Genitourinary Disorders and Urinary System Physiology Study Guide

Urinary System Physiology and Functions

The urinary system is responsible for several critical physiological processes necessary for maintaining homeostasis within the body.

• Waste Elimination: Processes and eliminates waste products from the blood.
• Homeostatic Regulation: Regulates body fluids, electrolyte balance, and acid-base balance.
• Erythropoietin Production: Produces erythropoietin, which stimulates the bone marrow to produce Red Blood Cells (RBCs), Hemoglobin (Hgb), and Hematocrit (Hct).
• Renin Production: Produces renin, which plays a significant role in hypertension when converted to angiotensin I and angiotensin II.

Differences Between Child and Adult Urinary Systems

There are distinct developmental differences that make children more susceptible to certain complications, particularly dehydration.

• Urine Production Onset: The kidneys begin producing urine at $13$ weeks gestation.
• Immature Concentration Ability: A child’s kidneys are immature at birth and cannot concentrate urine effectively. This leads to a lower specific gravity and less efficient waste removal, contributing to an increased risk of dehydration.
• Fluid Distribution: Children have more extracellular fluid than intracellular fluid, which further increases the risk for dehydration.
• Body Surface Area: A larger body surface area compared to actual body weight results in an increased amount of insensible fluid loss.
• Metabolic Rate: Children possess a higher metabolism, which requires more water to effectively remove body wastes.

Electrolyte Balance and Imbalance

Electrolytes are vital for fluid balance and muscular/nervous system activity.

Sodium ($Na^+$)

Sodium is the primary electrolyte controlling fluid balance in the body. Normal sodium levels range from $135-145\,mEq$.

• Hypernatremia (High Sodium): High sodium in the blood leads to low sodium in the cells. Water leaves the cells via osmosis, causing them to shrink.
  • Signs: Tachycardia, tachypnea, hypotension, thirst, nausea and vomiting, poor skin turgor, decreased urine output, altered level of consciousness (irritability or lethargy), muscle spasms, twitching, and seizures.
• Hyponatremia (Low Sodium): Low sodium in the blood leads to high sodium in the cells. Water enters the cells via osmosis, causing them to swell or burst.
  • Signs: Tachycardia, tachypnea, hypertension, edema, loss of appetite, headache, nausea and vomiting, change in mental status (lethargic or irritable), muscle weakness, cramps, and seizures.

Muscle Activity Control: Potassium, Calcium, and Magnesium

Potassium ($K^+$), Calcium ($Ca^{2+}$), and Magnesium ($Mg^{2+}$) regulate muscular activity and nervous impulse transmissions.

• Inhibition/Relaxation: Low potassium, low calcium, and high magnesium cause muscle relaxation and slow nervous impulse transmissions.
• Irritability/Excitation: High potassium, high calcium, and low magnesium cause muscle irritability and increased transmission of nervous impulses.

Other Mineral Functions and Normal Values

• Calcium ($Ca^{2+}$): promotes blood clotting. Normal range: $8.5-10.5$.
• Phosphorus ($P$): Interacts with calcium for bone growth and produces energy for rapid metabolism. Normal range: $2.5-4.5$ in adults and $4-7$ in children.
• Potassium ($K^+$): Normal range: $3.5-5$.
• Magnesium ($Mg^{2+}$): Normal range: $1.7-2.2\,mg/dL$.

Acid-Base Balance

• Acidosis: Characterized by an excess of hydrogen ions in the body. This is caused by too much $CO_2$ or too little $HCO_3$.
• Alkalosis: Characterized by too few hydrogen ions in the body. This is caused by not enough $CO_2$, an excess of $O_2$, or too much $HCO_3$.
• Regulation:
  • The lungs regulate $CO_2$ and $O_2$ levels.
  • The kidneys regulate $HCO_3$ (bicarbonate) levels.
  • Note: The kidneys take longer to regulate acid-base balance than the lungs.

