NLE Renal & Urinary Nursing — Renal & Urinary Assessment & DiagnosticsRevision Notes

Exam Tips

• NLE FAVORITE: If the stem says 'kidney failure + anemia,' the cause is absent erythropoietin — connect it to EPO supplementation.
• Remember the 5 functions of the kidney with the acronym E-F-B-E-V: Excretion, Fluid balance, Blood pressure (RAAS), Erythropoietin, Vitamin D activation.
• 30 mL/hr is the magic minimum urine output number — memorize it. Any output below this requires immediate nursing action.
• If a question involves low BP + low urine output: think RAAS activation → aldosterone → sodium and water retention — the body's compensation mechanism.
• Polyuria in early CKD occurs because damaged tubules lose concentrating ability; later, as nephrons are destroyed, oliguria/anuria develops.

Key Points

• Each kidney contains approximately ONE MILLION nephrons — the functional unit of the kidney.
• The nephron consists of the glomerulus (filtration), proximal tubule, loop of Henle, distal tubule, and collecting duct.
• Blood is filtered at the glomerulus; the filtrate undergoes selective reabsorption and secretion along the tubules to form final urine.
• KEY FUNCTION 1 — Excretion: removes urea (from protein metabolism) and creatinine (from muscle metabolism). When kidneys fail, BOTH rise in the blood.
• KEY FUNCTION 2 — Fluid & Electrolyte Balance: regulates sodium, potassium, water, and acid-base status (excretes H+ ions, reabsorbs bicarbonate).
• KEY FUNCTION 3 — Blood Pressure Control: via the Renin-Angiotensin-Aldosterone System (RAAS). Low renal perfusion → renin released → angiotensin II (vasoconstriction) → aldosterone (sodium and water retention) → increased BP.
• KEY FUNCTION 4 — Erythropoietin Production: stimulates red blood cell production in bone marrow. Kidney failure → no erythropoietin → ANEMIA.
• KEY FUNCTION 5 — Vitamin D Activation: converts vitamin D to its active form (calcitriol) for intestinal calcium absorption. Kidney failure → hypocalcemia and renal osteodystrophy (renal bone disease).
• Normal urine output: 1–2 mL/kg/hr, approximately 1,500 mL/day in adults.
• Adult minimum acceptable urine output: 30 mL/hr (or 0.5 mL/kg/hr) — signals adequate renal perfusion.
• Oliguria: less than 400 mL/day (or less than 0.5 mL/kg/hr).
• Anuria: less than 100 mL/day — severe; often signals complete kidney failure.
• Polyuria: excessive urine output, greater than 2,500–3,000 mL/day.

Definitions

Section Title

Review of Renal Structure & Function

Common Mistakes

• Confusing the nephron (functional unit) with the glomerulus — the glomerulus is just ONE part of the nephron.
• Forgetting that kidney failure causes BOTH anemia (no EPO) AND hypocalcemia (no active vitamin D) — not just waste retention.
• Mixing up oliguria cutoffs: oliguria is <400 mL/DAY or <0.5 mL/kg/hr; the bedside minimum is 30 mL/hr.
• Assuming dialysis replaces ALL kidney functions — dialysis replaces filtration/excretion only; hormonal functions (EPO, vitamin D) are NOT replaced.
• Forgetting the RAAS chain: confusing which step produces vasoconstriction (angiotensin II) versus sodium retention (aldosterone).

Exam Tips

• NLE TIP: 'Most reliable indicator of fluid status' = DAILY WEIGHT. This is tested repeatedly across multiple subjects (renal, cardiac, pediatric nursing).
• The formula: 1 kg weight gain = 1 liter of retained fluid. If a patient gained 3 kg overnight = approximately 3 liters of fluid retained.
• When a question asks about drug history in renal patients, always flag aminoglycosides, NSAIDs, and contrast dye as the top three nephrotoxic agents.
• CVA tenderness = kidney problem (pyelonephritis or stones). Suprapubic tenderness = bladder problem (cystitis, retention).
• If a question mentions periorbital edema in the morning — think nephrotic syndrome (massive proteinuria). It is gravity-dependent and shifts; worse in the morning, legs worsen by evening.

