Renal calculi (nephrolithiasis)

• Stones are crystal aggregates
• They form in collecting ducts and may be deposited anywhere from the renal pelvis to the urethra
• Lifetime incidence s 15%, peak age 20-40 M>F

Types of stone

• Calcium oxalate – 75%
• Magnesium ammonium phosphate
• Urate
• Hydroxyapatite

• Stones in the kidney cause loin pain
• Stones in the ureter cause renal colic
• Bladder or urethral stones cause pain on micturition
• Infection can co-exist

Tests

• FBC, U&Es, calcium, phosphate, bicarbonate, urate
• Urine dipstick – generally positive for haematuria
• MSU
• Urine pH
• 24h urine collection for – calcium, oxalate, urate, citrate, sodium creatine
• Imaging – x-ray of kidney, ureter, bladder – look over transverse process for stones
• Ultrasound for hydronephrosis or hydroureter

Remember a ruptured AAA may present similarly

Management

• Prompt analgesia – ideally NSAID e.g. diclofenac or morphine with anti-emetic
• Give IV fluids if unable to tolerate orally
• Give antibiotics if there is infection
• After imaging seek urological help urgently – delay may lead to infection and loss of renal function
• Procedures include;
  • Extracorporeal shockwave lithotripsy
  • Percutaneous nephrostomy
  • Ureteroscopy +/- laser
  • Percutaneous nephrolithotomy
• Stones not causing obstruction between attacks of renal colic can be managed conservatively – most pass within 48hr

Prevention

• Drink plenty of fluids
• A normal calcium intake is recommended as low calcium diets increase oxalte excretion
• Calcium stones – if hypercalciuria – thiazide diuretic
• Oxalate – reduce oxalate intake e.g. tea, chocolate, nuts, strawberries
• Magnesium ammonium phosphate – treat infection promptly
• Urate – allopurinal to reduce uric acid