Pathophysiology of Kidney Stones

Kidney stones develop through a process of mineral crystallization and clumping within the urine. This happens when urine becomes supersaturated with stone-forming substances.

The formation process typically begins in the kidney’s collecting ducts or renal papillae. From there, small crystals may move into the renal pelvis, the central collecting area of the kidney, where they can grow larger.

Problems arise when these stones become too large to pass naturally through the ureters, the tubes connecting the kidneys to the bladder. This blockage can obstruct urine flow, potentially leading to kidney damage due to back pressure. Stones that successfully reach the bladder may either be expelled during urination or, less favorably, increase in size and obstruct the urethra, the tube through which urine exits the body. In some cases, bladder stones can also form directly within the bladder itself.

The prevalence of different kidney stone types varies globally. This variation is influenced by a mix of factors such as:

• Dietary habits

• Environmental conditions

• Genetic predispositions

• Chronic urinary tract infections

• Stasis of urine (urine remaining too long in the urinary tract)

• Overproduction of substances that promote stone formation

Causes of Kidney Stones

1. Metabolic Diseases: Certain health conditions can disrupt the body’s metabolism, leading to elevated levels of stone-forming substances in the urine. Examples include:

   • Hyperparathyroidism: Overactive parathyroid glands causing high calcium levels.

   • Renal Tubular Acidosis: A condition affecting the kidney’s ability to manage acid balance.

   • Medications: Certain drugs can increase stone risk, such as:

     • Diuretics (certain types can increase calcium excretion)

     • Excessive Vitamin C and D intake

     • Antacids (containing calcium)

     • Acetazolamide (Diamox)

     • Indinavir (Crixivan)

2. Diet: What you eat and drink plays a significant role in urine composition and stone formation:

   • High Protein Intake: Can increase uric acid excretion.

   • Excessive Tea or Fruit Juices: May elevate urinary oxalate levels.

   • High Calcium and Oxalate Intake: Combined with low fluid intake can concentrate urine, increasing stone risk.

   • Inadequate Fluid Intake: Reduces urine volume and concentrates solutes.

3. Climate: Hot or arid climates can increase the risk of dehydration:

   • Warm Climates: Lead to increased fluid loss through perspiration.

   • Dehydration: Results in low urine volume and higher solute concentration, promoting stone formation.

4. Congenital and Inherited Diseases: Genetic factors can predispose individuals to kidney stones:

   • Family History: Having a family history of kidney stones increases risk.

   • Cystinuria: An inherited disorder causing excessive cystine excretion.

   • Gout: Associated with high uric acid levels.

   • Renal Tubular Acidosis (inherited forms)

   • Familial Hypercalciuria Hypercalcemia (FHH): Genetic conditions leading to high calcium levels.

   • Primary Oxaluria: A rare genetic disorder causing overproduction of oxalate.

5. Slow Urine Flow: When urine flow is sluggish, it allows more time for crystals to accumulate and potentially form stones:

   • Urine Stasis: Slow urine movement enables crystal buildup.

   • Damage to Urinary Tract Lining: Crystal accumulation can irritate and damage the urinary tract lining, creating sites for stone formation.

   • Reduced Inhibitor Substances: Slow flow may reduce the effectiveness of natural substances in urine that prevent crystal aggregation.

Clinical Manifestations

Symptoms of kidney stones vary depending on factors like stone location, blockage severity, presence of infection, and swelling (edema). Symptoms can range from mild discomfort to severe pain.

Stones in Renal Pelvis

• Intense, Deep Ache: Felt in the costovertebral region (area between the ribs and spine).

• Hematuria: Blood in the urine.

• Pyuria: Pus in the urine, indicating infection.

• Radiating Pain: Pain that extends anteriorly and downwards:

  • In females: towards the bladder.

  • In males: towards the testes.

• Renal Colic: Acute, severe pain characterized by waves, often accompanied by:

  • Nausea and vomiting.

  • Tenderness in the costovertebral area.