Key Points

• A thorough nursing history covers: voiding changes (frequency, urgency, dysuria, hesitancy, nocturia, incontinence, retention), urine appearance (color, odor, hematuria, frothiness), fluid intake patterns, weight changes, edema, and flank or suprapubic pain.
• Always obtain a complete drug history — many drugs are NEPHROTOXIC: aminoglycosides (gentamicin), NSAIDs (mefenamic acid — commonly used in the Philippines), iodinated contrast dye, and certain antibiotics (vancomycin).
• Review history of hypertension, diabetes mellitus (leading causes of CKD in the Philippines), recurrent UTIs, and renal calculi.
• DAILY WEIGHT is the SINGLE MOST RELIABLE indicator of fluid gain or loss: 1 kg weight gain ≈ 1 liter of fluid retained.
• Daily weight must be done consistently: same time (morning after first void), same scale, same clothing/bedding.
• Assess for fluid overload signs: dependent edema, periorbital edema (classic in nephrotic syndrome), sacral edema (bedridden patients), crackles/rales in lungs, jugular venous distension, hypertension.
• COSTOVERTEBRAL ANGLE (CVA) TENDERNESS: pain upon fist percussion at the angle between the 12th rib and the vertebral column — suggests pyelonephritis or renal calculi.
• A distended bladder is palpable and percussable as a dull area above the symphysis pubis — indicates urinary retention.
• Skin assessment: pallor (anemia from low EPO), dryness and poor turgor (dehydration), uremic frost (white crystalline deposits on skin — sign of severe uremia, extremely elevated BUN).
• Intake and Output (I&O) monitoring: both daily weight AND I&O together give the most complete fluid picture.

Definitions

Section Title

Nursing Assessment of Renal & Urinary Function

Common Mistakes

• Forgetting that daily weight, NOT I&O measurement, is the MOST RELIABLE fluid indicator — I&O is important but less accurate because insensible losses are estimated.
• Not asking about herbal/traditional remedies (e.g., tawas, herbal teas) — some are nephrotoxic and commonly used in Filipino communities.
• Confusing CVA tenderness location — it is at the BACK (posterior), between the 12th rib and spine, NOT over the abdomen.
• Omitting drug history — NSAIDs like mefenamic acid (Ponstan) are widely used in the Philippines and are a common cause of nephrotoxicity.
• Assessing edema only in the legs — in renal patients, check periorbital (around eyes), sacral (bedridden), and pulmonary edema signs too.

Formulas

Exam Tips

• MEMORIZE: BUN normal 10–20 mg/dL; Creatinine normal 0.6–1.2 mg/dL; BUN:Cr ratio normal 10:1 to 20:1; K+ normal 3.5–5.0 mEq/L; Ca2+ normal 8.5–10.5 mg/dL; GFR normal 90–120 mL/min/1.73 m².
• NLE TRICK QUESTION: 'What is the MOST SPECIFIC indicator of renal function?' → Serum Creatinine. 'What is the BEST OVERALL measure of kidney function?' → GFR (eGFR). These are different answers — know both.
• BUN:Cr ratio >20:1 = think DEHYDRATION first (prerenal) — the fix is fluids, not dialysis.
• High phosphate + low calcium in CKD = give phosphate binders WITH meals (calcium carbonate, sevelamer). The nurse must teach patients to take these WITH food, not on an empty stomach.
• ECG changes of hyperkalemia (peaked T-waves, wide QRS, sine-wave pattern) are an NLE-favorite emergency scenario. First drug given: IV calcium gluconate (to protect the heart while waiting for potassium to fall).

Key Points

• BLOOD UREA NITROGEN (BUN): Normal = 10–20 mg/dL. Rises when kidneys cannot excrete urea. NON-SPECIFIC — also increases with: dehydration/hypovolemia, high-protein diet, GI bleeding (blood digested as protein), and increased catabolism (fever, burns, trauma).
• SERUM CREATININE: Normal = 0.6–1.2 mg/dL. The MOST SPECIFIC AND RELIABLE indicator of renal function. Produced at a steady rate from muscle metabolism; excreted almost entirely by the kidney. NOT significantly affected by diet or hydration — makes it far more reliable than BUN.
• BUN-TO-CREATININE RATIO: Normally 10:1 to 20:1. A HIGH RATIO (>20:1) with near-normal creatinine = PRERENAL cause (dehydration, hypovolemia, poor renal perfusion). When BOTH BUN and creatinine rise proportionally (ratio stays near normal) = INTRINSIC RENAL disease. A LOW ratio (<10:1) can suggest malnutrition or liver disease.
• SERUM POTASSIUM: Normal = 3.5–5.0 mEq/L. HYPERKALEMIA is the DEADLIEST electrolyte complication of renal failure — failing kidneys cannot excrete K+. Leads to fatal cardiac dysrhythmias. Always tie rising potassium to ECG changes.
• SERUM SODIUM: Normal = 135–145 mEq/L. Dilutional hyponatremia can occur with fluid overload in renal failure.
• SERUM CALCIUM: Normal = 8.5–10.5 mg/dL. Often LOW (hypocalcemia) in CKD — kidney cannot activate vitamin D → impaired intestinal calcium absorption + phosphate retention draws calcium out.
• SERUM PHOSPHATE: Normal = 2.5–4.5 mg/dL. Often HIGH (hyperphosphatemia) in CKD — kidneys cannot excrete phosphate. Inversely related to calcium: high phosphate → low calcium.
• BICARBONATE / pH: Failing kidneys cannot excrete H+ ions or regenerate bicarbonate → METABOLIC ACIDOSIS (low HCO3-, low pH). Normal HCO3- = 22–26 mEq/L.
• GFR (Glomerular Filtration Rate): BEST OVERALL MEASURE of kidney function. Normal = 90–120 mL/min/1.73 m². Estimated from serum creatinine + age + sex + body size (eGFR formula). ESRD (Stage 5 CKD) = GFR <15 mL/min/1.73 m².
• CREATININE CLEARANCE: Classic timed measurement of GFR using a 24-hour urine collection plus a serum creatinine sample. Normal approximately 85–135 mL/min (slightly lower in women and older adults).

