Introduction to Urinalysis

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Introduction to Urinalysis

• Laboratory Procedures

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Urinary System

• Designed to maintain a balance between fluid,
  electrolytes, and acid-base homeostasis by
  selectively eliminating waste products from the
  body.
• Urine is formed through glomerular filtration,
  tubular reabsorption, and tubular secretion
  (remember everything you were taught in AP).
• These are influenced by hormones

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Medical Terminology

• Pollakiuria
• Frequent urination
• Polyuria
• Increased urine output or production
• Oliguria
• Decrease in the formation or elimination of urine
• Anuria
• Complete absence of urine formation or
  elimination
• Dysuria
• Difficult urination

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Urinalysis

• Urine collection can be accomplished through
  mid-stream free catch, manual expression,
  catheterization, and cystocentesis.

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Advantages to Urinalysis

• Fast
• Simple
• Inexpensive
• Provides useful information (urinary tract and/or
  other body systems)

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Voided Urine Sample

• Easiest to obtain
• May be contaminated from distal genital tract
• Not satisfactory if examining for bacteria.

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Voided Urine Sample Collection

• Use a clean container
• Wash prepuce or vulva (when possible)
• Try to collect mid-stream urine

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Disadvantages to Voided Sample

• Contamination
• Difficult in cats
• May be difficult in easily scared dogs and short
  breeds

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Expressing the Bladder

• Use steady gentle pressure
• Will feel like a balloon or ball under your
  hands.
• Make sure you are expressing in a squeezing
  motion where you are forcing urine down urethra.
• Wash external genitalia
• Contamination from lower urinary tract/genital
  tract is a concern.
• DO NOT DO MANUAL EXPRESSION WHEN THERE IS AN
  URETHRAL OBSTRUCTION!!!

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Urinary Catheterization

• Act of placing a catheter through urethra into
  bladder
• Advantages
• Less possibility of contamination from lower
  genital tract.
• Helpful in obese animals when bladder is
  difficult to palpate
• Disadvantages
• Trauma to sensitive urethral mucosa
• Possible contamination

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Cystocentesis

• Act of obtaining a urine sample via a needle and
  syringe directly from the bladder
• Advantages
• Sterile sample
• Disadvantages
• Difficult to obtain in obese animals
• Trauma to organs if not done correctly

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Urine Sample Preservation

• Analyze all urine within 30 minutes if possible
• May refrigerate for 6-12 hours if needed
• Bring to room temperature before anlaysis
• Morning samples are more concentrated
• If allowed to stand at room temperature, may get
  false results.

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Physical Characteristics of Urine

• Color
• Transparency
• Odor
• Specific gravity
• Volume

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Urine Color

• Normal color is due to pigments called urochromes
• Normal light yellow to amber color
• Abnormals
• Red blood (hematuria)
• Reddish-brown Hemoglobin or Myoglobin
• Dark yellow-brown Bilirubin (bilirubinuria)
• Orange-Reddish brown Normal in rabbits

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Urine Transparency

• Clear vs. Cloudy
• Cloudy could indicate increase cells, mucus,
  casts, crystals and bacteria.
• Horses and some rabbits have cloudy urine due to
  high content of mucus and calcium carbonate
  crystals.

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Urine Odor

• Not Very diagnostic
• Strong odor may suggest bacterial production
• Male cats, goats, and pigs have a very strong
  urine odor

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Urine Specific Gravity

• Measure urine concentration which is dependent on
  the number, molecular size, and weight of urine
  solutes
• Measures the density of urine as it compares to
  water
• Specific gravity of water is always 1.000

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Normal Urine Specific Gravities

• Man 1.003-1.037
• Dog 1.013-1.030
• Cat 1.013-1.050
• Horse 1.015-1.045

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Methods of collecting a urine specific gravity

• Refractometer
• Reagent strip
• Urinometer

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Causes of Altered Specific gravity

• Increased specific gravity
• Dehydration
• Increase fluid loss
• Decreased water intake
• Decreased specific gravity
• Kidney disease
• Excessive water
• Pyometra
• Some drugs

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Urine Volume

• Influenced by several factors
• Water intake
• Size of animal
• Species of animal

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Crystals

• The presence of crystals in the urine is called
  crystalluria.
• There are many types of crystals that can form in
  urine, we are going to cover just a few. (More
  to come in Clinical Pathology!)
• Crystalluria may or may not be of clinical
  significance.
• Certain crystals form as a result of elements
  being secreted into the urine by normal renal
  activity.

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Crystal formation

• Crystal formation depends on the pH of the
  patients urine.
• Some crystals form in acidic urine, while others
  form in basic or neutral urine.
• If a urine sample is allowed to stand and cool to
  room temperature, the number of crystals in the
  urine will increase because the material that
  forms the crystals is less likely to dissolve at
  cooler temperatures.

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Types of crystals

• Triple phosphate
• Includes Struvite, and Ammonium Magnesium
  Phosphate.
• While their name may be interchanged, these
  crystals have slightly different composition.
• Generally appear as coffin lids or roof-tops
• Form in alkaline to slightly acidic urine.
• May take a fern-leaf shape if urine has high
  concentration of ammonia

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Calcium Oxalate Dihydrate

• Generally appear as small squares with a visible
  X across the top of the crystal.
• Most often form in acidic and neutral urine.
• Are commonly seen in small numbers in dogs and
  horses.
• If seen in large numbers, can indicate calculi
  formation.

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Calcium Oxalate Monohydrate

• May be small and dumbbell shaped, can also
  appear as a slat from a picket fence.
• Generally form in any pH urine, but are a key
  indicator if an animal is experiencing ethylene
  glycol toxicity!

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Uric Acid/Ammonium Urate Crystals

• Uric Acid crystals often appear as yellow-brown
  rosettes or as diamond-shaped plates.
• Can form in any pH urine!
• Ammonium Urates often appear as thorn-apples
• Generally form in neutral to alkaline urine.
• Are very rarely seen in dogs and cats. (Except
  Dalmatians!!)

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Uric Acid Crystals
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Ammonium Urate Crystals