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Urolithiasis

Title

Ñ    Urolithiasis

Definition

Ñ    Stones in the urinary tract

Pathogenesis

Types of stone

Ñ    Calcium oxalate

Ñ    Calcium oxalate + hydroxyapatite

Ñ    Calcium phosphate

Ñ    Uric acid

Ñ    Cystine

Ñ    Struvite:

Magnesium ammonium phosphate + calcium phosphate

Risk Factors

KUS

Ñ    Urinary tract infections

Ñ    Cystinuria

Ñ    Renal tubular acidosis

Ñ    Hypercalciuria:

Renal leak of calcium

GIT

Ñ    Dehydration

Ñ    Hypercalciuria:

Increased absorption of calcium

Ñ    Increased dietary oxalates

Ñ    Small intestinal resection:

Increased absorption of oxalate from the colon

E&M

Ñ    Hypercalcaemia

Drugs

Ñ    Triamterene

Toxins

Ñ    Beryllium

Ñ    Cadmium

Pathological Process

Stone formation occurs as a consequence of:

Ñ    Chemical composition of urine favouring formation of stones

Ñ    Concentrated urine as a consequence of dehydration

Ñ    Impairment of inhibitors of crystal formation in urine:

Citrate

Pyrophosphate

Glycosaminoglycans

Glycoproteins (nephrocalcin)

This results in:

Ñ    Single or multiple stones

Ñ    Varied size

Ñ    Within renal parenchymal or within collecting system

They may cause:

Ñ    Pressure necrosis

Ñ    Obstruction

Ñ    Infection

Clinical Features

E&M

Ñ    Fever

Ñ    Rigors

KUS

Ñ    Pain:

Ureteric colic

Lumbar pain

Pain on micturition

Ñ    Dysuria

Ñ    Increased frequency of micturition

Ñ    Strangury:

Severe pain in the urethra and intense desire to pass urine caused by the base of the bladder being irritated by a stone

Ñ    Interruption of urinary stream

Ñ    Calculus anuria

Ñ    Haematuria

Ñ    Sterile pyuria

Ñ    Asymptomatic proteinuria

Investigations

Fluids

Blood

Tests to determine cause of stones:

Biochemistry

Ñ    Calcium, phosphate

Ñ    Urea and electrolytes, creatinine

Ñ    Serum proteins

Urine

Biochemistry

Tests to determine cause of stones:

Ñ    Urinary cystine

Ñ    pH

Ñ    24 hour excretion of:

Oxalate, calcium, creatinine, uric acid

Ñ    Nitroprusside test:

Cystine

Microbiology

Ñ    Microscopy, culture and sensitivity

Imaging

Ñ    Abdominal ultrasound

Ñ    X-ray KUB:

·          Radiopaque stones

Calcium oxalate

Calcium oxalate + hydroxyapatite

Calcium phosphate

Struvite

Cystine stones

·          Radiolucent stones

Urate

Ñ    Spiral CT scan:

Best test

Ureteric stones may be missed on ultrasound

Ñ    MRI

Ñ    IVU

Tissue Diagnosis

Ñ    Qualitative analysis of stone

Management

Control

Drugs

Ñ    Uric acid stones:

Allopurinol

Ñ    Cystine stones:

Alkalinise urine with sodium or potassium citrate

D-penicillamine

Ñ    Triple phosphate stones:

Antibiotics

Ñ    Idiopathic hypercalciuria:

Thiazide/amiloride

Cellulose phosphate to decrease intestinal absorption

Surgery

Ñ    Extracorporeal shock wave lithotripsy

Ñ    Ureteroscopy with Yag laser

Ñ    Percutaneous nephrolithotomy

Ñ    Rarely open surgery

Ñ    Stent insertion:

Palliate obstruction until definitive treatment

Lifestyle Adjustments

Ñ    Increased fluid intake

Ñ    Dietary adjustments

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