Kidney Stones Lecture Notes

Introduction

• Kidney stones, also known as urinary stones, urolithiasis, or nephrolithiasis.
• Can also be referred to as renal or urinary calcula.

Anatomy Review

• Adrenal Glands: Endocrine glands located above the kidneys.
• Kidneys:
  • Responsible for urine formation.
  • Urine flows down into the ureter and is stored in the bladder.
  • When full, urine is expelled through the urethra.
• Ureter Constriction Sites:
  • Pelvic ureteric junction
  • Pelvic brim
  • Vesiculoureteric junction (connection between ureter and bladder)
• Kidney Functions:
  • Filters blood, disposes of waste, regulates blood pressure, electrolyte balance.
  • Produces hormones such as erythropoietin and active vitamin D.
• Kidney Structure:
  • Composed of medulla (pyramids) and cortex.
  • Medullary pyramids drain into the renal pelvis.

Nephrons

• Functional units of kidneys that filter blood.
• Key parts of the nephron:
  • Bowman's Capsule:
    • Afferent arteriole brings blood to glomerulus, efferent arteriole exits.
  • Tubule Pathway:
    • Proximal convoluted tubule → Loop of Henle → Distal convoluted tubule → Collecting duct.
• Crystal-like structures (precipitants of electrolytes) can form in the nephron, becoming kidney stones if large enough.

Kidney Stones Formation

• Obstruction:
  • Can occur in tubules or ureters, leading to increased pressure and irritation (renal colic).
• Common Symptoms:
  • Acute flank pain (may radiate to groin/back), fever, nausea, vomiting, urinary frequency/urgency, hematuria.

Risk Factors

• High protein/salt diet, male Caucasian, obesity, dehydration.
• Medications: Antacids, carbonic anhydrase inhibitors, sodium/calcium medications.
• Family history and conditions like crystal urea.

Mechanisms of Stone Formation

• Increased urinary solute concentration (calcium, uric acid, calcium oxalate, sodium).
• Decreased stone-forming inhibitors (citrate, magnesium).
• Urine supersaturation leads to crystal formation.
• Types of stones:
  • Calcium Oxalate Stones (75% of cases)
  • Calcium Phosphate
  • Struvite (related to UTIs)
  • Uric Acid
  • Cystine

Investigations

• Tests include:
  • Full blood count, CRP, electrolytes (calcium, phosphate, oxalate, urate, cysteine, xanthine).
  • Urinalysis (may show hematuria)
  • Imaging (X-ray, ultrasound, CT scan).

Management of Kidney Stones

• Acute Presentation:
  • Fever, nausea, vomiting, acute flank pain, tachycardia, hematuria.
  • Triad for diagnosis: Fever, vomiting, acute flank pain.
• Initial Management:
  • Analgesia and IV fluids.
• Spontaneous Passage:
  • Small stones (<0.5 cm) often pass without intervention.
• Surgical Interventions:
  • Percutaneous Nephrostomy: Drain urine from obstructed kidney.
  • Ureteric Stent Insertion: Bypass blockage in the ureter.
  • Percutaneous Nephrolithotomy: Remove stones >2 cm from kidney.
  • Endoscopic Procedures: Break down stones in kidneys or ureters.
  • Extracorporeal Shockwave Lithotripsy: Uses shockwaves to fragment stones for easier passage.

Conclusion

• Understanding kidney stones includes knowledge of anatomy, risk factors, formation mechanisms, and management strategies.