Quick Anatomy Review
The basics you need to visualize before diving into pathology.
The urinary system consists of two kidneys, two ureters, the bladder, and the urethra. The kidneys are located retroperitoneally (behind the peritoneum) at the level of T12–L3. Each kidney contains approximately one million nephrons — the functional unit responsible for filtering blood, reabsorbing needed substances, and excreting waste as urine.
Key Functions of the Kidneys
- Filtration: Removes waste products (urea, creatinine, ammonia) from the blood
- Fluid & electrolyte balance: Regulates sodium, potassium, calcium, phosphorus, and water
- Acid-base balance: Regulates bicarbonate (HCO₃⁻) and hydrogen ions to maintain pH 7.35–7.45
- Blood pressure regulation: Via the renin-angiotensin-aldosterone system (RAAS)
- Erythropoietin production: Stimulates red blood cell production in bone marrow
- Vitamin D activation: Converts to active form for calcium absorption
When kidney function declines, expect to see: fluid overload, electrolyte imbalances (especially hyperkalemia), metabolic acidosis, anemia (low erythropoietin), and hypertension. These connections are heavily tested.
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Acute Kidney Injury (AKI) vs Chronic Kidney Disease (CKD)
One of the most commonly tested comparisons on the LPN/LVN exit exam.
- OnsetAKI
- Sudden (hours to days)
- OnsetCKD
- Gradual (months to years)
- ReversibilityAKI
- Often reversible if caught early
- ReversibilityCKD
- Irreversible and progressive
- Common causesAKI
- Dehydration, sepsis, nephrotoxic drugs (NSAIDs, aminoglycosides, contrast dye), obstruction
- Common causesCKD
- Diabetes (#1 cause), hypertension, glomerulonephritis
- Urine outputAKI
- Oliguria (<400 mL/day) or anuria
- Urine outputCKD
- May be normal early; polyuria → oliguria in late stages
- Kidney sizeAKI
- Normal or enlarged
- Kidney sizeCKD
- Small, shrunken
Three Types of AKI (Know These!)
- Prerenal: Decreased blood flow TO the kidney (dehydration, hemorrhage, heart failure, sepsis). Think: "before the kidney." Most common type.
- Intrarenal (Intrinsic): Damage WITHIN the kidney itself (nephrotoxic drugs, acute glomerulonephritis, acute tubular necrosis). Think: "inside the kidney."
- Postrenal: Obstruction of urine flow AFTER the kidney (kidney stones, BPH, tumors, blood clots). Think: "after the kidney."
Monitor strict I&O, daily weights (same time, same scale, same clothing), BUN/creatinine trends, potassium levels (hyperkalemia is the life-threatening complication), and watch for fluid overload (edema, crackles, JVD, hypertension). Avoid nephrotoxic medications.
CKD Stages (by GFR)
- Stage 1≥90 mL/min
- Kidney damage with normal GFR
- Stage 260–89 mL/min
- Mild decrease
- Stage 330–59 mL/min
- Moderate decrease
- Stage 415–29 mL/min
- Severe decrease
- Stage 5 (ESRD)<15 mL/min
- Kidney failure — dialysis or transplant needed
CKD Complications to Remember
- Hyperkalemia — #1 life-threatening electrolyte imbalance in renal failure
- Metabolic acidosis — kidneys can't excrete H⁺ or reabsorb HCO₃⁻
- Anemia — decreased erythropoietin production
- Uremia — buildup of waste in blood (fatigue, nausea, confusion, metallic taste, uremic frost)
- Fluid overload — leads to hypertension, edema, heart failure
- Renal osteodystrophy — bone disease from calcium/phosphorus imbalance
Low sodium, low potassium, low phosphorus, and fluid restricted. Protein may be restricted in early CKD but increased if on dialysis (protein is lost during treatment). Think: "Limit what the kidneys can't get rid of."
Urinary Tract Infections (UTIs)
One of the most common infections seen in clinical practice — and heavily tested.
UTIs can involve the lower urinary tract (cystitis — bladder infection) or the upper urinary tract (pyelonephritis — kidney infection). Women are at higher risk due to shorter urethra length. In older adults, confusion or altered mental status may be the ONLY presenting symptom.
Signs & Symptoms
- DysuriaLower UTI (Cystitis)
- Painful urination; also frequency and urgency, cloudy/foul-smelling urine, suprapubic pain, possible hematuria
- PyelonephritisUpper UTI
- All lower UTI symptoms PLUS: flank pain (costovertebral angle tenderness), high fever and chills, nausea and vomiting — can lead to sepsis if untreated
Key Nursing Interventions
- Encourage fluid intake (2–3 liters/day unless restricted)
- Administer antibiotics as prescribed (common: TMP-SMX, ciprofloxacin, nitrofurantoin)
- Teach to wipe front to back
- Encourage voiding after intercourse
- Avoid irritants (caffeine, alcohol, spicy foods)
- Cranberry juice may help prevent (not treat) UTIs — prevents bacteria from adhering to bladder wall
In older adults, UTI symptoms may NOT include the classic dysuria/frequency. Instead, look for sudden onset confusion, agitation, or behavioral changes. Always consider UTI when an elderly patient presents with new-onset altered mental status.
