Kidney Stones Lecture Notes

Introduction to Kidney Stones

• Also known as urinary stones, urolithiasis (urinary tract) or nephrolithiasis (kidneys).
• Other terms: renal or urinary calcula (calcula means stones).

Anatomy of the Urinary System

• Adrenal glands: Endocrine glands located above the kidneys.
• Kidneys: Responsible for urine formation, blood filtration, and waste disposal.
• Urine Pathway:
  • Travels from kidneys down the ureters to the bladder.
  • Stored in the bladder until urination through the urethra.
• Ureter Constriction Sites (where stones can lodge):
  • Pelvic Ureteric Junction
  • Pelvic Brim
  • Vesiculoureteric Junction (between ureter and bladder).

Kidney Function

• Regulates:
  • Blood pressure
  • Electrolyte balance
  • Hormone production (e.g., erythropoietin, vitamin D activation).
• Structure:
  • Medulla pyramids and cortex.
  • Nephrons: Functional units filtering blood, secreting waste, and reabsorbing substances.
  • Nephron Pathway: Bowman's capsule → Proximal convoluted tubule → Loop of Henle → Distal convoluted tubule → Collecting duct.

Formation of Kidney Stones

• Crystals form in nephron tubules due to the accumulation of electrolytes.
• Small crystals can pass, but larger crystals become kidney stones.
• Kidney stones can obstruct the tubule, leading to:
  • Increased pressure and irritation = renal colic (pain).
  • Obstruction in ureter can cause pain due to pressure buildup.

Clinical Presentation

• Symptoms include:
  • Acute flank pain (radiating to back/groin)
  • Fever
  • Nausea and vomiting
  • Urinary frequency and urgency
  • Hematuria (blood in urine).

Risk Factors for Kidney Stones

• High protein and salt diets.
• Demographics: Male, Caucasian, and obese individuals.
• Dehydration.
• Medications: Antacids, carbonic anhydrase inhibitors, sodium and calcium medications.
• Family history and crystal urea.

Mechanism of Stone Formation

• Risk factors lead to:
  • Increased urinary solute concentrations (calcium, uric acid).
  • Decreased stone-forming inhibitors (citrate, magnesium).
• Results in urine supersaturation and crystal formation.

Types of Kidney Stones

1. Calcium Oxalate: 75% of stones.
2. Calcium Phosphate.
3. Struvite: Associated with chronic urinary tract infections.
4. Uric Acid.
5. Cystine.

Investigations for Kidney Stones

• Blood tests: Full blood count, CRP, calcium, phosphate, magnesium levels.
• Urinalysis: May show hematuria.
• 24-hour urine collection for calcium, phosphate, oxalate, urate, cysteine levels.
• Imaging:
  • X-ray, ultrasound (detects hydronephrosis), CT scan.

Management of Kidney Stones

Initial Management

• Acute presentation: Analgesia and IV fluids.
• Most stones < 0.5 cm pass spontaneously.

Surgical Management

• Depends on stone size and location:
  • Percutaneous Nephrostomy: For drainage in cases of obstruction.
  • Ureteric Stent Insertion: Bypasses blockage to allow urine drainage.
  • Percutaneous Nephrolithotomy: For larger stones (>2 cm) in the kidney.
  • Endoscopic Procedures: Break stones within the kidney/ureter.
  • Open Surgery: For stone removal.
  • Extracorporeal Shockwave Lithotripsy: Breaks stones using shockwaves for easier passage.

Summary

• Kidney stones are a significant health issue with various types and treatment options.
• Understanding anatomy, risk factors, and management is crucial for effective treatment.