• Abdominal Discomfort

• Diarrhea

Ureteral Colic (Stones Lodged in Ureter)

• Excruciating Colicky Pain: Acute, severe, wave-like pain.

• Radiating Pain: Pain that travels down the thigh to the groin and genitalia.

• Frequent Urge to Void: Feeling the need to urinate often.

• Small Urine Volume: Passing only a small amount of urine when attempting to void.

• Hematuria: Blood in the urine, often present due to the stone’s abrasive action on the ureter lining.

• Associated Symptoms: Pallor (paleness), sweating, vomiting, increased urinary frequency, painful urination (dysuria), and hematuria.

Stones Lodged in Bladder

• Urinary Tract Irritation Symptoms: Similar to urinary tract infections (UTIs).

• Hematuria: Blood in the urine.

• Urinary Retention: Inability to urinate if the stone blocks the bladder neck.

• Urosepsis (potential): Severe infection of the urinary tract and bloodstream if an infection is present with the stone.

• Increased Urinary Frequency

• Dysuria: Painful urination.

• Hematuria: Blood in urine.

• Severe Intraurethral or Perineal Pain: If trigonitis (inflammation of the bladder trigone) occurs.

• Distended Bladder: If urine outflow is obstructed.

Diagnosis of Renal Stones

Suspicion of kidney or ureter stones arises from a patient’s history of colicky abdominal pain accompanied by blood in the urine (hematuria).

Confirmation and further investigation typically involve:

• Imaging Studies:

  • X-rays (KUB): X-rays of the kidneys, ureters, and bladder to visualize radiopaque stones (calcium stones).

  • Ultrasonography: Ultrasound imaging to detect stones and assess kidney structure.

• Intravenous Urography (IVU) or Retrograde Pyelography: Contrast imaging techniques to show:

  • Hydronephrosis (kidney swelling due to urine backup).

  • Stone impaction location.

• CT Scan: Computed Tomography scan, especially useful for:

  • Confirming non-radiopaque stones like uric acid stones, which may not be visible on standard X-rays.

• Laboratory Tests:

  • Urinalysis: To assess urine for crystals, blood, infection.

  • Serum Calcium and Uric Acid Levels: To evaluate for metabolic factors contributing to stone formation.

  • Blood Chemistries: General blood tests to assess kidney function and electrolyte balance.

  • 24-Hour Urine Test: To measure:

    • Calcium, uric acid, creatinine, sodium excretion.

    • Urine pH, to help determine stone type and risk factors.

• Complete Blood Count (CBC):

  • Hemoglobin/Hematocrit (Hb/HCT): To assess:

    • Dehydration (elevated levels).

    • Polycythemia (increased red blood cell production, which can encourage solid precipitation).

    • Anemia (low levels, indicating hemorrhage or kidney dysfunction).

• Cystourethroscopy: A procedure using a thin, lighted scope to directly visualize:

  • Bladder and urethra.

  • Presence of stones and any obstructive effects.

Management of Kidney Stones

Acute Attack Management:

The primary aims during an acute kidney stone attack are to:

• Alleviate Pain: Provide effective pain relief.

• Maintain Renal Function: Support adequate kidney function.

• Prevent Complications: Avoid secondary issues like infection or obstruction.

• Provide Education: Inform the patient about the disease, prognosis, and treatment plan.

Medical management also focuses on:

• Stone Eradication: Removing the stone.

• Stone Type Determination: Analyzing the stone composition to guide prevention.

• Nephron Protection: Preventing kidney tissue damage.

• Infection Control: Treating any associated infections.

• Obstruction Relief: Addressing any urinary flow blockage.

1. Pain Relief and Rest: During acute renal colic (severe pain), rest is recommended to help manage discomfort. Applying warmth to the painful area can also provide relief.

2. Narcotic Analgesics: Strong pain relievers like morphine may be necessary to manage severe renal colic.

3. Alpha-Blockers: For stones less than 5mm in diameter, alpha-blockers like tamsulosin can aid in stone passage by relaxing ureteral muscles.

