NSG210 Hinkle Ch. 47: Assessment of Kidney and Urinary Function

Source: Hinkle & Cheever, Brunner & Suddarth’s Medical-Surgical Nursing 15e, Chapter 47, pp. 1534-1553 (textbooks/HINKLE_MS_CH47.pdf, also in textbooks/exam04/). Week 13 (elimination and GU disorders); Exam 4 content. Numbering note: the Week 13 syllabus lists 16e Ch. 50, 49, and 54; this 15e assessment chapter (16e Ch. 48) is not on the syllabus list but is in the curated exam04/ folder as background for the kidney and urinary disorder chapters. See nsg210-textbook-chapter-crosswalk.

Learning Outcomes

1. Describe the structure and function of the renal and urinary systems.
2. Explain the kidneys’ role in fluid and electrolyte balance, acid-base balance, and blood pressure.
3. Identify diagnostic studies of upper and lower urinary tract function and related nursing implications.
4. Discriminate normal from abnormal assessment findings.
5. Educate and prepare patients for urinary system assessment.

Key Terms

• Aldosterone: adrenal cortex hormone; kidneys reabsorb sodium
• ADH (vasopressin): posterior pituitary; kidneys reabsorb more water
• Anuria: urine output under 50 mL in 24 hours
• Oliguria: under 400 mL in 24 hours or under 0.5 mL/kg/h over 6 hours
• Bacteriuria: bacteria in urine (count over 100,000 colonies/mL)
• Creatinine: waste product of muscle energy metabolism
• Diuresis: increased urine volume
• Dysuria: painful or difficult urination
• Erythropoietin: kidney glycoprotein that stimulates RBC production
• GFR: plasma filtered through glomeruli per unit time. Glomerulus: capillary tuft where filtration occurs
• Glycosuria, hematuria, proteinuria, pyuria: glucose, RBCs, protein, WBCs in urine
• Micturition: voiding
• Nephron: functional unit that forms urine
• Nocturia: waking at night to urinate
• Renal clearance: kidneys’ ability to clear solutes from plasma
• Specific gravity: urine concentration
• Urea nitrogen (BUN): end product of protein metabolism
• Urinary frequency: voiding more often than every 3 hours

I. Anatomy

A. Kidneys

• Retroperitoneal, T12 to L3; right kidney slightly lower (liver). 113 to 170 g; 10 to 12 cm long, 6 cm wide, 2.5 cm thick. Protected by ribs, muscles, fat, renal fascia; adrenal gland on top of each.
• Hilum: renal artery in; renal vein and ureter out. Receive 20 to 25 percent of cardiac output; all blood passes through about 12 times per hour.
• Cortex (about 1 cm; nephrons) and medulla (about 5 cm; loops of Henle, vasa recta, collecting ducts; 8 to 18 pyramids drain to minor and major calyces, then renal pelvis). Urine composition does not change after leaving the renal pelvis.
• Blood flow: renal artery to afferent arteriole to glomerulus to efferent arteriole to peritubular capillaries to veins.

B. Nephrons

• About one million per kidney; replacement therapy considered when functioning nephrons fall under 20 percent of normal.
• Cortical (80 to 85 percent) and juxtamedullary (15 to 20 percent; long loops of Henle and vasa recta; concentrate urine).
• Glomerulus in Bowman capsule: three-layer membrane (endothelium, basement membrane, epithelium) filters fluid and small molecules, not blood cells or albumin.
• Tubule: proximal tubule, loop of Henle, distal tubule, collecting ducts. Macula densa plus afferent arteriole = juxtaglomerular apparatus, site of renin production.

C. Ureters, Bladder, Urethra

• Ureters: 24 to 30 cm; urothelium; peristalsis. Three narrow areas prone to stones or stricture: ureteropelvic junction (most serious, near kidney), near sacroiliac junction, ureterovesical junction. Angle of ureterovesical junction prevents vesicoureteral reflux.
• Bladder: behind pubic bone; capacity 400 to 500 mL; detrusor muscle; internal sphincter at bladder neck; external sphincter at anterior urethra maintains continence. Bladder is only completely empty in the last seconds of voiding.
• Urethra: through penis in males; anterior to vagina in females. Prostate surrounds male urethra below bladder neck.