Fluid Maintenance and Output Calculations

Minimum Urine Output

• The minimum acceptable urine output for a child is $1-2\,mL/kg/hour$.

Holliday Segar Method of Fluid Maintenance

This method calculates the hourly replacement requirements based on body weight:

• First $10\,kg$: $4\,mL/kg/hour$.
• Next $10\,kg$ ($11-20\,kg$): $2\,mL/kg/hour$.
• Weight over $20\,kg$: $1\,mL/kg/hour$.
• Daily Calculation: Multiply the hourly rate by $24$ hours to find the total daily requirement.

Calculation Examples:

• $5\,kg$ child: $4 \times 5 = 20\,mL/hour$.
• $15\,kg$ child: $(4 \times 10) + (2 \times 5) = 40 + 10 = 50\,mL/hour$.
• $30\,kg$ child: $(4 \times 10) + (2 \times 10) + (1 \times 10) = 40 + 20 + 10 = 70\,mL/hour$.

Monitoring Fluid Balance

• Daily Weights: More accurate than intake and output (I&O). Must be performed using the same scale, same clothes, and at the same time of day.
• Intake and Output (I&O):
  • Diapers and Dressings: Weigh on a gram scale. Subtract the weight of the dry item from the weight of the wet or soiled item ($1\,g = 1\,mL$).
  • Ice: Ice melts to half its volume for intake tracking.
  • Intake Criteria: Only liquids or what melts to liquid (e.g., popsicles, jello, ice cream). Solids or semi-solids like pudding, cream of wheat, and oatmeal do not count as liquid intake.
  • Output Criteria: Only liquid diarrhea is counted as output; solid stool is not included.

Common Urinary Diagnostic Tests

• Urinalysis: Checks for infection (blood, leukocytes, nitrites), diabetes (glucose, ketones), dehydration (ketones, increased specific gravity), and protein.
• Urine Culture and Sensitivity (C&S): Crucial to obtain and send to the lab BEFORE administering any antibiotics.
• Specific Gravity (SG): Measures the concentration of the urine.
• Intravenous Pyelogram (IVP): Requires checking for iodine and shellfish allergies. Nowadays, it is frequently replaced by CT scans of the kidneys (with and without contrast).
• Voiding Cystourethrogram (VCUG): An imaging test used to see how the bladder and urethra function during voiding.
• Blood Tests: Blood Urea Nitrogen (BUN), Blood Creatinine, and Creatinine Clearance.

Dehydration

Dehydration occurs when fluid intake is significantly reduced or when a condition causes excessive loss of water and electrolytes, potentially leading to hypovolemia, circulatory collapse, and shock.

Severity and Evaluation

• Mild: Up to $5\%$ weight loss (treated with oral rehydration).
• Moderate: $5-10\%$ weight loss (treated with IV hydration).
• Severe: $10\%$ or more weight loss (treated with IV hydration; may require the ICU).
• Clinical Signs to Report: Dry skin, poor tissue turgor, dry mucous membranes, sunken fontanels, sunken eye sockets, pale skin, poor perfusion, delayed capillary refill ($> 2\,s$), hypotension, decreased body temperature, rapid pulse (tachycardia), tachypnea, lethargy, weak cry, and poor muscle tone.

Interventions and Nursing Considerations

• Rehydration Amounts by Age:
  • Under $1$ year: $1-2$ teaspoons ($5-10\,mL$) every $5-10\,minutes$.
  • Older children: $\frac{1}{2}$ to $1\,ounce$ ($15-30\,mL$) every $20\,minutes$.
• Fluid Replacement for Ongoing Losses:
  • Watery Stool: $10\,mL/kg$ of body weight.
  • Vomiting: $2\,mL/kg$ of body weight.
• IV Therapy: Indicated for moderate to severe dehydration or if PO (oral) fluids are not tolerated; involves normal saline boluses.

Urinary Tract Infections (UTI)

UTIs are one of the most common bacterial infections in childhood.