Kidney Stones (Nephrolithiasis)
Know the pain pattern, straining protocol, and when surgery is needed.
Kidney stones form when minerals crystallize in the urinary tract. The most common type is calcium oxalate. Risk factors include dehydration, high sodium diet, family history, gout (uric acid stones), and recurrent UTIs (struvite stones).
Classic Presentation
- Severe, colicky flank pain — radiates from flank to groin ("worst pain of my life")
- Pain comes in waves as the stone moves through the ureter
- Hematuria (blood in urine)
- Nausea and vomiting
- Restlessness — patient cannot get comfortable (unlike peritonitis where patient lies still)
Nursing Interventions
- Strain ALL urine — save the stone for lab analysis to determine composition
- Push fluids aggressively (3–4 L/day) to flush the stone
- Administer pain medication as ordered (often opioids for acute episodes)
- Administer alpha-blockers (tamsulosin/Flomax) to relax ureter and help pass the stone
- Monitor for signs of obstruction or infection
Procedures
- Lithotripsy (ESWL): Shock waves break up the stone externally — non-invasive, most common. Expect bruising and blood-tinged urine after.
- Ureteroscopy: Scope inserted through urethra to retrieve or laser the stone
- Stent placement: Keeps ureter open for drainage
Calcium oxalate: limit oxalate-rich foods (spinach, chocolate, nuts, tea). Uric acid: limit purine-rich foods (organ meats, shellfish, red meat) and maintain alkaline urine. Struvite: treat underlying infection. ALL types: increase fluid intake.
Dialysis
Hemodialysis vs peritoneal dialysis — know the differences and nursing care for both.
- How it worksHemodialysis
- Blood filtered through external machine
- How it worksPeritoneal Dialysis
- Dialysate infused into peritoneal cavity; peritoneum acts as filter
- AccessHemodialysis
- AV fistula (preferred), AV graft, or temporary CVC
- AccessPeritoneal Dialysis
- Tenckhoff (peritoneal) catheter
- FrequencyHemodialysis
- 3x/week, 3–4 hours/session
- FrequencyPeritoneal Dialysis
- Daily; can be done at home (CAPD or APD)
- Major complicationHemodialysis
- Hypotension, disequilibrium syndrome
- Major complicationPeritoneal Dialysis
- Peritonitis (cloudy effluent = #1 sign)
AV Fistula & Graft Nursing Care (Heavily Tested!)
- Assess for thrill (palpation) and bruit (auscultation) — confirm patency. No thrill/bruit = possible clot → notify provider immediately
- NO blood pressures, venipunctures, or IVs on the access arm
- No tight clothing, jewelry, or watches on the access arm
- Do not sleep on the access arm
- Check distal circulation (pulses, capillary refill, color, sensation)
- AV fistula needs 4–6 weeks to mature; graft can be used in 2–4 weeks
Signs: cloudy outflow (effluent), abdominal pain, fever, rebound tenderness. #1 prevention: strict sterile technique during exchanges. If effluent is cloudy, stop the exchange and notify the provider.
Post-hemodialysis: monitor for hypotension (most common complication), weigh the patient (expect weight loss), monitor access site for bleeding, assess electrolytes. Hold antihypertensives before dialysis to prevent hypotension.
Benign Prostatic Hyperplasia (BPH) & Urinary Retention
Common in older males — know the symptoms, meds, and post-surgical care.
BPH is a non-cancerous enlargement of the prostate gland that compresses the urethra, causing urinary obstruction. Most common cause of urinary obstruction in males age 50+.
Signs & Symptoms
- Hesitancy (difficulty starting urination)
- Weak urine stream
- Frequency, urgency, and nocturia
- Incomplete emptying (increased post-void residual)
- Urinary retention in severe cases
Medications
- Alpha-blockers (tamsulosin/Flomax, doxazosin): Relax smooth muscle in prostate and bladder neck → improves flow. Side effects: orthostatic hypotension, dizziness. Teach to rise slowly.
- 5-alpha reductase inhibitors (finasteride/Proscar): Shrink the prostate over 6–12 months. Side effect: decreased libido. Pregnant women must NOT handle crushed tablets (teratogenic).
TURP (Transurethral Resection of the Prostate)
Most common surgical treatment. Prostate tissue removed through the urethra.
- Three-way Foley catheter with continuous bladder irrigation (CBI) used post-op
- Expect blood-tinged urine: dark red → pink → clear
- Monitor for clots that could obstruct the catheter
- If catheter obstructed (bladder pain, distension, no output) → irrigate per orders or notify provider
- Teach: avoid straining, heavy lifting, and sexual activity for 4–6 weeks post-op
Caused by absorption of hypotonic irrigation fluid → dilutional hyponatremia. Signs: confusion, nausea, vomiting, hypertension, bradycardia, seizures. Medical emergency — notify provider immediately.