Definitions

Section Title

Laboratory Tests — Blood Studies (Memorize All Normal Values)

Common Mistakes

• Calling BUN the 'most reliable' test — this is WRONG. Creatinine is most specific and reliable. BUN is non-specific.
• Forgetting that creatinine is lower in women, elderly, and malnourished patients due to lower muscle mass — a 'normal' creatinine of 1.0 mg/dL in a frail elderly woman may actually represent significant renal impairment.
• Misinterpreting the BUN:Cr ratio: a HIGH ratio means PRERENAL (not renal failure), because the kidney tubules are intact and still reabsorbing urea, raising BUN disproportionately.
• Assuming calcium is HIGH in CKD — it is typically LOW (hypocalcemia) because vitamin D activation is lost and phosphate is high (inverse relationship).
• Confusing metabolic acidosis with respiratory acidosis in renal failure — renal failure causes METABOLIC acidosis (kidneys cannot excrete H+ or regenerate HCO3-).

Exam Tips

• NLE MEMORY AID for casts: 'RBC casts = Red cell = gloRed = glomeRulonephritis' vs 'WBC casts = White = pyelonephritis.' Muddy brown granular casts = ATN (acute tubular necrosis).
• First-morning urine = most concentrated = best for: protein detection, cytology, routine UA. Midstream clean catch = best for: C&S culture.
• Fixed specific gravity ~1.010 = ISOSTHENURIA = kidneys cannot concentrate or dilute = sign of RENAL FAILURE. This is a high-yield NLE fact.
• Normal pH range 4.5–8.0 is wide; the NLE may test which condition causes acidic vs. alkaline urine — high-protein diets and metabolic acidosis → acidic; UTI with urea-splitting organisms (Proteus) → alkaline.
• Leukocyte esterase POSITIVE + nitrites POSITIVE on dipstick = high likelihood of UTI. Confirm with C&S. This combination is the most reliable dipstick indicator of bacterial infection.

