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