Kidney Stones and Obstructive Uropathy

Kidney Stones: Types & Risks - Stone Cold Facts

• Types & Radiopacity:

  • Calcium Oxalate (≈80%): Radiopaque. Risks: ↓Fluids, ↑Oxalate/Na/Animal protein, hypercalciuria, hypocitraturia.
  • Struvite (MAP) (≈10-15%): Staghorn, radiopaque. Risks: UTI (urease+ (Proteus)), alkaline urine.
  • Uric Acid (≈5-10%): Radiolucent. Risks: Gout, acidic urine, ↑purines.
  • Cystine (≈1-2%): Faintly radiopaque. Risks: Cystinuria, acidic urine.

• Major Risk Factors:

  • ↓ Fluid intake (primary).
  • Diet: ↑Oxalate, ↑Sodium, ↑Animal protein.
  • Family Hx, metabolic (e.g., hyperpara).

⭐ Most common kidney stones are Calcium Oxalate (≈80%); key dietary risk factor is low fluid intake & high oxalate/sodium/animal protein diet.

Kidney Stones: Clinical Picture & Diagnosis - Symptom & Scan

• Symptoms (Clinical Picture):
  • Renal Colic: Severe, acute, intermittent flank pain.
    • Radiation: "Loin to groin", testes/labia.
  • Hematuria: Gross or microscopic; common (~90%).
  • Nausea/Vomiting: Common.
  • Irritative Voiding: Dysuria, urgency, frequency (stone at VUJ/bladder).
  • Fever/Chills: Suspect infection (obstructive pyelonephritis = emergency!).
• Diagnosis (Investigations & Scans):
  • Urinalysis: Hematuria, pyuria, crystals, pH.
  • Imaging:
    • USG KUB: First-line in pregnancy & children. Detects hydronephrosis, stones.
    • X-ray KUB: Shows radio-opaque stones (Calcium, Struvite). Limited for small/lucent stones.
    • ⭐ > Non-contrast CT (NCCT) KUB is the gold standard. Highly sensitive for most stones (except pure indinavir). Details size, location, density (HU).

Kidney Stones: Management Strategies - Crush & Conquer

• Conservative:
  • Analgesia (NSAIDs), Hydration (>2.5L/day).
  • Medical Expulsive Therapy (MET): For stones <10mm (e.g., Tamsulosin 0.4mg).
• Interventions (Size/Symptom-Driven):
  • ESWL: Renal stones <2cm, proximal ureteric <1cm.
  • URS: Ureteric stones, smaller renal stones; laser lithotripsy.
  • PCNL: Large stones >2cm, staghorn, complex, lower pole.
  • Open surgery: Rare.
• Specific Stone Management:
  • Uric Acid: Allopurinol, K-citrate (urine pH 6.5-7.0).
  • Struvite: Antibiotics, complete removal (often PCNL).
  • Cystine: ↑Fluids, D-penicillamine/Tiopronin, K-citrate (urine pH >7.5).

⭐ For stones <10mm likely to pass, Medical Expulsive Therapy (MET) with alpha-blockers (e.g., Tamsulosin) is often used. Stones >2cm or complex staghorn calculi often require PCNL.

Obstructive Uropathy: Causes, Effects & Fixes - Flow Failures

Blockage to urine flow from calyces to urethra.

• Causes:
  • Intrinsic: Stones, tumors, strictures, BPH.
  • Extrinsic: Retroperitoneal fibrosis, external tumors, pregnancy.
  • Functional: Neurogenic bladder.
• Effects:
  • ↑ Pressure → hydroureter/hydronephrosis.
  • Prolonged: Tubular damage, fibrosis, ↓ GFR, atrophy.
  • Complications: AKI, CKD, infection.
• Features: Pain (flank/suprapubic), anuria/oliguria, voiding issues.
• Diagnosis: Ultrasound (hydronephrosis), CT (level/cause), RFTs.
• Fixes: Relieve obstruction (catheter, PCN, stent), treat cause.

⭐ In elderly males, Benign Prostatic Hyperplasia (BPH) is the most common cause of bilateral hydronephrosis and post-renal acute kidney injury.

High‑Yield Points - ⚡ Biggest Takeaways

• Calcium oxalate: Most common kidney stone type.
• Struvite stones: Associated with UTIs (Proteus); form staghorn calculi.
• Uric acid stones: Radiolucent; manage with urine alkalinization.
• Cystine stones: Hexagonal crystals, genetic (autosomal recessive).
• Renal colic investigation: NCCT KUB is the investigation of choice.
• Obstructive uropathy: Leads to hydronephrosis and post-renal AKI.
• BPH: Common cause of bilateral urinary obstruction in older men.