Renal Urinary System

Overview

• Focus: Assessment of the Renal/Urinary System

• Key purpose: Understand structure, function, assessment, diagnostics, and common clinical considerations related to the kidneys, urinary tract, and urine output.

Concepts

• Elimination: Excretion of waste from the body

• Fluid and electrolyte (F&E) balance

• Acid–base balance

Anatomy Review

• Structural components of the urinary system:

  • Two kidneys

  • Two ureters

  • One urinary bladder

  • One urethra

• Additional note: The term CC on the slide likely refers to Chief Complaint (clinical context for assessment)

Excretory System (Urinary System)

• Major components: bladder, kidney, urethra, ureter

Anatomy Review — Renal Kidneys

• Normal anatomy: 2 kidneys (normally)

• Location: behind the peritoneum, outside the abdominal cavity

• Size: about 4-5\text{ inches} long, 2-3\text{ inches} wide, 1\text{ inch} thick

• Left kidney: slightly longer and narrower than the right

• Variation: shape and number can vary

Function of the Kidney

• Formation of urine

• Excretion or conservation of water

• Electrolyte balance

• Acid–base balance

• Activation of Vitamin D

• Production of erythropoietin

• Production of renin

Interior of the Kidney

• Renal cortex: outer region

• Renal medulla: inner region

• Renal columns: extensions of cortex dividing the interior into cone-shaped sections

• Renal pyramids: cone-shaped sections

• Renal tubules transport urine away from the cortex; base faces outward toward the cortex; apex (renal papilla) faces the hilum

• Renal papilla extends into a cup called a minor calyx; minor calyces collect urine leaving the papilla

• Major calyces: two or three minor calyces join to form a major calyx

• Renal pelvis: major calyces converge to form the renal pelvis

• Ureter: renal pelvis continues as the ureter, channeling urine to the urinary bladder

• Additional terms: fibrous capsule, hilum, renal papilla, calyx, ureter

Nephron (Structure and Blood Flow)

• Afferent arteriole: arises from larger arteries and supplies blood to one nephron

• Glomerulus: capillary cluster supplied by afferent arteriole

• Bowman's capsule: surrounds the glomerulus

• Efferent arteriole: drains blood from the glomerulus

• Peritubular capillaries: surround renal tubules; reabsorb water and solutes from tubular fluid

• Cortex and Medulla: arrangement of nephron segments

• Loop of Henle: descending and ascending limbs; key in concentration of urine

• Proximal convoluted tubule (PCT)

• Distal convoluted tubule (DCT)

• Collecting duct

Physiology — Glomeruli (Filtration)

• Glomerular filtration: about 20\% of renal plasma flow is filtered through the glomeruli

• Filtration contents: water, electrolytes, sugars, amino acids, water-soluble toxins & drugs pass into Bowman's capsule

• Blood cells and most plasma proteins are too large to pass through the pores

Physiology — Tubuli (Reabsorption & Secretion)

• Tubular reabsorption: most water and most electrolytes and amino acids are reabsorbed from tubular filtrate back into the blood

• Secretion: some drugs and toxins are secreted into tubular fluid; acids (H^+) are secreted

Urine Formation (Overview of Processes)

• Glomerular filtration: movement of substances from blood in the glomerulus into the capsular space

• Tubular reabsorption: movement of substances from tubular fluid back into the blood

• Tubular secretion: movement of substances from the blood into the tubular fluid

• Key components related to nephron segments: glomerulus, Bowman's capsule, proximal tubule, loop of Henle, distal tubule, collecting duct

Glomerular Filtration Details

• Blood enters the glomerulus via the afferent arteriole and leaves via the efferent arteriole; afferent is larger than efferent, increasing glomerular pressure

• Filtration occurs across pores in glomerular capillaries; filtrate enters Bowman's capsule

• Filtration rate (GFR) is about 180\text{ L/day} (approximately 60× the body's total blood volume)

• The body reabsorbs about 99\% of filtrate, leaving roughly 1-2\text{ L/day} to be excreted as urine

Glomerular Filtration Rate (GFR)

• GFR reference: \text{GFR} \approx 100-125\,\text{mL/min}

• Factors affecting GFR:

  • Permeability of capillary walls

  • Vascular pressure

  • Filtration pressure

Tubular Reabsorption & Secretion (Details)

• Tubular reabsorption: movement of substances from tubular fluid back into the blood

• Tubular secretion: movement of substances from blood into tubular fluid

• Overall: fine-tuning of filtrate composition through selective reabsorption and secretion

Ureters, Urinary Bladder, & Urethra

• Ureters: carry urine from kidneys to the bladder

• Urinary bladder: temporary storage of urine

• Urethra: carries urine from bladder to the exterior

Normal Urine Characteristics

• Volume: 1000-2000\ \text{mL/24 h}

• Color: pale yellow to amber

• Specific Gravity: 1.005-1.030

• pH: 4.5-8.0

• Constituents: 95\%\text{ water}; waste products include urea, creatinine, uric acid

