Urinalysis & Renal Study Guide

Vocabulary flashcards covering key terms, anatomy, physiology, testing methods, disorders, and metabolic diseases from the MLS4601 Urinalysis study guide.

Urine Composition

95 % water and 5 % solutes (≈50 % urea plus creatinine, uric acid, sodium, potassium, hormones, vitamins, drugs).

Daily Urine Volume (Normal)

Average 1 200–1 500 mL/day; safe range 600–2 000 mL/day.

Oliguria

Decreased urine output < 400 mL/day.

Anuria

Complete stoppage of urine flow.

Polyuria

Urine output > 2.5 L/day.

Nocturia

Excessive urination at night.

Urine Collection Container

Wide-mouth, clear, sterile, 50 mL capacity.

Minimum Urine Volume for Testing

Approximately 12 mL.

Urine Transport Rule

Test within 2 h or refrigerate/use preservative.

Refrigeration (Preservative)

Easiest; slows bacterial growth and metabolism.

Thymol

Preserves glucose & sediment; inhibits bacteria/yeast.

Boric Acid

Preserves protein & formed elements; bacteriostatic 24 h.

Formalin

Excellent for preserving cells/casts (sediment).

Acetic Acid (Preservative)

Bactericidal; used for hormone studies (e.g., catecholamines).

Unpreserved Urine Changes

↑Color/odor, ↓clarity, false-negatives chemically, cell lysis.

Random Urine

Collected anytime; routine screen; most common type.

First-Morning Urine

8-h retained specimen; best for proteins, cells, chemicals.

2-Hour Post-prandial Urine

Collected 2 h after meal to assess glucose handling.

24-Hour Timed Urine

Quantitative chemistry; entire day’s output collected.

Midstream Clean-Catch

Patient cleanses; collects mid-void to reduce contamination.

Catheterized Specimen

Sterile tube into bladder; ideal for culture & sensitivity.

Suprapubic Aspiration

Needle through abdomen into bladder; contamination-free.

Pediatric Bag Collection

Adhesive bag on infant’s genitals to collect urine.

Specimen Rejection Reasons

Unlabeled, contaminated, insufficient, wrong preservative, improper transport/time.

Kidney

Filters blood, regulates electrolytes, acid-base, BP.

Ureter

Tube carrying urine from kidney to bladder.

Bladder

Temporary urine reservoir.

Urethra

Conveys urine from bladder to exterior.

Renal Cortex

Outer kidney region; site of plasma filtration.

Renal Medulla

Inner region containing loops & collecting ducts.

Renal Pelvis

Funnel-shaped collecting area at hilum.

Papilla

Tip of medulla; ducts empty into calyces.

Nephron

Functional unit that forms urine (~1 million/kidney).

Glomerulus

Capillary tuft filtering plasma.

Mesangium

Support cells within glomerulus between capillaries.

Basement Membrane (Glomerular)

Three-layer filtration barrier; size/charge selective.

Podocyte

Epithelial cell with foot processes on Bowman’s capsule.

Proximal Convoluted Tubule (PCT)

Major site of reabsorption; phagocytic/pinocytic.

Loop of Henle

U-shaped segment with descending/ascending limbs for concentrating mechanism.

Distal Convoluted Tubule (DCT)

Tubular segment fine-tuning electrolyte & acid-base balance.

Collecting Duct

Final site for water reabsorption; concentrates urine.

Afferent Arteriole

Brings blood into glomerulus.

Efferent Arteriole

Drains glomerulus; forms peritubular capillaries.

Peritubular Capillaries

Surround tubules; reabsorb/secrete solutes.

Vasa Recta

Capillaries around Loop of Henle aiding countercurrent exchange.

Plasma Filtration

First step in urine formation at glomerulus.

Tubular Reabsorption

Recovery of needed substances back to blood.

Tubular Secretion

Active transport of wastes into filtrate.

Renin-Angiotensin-Aldosterone System (RAAS)

Hormonal cascade controlling BP & Na⁺; renin → angiotensin II → aldosterone.

Low Plasma Sodium Effect

Stimulates renin, angiotensin II, aldosterone → Na⁺/water retention, ↑BP.

High Plasma Sodium Effect

Inhibits renin; enhances Na⁺ excretion.