Key Points

• Urinalysis (UA) is the single most useful, most cost-effective initial renal test. Collect a CLEAN-CATCH MIDSTREAM specimen for routine UA and C&S.
• For most accurate results (especially for cytology or routine screening), use a FIRST-MORNING specimen — most concentrated, highest solute levels.
• ALWAYS obtain urine culture and sensitivity (C&S) BEFORE starting antibiotics — antibiotics will destroy the bacteria and give a false-negative culture.
• COLOR: Normal = pale yellow to amber. Cola/tea/brown color = hematuria or myoglobin (rhabdomyolysis). Cloudy/turbid = infection (pus, WBCs). Frothy = proteinuria. Very pale/colorless = very dilute urine or polyuria.
• pH: Normal = 4.5–8.0 (average approximately 6). Acidic urine can be caused by diet (high protein, meat), metabolic acidosis, or urinary tract infection with certain bacteria. Alkaline urine from vegetarian diet, UTI (urea-splitting bacteria), or metabolic alkalosis.
• SPECIFIC GRAVITY: Normal = 1.005–1.030. HIGH (>1.020) = concentrated, possibly dehydration. LOW (<1.005) = very dilute. FIXED SPECIFIC GRAVITY at approximately 1.010 = the kidney has LOST its ability to concentrate or dilute urine = RENAL FAILURE (isosthenuria).
• PROTEIN: Normally NEGATIVE or trace only. Significant PROTEINURIA (>150 mg/day) = glomerular damage. Classic in nephrotic syndrome (>3.5 g/day) and diabetic nephropathy. Frothy urine is a patient's self-reported sign of proteinuria.
• GLUCOSE: Normally NEGATIVE in urine. Glycosuria appears when blood glucose exceeds the RENAL THRESHOLD of approximately 180 mg/dL (tubules cannot reabsorb all the filtered glucose). Seen in diabetes mellitus. Note: urine glucose is NOT a reliable indicator of current blood glucose level.
• KETONES: Normally NEGATIVE. Ketonuria in diabetic ketoacidosis, starvation, or prolonged fasting.
• BLOOD/RBCs (Hematuria): Normally NEGATIVE. Hematuria causes: UTI, kidney stones (renal calculi), glomerulonephritis, renal tumor, trauma, strenuous exercise.
• WBCs / Leukocyte Esterase / Nitrites: Presence of WBCs (pyuria) + leukocyte esterase + nitrites = strong indication of URINARY TRACT INFECTION. Nitrites are produced when gram-negative bacteria (e.g., E. coli) convert urinary nitrates.
• CASTS: Cylindrical molds formed in the tubules. RBC casts = GLOMERULONEPHRITIS (pathognomonic). WBC casts = PYELONEPHRITIS (kidney infection). Hyaline casts = normal in small numbers, dehydration. Granular/muddy brown casts = acute tubular necrosis (ATN).
• URINE CULTURE & SENSITIVITY (C&S): Definitive diagnosis of UTI; identifies the pathogen and which antibiotics it is sensitive to. >100,000 colony-forming units (CFU)/mL = significant bacteriuria (in a symptomatic patient, even lower counts may be significant).

Definitions

Section Title

Urinalysis — Normal Findings & Clinical Significance

Common Mistakes

• Collecting a C&S culture AFTER starting antibiotics — this invalidates the culture. Always collect first, then administer antibiotics.
• Forgetting that glycosuria (glucose in urine) appears at a blood glucose of approximately 180 mg/dL (the renal threshold) — a patient with poor glucose control may have normal urine glucose if their blood glucose is just below this threshold.
• Confusing RBC casts (glomerulonephritis) with WBC casts (pyelonephritis) — remember: 'Red cells from the glomerulus, White cells from a pyelon/kidney infection'.
• Missing the significance of a fixed specific gravity of 1.010 — this is isosthenuria, meaning the kidney can neither concentrate nor dilute = kidneys are failing.
• Not instructing patients on the correct clean-catch technique, leading to specimen contamination and false-positive results.

Exam Tips

• NLE SEQUENCE for IVP/contrast prep: (1) Allergy check → (2) Renal function check → (3) Hold metformin → (4) Hydration → (5) Bowel prep if ordered → (6) Post-procedure: fluids + allergy monitoring.
• For 24-hour urine: remember '7 AM DISCARD, then collect until 7 AM the next morning' — all of it, including the final void at the end time.
• Renal biopsy post-care priority = BLEEDING PREVENTION + DETECTION. Bed rest, VS monitoring, urine color assessment, flank pain assessment. Patient must not lift heavy objects for 2 weeks.
• Renal ultrasound is the SAFEST diagnostic test: no contrast, no radiation, no prep — ideal for pregnant patients, patients with contrast allergies, and patients with already-impaired kidney function.
• Cystoscopy teach-back: pink urine = normal; bright red + clots = call the nurse immediately. Encourage fluids to irrigate the urinary tract and prevent clot formation.

