Urinalysis & Body Fluids Exam 2 Study Guide

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.

Parts of Urine Flow

Bowman's capsule, PCT, Loop of Henle, DCT, Collecting duct, Renal pelvis, Ureter, Bladder, Urethra.

Blood Flow Pathway

Renal artery, Afferent arteriole, Glomerulus, Efferent arteriole, Peritubular capillaries/Vasa recta, Renal vein.

Glomerulus function

Filters plasma to form filtrate.

Tubules function

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.

Nephron

Functional unit of the kidney.

Capsule

Fibrous covering surrounding the kidney.

Medulla

Inner portion of the kidney.

Cortex

Outer portion of the kidney.

Types of microscopy for urine analysis

Brightfield, Polarized, Darkfield.

Methylene Blue

Stains nucleated cells, specifically white blood cells.

Hansel Stain

Used for identification of urinary eosinophils; gives a raspberry appearance.

Acetic Acid

Lyses red blood cells (RBCs); useful in distinguishing RBCs from yeast.

Squamous Epithelial Cells

Few = normal; more common in females due to contamination.

Bacteria presence in urine

Few may indicate contamination; large numbers with WBCs suggest infection.

Whole RBCs in urine

Indicate hematuria or bleeding.

RBC Casts

Indicate glomerular bleeding, often seen in glomerulonephritis.

Actual RBC characteristics

Smooth, round discs.

Dysmorphic RBCs

Misshapen RBCs indicating glomerular bleeding or strenuous exercise.

WBCs as pathological indicator

Indicate infection, allergic reactions, or damage.

Most Common WBC in urine

Neutrophils.

Glitter Cells

Granules show sparkling appearance in hypotonic urine.

Eosinophils

Seen with allergic reactions or interstitial nephritis, identified with Hansel stain.

Causes of Elevated WBCs (Non-bacterial)

Interstitial nephritis, inflammation.

Causes of Elevated WBCs (Bacterial)

UTI, Pyelonephritis.

Chemical Indicators in urine test

Leukocyte esterase positive indicates infection.

Presence of Yeast in Urine

Single oval cells or budding daughter cells; often occurs with WBCs.

Distinguishing RBCs from Yeast

Use acetic acid to lyse RBCs.

Casts General Identification

Scan on low power, confirm on high power. Look at edges and low-light areas.

Hyaline Casts

May be normal in small numbers; appear with exercise, dehydration, or fever.

RBC Casts Origin

RBCs trapped in cast matrix.

WBC Casts Origin

WBCs incorporated into cast matrix, associated with pyelonephritis or interstitial nephritis.

Bacterial Casts

Bacteria embedded within cast matrix indicate pyelonephritis.

Granular Casts Origin

Degeneration of cellular casts indicates renal disease/tubular damage.

Fatty Casts Causes

Indicate nephrotic syndrome with lipid droplets appearance under polarized light.

Waxy & Broad Casts Importance

Indicate advanced chronic kidney disease and poor renal function.