- Form from crystalline aggregates of organic molecules
- Factors favouring formation
- Increased urinary concentration of constituents
- Presence of promoter substances
- Reduction in concentration of inhibitors
- Life time risk of developing a ureteric calculus is about 5%
- Occur most commonly in men aged between 30 - 60 years
- 90% are idiopathic
- 10% are due to:
- Hyperparathyroidism
- Vitamin D excess
- Primary hyperoxaluria
- Recurrence rate at 10 years is about 50%
Chemical composition
- Calcium oxalate (40%)
- Calcium phosphate (15%)
- Mixed oxalate / phosphate (20%)
- Struvite (15%)
- Uric acid (10%)
Clinical features
- Stones usually present with pain due to obstruction of urinary flow
- May cause few symptoms or may present with typical ureteric colic
- Ureteric colic typically is severe colicky loin to groin pain
- Pain may radiate into scrotum in men and labia in women
- May also cause frequency, urgency and dysuria
- Pain may settle with passage of the stone or if stone fails to migrate
- Abdominal examination is usually unremarkable
- Microscopic haematuria is often present
Differential diagnosis
- The differential diagnosis included renal and non-renal causes
- Non-renal causes include:
- Appendicitis
- Diverticulitis
- Ectopic pregnancy
- Salpingitis
- Torted ovarian cyst
- Abdominal aortic aneurysm
- Renal causes include:
- Tumour (clot colic)
- Pyelonephritis
- Retroperitoneal fibrosis
- Stricture
- Papillary necrosis
Investigation
- The following investigations should be considered
- Midstream urine specimen
- KUB plus ultrasound
- Intravenous urogram (IVU)
Complications
- Complications of ureteric calculi include:
- Obstruction
- Ureteric strictures
- Infection
- Acute infection in an obstructed kidney is a urological emergency
- Patient is usually unwell with loin pain, swinging pyrexia and dysuria
- Without drainage, rapid renal destruction may occur
- Requires emergency percutaneous nephrostomy
- Chronic infection with urease-producing organisms (e.g. Proteus) precipitates stone formation
- Magnesium ammonium phosphate or staghorn calculi result
- Large staghorn calculi may be asymptomatic
- Staghorn calculi can lead to a deterioration in renal function
Management
- Initial conservative treatment with oral fluids and adequate analgesia
- Check serum electrolytes and calcium
- Urinalysis will normally show microscopic haematuria
- IVU to confirm diagnosis and ureteric obstruction
- Most stones < 5 mm in diameter pass spontaneously
- If more than 5-10 mm in diameter and fail to pass spontaneously consider:
- Upper third of ureter - extracorporeal shock wave lithotripsy (ESWL)
- Lower third of ureter - ureteroscopy (USC) + lithotripsy
- Middle third of ureter - either ESWL or USC
- If total obstruction occurs in the presence of infected urine need urgent decompression
- Decompression usually achieved with percutaneous nephrostomy
- If large stones in renal pelvis or upper ureter consider percutaneous nephrolithotomy.
- Particularly if stone more than 3 cm in diameter or a 'staghorn calculus'
- Less than 1% patients with stones require open surgery - uretero- or nephrolithotomy
Lithotripsy
- Is the use of shock waves to break up stones
- Lithotripsy requires:
- An energy source - spark-gap electrode or piezoceramic array
- A coupling device between patient and electrode - water bath or cushion
- A method of stone localisation - fluoroscopy or ultrasound
Bibliography
Birch B. The management of urinary calculi.
In: Johnson C D, Taylor I eds. Recent advances in surgery 20.
Churchill Livingstone, Edinburgh 1997: 177-202.
Coe F L, Parks J H, Asplin
J R. The pathogenesis and treatment of kidney stones.
N Eng J Med 1992; 327: 1141-1152.
Westenberg A, Harper M, Zafirakis H, Shah P J. Bladder and renal stones:
management and treatment. Hosp Med 2002; 63: 34-41.
Wickham J E A. Treatment of urinary stones.
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