II. Physiology

A. Urine Formation

• Three steps: glomerular filtration, tubular reabsorption, tubular secretion.
• Renal blood flow 1000 to 1300 mL/min; about 20 percent filtered; 180 L/day filtrate; 99 percent reabsorbed; 1 to 2 L urine/day.
• Glucose and amino acids normally fully reabsorbed; glycosuria when blood glucose exceeds tubular capacity (poorly controlled diabetes most common). Protein normally absent (small amounts possible).
• Filtration depends on hydrostatic pressure; reduced by hypotension, low oncotic pressure, tubular obstruction.
• Tubular secretion eliminates potassium, hydrogen ions, ammonia, uric acid, drugs.

B. ADH, Osmolality, Water

• High blood osmolality (low intake) releases ADH: water reabsorbed. Excess water suppresses ADH: diuresis.
• Fixed specific gravity (about 1.010) or fixed osmolality (about 300 mOsm/L) = cannot concentrate or dilute: early sign of kidney disease.
• 1 to 2 percent rise in serum osmolarity triggers thirst. Filtrate osmolality equals blood: 280 to 300 mOsm/kg.
• Typical intake: about 1300 mL drinks plus 1000 mL in food; insensible loss about 800 mL (skin, lungs) and 200 mL (feces). Daily weight is the most reliable fluid measure: 1 lb about 500 mL; 1 kg about 1000 mL.

C. Electrolytes and Blood Pressure

• Diet contains 6 to 15 g sodium chloride and 8 g potassium chloride; normally an equal amount is excreted.
• Renin-angiotensin-aldosterone: low renal arteriole pressure (shock, dehydration, low sodium chloride delivery) releases renin; renin converts angiotensinogen to angiotensin I, then angiotensin II (most powerful vasoconstrictor); aldosterone increases sodium and water retention; BP rises; renin stops when BP normal. Failure of this feedback is a primary cause of hypertension.

D. Acid-Base

• Serum pH 7.35 to 7.45. Kidneys reabsorb and generate bicarbonate, excrete acid (about 70 mEq/day), make ammonia. Urine pH can drop to 4.5. Buffers: phosphate and ammonia (ammonium). Phosphoric and sulfuric acids from protein breakdown cannot be excreted by the lungs.

E. Renal Clearance and GFR

• Creatinine clearance (24-hour urine with serum creatinine midway) approximates GFR: (urine volume in mL/min x urine creatinine) / serum creatinine.
• Normal GFR about 125 mL/min (up to 200). Creatinine clearance is the best approximation of renal function.

F. Other Functions

• Erythropoietin released with low oxygen tension (anemia, hypoxia, poor flow).
• Activates vitamin D (1,25-dihydroxycholecalciferol) for calcium balance.
• Prostaglandins, prostacyclin, thromboxanes, leukotrienes regulate renal blood flow.
• Waste excretion: urea 25 to 30 g/day; creatinine, phosphates, sulfates, uric acid, drug metabolites.

G. Bladder Storage and Emptying

• Sympathetic (T10 to T12) allows filling; parasympathetic (S1 to S4) mediates voiding. Filling pressure must stay under 40 cm H2O to protect kidneys.
• First urge at 150 to 200 mL; strong urge and discomfort at 400 to 500 mL. Neurologic problems may allow up to 2000 mL with little urge.
• Bladder holds urine 2 to 4 hours by day; 6 to 8 hours at night (vasopressin). Voids about 8 times per 24 hours.
• Voiding pressure 20 to 40 cm H2O in women; higher in men over 45 (prostate); BPH raises voiding pressure, making it hard to start and maintain flow.
• Spinal cord injury: reflex contraction persists, voluntary control lost, residual urine remains.
• Normal postvoid residual: no more than 50 mL in middle age; under 50 to 100 mL in older adults.

H. Older Adults

• GFR falls about 1 mL/min per year after 35 to 40; less renal reserve; more AKI and CKD risk; drug accumulation and interactions.
• Diminished thirst: hypernatremia and fluid deficit (rare before 60).
• Incomplete emptying (weak detrusor, BPH); vaginal and urethral atrophy (low estrogen).
• Urinary incontinence: 15 to 30 percent community, 50 percent institutionalized, 30 percent hospitalized; often treatable.
• Urologic symptoms may mimic appendicitis, peptic ulcer, cholecystitis.
• Avoid dehydration during test prep. Concept Mastery Alert: teach older adults to drink throughout the day even without thirst.

