Urinalysis & Body Fluids Exam 2 Study Guide
Anatomy of the Kidney
Flow rate of plasma through the kidneys
Approximately 600–700 mL/min of plasma flows through the kidneys.
General functions of the kidneys
Filter blood
Remove waste products
Regulate water and electrolytes
Maintain acid-base balance
Produce hormones (EPO, renin)
Regulate blood pressure
Urine Flow
Bowman's capsule
PCT
Loop of Henle
DCT
Collecting duct
Renal pelvis
Ureter
Bladder
Urethra
Blood Flow
Renal artery
Afferent arteriole
Glomerulus
Efferent arteriole
Peritubular capillaries/Vasa recta
Renal vein
Functions
Glomerulus
Filters plasma to form filtrate.
Tubules
Reabsorb needed substances and secrete wastes.
PCT
Major site of reabsorption.
Loop of Henle (LOH)
Concentrates urine.
DCT
Fine-tunes electrolyte and acid-base balance.
Collecting Duct (CD)
Final urine concentration.
Juxtaglomerular Apparatus
Regulates blood pressure and GFR through renin release.
Bowman’s Capsule
Collects filtrate from glomerulus.
Definitions
Nephron
Functional unit of the kidney.
Capsule
Fibrous covering surrounding the kidney.
Medulla
Inner portion of kidney.
Cortex
Outer portion of kidney.
Microscopic Examination of Urine
Types of Microscopy
Brightfield
Most common.
Dark entity on a bright
background
Polarized
Polarizing reduces to a single plane
Useful for crystals and lipids.
Darkfield
Treponema species
Stains and Cell Removers
Methylene Blue
Stains nucleated cells
White blood cells
Hansel Stain
Identification of urinary
eosinophils
• “Raspberries”
Eosin → granules
• Methylene blue → nuclei
Acetic Acid
Lyses (removes) red blood
cells (RBC’s)
Useful in distinguishing RBC’s
from yeast
Microscopic Components
Male vs Female Samples
Squamous Epithelial Cells
Few = normal.
More common in females due to contamination.
Bacteria
Few may be contamination.
Large numbers with WBCs suggest infection.
RBCs
Whole RBCs Indicate
Hematuria. / bleeding
RBC Casts Indicate
Glomerular bleeding.
Often glomerulonephritis.
Identification
Actual RBC
Smooth, round discs.
Not RBCs
Yeast: budding forms.
Oil droplets: highly refractile, size
Air bubbles: refractility, size and possibly in a different plane
Starch: refractile, polarizes
Dysmorphic RBCs
Misshapen
• Glomerular
bleeding
• Strenuous
exercise
WBCs
Pathological Indicator
• Infection
• Allergic reactions
• Damage
Most Common Form
Neutrophils.
Glitter Cells
Hypotonic urine
Granules show sparkling appearance.
Eosinophils
Seen with allergic reactions or interstitial nephritis.
Identified with Hansel stain.
Causes of Elevated WBCs
Non-bacterial
Interstitial nephritis
Inflammation
Bacterial
UTI
Pyelonephritis
Yeast
Fungal infection
Chemical Indicators
Leukocyte esterase positive.
If Chemical Test is Negative
WBCs are less likely but can still be present.
Important when evaluating casts.
Other Cellular Components
Epithelial Cells
Squamous
Large, flat cells.
Usually contamination.
non patholohical
Transitional
Spherical
Round transitional cells.
Caudate
Tail-like projection.
Polyhedral
Multiple sides.
Renal Tubular Epithelial (RTE)
Smaller cells with large eccentric nucleus.
Indicates tubular injury.
Uses of Squamous Cells
For Focusing
Easy structure to focus microscope.
As Clue Cells
Squamous cells coated with bacteria.
Used to Identify
Bacterial vaginosis.
Syncytia
Definition
Group of fused cells.
Pathological
Viral infections.
Not Pathological
Occasional benign occurrence.
RTE Cells
Condition Indicated
Tubular damage.
Physical Characteristics
Large eccentric nucleus.
Smaller than transitional cells.
Mucus
Pathological?
Usually not significant.
Yeast
Single
Oval cells.
Budding
Daughter cell attached.
Hyphae
Elongated filamentous structures.
Presence of WBCs
Often accompanies yeast infection.
Distinguishing from RBCs
Use acetic acid to lyse RBCs.
Bacteria
Normal or Pathological?
Consider quantity, symptoms, and WBC presence.
Trichomonas
Structure
Pear-shaped organism.
Motile with flagella.
Casts
General Identification
Objective Power
Scan on low power.
Confirm on high power.
Where to Look
Edges and low-light areas of sediment.
General Shape
Cylindrical with parallel sides.
Where Formed
Distal tubules and collecting ducts.
Cast Matrix
Importance
Holds cellular contents together.
Made Of
Tamm-Horsfall protein (uromodulin).
Conditions Favoring Formation
Acidic urine
High solute concentration
Urinary stasis
Specific Casts
Hyaline Casts
Pathological?
May be normal in small numbers.
When They Appear
Exercise
Dehydration
Fever
RBC Casts
Origin
RBCs trapped in cast matrix.
Confirmation
Positive blood chemistry and RBCs within cast microscopically.
WBC Casts
Origin
WBCs incorporated into cast matrix.
Associated Conditions
Pyelonephritis
Interstitial nephritis
Not WBC Casts / May Be Clumps
Free-floating WBC aggregates.
Non-Infection Causes
Interstitial nephritis.
Cast vs Clump
True cast has defined cylindrical matrix.
Bacterial Casts
Confirmation
Bacteria embedded within cast matrix.
Associated Conditions
Pyelonephritis.
Granular Casts
Kidney Health Indication
Renal disease/tubular damage.
Origin
Degeneration of cellular casts.
RTE Casts
Pathological Indication
Acute tubular injury/necrosis.
Unique Feature
Cells have large eccentric nuclei.
Fatty Casts
Causes
Nephrotic syndrome.
Identification
Lipid droplets.
Maltese cross appearance under polarized light.
Waxy Casts & Broad Casts
Why is a Broad Cast Broad?
Formed in enlarged, dilated tubules.
General Kidney Health Indication
Advanced chronic kidney disease and poor renal function.
Tip: For the cast section, spend extra time memorizing the textbook pictures since your instructor specifically mentions image identification.