Renal & Urinary System – Comprehensive Lecture Notes

Urinary System – Core Components

• Organs: 2 kidneys, 2 ureters, 1 bladder, 1 urethra (✅ know numbers)
• Primary kidney roles
  • Remove metabolic waste, excess water & electrolytes
  • Concentrate filtrate ➜ urine
  • Clinical link: Dialysis replaces these functions when pts. in renal failure produce little/no urine

Kidney Gross Anatomy

• Bean-shaped, dark red; outer renal capsule for protection
• Interior layers
  • Cortex (outer)
  • Medulla (inner), contains pyramids & collecting ducts
• Contains ≈ 1{,}250{,}000 renal tubules

Microscopic Anatomy – The Nephron

• Basic functional unit (≈ >1{,}000{,}000 per kidney)
• Site where urine formation BEGINS (test fav.)
• Processes (occur ≈ 60×/day for full blood vol.):
  1. Filtration (glomerulus)
  2. Reabsorption/Secretion (tubules)
• Juxtaglomerular apparatus
  • Sits between afferent arteriole & distal convoluted tubule
  • Regulates GFR & secretes renin

Renin–Angiotensin System (review from A&P)

• Renin released by JGA ➜ activates cascade ➜ Ang II ➜ vasoconstriction & aldosterone release ➜ ↑BP
• Clinical: ACE-Is/ARBs target this pathway

Urine Composition & Physical Characteristics

• Daily volume: 1000\text{–}2000\,\text{mL} (95 % water)
• Color: transparent yellow (urochrome pigment from Hb breakdown)
• pH: 4.6\text{–}8.0 (slightly acidic)
• Specific gravity: 1.005\text{–}1.030
• Fresh urine sterile; standing at room-T ➜ urease → NH₃ odor

Urinalysis: Abnormals & Meaning

Ureters

• Transport urine kidney ➜ bladder (retro-peritoneal path, pass under bladder wall)
• Qty: 2 (know!)

Urinary Bladder

• Muscular, collapsible reservoir
• Capacity: 750\text{–}1000\,\text{mL} (can exceed)
• First urge around 250\,\text{mL}
• Two sphincters regulate outflow

Urethra

• Conducts urine bladder ➜ exterior (peristalsis)
• Female outlet: urinary meatus; Male length ≈ 8\,\text{in} & dual function (urine + semen)

Aging Effects & Lifespan Considerations

• By age 70: renal filtering only ≈ 50\% of that at 40
• Women: ↓pelvic floor tone ➜ stress incontinence
• Men: BPH ➜ hesitancy, dribbling (Tx: tamsulosin/Flomax®)
• Common geriatric issues: frequency, urgency, nocturia, retention, incontinence
• Incontinence affects self-esteem & socialization

Laboratory Tests & Normal Ranges

• Specific gravity 1.005\text{–}1.030 ➜ ↑ = dehydration; ↓ = over-hydration / DI
• BUN 7\text{–}20 mg/dL
• Serum creatinine
  • Female 0.6\text{–}1.2 mg/dL
  • Male 0.6\text{–}1.4 mg/dL
• Creatinine clearance: 24-h urine vs blood; ↓ ⇒ renal disease
• PSA < 4 ng/mL (elevates with age, cancer, prostatitis)
• Urine osmolarity: finer measure than SG

Diagnostic Imaging & Endoscopy

• KUB X-ray: size, structure, position; detects tumors, calculi, cysts
• IVP/IVU (contrast)
  • Prep: light evening meal, non-gas laxative, NPO 8 h; assess iodine/shellfish allergy
  • Warn pt: warm flush & metallic taste on injection
• Retrograde pyelography, VCUG (voiding cystourethrogram)
  • Enema prep, catheter with contrast; pics during voiding (embarrassment—address anxiety)
• Cystoscopy
  • Lithotomy position, local + sedation, continuous bladder irrigation
  • Post-care: hydrate to dilute urine; first void may be blood-tinged
• Renal angiography/venography
  • Femoral access; post-procedure flat x hrs, assess site & distal pulses q15 min ×1 h then q2 h ×24 h
• MRI: hold metformin; CT similar dye precautions
• Renal biopsy
  • Post: lie flat 4–6 h, limited activity 12–48 h, expect light hematuria 1–2 days