4. Increased Fluid Intake: Drinking plenty of fluids is crucial to help flush out smaller stones. Unless contraindicated due to vomiting, patients should aim for 8-10 glasses of water daily or receive IV fluids to maintain dilute urine.

5. Vital Signs Monitoring: Regularly monitor temperature, pulse, respiration, and blood pressure. Observe for signs of infection, such as dark or cloudy urine with abnormal odor.

6. Antiemetics: Prochlorperazine or similar medications can be given to manage nausea and vomiting.

7. Infection Management: Investigate for and treat any urinary tract infections promptly with appropriate antibiotics.

8. Extracorporeal Shock Wave Lithotripsy (ESWL): For larger stones (over 1cm), ESWL can be used to break stones into smaller fragments that can be passed in urine.

9. Chemolysis (Stone Dissolution): Chemical dissolution may be considered for patients who are not suitable for other therapies or have stone types that are easily dissolved (e.g., struvite stones).

10. Surgical Intervention: For large, impacted stones, endoscopic surgery or open surgery (nephrolithotomy or ureterolithotomy) may be required. Surgical removal is typically needed in a small percentage of cases (1-2%).

Continuous Care/Prevention of Further Kidney Stone Development:

1. Dietary Modifications:

   • Moderate Protein Intake

   • Sodium Restriction

2. High Fluid Intake: Aim for 3-4 liters of fluids daily to maintain dilute urine.

3. Calcium-Rich Diet (for Oxalate Stone Prevention): Adequate calcium intake from sources like milk, cheese, yogurt, beans, dried fruits, and fish with fine bones can help reduce oxalate stone formation.

4. Oxalate-Restricted Diet: Limit foods high in oxalate, such as peanuts, spinach, rhubarb, cabbage, tomatoes, chocolate, cocoa, and tea.

5. Thiazide Diuretics: May be prescribed for calcium stones in patients with hypercalciuria to reduce urinary calcium excretion.

6. Allopurinol: Used to prevent urate stones in patients with hyperuricemia by reducing uric acid production.

7. Vitamin D Avoidance: Limit or avoid vitamin D supplements as they can increase calcium absorption and excretion, potentially increasing calcium stone risk.

8. Calcium Lactate or Cholestyramine:

   • Calcium lactate can be given to bind oxalate in the gut, reducing oxalate absorption.

   • Cholestyramine can also bind oxalate in the gastrointestinal tract to prevent its absorption for calcium oxalate stones.

9. Cystine Stone Management:

   • Alpha-penicillamine and tiopronin may be prescribed to prevent cystine crystallization in cystine stones.

10. Potassium Citrate: May be given for all stone types to maintain alkaline urine, which can help prevent stone formation.

SPECIFIC NURSING MANAGEMENT

1. Pain Management: Regularly assess pain levels using a pain scale. Administer prescribed pain medications and evaluate their effectiveness. Document pain assessments and medication administration.

2. Fluid Intake Promotion: Encourage oral fluid intake to achieve high urine output. Explain the importance of hydration in stone passage and prevention.

3. Vital Signs Monitoring: Monitor and record vital signs (blood pressure, heart rate, temperature) regularly to detect signs of infection or complications.

4. Urine Straining: Provide and instruct the patient on using a urine strainer to collect any passed stone fragments for laboratory analysis. Document any stones or fragments collected.

5. Hematuria Assessment: Monitor urine for blood, noting the color and amount. Document findings.

6. Patient Education: Educate the patient about kidney stones, treatment plans, prevention strategies, and lifestyle modifications. Ensure understanding and address any questions.

7. Nutritional Counseling: Provide dietary guidance on a balanced diet, emphasizing fluid intake and appropriate limitations on oxalate, sodium, and animal protein as indicated. Refer to a dietitian if needed.

8. Encourage Ambulation: Promote activity and walking, as mobility can aid in stone passage.

9. Medication Administration: Administer prescribed medications (analgesics, alpha-blockers, antibiotics, etc.) as ordered and monitor for therapeutic and adverse effects.