• Locations: Cystitis (bladder), urethritis (urethra), and pyelonephritis (kidney).
• Causes: Urine refluxing into ureters, incomplete bladder emptying, or inadequate perineal cleansing.
• Pathogen: $E.\,coli$ is responsible for $80\%$ of infections.
• Clinical Manifestations: Frequency, urgency, pain, foul-smelling/cloudy/bloody urine, fever, dehydration, hematuria, and low pH. Lethargy and poor feeding are common in infants.
• Key Indicators:
  • Nitrites on a dipstick almost always indicate infection.
  • Flank pain (costovertebral tenderness) indicates pyelonephritis or renal calculi (kidney stones).
  • Pyelonephritis symptoms: Higher fever, nausea, and vomiting.
• Nursing Interventions:
  • Maintain hydration (PO or IV) and treat fever/discomfort.
  • Administer ordered antimicrobial medications.
  • Prevention Education: Avoid bubble baths, douches, and feminine hygiene sprays. Wear cotton panties and avoid tight pants. Empty the bladder every $3-4\,hours$. Urinate before and after sexual activity. Use cranberry juice to increase urine acidity while pushing fluids. Ensure a high-fiber diet and activity for regular elimination.

Enuresis (Bed-Wetting)

• Nocturnal: Involuntary voiding at night after toilet training (most common form).
• Diurnal: Daytime incontinence; associated with an unstable bladder.
• Bladder Capacity Formula: $\text{Age in years} + 2\,oz$.
• Physical Causes: Heavy sleepers, UTI, excessive fluid or caffeine before bed.
• Psychological Causes: Regression due to stress, rigorous toilet training, anger/resentment (e.g., new sibling), or conversion reaction from sexual abuse.
• Developmental Note: Boys normally achieve control later (around age $6$) than girls (around age $4-5$).
• Interventions: Reassurance, parents education, fluid restriction after the evening meal, potty pagers, and medications for older children (oxybutynin [Ditropan] or desmopressin [DDAVP]).

Nephrotic Syndrome

an autoimmune, typically idiopathic disease where large pores in the kidney's filtering system allow protein to leak into the urine.

• Pathophysiology: Proteinuria leads to hypoalbuminemia (low blood protein). Low protein causes third spacing (massive edema) because water follows protein. The liver compensates by producing more cholesterol, leading to hyperlipidemia.
• Clinical Manifestations: Fatigue, decreased appetite, pitting edema (facial, abdominal/ascites, limbs), weight gain, and golden-yellow, foamy urine.
• Treatment:
  • Supportive care; diuretics are generally ineffective.
  • Steroids: Used to shut down the autoimmune process and induce diuresis.
  • DMARDs: Cyclophosphamide (Cytoxan) if steroids fail.
• Nursing Care: Fluid/sodium restrictions, high protein/low fat diet, infection control, and daily weights (Report weight gain $> 1\,lb/day$ or $> 5\,lb/week$). Teach parents to check urine for protein daily.

Acute Glomerulonephritis (AGN)

Damage to the glomeruli, typically following a toxin release from untreated or partially treated group A beta-hemolytic streptococci.

• Manifestations:
  • Hematuria: Grossly bloody or "smoky brown" color (like coffee or tea).
  • Hypertension: $70\%$ of cases have hypertension severe enough to cause seizures.
  • Oliguria (low output) or anuria (no output).
  • Periorbital edema and elevated BUN/Creatinine.
• Interventions: Supportive care, daily weights, I&O, fluid/sodium restrictions, and antihypertensives/diuretics.
• Timeline: Hematuria can persist for a year; if microscopic hematuria remains after $1$ year, it is classified as chronic glomerulonephritis.

Hemolytic Uremic Syndrome (HUS)

A rare, potentially lethal kidney failure usually caused by bacterial infections like $E.\,coli\,0:157$.

