- 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%
- Recurrence rates are close to 50%
- 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)
- CT scanning is replacing IVU as the investigation of choice
- Has higher sensitivity for the detection of stones
- Also allows identification of other causes of loin pain
- Radiation dose from IVU = 1.5 mSv
- Radiation does from CT scan = 4.5 mSv
Pictures provided by H Houng, Epsom General Hospital,
United Kingdom
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
Indication for urgent intervention
- Presence of infection with urinary tract obstruction
- Urosepsis
- Intractable pain or vomiting
- Impending acute renal failure
- Obstruction in a solitary or transplanted kidney
- Bilateral obstruction stones
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
Indication for metabolic evaluation
- Family history of urolithiasis
- Bilateral stone disease
- Presence of inflammatory bowel disease, chronic diarrhoea or
malabsorption
- History of bariatric surgery
- Medical conditions associated with urolithiasis
- Primary hyperparathyroidism
- Gout
- Renal tubular acidosis
- Nephrocalcinosis
- Osteoporosis or pathological fracture
- Stones formed from cystine, uric acid or calcium phosphate
- The patient is a child
Components of metabolic evaluation
- Analysis of stone composition
- Two 24 hour urine collections for:
- Volume
- pH
- Calcium
- Oxalate
- Citrate
- Uric acid
- Ammonium
- Magnesium
- Phosphate
- Creatinine
- Cystine screen
- Serum
- Calcium
- Bicarbonate
- Creatinine
- Magnesium
- Phosphate
- Uric acid
- Blood urea nitrogen
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.
Miller N L, Lingeman J E. Management of kidney stones.
BMJ 2007; 334: 468-472.
Moe O W. Kidney stones: pathophysiology and medical
management. Lancet 2006; 367: 333-344.
Westenberg A, Harper M, Zafirakis H, Shah P J.
Bladder and renal stones: management and treatment. Hosp
Med 2002; 63: 34-41.
Whitfield A H N, Whitfield H N. Is there a role for the
intravenous urogram in the 21st century. Ann R Coll Surg Engl
2006; 88: 62-65.
Wickham J E A. Treatment
of urinary stones.
Br Med J 1993; 307: 1414-1417. |