Urinary Catheter Care
CAUTI prevention is a major patient safety focus.
Indwelling (Foley) Catheter Care
- Use strict aseptic technique during insertion
- Perineal care with soap and water every shift and after bowel movements
- Drainage bag BELOW the level of the bladder at all times (prevent reflux)
- Do NOT rest the bag on the floor
- Secure tubing to upper thigh (female) or lower abdomen (male) to prevent traction
- Keep tubing free of kinks and dependent loops
- Empty the bag every 8 hours or when ⅔ full — do not let spigot touch the container
- Normal output ≥30 mL/hour; <30 mL/hour may indicate renal impairment — report to provider
- Assess for CAUTI signs: fever, cloudy/foul-smelling urine, suprapubic pain, new-onset confusion
Remove the catheter as soon as clinically possible — duration is the #1 risk factor for CAUTI. Daily reassessment of catheter necessity is required.
Key Labs & Electrolytes
Ranges vary by lab, facility, and textbook — for exams, use the range given in the question. See the full NCLEX-PN lab-value reference & sources →
You WILL see these values on your exam — memorize the normals.
- BUN7–20 mg/dL
- Elevated in dehydration, renal failure, GI bleeding, high-protein diet
- Creatinine0.6–1.2 mg/dL
- Most reliable indicator of kidney function; elevated = decreased GFR
- GFR≥90 mL/min
- Best overall measure of kidney function
- Potassium (K⁺)3.5–5.0 mEq/L
- Hyperkalemia in renal failure — cardiac risk! Peaked T waves on EKG
- Sodium (Na⁺)135–145 mEq/L
- Can be diluted (hyponatremia) in fluid overload
- Calcium (Ca²⁺)9.0–11.0 mg/dL (varies by lab)
- Often LOW in CKD (kidneys can't activate Vitamin D)
- Phosphorus2.5–4.5 mg/dL
- Often HIGH in CKD (inverse relationship with calcium)
- UrinalysisClear, amber, pH 4.5–8
- WBCs/nitrites = infection; RBCs = bleeding; protein = kidney damage
K⁺ > 5.0 mEq/L is dangerous. Signs: peaked T waves, muscle weakness, bradycardia, cardiac arrest. Treatment order: calcium gluconate (protect heart FIRST) → insulin + D50 (shift K⁺ into cells) → Kayexalate (excrete K⁺ via GI) → dialysis if severe.
? A CKD patient has a K⁺ of 6.2 mEq/L. What is administered FIRST?
Key Medications
The renal medications you need to know for the exam.
- Furosemide (Lasix)Loop diuretic
- Monitor K⁺ (causes hypokalemia), daily weights, I&O. Ototoxic at high doses. Give in AM.
- SpironolactoneK⁺-sparing diuretic
- SAVES potassium — monitor for hyperkalemia. No K⁺ supplements with this drug.
- HCTZThiazide diuretic
- Used for HTN. Causes hypokalemia. Can raise blood sugar.
- ACE Inhibitors (-pril)Antihypertensive
- Renoprotective in diabetic nephropathy. Side effects: dry cough, hyperkalemia, angioedema.
- Tamsulosin (Flomax)Alpha-blocker
- BPH — relaxes prostate. Orthostatic hypotension. Take 30 min after same meal daily.
- Finasteride (Proscar)5-alpha reductase inhibitor
- Shrinks prostate over months. Pregnant women must NOT handle crushed tablets.
- Phenazopyridine (Pyridium)Urinary analgesic
- Relieves UTI pain. Turns urine orange/red — warn patient. NOT an antibiotic.
- Epoetin alfa (Epogen)ESA
- Treats CKD anemia. Monitor H&H, BP (can cause HTN). Don't shake vial.
- Calcium gluconateElectrolyte
- IV for hyperkalemia — stabilizes cardiac membrane. Give FIRST. Does not lower K⁺ itself.
- KayexalateCation-exchange resin
- Exchanges Na⁺ for K⁺ in GI tract to lower potassium. Can cause constipation.
Loop diuretics (furosemide) = Lose potassium. Potassium-sparing (spironolactone) = Saves potassium. If on a loop diuretic → potassium-rich foods (bananas, oranges, potatoes) or supplement. If on spironolactone → AVOID extra potassium.
Frequently Asked Questions
Common student questions on this topic.
What is the difference between acute kidney injury (AKI) and chronic kidney disease (CKD)?
What are the dietary restrictions in chronic kidney disease?
What is the difference between hemodialysis and peritoneal dialysis?
How do I care for a patient with an AV fistula?
What are the signs of a urinary tract infection (UTI)?
What are the priority assessments for a kidney stone (renal calculi)?
Quick-Reference Cheatsheet
Every key point from this guide on a single printable page.
Renal / Urinary System Cheatsheet
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