24-Hour Urine Collection

1. Discard FIRST void ➜ note start time
2. Collect ALL urine next 24 h, keep chilled & light-protected
3. End by voiding at same clock time

Diuretic Classes (mechanism, cautions)

• Thiazides (HCTZ): distal tubule; risk \downarrow K^+, \downarrow Na^+, \uparrow Ca^{2+}; full BP effect ≈ 1 mo.
• Loop (furosemide): ascending loop; potent, ok in ↓renal Fx; monitor K^+, BP, dizziness
• K-sparing (spironolactone): distal tubule; conserves K^+; CONTRA in hyper-kalaemia
• Osmotic (mannitol): proximal tubule; pulls fluid ➜ circulation; ↓ICP/IOP, ARF; watch fluid overload
• Carbonic anhydrase inhibitor (acetazolamide): proximal tubule; diuresis & ↓IOP General nursing:
  • VS q4, daily weight & strict I/O, monitor lytes, BUN, creatinine
  • Promote low-sodium diet; teach potassium-rich foods unless K-sparing used

UTI Pharmacology

• Fluoroquinolones
  • Ciprofloxacin (gram-), Levofloxacin (±gram+)
  • Take with full glass water 1 h before / 2 h after meals
• Nitrofurantoin (Macrodantin): chronic prophylaxis in LTC
• Methenamine: needs acidic urine (teach acid-ash diet) for recurrent UTIs
• ALWAYS finish full antibiotic course; hydrate to ≥ 2000\,\text{mL/day} unless contraindicated

Acid-Ash Diet (maintain urinary pH ≈ 5.5)

• Includes: meat, eggs, cheese, whole grains, cranberries, plums; avoids citrus & most veggies

Urinary Catheters & Drainage Systems

• Coude: firm curved tip — easier past BPH obstruction (male)
• Foley: retention balloon (≈ 10 mL sterile water)
• External devices
  • Condom cath (male)
  • PureWick (female); change q8–12 h & when soiled; low–med suction only to avoid skin damage
• Bag types
  • Urometer (hourly grad) in ICU; standard bag; large-capacity postop TURP
• Expected output: \ge 30\,\text{mL/hr} (≈ 240\,\text{mL/8 h})

Specimen Collection From Foley

1. Clamp tubing 30 min
2. Swab port with alcohol
3. Aspirate with STERILE 10\,\text{mL} syringe ➜ sterile cup
4. Un-clamp & send to lab immediately

Catheter-Related Nursing Care

• Keep bag below bladder; never on floor/bed
• Inspect tubing for kinks; assess abdomen for distension & bladder scan PRN
• Peri-care & meatal cleansing each shift
• Encourage ambulation when possible; ensure slack in StatLock® to prevent traction
• Post-removal: document first void time/amount; may dribble d/t sphincter dilation—reassure pt.

Fluid Management & Infection Prevention

• Hydration goal (if not CHF/ESRD): \approx 2000\,\text{mL} intake daily
• Strict asepsis during insertion & irrigation; minimize “breaking” closed system
• Catheter-associated UTI risk ↑ with dwell time ➜ remove ASAP

Key Numbers / Quick Facts (Exam Favs)

• Blood filtered by kidneys ≈ 60 × per day
• Bladder urge threshold ≈ 250\,\text{mL}
• Bladder max ≈ 750\text{–}1000\,\text{mL} (can stretch >)
• Male urethra 8\,\text{in}
• Normal hourly urine output \ge 30\,\text{mL}
• 24-h urine: discard 1st void & start clock
• pH normal 4.6\text{–}8; SG 1.005\text{–}1.030
• BUN 7\text{–}20 mg/dL; Creatinine 0.6\text{–}1.4 mg/dL

Practical / Ethical / Psychosocial Points

• Altered mental status in renal failure ➜ lactulose example (pts. become combative/confused)
• Catheter embarrassment & lithotomy positioning: provide privacy, allow expression
• Incontinence impacts dignity & social life; teach pelvic-floor (Kegel) exercises
• Explain test sensations (e.g., IVP dye "warm flush & metallic taste") to reduce anxiety
• Always verify informed consent: physician must explain risks/benefits; nurse witnesses signature if pt. understands