Types
- Renal stones vary in size
- Calcium oxalate forms 80% of stones
- Calcium phosphate
- Uric acid (not visible on xray)
- Struvite (magnesium ammonium phosphate)
Staghorn Calculus
- Renal calculus that forms the shape of a staghorn
- The body sits in the renal pelvis with horns extending into renal calyxes
- Usually composed of struvite
- In recurrent upper urinary tract infections, the bacteria can hydrolyse the urea in urine to ammonia, creating the solid struvite
- Can be seen on plan xray films
Presentation
- May be asymptomatic and never cause an issue
- Renal colic
- Excruciating loin to groin pain
- Colicky (fluctuating in severity) as the stone moves and settles
- May have haematuria, nausea, vomiting and oliguria
- May have symptoms of sepsis if infection present (i.e. fever)
Diagnosis
- Urine dipstick (haematuria in stones but also exclude infection)
- Bloods for infection and kidney function
- Renal stones may not be visible on abdominal xray
- CT KUB (non-contrast scan of kidney, ureters and bladder) is gold standard for identifying stones
Management
- NSAIDs are usually the most effective type of analgesia (e.g. PR diclofenac)
- Antiemetic if nausea and vomiting
- Fluids
- Antibiotics if infection is present
- Stones less than 6mm have greater than 50% chance of passing without intervention
- Spontaneous passage can take several weeks
- Tamsulosin (an alpha-blocker) can be used to help aid spontaneous passage of stones
- Surgical Interventions in large stones or stones that do not pass
Surgical Interventions
- Extracorporeal Shock Wave Lithotripsy
- An external machine generates shock waves and directs them at the stone under xray guidance.
- Breaks the stone to smaller parts to make them easier to pass.
- Ureteroscopy and Laser Lithotripsy
- Camera inserted via urethra, bladder and ureter
- Stone identified
- The stone is broken up by targeted lasers
- The smaller parts are easier to pass
- Percutaneous Nephrolithotomy
- Performed in theatres under anaesthetic
- A nephroscope (small camera on a stick) is inserted via a small incision at the patient’s back
- The scope is inserted through the kidney to assess the ureter
- Stones can either be removed or broken up to small stones
- Open Surgery
Recurrent Stones
- One episode of renal stones predisposes patients to further episodes
- Advice to
- Increase oral fluids
- Reduce dietary salt intake
- Reduce intake of oxalate-rich foods for calcium stones (e.g. spinach, nuts, rhubarb, tea)
- Reduce intake of urate- rich foods for uric acid stones (e.g. kidney, liver, sardines)
- Limit dietary protein