Active Reabsorption

Energy-dependent transport against gradient (e.g., glucose in PCT).

Passive Reabsorption

Diffusion along gradient (e.g., water everywhere but ascending loop).

Renal Threshold

Plasma concentration at which a substance appears in urine.

Antidiuretic Hormone (ADH)

Increases collecting-duct water permeability; ↓urine volume.

Isothenuric Urine

Specific gravity fixed at 1.010 (same as plasma ultrafiltrate).

Hyposthenuric Urine

Specific gravity < 1.010 (dilute).

Hypersthenuric Urine

Specific gravity > 1.010 (concentrated).

Urochrome

Pigment producing normal yellow urine color.

Amber Urine

Concentrated urine or urobilin, fever, dehydration.

Dark Amber/Yellow-Green

Bilirubin or biliverdin present.

Orange Urine

Pyridium, nitrofurantoin, or bilirubin.

Red Urine

RBCs, hemoglobin, myoglobin, beets, menstrual contamination.

Brown/Black Urine

Methemoglobin, melanin, homogentisic acid.

Blue/Green Urine

Pseudomonas, dyes, indican, medications.

Urine Clarity Scale

Clear, hazy, cloudy, turbid based on ability to read print.

Pathologic Turbidity

Due to RBCs, WBCs, bacteria, yeast, casts.

Urine Foam Significance

White foam → protein; yellow foam → bilirubin.

Specific Gravity (SG)

Density of urine vs water; normal 1.005–1.030.

Urinometer

Float device to measure SG.

Refractometer

Uses refractive index to determine SG.

Reagent-Strip SG Test

Polyelectrolyte pad detects ionic solute concentration.

Osmolality

Number of dissolved particles per kilogram of water.

Diabetes Mellitus vs Insipidus

Mellitus: polyuria + glucose; Insipidus: polyuria without glucose, low SG.

Free Water Clearance

Calculates kidney’s ability to excrete concentrated/dilute water independent of solute.

Inulin Clearance

Gold standard for measuring glomerular filtration rate (GFR).

Creatinine Clearance

GFR estimate using endogenous creatinine; elevated serum creatinine signals reduced GFR.

β2-Microglobulin

↑ in urine when proximal tubular reabsorption impaired.

Cystatin C

Small protein; ↑serum or urine indicates reduced GFR/tubular damage.

Microalbuminuria

Small albumin increase; early diabetic nephropathy indicator.

p-Aminohippuric Acid (PAH) Test

Assesses renal plasma flow & tubular secretion capacity.

Isosthenuria

Fixed SG 1.010 indicating loss of concentrating/diluting ability.

Proteinuria Categories

Pre-renal, renal (glomerular/tubular), post-renal.

Sulfosalicylic Acid (SSA) Test

Confirmatory test for urine protein.

Clinitest

Tablet test detecting reducing sugars (e.g., glucose).

Acetest

Tablet test for ketones in urine.

Ictotest

Tablet test confirming urine bilirubin.

Watson-Schwartz Test

Differentiates urobilinogen from porphobilinogen.

Hematuria

Intact RBCs in urine.

Hemoglobinuria

Free hemoglobin in urine (lysed RBCs).

Myoglobinuria

Myoglobin in urine from muscle damage.

Glomerular Disorder

Disease primarily damaging glomerular filtration barrier.

Acute Post-streptococcal Glomerulonephritis

Immune complex deposition after strep infection; hematuria, proteinuria, RBC casts.

Rapidly Progressive (Crescentic) GN

Severe GN forming crescents; rapid renal failure.

Chronic Glomerulonephritis

Long-term glomerular scarring; progressive renal failure.

IgA Nephropathy (Berger)

IgA deposits; episodic hematuria after infection/exercise.

Nephrotic Syndrome

Massive proteinuria > 3.5 g/day, hypoalbuminemia, edema, lipiduria.

Acute Tubular Necrosis (ATN)

Ischemic/toxic injury to tubules; RTE cells & casts.

Fanconi Syndrome

Generalized PCT reabsorption failure; glycosuria, aminoaciduria, phosphaturia.

Renal Glycosuria

Selective glucose reabsorption defect; benign glycosuria with normal plasma glucose.