Key Points

• 24-HOUR URINE COLLECTION (for creatinine clearance, protein quantification): DISCARD the first morning void (note the time), collect ALL urine for exactly 24 hours (ending with the collection of urine at the same time the next morning), keep specimen chilled/refrigerated throughout. Missing even ONE specimen invalidates the entire test.
• KUB X-RAY (Kidneys-Ureters-Bladder): Plain abdominal X-ray, no contrast, no special prep. Identifies calcium-containing stones, gross structural abnormalities.
• RENAL ULTRASOUND: No radiation, no contrast dye, NO SPECIAL PREPARATION required. Best for: assessing kidney size, detecting hydronephrosis (obstruction), cysts, tumors, and guiding biopsy. A safe first-line imaging choice.
• IVP (Intravenous Pyelogram) / CT UROGRAPHY WITH CONTRAST: Iodinated contrast dye is injected IV to visualize the urinary tract. NURSING PREP: (1) Assess for iodine/shellfish allergy — contrast allergy risk; (2) Check BUN/creatinine — contrast is nephrotoxic, should not be given if creatinine is significantly elevated; (3) Ensure patient is well-hydrated before AND after procedure; (4) HOLD METFORMIN (Glucophage) 48 hours before contrast — risk of lactic acidosis; (5) Bowel prep may be required (cleansing enemas or laxatives) for better visualization; (6) After procedure: push oral fluids to flush the dye; monitor for delayed allergic reaction.
• CYSTOSCOPY: Direct endoscopic visualization of the bladder and urethra. May include biopsy or stone removal. POST-PROCEDURE CARE: expect pink-tinged urine (normal for 24–48 hrs); encourage increased fluid intake; warm sitz baths for comfort; REPORT immediately: bright-red bleeding, blood clots in urine, inability to void, fever/chills (infection), or severe/worsening pain.
• RENAL BIOPSY: Needle biopsy of the kidney to obtain tissue for histopathologic diagnosis (definitive for glomerular diseases). POST-BIOPSY NURSING PRIORITY: BED REST (supine) for several hours; monitor VITAL SIGNS frequently for signs of hemorrhage; assess for HEMATURIA (normally pink-tinged urine for up to 24 hrs, but frank red blood = concern); assess FLANK PAIN (hematoma formation); avoid strenuous activity and heavy lifting for approximately 2 weeks. The kidney is HIGHLY VASCULAR — bleeding is the primary risk.
• CT SCAN / MRI: Detailed structural imaging; CT provides excellent stone detection and vascular detail; MRI best for soft tissue/vascular structures without radiation (but expensive and less available in many Philippine provincial hospitals).

Definitions

Section Title

Diagnostic Procedures — Preparation & Post-Procedure Nursing Care

Common Mistakes

• Starting the 24-hour urine collection with the FIRST void instead of discarding it — the collection must begin AFTER the first morning void is discarded.
• Not holding metformin before contrast-enhanced CT or IVP — this is a serious patient safety issue and a common NLE scenario.
• Not checking renal function (BUN/creatinine) before administering contrast dye — nephrotoxic contrast given to a patient with already impaired renal function can trigger acute kidney injury.
• Teaching patients that pink-tinged urine after cystoscopy is abnormal — it is expected and normal for 24–48 hours.
• Allowing early ambulation after renal biopsy — bed rest is required because the kidney is highly vascular and bleeding risk is high in the first several hours.

Exam Tips

• NLE CAUTI PREVENTION BUNDLE: Sterile insertion + closed system + bag BELOW bladder + no dependent loops + daily perineal care + REMOVE ASAP. This is a complete answer.
• For catheter specimen collection: use the NEEDLELESS PORT on the catheter tubing, clamp the tubing below the port for a few minutes to allow fresh urine to pool, clean the port with alcohol, aspirate with sterile syringe.
• Gradual decompression principle: if a question mentions a very full bladder and asks what the nurse should do after inserting a catheter — the answer involves gradual drainage, not rapid drainage all at once.
• If resistance is met during catheter insertion: STOP — do not force. Report to physician/urologist. This is a safety principle tied to RA 9173 standards of safe nursing practice.
• The MOST EFFECTIVE CAUTI prevention strategy is removing the catheter as early as possible — more effective than any catheter care measure alone.

