilirubinuria in healthy cats is uncommon.

d. The capacity to concentrate urine to this degree eliminates a diagnosis of primary renal failure.

e. See preceding comment in b. Although idiopathic lower urinary tract disease in cats is often associated with hematuria (i.e. RBC and proteinuria without significant WBC), the most likely explanation of the hematuria is trauma associated with collection of the sample by cystocentesis.

• 7. Consider the following results obtained by analysis of a voided urine sample obtained from a 14-year-old male domestic shorthair cat.

Color = Yellow

Protein = Negative

Turbidity = Clear

RBC = Negative

Specific gravity = 1.011

WBC = Negative

PH = 6.0

Casts = Negative

Glucose = Negative

Epithelial cells = Negative

Acetone = Negative

Bacteria = Negative

Occult blood = Negative

Crystals = Negative

The best interpretation of the results of this urinalysis is that:

a. The patient's kidneys have lost the ability to concentrate and dilute urine.

b. The patient's kidneys have lost the ability to concentrate urine.

c. The patient's kidneys have lost the ability to dilute urine.

d. The patient has a fixed urine specific gravity, probably as a result of primary renal failure.

e. No conclusions can be established about the ability of the patient's kidneys to concentrate and dilute urine.

The most probable answer to question 7 = option e.

Comments about answers:

a. Since a urine specific gravity of 1.010 may represent a normal or abnormal value, further information (such as hydration status and serum creatinine concentration) must be obtained before renal concentrating and diluting capacity can be assessed. However, this specific gravity value should arouse suspicion that an underlying disorder may be present.

b. See comments for option a.

c. See comments for option a.

d. See comments for option a

e. See comments for option a.

• 8. Consider the following results obtained by analysis of a voided urine sample from a 9-year-old, male German Shepherd:

Color = Yellow

Protein = 1+

Turbidity = Cloudy

RBC = 5 - 10/hpf

Specific gravity = 1.035

WBC = 10 - 12/hpf

PH = 6.5

Cast = 8 - 10 granular/lpf

Glucose = Negative

Epithelial cells = Moderate

Acetone = Negative

Bacteria = None

Bilirubin = Negative

Crystals = Occasional Ca0x 2H20

Occult blood = 1+

The best interpretation of the results of this urinalysis is that the patient:

a. Has acute primary renal failure

b. Has chronic primary renal failure

c. Has acute renal disease

d. Has chronic renal disease

e. The patient has inflammatory disease somewhere in the urinary tract, but it cannot be localized on the basis of this information.

The most probable answer to question 8 = option c.

Comments about answers:

a. Concentration of urine to this degree indicates that an adequate population of nephrons are functional to prevent primary renal failure. The small quantity of protein and high specific gravity indicate that primary renal failure and glomerulotubular imbalance are improbable.

b. See preceding comments in option a.

c. Detection of many granular casts is indicative of renal disease, even though urine concentration indicates that the disease is not of sufficient magnitude to cause renal failure. The large number of casts suggests (but does not prove) that the disorder is acute. The acute renal disease is associated with an inflammatory response.

d. This answer is possible; however answer c is probable. Additional information would be required to prove or disprove either answer.

e. Detection of granular casts is reliable evidence of tubular involvement in the inflammatory process. However, concurrent involvement of other portions of the urinary tract cannot be excluded.