III. Assessment

A. Health History

• Chief concern; dysuria (location, character, triggers); prior UTIs; fever, chills; prior tests, surgeries, catheters; hesitancy, straining, frequency; incontinence (stress, urge, overflow, functional); hematuria or color/volume change; nocturia; stones; women: number and type of deliveries, forceps, vaginal infection, contraception; anuria or kidney problems; genital lesions or STIs; tobacco, alcohol, drugs; all medications.
• Risk factors (Table 47-1): advanced age (incomplete emptying, urosepsis); BPH (obstruction); diabetes (CKD, neurogenic bladder); gout, hyperparathyroidism, Crohn disease, ileostomy, immobilization (stones); hypertension (CKD); instrumentation (UTI); MS, Parkinson, spinal cord injury (neurogenic bladder, incontinence); chemical exposure (AKI); obstetric injury (incontinence); pregnancy (proteinuria, frequency); pelvic radiation (cystitis, fibrosis, fistula); pelvic surgery (ureter or bladder trauma); sickle cell, multiple myeloma (CKD); strep throat, impetigo, nephrotic syndrome (CKD); SLE (nephritis).
• Multiparous women with vaginal births: high risk for stress incontinence.

B. Pain (Table 47-2)

• Severity relates to suddenness of distention, not its extent. Kidney disease may be painless.
• Kidney: costovertebral angle (CVA), may extend to umbilicus; dull constant ache; sudden capsule distention gives severe, sharp, stabbing colicky pain; nausea, vomiting, diaphoresis, pallor, shock (obstruction, stone, clot, acute pyelonephritis, trauma).
• Bladder: suprapubic; dull, continuous, worse with voiding; urgency (overdistention, infection, interstitial cystitis, tumor).
• Ureteral: CVA, flank, lower abdomen, testis or labium; severe sharp colicky; nausea, vomiting, paralytic ileus (stone, edema, stricture, clot).
• Prostatic: perineum and rectum; vague fullness, back pain; frequency, urgency, dysuria, nocturia (cancer, prostatitis).
• Urethral: along penis or urethra to meatus; worst during and right after voiding (bladder neck irritation, urethral infection, trauma, foreign body).

C. Changes in Voiding (Table 47-3)

• Normal: about 8 voids, 1 to 2 L per 24 hours.
• Increased urgency and frequency with decreasing volumes strongly suggests retention: may need immediate catheterization.
• Hematuria causes: GU cancer, glomerulonephritis, stones, TB, blood dyscrasias, trauma, extreme exercise, sickle cell, leukemia.
• Nocturia causes: decreased concentrating ability, heart failure, diabetes, incomplete emptying, bedtime fluids, nephrotic syndrome, cirrhosis with ascites.
• Polyuria: diabetes, DI, diuretics, excess fluids, lithium toxicity.
• Proteinuria: AKI or CKD, nephrotic syndrome, exercise, heatstroke, heart failure, diabetic nephropathy, multiple myeloma.
• GI symptoms (nausea, vomiting, diarrhea, distention) from shared innervation and nearby organs. Unexplained anemia (anemia of inflammation): fatigue, dyspnea, exercise intolerance.

D. Physical Assessment

• Head to toe, focus on abdomen, suprapubic region, genitalia, lower back, legs.
• Kidneys usually not palpable; right easier (lower). CVA tenderness (12th rib and spine) suggests renal dysfunction. Auscultate upper quadrants for bruits (renal artery stenosis, aortic aneurysm). Check for ascites.
• Bladder: percuss after voiding from umbilicus downward (tympany to dullness); palpable only if moderately distended (smooth, firm, round midline mass); dullness after voiding = incomplete emptying. Portable bladder ultrasound after voiding detects retention (reduced UTIs and length of stay in stroke patients).
• Men: DRE yearly from 40 with PSA; draw PSA before DRE (DRE raises PSA). Inguinal nodes, hernia, varicocele.
• Women: vulva, meatus, vagina; urethral diverticula; estrogen effect; prolapses: urethrocele, cystocele (bladder into vagina), pelvic prolapse (cervix), enterocele (bowel), rectocele (rectum). Cough or Valsalva for leakage; Marshall-Bonney maneuver (support urethra, repeat Valsalva).
• Edema (face, ankles, sacrum) and weight gain (1 kg about 1000 mL).
• Knee reflexes (sacral innervation shared with continence); gait and heel-to-toe walking for supraspinal causes.