Key Points

• INDICATIONS for urinary catheterization: (1) Acute urinary retention; (2) Accurate measurement of urinary output (critically ill patients); (3) Perioperative bladder management for selected procedures; (4) Bladder irrigations; (5) Facilitating healing in patients with Stage III–IV sacral pressure ulcers; (6) Comfort care at end of life.
• CATHETER TYPES: Foley/indwelling catheter (retention balloon, continuous drainage); intermittent straight catheter (in-and-out for retention or drainage); suprapubic catheter (inserted through abdominal wall for long-term use or urethral obstruction).
• CAUTI (Catheter-Associated Urinary Tract Infection) is one of the MOST COMMON healthcare-associated infections (HAI) in Philippine hospital settings. The DURATION of catheterization is the single biggest risk factor for CAUTI.
• STERILE (ASEPTIC) TECHNIQUE is mandatory for catheter insertion — this is non-negotiable under RA 9173 standards of safe nursing practice.
• KEEP DRAINAGE BAG BELOW THE LEVEL OF THE BLADDER AT ALL TIMES — prevents urine backflow into the bladder (retrograde flow = infection risk). The bag must NEVER rest on the floor.
• MAINTAIN A CLOSED DRAINAGE SYSTEM — do not disconnect tubing unnecessarily. Disconnect only when changing the bag, irrigation, or specimen collection (using the port).
• PREVENT DEPENDENT LOOPS in tubing — loops of tubing that hang below the bag level trap urine and allow backflow when the patient moves. Secure tubing to the inner thigh (female) or upper thigh (male) to prevent traction and maintain drainage direction.
• ROUTINE PERINEAL/CATHETER CARE: Clean the urethral meatus and proximal catheter with soap and water at least every 8 hours and after each bowel movement. Avoid antiseptic solutions on the catheter unless ordered — can irritate tissue and alter urethral flora.
• REMOVE THE CATHETER AS EARLY AS CLINICALLY POSSIBLE — the most effective CAUTI prevention strategy. Reassess catheter necessity DAILY.
• GRADUAL BLADDER DECOMPRESSION: After relieving acute urinary retention of a VERY FULL BLADDER (>1,000 mL), drain gradually (institutional policy may limit initial drainage to 300–500 mL at a time, then clamp, then release). Rapid decompression of a very distended bladder can cause: hematuria (from sudden mucosal vessel rupture), hypotension (from sudden shift of blood to the decompressed pelvic vessels), and bladder spasm.
• NEVER FORCE A CATHETER against resistance — if resistance is met (possible urethral stricture in adults, enlarged prostate/BPH in older Filipino males), stop and notify the physician.
• For specimen collection from an indwelling catheter: use the SPECIMEN PORT on the tubing (NOT the drainage bag) using a sterile syringe after cleansing the port — the bag specimen is contaminated and not valid for C&S.
• Inflate the Foley balloon ONLY AFTER CONFIRMING the catheter is in the bladder (urine must flow freely before inflating the balloon). Inflating in the urethra causes urethral trauma.

Definitions

Section Title

Urinary Catheterization — Principles, Technique & CAUTI Prevention

Common Mistakes

• Placing the drainage bag on the bed at the same level as the bladder — must always be LOWER than the bladder to prevent backflow.
• Collecting a urine C&S specimen from the drainage BAG instead of the SPECIMEN PORT — bag urine is hours old, warm, and contaminated; always collect from the port.
• Inflating the Foley balloon before confirming urine flow — if the catheter tip is still in the urethra when the balloon is inflated, it causes urethral rupture and severe pain.
• Forcefully inserting a catheter against resistance — in older Filipino males, BPH is common and causes resistance; forcing can cause urethral injury.
• Leaving the catheter in place indefinitely 'for convenience' — prolonged catheterization is the number one CAUTI risk factor; reassess need daily.

Exam Tips

• AEIOU mnemonic for dialysis indications: Acidosis, Electrolytes (K+), Intoxication, Overload, Uremia. If any of these are severe and unresponsive to conservative treatment = dialysis NOW.
• Thrill + bruit = patent fistula. Loss of thrill or bruit = possible clot = medical emergency. Teach patients to check their own fistula daily.
• NLE COMPARISON: Hemodialysis = faster, more efficient, hospital/center-based; Peritoneal dialysis = slower, continuous, home-based, better for hemodynamically unstable patients. Both use diffusion and osmosis/ultrafiltration.
• Dialysate is always warm (body temperature) and always LOW/ZERO in wastes (urea, creatinine, K+) to maintain the concentration gradient for removal — this is the reason dialysis works.
• A question asking 'what dialysis does NOT do for a kidney failure patient' → answer: it does NOT produce EPO, it does NOT activate vitamin D, it does NOT regulate BP independently. External supplementation is still needed.