10. Infection Monitoring: Assess for signs of urinary tract infection (fever, chills, cloudy/foul-smelling urine) and report any concerns to the healthcare provider.

11. Prevention Education: Discuss long-term preventive measures, including sustained high fluid intake, dietary adjustments, and medication adherence to reduce stone recurrence risk.

12. Emotional Support: Acknowledge the pain and distress associated with kidney stones. Offer emotional support, address anxieties, and provide reassurance regarding treatment and management.

Diagnosis

Nursing Diagnoses

• Acute pain related to inflammation, obstruction, and abrasion of the urinary tract.

• Deficient knowledge regarding prevention of recurrence of renal stones.

Nursing Plan

Assessment

• Acute Pain: Patient experiencing acute pain due to tissue injury, as indicated by reports of cramping pain, agitation, vocalizations (moaning), and facial grimacing.

• Impaired Urinary Elimination: Altered Urinary Elimination patterns associated with bladder inflammation or obstruction due to calculi, renal, or ureteral irritation, manifested by urinary urgency, increased frequency (oliguria), and hematuria.

• Risk for Deficient Fluid Volume: Potential for Deficient Fluid Volume related to nausea and vomiting.

Nursing Diagnosis

• Acute Pain related to tissue trauma evidenced by reports of colicky pain, restlessness, moaning, facial mask of pain.

• Impaired Urinary Elimination related to inflammation or obstruction of the bladder by calculi, renal or ureteral irritation as evidenced by urgency and frequency of urination(oliguria) and haematuria.

• Risk for Deficient Fluid Volume may be related to nausea and vomiting.

Expected Outcomes/Goals

• Acute Pain:

  • Patient verbalizes pain reduction and management of spasms.

  • Patient demonstrates relaxed demeanor and ability to rest/sleep adequately.

• Impaired Urinary Elimination:

  • Patient will void urine in sufficient quantities and a regular pattern.

  • Patient will exhibit no indications of urinary obstruction.

• Risk for Deficient Fluid Volume:

  • Maintain adequate fluid balance, evidenced by stable vital signs and weight within normal parameters.

Interventions

• Acute Pain:

  • Assess and document pain characteristics: location, duration, intensity (using 0-10 scale), and radiation.

  • Record nonverbal pain cues, including vital sign changes (elevated BP/pulse), restlessness, and moaning.

• Impaired Urinary Elimination:

  • Monitor and document fluid intake and output, noting urine characteristics.

  • Encourage ambulation as tolerated.

  • Promote adequate fluid hydration.

  • Assess reports of bladder fullness; palpate suprapubic area for distention.

  • Observe for decreased urine output and signs of edema (periorbital, dependent).

• Risk for Deficient Fluid Volume:

  • Monitor and record fluid intake, output, and daily weight.

  • Encourage fluid consumption of 3-4 Liters per day, respecting cardiac limitations.

Rationale

• Acute Pain:

  • Facilitates assessment of obstruction site and stone progression.

  • Provides justification for pain etiology and communication needs with healthcare team regarding pain changes and characteristics.

• Impaired Urinary Elimination:

  • Provides data on renal function and potential complications (infection, hemorrhage).

  • Promotes natural stone passage.

  • Calculi can irritate nerves, leading to urinary urgency.

  • Increased fluids help eliminate bacteria, blood, debris, and aid stone passage.

  • Urinary retention can cause tissue distension (bladder, kidneys) and increase risk of infection and renal failure.

• Risk for Deficient Fluid Volume:

  • Comparison of intake and output assists in assessing renal stasis or impairment.

  • Maintaining fluid balance supports homeostasis and promotes a “flushing” effect to aid stone expulsion.

Evaluation

• Acute Pain: Patient reported no pain episodes. Patient appeared relaxed and able to sleep adequately.

• Impaired Urinary Elimination: Patient successfully voided sufficient urine volumes in a regular pattern. Urinary obstruction resolved.

• Risk for Deficient Fluid Volume: Potential diagnosis; fluid volume deficit did not develop.