Urinary Tract Obstructions – Kidney Stones (Urolithiasis, Renal Calculi)

Types & Causes:

• Kidney stones (also called calculi or urolithiasis) can develop anywhere along the urinary tract.
• Composed of crystallized solutes:
  • Calcium salts: most common (~75% calcium oxalate), especially in alkaline urine.
  • Uric acid: linked to hyperuricemia, gouty arthritis, and high purine diets (e.g., high protein diets).
  • Sometimes struvite (Mg) stones due to UTI.
  • Sometimes cystine stones, due to genetic disorders (creating too much cystine amino acid).

Risk Factors:

• Dehydration: too little fluid intake, abuse of laxatives, concentrates urine, promoting crystallization.
• Infections: bacteria can lead to stone formation or incorporate into stones.
• Immobility: due to stasis of urine
• Genetics: family history increases susceptibility.
• Diet: high salt, protein, or sugar intake. Foods high in oxalates, such as spinach, Swiss chard, and chocolate

• Hyperparathyroidism: Excessive parathyroid hormone increases calcium release from bones, leading to hypercalcemia, increases risk of calcium-based stones

• Other factors: obesity, metabolic disturbances, or certain metabolic diseases.

Formation & Pathology:

• Excess solutes crystallize and grow, forming stones.
• Stones can remain small and asymptomatic or grow large enough to cause problems.
• Obstruction:  Stones lodged in the ureter block urine flow.

Possible Complication:

• • causes hydronephrosis—urine buildup in the kidney, increases pressure, compresses blood vessels, reduces renal blood flow (ischemia), damages nephrons, and causes necrosis and atrophy.

Symptoms & Signs:

• Small stones: Usually silent (asymptomatic) or cause mild irritation.
• Large stones or obstructing stones:
  • Flank pain: Due to distension of the kidney capsule.
  • Renal colic: Severe, episodic spasm in flank area radiating towards groin as the stone moves down the ureter.  Pain flares and subsides as the stone is pushed through the ureter.
  • Nausea and vomiting, cool moist skin, rapid pulse
  • Hematuria: Blood in urine from ureter or bladder irritation.
  • Infection signs: Fever, chills if infection occurs.

Diagnosis:

• Imaging:  X-ray or CT scan to locate and size stones.
• Urine analysis: Detects crystals, blood, and possible infection.
• Blood tests: Check for calcium, uric acid, and other metabolic contributors.

Treatment:

• Small stones: Often pass spontaneously with increased fluid intake and pain management.
• Moderate to large stones:
  • Extracorporeal shockwave lithotripsy (ESWL): Non-invasive method using ultrasound shockwaves to break stones so that they can pass on their own.
  • Medications:
    • Alpha blockers (e.g., tamsulosin) relax ureter muscles and facilitate passage.
    • Medications to dissolve stones partially
    • Painkillers for discomfort.
  • Surgical options:
    • Ureteroscopy: Inserted via the urethra to locate and break stones.
    • Laser lithotripsy: Use ureteroscope with laser at tip for more precise stone fragmentation (and expandable basket to collect fragments.
    • Percutaneous nephrolithotomy: Small incision in back, through the skin into the renal pelvis to remove larger or harder stones through tube.

Prevention:

• Increase fluid intake.
• Dietary modifications to reduce calcium, oxalate, or purine levels.
• Treat underlying metabolic disorders.
• Reduce intake of excess calcium if hypercalcemia is present, under medical guidance.

Summary:

Kidney stones form from crystallized solutes, often related to dehydration, infection, or diet. They may stay silent or cause severe pain and obstruction. Diagnostic imaging guides treatment, which may include medical therapy, lithotripsy, or surgery. Preventive measures involve hydration and dietary management to minimize recurrence risk.