Urine Assessment Indicators

• pH indicators: acidic versus alkaline (acidic with high-protein diet or ketoacidosis; alkaline with UTI)

• Specific Gravity: assess concentration (reference ranges provided above)

• Ketones: presence suggests altered metabolism or dietary issues

Hormones & the Kidneys

• Antidiuretic Hormone (ADH)

  • Produced by the pituitary gland

  • Increases water reabsorption and urine concentration

  • Low ADH: high-volume, low-concentration urine

  • High ADH: high-concentration, low-volume urine

Aldosterone

• Produced by the adrenal glands

• Regulates Na^+ retention and K^+ secretion by tubular reabsorption

• Effects:

  • High aldosterone: increased Na^+ and water retention; K^+ excretion

  • Low aldosterone: increased Na^+ and water excretion; K^+ retention

Aging and the Urinary System

• Bladder changes: decreased size and detrusor muscle tone

• Kidneys: decreased ability to concentrate urine; nephrons decrease with age

• Prostate enlargement in males affects urinary function

• GFR decreases with age

• Consequences: increased risk from nephrotoxic agents, medications, and dyes; pelvic floor muscles weaken

• Symptoms/issues: incontinence, urinary infections, urethral irritation; difficulty with urine retention/voiding

Nursing Assessment

• Demographic information: age, gender, race, ethnicity

• Health history

• Symptoms: flank pain, burning on urination, edema, SOB, weight gain

• Fluid intake

• Functional ability

Physical Assessment

• Vital signs: monitor for hypertension (HTN)

• Respiratory: lung sounds; crackles

• Edema assessment

• Daily weights

• Intake and Output (I&O)

• Skin: note color (yellow/gray)

Laboratory Tests

• Blood studies:

  • Serum Creatinine: men 0.6-1.2\ \text{mg/dL}; women 0.5-1.1\ \text{mg/dL}

  • BUN (Blood Urea Nitrogen): 7-20\ \text{mg/dL}

• Urinalysis:

  • 1st morning specimen

  • Collection: clean-catch void or sterile catheter; volume ~10 mL needed for testing

  • Must be examined within 1\ \text{hour}

24-Hour Urine Specimen

• Start at the 1st void (discard that sample)

• Collect all subsequent urine for the next 24 hours

• Specimens must be kept iced or refrigerated

• If any urine is missed, the collection must be restarted

• Urine Culture: identifies organisms present; collect before antibiotics; sensitivity testing determines appropriate antibiotic treatment

Check Your Knowledge — Practice Questions

25. A nurse is preparing to begin a 24-hour urine collection for a client. Which actions should the nurse take?

• 1) Store collected urine in a designated container at room temperature

• 2) Discard the 1st voiding when beginning the test

• 3) Post a notice on the client’s door regarding the testing

• 4) Document any urine collection that was missed during the 24-hour testing

• Answer options: 1, 2, 3, 4

Renal Diagnostic Procedures

• Radiography options:

  • KUB (kidneys, ureter, bladder): detects tumors, swollen kidneys, stones

  • CT Scan (with or without contrast): assess anatomy; verify allergies; check GFR impact

  • MRI

  • Ultrasound

  • Cystography, cystourethrography, VCUG

Renal Biopsy

• Procedure: percutaneous or small open incision

• Pre-care: NPO status; mild sedative

• Post-care: monitor vital signs frequently; place patient supine with back support (roll)

• Monitor for bleeding; assess biopsy site; first urine void after biopsy evaluated; apply pressure dressing

Check Your Knowledge — Post-Biopsy Action

• Which assessment finding would require immediate action in a client 1 hour post-kidney biopsy?

  • A) Pink-tinged urine

  • B) Nausea and vomiting

  • C) Increased bowel sounds

  • D) Reports of flank pain

Summary of Key Quantities and Concepts (Compact Reference)

• GFR: ext{GFR} \approx 100-125\,\text{mL/min}

• Filtration rate: \approx 180\,\text{L/day} in the kidneys

• Urine production: approximately 1-2\ \text{L/day} (after filtration and reabsorption)

• Normal urine volume range per 24 h: 1000-2000\ \text{mL}

• Urine specific gravity: 1.005-1.030

• Urine pH: 4.5-8.0

• Urine constituents: ~95\%\text{ water}; waste products include urea, creatinine, uric acid

• ADH effects: low ADH → high-volume dilute urine; high ADH → high-concentration low-volume urine

• Aldosterone effects: high aldosterone → Na^+ and water retention; K^+ secretion; low aldosterone → Na^+ and water excretion; K^+ retention

Note: All mathematical expressions and numeric ranges are rendered in LaTeX format within double dollar signs as requested, e.g., 180\text{ L/day}, 100-125\ \text{mL/min}, 1-2\ \text{L/day}, etc.