Key Points

• DIALYSIS substitutes for the kidney's filtration/excretion function when the kidneys can no longer clear wastes and fluid adequately — typically when GFR falls to <15 mL/min/1.73 m² (Stage 5 CKD/ESRD), or earlier in acute settings with life-threatening complications (refractory hyperkalemia, severe pulmonary edema, uremic pericarditis, acidosis).
• PHYSICAL PRINCIPLE 1 — DIFFUSION: Solutes (urea, creatinine, potassium, hydrogen ions) move from an AREA OF HIGH CONCENTRATION (the patient's blood) across a SEMIPERMEABLE MEMBRANE into the DIALYSATE (which has low or zero concentrations of these waste products). This removes wastes from the blood.
• PHYSICAL PRINCIPLE 2 — OSMOSIS / ULTRAFILTRATION: Water (and with it, excess fluid/electrolytes) moves across the semipermeable membrane from blood to dialysate due to a PRESSURE GRADIENT (hydrostatic pressure in hemodialysis) or an OSMOTIC GRADIENT (high-dextrose dialysate in peritoneal dialysis). This removes excess fluid from the patient.
• DIALYSATE COMPOSITION: A balanced electrolyte solution containing normal physiologic concentrations of sodium, calcium, bicarbonate (to correct acidosis), and magnesium. Critically: it contains ZERO UREA, ZERO CREATININE, and NO POTASSIUM (or very low potassium) — so the concentration gradient always favors waste removal from blood into dialysate.
• DIALYSATE TEMPERATURE: Warmed to body temperature (approximately 37°C) to prevent hypothermia and vasoconstriction.
• HEMODIALYSIS: Blood is removed from the patient (via AV fistula, AV graft, or central venous catheter), circulated through an artificial kidney (dialyzer) where diffusion and ultrafiltration occur, and returned to the patient. Requires vascular access. Typically 3–4 hours per session, 3 times per week.
• PERITONEAL DIALYSIS (PD): The peritoneum serves as the semipermeable membrane. Dialysate is instilled into the peritoneal cavity via a PD catheter (Tenckhoff catheter). Wastes diffuse into the dialysate; the dextrose in the dialysate creates an osmotic gradient to pull fluid out. After dwell time, the dialysate (now containing wastes) is drained out. Done at home (CAPD) or with a machine overnight (APD/CCPD). More common in Philippine home settings due to lower equipment cost.
• DIALYSIS DOES NOT REPLACE HORMONAL FUNCTIONS: Patients on dialysis still require: (1) ERYTHROPOIETIN supplements (epoetin alfa/darbepoetin) for anemia; (2) ACTIVE VITAMIN D (calcitriol/alfacalcidol) and calcium supplements for bone disease; (3) PHOSPHATE BINDERS to control hyperphosphatemia; (4) ANTIHYPERTENSIVES for blood pressure control.
• INDICATIONS FOR URGENT DIALYSIS (AEIOU Mnemonic): A = Acidosis (severe metabolic acidosis, pH <7.1); E = Electrolytes (life-threatening hyperkalemia); I = Ingestion/Intoxication (dialyzable toxins: methanol, ethylene glycol, salicylates, lithium); O = Overload (pulmonary edema not responding to diuretics); U = Uremia (uremic pericarditis, encephalopathy, neuropathy).

Definitions

Section Title

Principles of Dialysis

Common Mistakes

• Thinking dialysis replaces ALL kidney functions — it only replaces FILTRATION/EXCRETION. Hormonal functions (EPO, vitamin D) still require supplementation.
• Confusing the direction of diffusion — wastes move FROM BLOOD (high) TO DIALYSATE (low), not the other way around. The dialysate is the 'clean' side.
• Assuming peritoneal dialysis is less effective than hemodialysis — PD is effective, gentler on hemodynamics, and more suitable for patients with cardiovascular instability or difficult vascular access.
• Forgetting to check AV fistula for thrill and bruit — never take blood pressure, give injections, or draw blood from the fistula arm (risk of thrombosis and infection).
• Not connecting dialysis initiation to GFR <15 — students sometimes say dialysis starts when 'kidneys fail completely' (anuria), but it is often started earlier to prevent uremic complications.

Exam Tips

• RENAL DIET MEMORY AID: 'NSA-PK-F' = No/low Sodium, restrict phoSphate, avoid potAssium (high-K foods), Protein restriction (pre-dialysis), control Fluid. Once on dialysis, protein restriction is reversed.
• NLE QUESTION PATTERN: 'A patient with CKD Stage 4 asks what foods to avoid.' Answer must include: high-sodium foods, bananas/potatoes/tomatoes (high K+), dairy/nuts (high phosphate), and all liquid volumes if fluid-restricted.
• Phosphate binders WITH meals — this medication timing is a recurring NLE question. 'When should the nurse administer calcium carbonate to a CKD patient?' → WITH or just BEFORE MEALS.
• Daily weight gain of >2 lbs (approximately 1 kg) per day in a dialysis patient = too much fluid intake → needs dietary counseling and possible adjustment of dialysis prescription.
• For elderly patients: when in doubt about drug safety → check renal function (creatinine, GFR) before administering drugs that are renally cleared or nephrotoxic.