• Symptoms: Bloody diarrhea followed by acute renal failure as toxins attack the kidneys.
• Interventions: Typically requires PICU stay. Treatment includes IV fluids, antibiotics, and often temporary or permanent dialysis to manage dehydration and electrolyte imbalance.

Nephroblastoma (Wilms Tumor)

The most common kidney cancer in young children, usually diagnosed between ages $3-4$.

• Presentation: A large abdominal mass, often felt by parents while playing or by a doctor during a checkup. Hematuria and pain are late findings.
• Treatment: Surgical removal of the tumor and kidney, followed by chemotherapy and radiation. The $5$-year survival rate is $90\%$.
• CRITICAL PRECAUTION: Avoid palpation of the abdomen pre-operatively to prevent tumor rupture.
• Post-op Education: Avoid contact sports and nephrotoxic drugs.

Congenital and Structural Disorders

Bladder Exstrophy

• Condition: Bladder is partially open and exposed on the abdomen at birth.
• Care: Keep the area covered with sterile saline-soaked nonadherent dressings. Perform meticulous skin care to prevent breakdown from constant urine trickling. Position the infant supine pre-operatively.
• Surgery: Multiple surgeries are usually required.

Hypospadias and Epispadias

• Hypospadias: Urethral opening is on the bottom (ventral) of the penis shaft.
• Epispadias: Urethral opening is on the top (dorsal) of the penis shaft.
• Surgical Repair: Done between $6-12$ months old. The child must NOT be circumcised before repair, as the foreskin is needed for reconstruction.
• Post-op Care: Discharge with a Foley or suprapubic tube. No pressure to the groin (do not carry straddling the hip, no tricycles or rocking horses). Notify HCP of infection signs.

Hydrocele

• Condition: Fluid accumulates in the scrotum due to the process vaginalis failing to close after testicular descent in newborns.
• Management: Watchful waiting; usually closes by $12$ months. If not resolved, surgery may be needed to drain fluid and close the opening.

Cryptorchidism

• Condition: Undescended testicles. Testicles must not remain in the abdomen due to high core body temperature which inhibits sperm production and increases malignancy risk.
• Management: Most descend by $3$ months. If not descended by $6$ months, surgery (orchiopexy) is recommended between $6-18$ months.
• Note: The AAP recommends HCG injections for children with Prader-Willi, but the American Urology Association advises against hormone therapy.

Intersex Anomalies and Acquired Disorders

Intersex Anomalies

• Turner Syndrome (45,X): Girls with only one X chromosome; causes short stature and underdeveloped gonads. Managed with growth hormone.
• Klinefelter Syndrome (47,XXY): Extra X chromosome; causes infertility, learning disabilities, impulsivity, and anxiety. Managed with long-acting testosterone.
• Ambiguous Genitalia: Disorder where external genitals are not clearly male or female. Requires chromosome testing. Management involves surgery and hormone therapy based on gender determination.

Acquired Disorders

• Vaginal Foreign Objects: Conduct evaluations for sexual abuse or mental health issues.
• Pediatric Vulvovaginitis: Often fungal; or labial adhesions which may result from FGM complications, poor hygiene, or burns. Treated with Premarin cream.

Questions & Discussion

Question 1: The nurse is preparing to weigh an infant’s diaper for urine output. What should the nurse do first?

• Options: A. Cleanse the infant; B. Weigh a dry diaper; C. Perform hand hygiene; D. Apply a clean diaper to the infant.
• Answer: B. Before weighing a diaper for output, the weight of a dry diaper must be determined to provide a baseline for subtraction.

Question 2: A diagnosis of strep throat was missed in a school-age child. Which potential health problem should the nurse be watchful for?

• Options: A. Hypospadias; B. Neurogenic bladder; C. Urinary tract infection; D. Acute glomerulonephritis.
• Answer: D. Acute glomerulonephritis often follows a severe infection like group A beta-hemolytic streptococci (strep throat).