IV. Diagnostic Evaluation

• Provide privacy and explanation; anxiety causes guarding (reflex inhibition of voiding).
• Urodynamic testing (Chart 47-4): interview; urethral catheters (and rectal or vaginal catheter) measure pressure; EMG electrodes; bladder filled one or more times; afterward frequency, urgency, dysuria, slight hematuria (drink fluids; avoid caffeine, carbonated, alcoholic drinks; warm sitz bath); report fever, chills, back pain, continued dysuria or hematuria; finish prophylactic antibiotic.
• Plan of care (Chart 47-5): assess understanding; explain in plain language; encourage fluids; sitz baths; analgesics and antispasmodics; privacy; correct terminology.

A. Urinalysis and Culture

• Color (Table 47-4): colorless to pale (dilute, diuretics, alcohol); yellow to milky white (pyuria, infection, vaginal cream); bright yellow (multivitamins); pink to red (blood, menses, surgery, beets, blackberries, phenytoin, rifampin, senna); blue or blue-green (dyes, methylene blue, Pseudomonas, amitriptyline, triamterene); orange to amber (concentrated urine, fever, bilirubin, phenazopyridine, nitrofurantoin); brown to black (old RBCs, bilirubin, melanin, iron, metronidazole, methyldopa).
• Also clarity, odor, pH, specific gravity, protein, glucose, ketones, microscopic sediment (RBCs, WBCs, casts, crystals, bacteria). Culture and sensitivity guide antibiotics.
• Hematuria: more than three RBCs per high-power field; more common in women; infection, stones, neoplasm, bleeding disorders, warfarin, heparin; confirm with 24-hour collection.
• Proteinuria: up to 150 mg/day normal; dipstick (30 to 1000 mg/dL) is a screen only; cannot detect early diabetic nephropathy. Microalbuminuria (20 to 200 mg/dL) is an early sign of diabetic nephropathy. Transient benign causes: fever, strenuous exercise, prolonged standing. Persistent: glomerular disease, malignancy, collagen disease, diabetes, preeclampsia, hypothyroidism, heart failure, heavy metals, NSAIDs, ACE inhibitors.
• Specific gravity: normal 1.005 to 1.025; dipstick most common; refractometer most accurate; urinometer least accurate. Fixed specific gravity in kidney disease. Low: DI, glomerulonephritis, severe renal damage. High: diabetes, nephritis, fluid deficit.
• Osmolality: most accurate measure of concentrating ability; serum 275 to 290 mOsm/kg; urine 200 to 800 (random 50 to 1200); 24-hour 300 to 900.

B. Renal Function Tests (Table 47-5)

• Results may stay normal until GFR falls under 50 percent of normal.
• Creatinine clearance: tracks progression; normal ranges (mL/min/1.73 m2) fall with each decade of age and differ by sex (see Table 47-5; extracted table was garbled).
• Serum creatinine: men 0.6 to 1.2 mg/dL; women 0.4 to 1.0 mg/dL.
• BUN: 8 to 20 mg/dL (over 60: 8 to 23); affected by protein intake, tissue breakdown, fluid volume.
• BUN to creatinine ratio about 10:1; elevated ratio = hypovolemia; normal ratio with both elevated = intrinsic kidney disease.