Key Points

• PRIORITY NURSING DIAGNOSIS FRAMEWORK: Using Maslow's Hierarchy — physiological needs first. In renal patients: fluid/electrolyte imbalance (MOST physiologically urgent) > infection risk > skin integrity > knowledge deficit.
• FLUID VOLUME EXCESS (Hypervolemia): Signs = weight gain, edema (dependent, periorbital, sacral), crackles, hypertension, jugular venous distension, dyspnea. Nursing interventions: fluid restriction, low-sodium diet, daily weights, I&O monitoring, diuretics as ordered (may be ineffective in severe renal failure), dialysis.
• FLUID VOLUME DEFICIT (Hypovolemia/Dehydration): Signs = weight loss, poor skin turgor, dry mucous membranes, decreased urine output, hypotension, tachycardia, elevated BUN (prerenal). Nursing interventions: IV fluid replacement, encourage oral fluids if not restricted, daily weights, I&O.
• RISK FOR HYPERKALEMIA: The deadliest electrolyte complication of renal failure. Monitor K+ levels, ECG changes (peaked T-waves → widened QRS → sine wave → asystole). Dietary restriction: avoid bananas, oranges, potatoes, tomatoes, salt substitutes (contain potassium chloride), melons, avocado.
• RISK FOR INFECTION: From Foley catheters (CAUTI), dialysis access (AV fistula, PD catheter, central line), immunosuppression in transplant patients. Strict aseptic technique; assess access sites for redness, swelling, drainage; monitor temperature.
• IMPAIRED SKIN INTEGRITY: From edema (stretched, fragile skin), uremic pruritus (itching from urea deposits), immobility. Interventions: reposition every 2 hours, moisturizing lotions for dry/pruritic skin, avoid scratching, keep nails short, pressure-relieving mattresses.
• KNOWLEDGE DEFICIT: Teach patients about their diet (sodium, potassium, phosphate, protein, fluid restrictions), medication schedule (phosphate binders WITH meals, antihypertensives, EPO injections), fistula/catheter care, when to seek medical attention.
• RENAL DIET — SODIUM: Restrict to reduce fluid retention and control blood pressure. Teach patients to read food labels; processed foods, canned goods, instant noodles (common in the Philippines — Lucky Me, Nissin, etc.) are very high in sodium.
• RENAL DIET — POTASSIUM: Restrict as GFR falls. Foods to limit: bananas, oranges, avocados, tomatoes, potatoes, camote (sweet potato), squash, dried fruits, salt substitutes (KCl). Low-potassium alternatives: apples, grapes, pineapple (canned/rinsed), white rice, white bread.
• RENAL DIET — PHOSPHATE: Restrict and take PHOSPHATE BINDERS WITH MEALS (e.g., calcium carbonate, sevelamer). Foods high in phosphate: dairy products (milk, cheese, yogurt), nuts, legumes (monggo, beans), cola drinks, processed meats.
• RENAL DIET — PROTEIN: RESTRICTED before dialysis (to limit urea generation). INCREASED once on dialysis (dialysis removes protein; sessions cause protein losses, especially in peritoneal dialysis).
• RENAL DIET — FLUID: Individualized restriction based on urine output plus estimated insensible losses. General guideline: daily fluid allowance = previous day urine output + 500–700 mL (for insensible loss). Teach patients to count all liquids: water, soup, ice cream, gelatin (sorbetes, gulaman), fruits with high water content.
• OLDER ADULT CONSIDERATIONS: Normal age-related decline in GFR (decreases approximately 1 mL/min/year after age 40); reduced concentrating ability → dehydrate easily; more sensitive to nephrotoxic drugs and drugs excreted by the kidney (digoxin, metformin, NSAIDs, aminoglycosides). ALWAYS check for renal dosing adjustments in elderly patients.

Definitions

Section Title

Renal Nursing Diagnoses, Priorities & Dietary Principles

Common Mistakes

• Giving phosphate binders on an empty stomach — they must be given WITH meals to bind dietary phosphate during absorption.
• Not recognizing salt substitutes as a high-potassium food — patients with renal failure often switch to salt substitutes to avoid sodium, not realizing these contain potassium chloride (KCl) and can cause life-threatening hyperkalemia.
• Restricting protein on dialysis patients — once on dialysis, protein restriction is LIFTED and may actually need to be INCREASED due to dialysis-related protein losses.
• Applying the same medication doses to elderly renal patients — always assess for renal dosing adjustments. Many drugs (metformin, NSAIDs, aminoglycosides) are contraindicated or require dose reduction in renal impairment.
• Forgetting that fluid restriction includes ALL fluid sources — not just water. Ice cream (sorbetes), soup (sabaw), gelatin (gulaman), and high-water-content fruits all count toward the daily fluid allowance.