C. Imaging

• KUB x-ray: size, shape, position, abnormalities.
• Ultrasound: noninvasive; requires a full bladder (encourage fluids before).
• Bladder ultrasound (portable scanner): frequency, inability to void after catheter removal or surgery, postvoid residual, need for catheterization; gel about 2.5 cm (1 inch) above symphysis pubis.
• CT and MRI: masses, stones, infection, trauma, metastases. MRI: remove all metal, credit cards, metal-backed patches (nicotine, nitroglycerin: burns); no metal equipment in room; screen implanted devices (cardiac devices, aneurysm clips, hardware, valves, IUDs); cochlear implants inactivated; sedation for claustrophobia; avoid alcohol, caffeine, smoking 2 hours and food 1 hour before; hold iron supplements.
• Nuclear scans: technetium (perfusion), I-123 hippurate (function, GFR); drink fluids afterward to excrete isotope.
• IV urography (IVP, excretory urography, infusion drip pyelography): contrast shows kidneys, ureters, bladder; nephrotomogram distinguishes masses from cysts.
• Retrograde pyelography: catheters via cystoscope into renal pelvis; complications: infection, hematuria, ureteral perforation.
• Cystography: contrast via catheter; reflux and bladder injury. Voiding cystourethrography: images while voiding; identifies vesicoureteral reflux.
• Renal angiography: femoral (or axillary) catheter; trauma, cyst vs tumor, hypertension, pre-transplant. Before: laxative, mark peripheral pulses. After: VS until stable; BP in opposite arm if axillary; check site for swelling and hematoma; compare pulses, color, temperature of extremities; cold compresses. Complications: hematoma, thrombosis or dissection, false aneurysm, renal function change.
• MAG3 renogram: radioactive tracer; lie still about 35 minutes.
• Contrast precautions (Chart 47-6): emergency equipment (epinephrine, steroids, vasopressors, oxygen, airway, suction); ask about iodine, shellfish, seafood allergy; caution in older adults, multiple myeloma, renal impairment, volume depletion; hold nephrotoxic drugs (vancomycin, amphotericin B, metformin, NSAIDs); check kidney function; IV hydration before; warn of warmth, facial flushing, seafood-like taste; monitor for allergic reaction and urine output; maintain hydration.

D. Endoscopic Procedures

• Cystoscopy: visualizes urethra, bladder, ureteral orifices, prostatic urethra; can collect urine from each kidney, biopsy, remove stones. Lower tract: patient awake, viscous lidocaine beforehand. Upper tract: sedation or general anesthesia; NPO several hours.
• After cystoscopy: expect burning on voiding, blood-tinged urine, frequency; moist heat and warm sitz baths; monitor for retention (especially BPH; edema); antispasmodic (flavoxate) for temporary retention; intermittent catheterization if needed; watch for UTI and obstruction.

E. Biopsy

• Renal and ureteral brush biopsy via cystoscope and ureteral catheter: tumor vs stone vs clot vs artifact.
• Kidney biopsy: indications: unexplained AKI, persistent proteinuria or hematuria, transplant rejection, glomerulopathy. Coagulation studies first. Contraindications: bleeding tendency, uncontrolled hypertension, sepsis, solitary kidney, large polycystic kidneys, kidney neoplasm, UTI, morbid obesity.
• Preparation: fast 6 to 8 hours; IV line; save a prebiopsy urine specimen for comparison. Needle biopsy: prone with sandbag under abdomen; patient holds breath during insertion (keeps kidney still); local anesthetic; imaging guidance. Open biopsy through flank incision.
• After: VS for bleeding and infection; internal bleeding signs (pallor, dizziness, flank or back pain); IV fluids to clear kidneys and prevent clots; hematuria usually clears in 24 to 48 hours; bed rest and pressure dressing as prescribed; check puncture site; analgesics.

High-Yield Numbers

Priority Nursing Actions and Red Flags

• Increasing urgency and frequency with small voids: suspect retention; bladder scan; catheterize if acute.
• Older adults: encourage fluids even without thirst; prevent dehydration before tests.
• Contrast studies: allergy history, kidney function, hold metformin and NSAIDs, hydrate, emergency equipment ready.
• MRI: remove metal-backed patches (burns), screen implants.
• After cystoscopy: watch for urine retention (especially BPH) and UTI.
• After kidney biopsy: bleeding (VS, flank pain, dizziness, pallor), bed rest, compare urine to prebiopsy sample.
• After renal angiography: check site, distal pulses, color, temperature; BP on opposite arm if axillary approach.
• Draw PSA before DRE.

Medications and Agents

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• INDEX