Stones in the kidneys, ureters and urinary bladder – Types and causes

Renal and urinary bladder stones (calculi)

Urinary stone is a fairly common throughout the world particularly in the Middle East. Most urinary stones are composed of calcium oxalate and phosphate; these are more common in men. Mixed infective stones, which account for about 15% of all calculi, are twice as common in women as in men. The overall male to female ratio of stone disease is 2 :1. Stone disease is frequently a recurrent problem. More than 50%of patients with a history of nephrolithiasis will develop a recurrence within 10 years. The risk of recurrence increases if a metabolic or other abnormality predisposing to stone formation is present and is not modified by treatment.


Composition of urinary stones

Calcium oxalate usually with calcium phosphate - 65%
Calcium phosphate alone – 15%
Magnesium ammonium phosphate (struvite) -10-15%
Uric acid 3-5%
Cystine 1-2%




How urinary stone is formed?

Inhibitors of crystal formation are present in normal urine preventing the formation of stones, as the concentrations of stone-forming substances exceed their maximum solubility in water. Many stone-formers have no detectable metabolic defect, although microscopy of warm, freshly passed urine reveals both more and larger calcium oxalate crystals than are found in normal subjects. Factors predisposing to stone formation in these so-called 'idiopathic stone-formers' are:

#chemical composition of urine that favors stone crystallization
#production of a concentrated urine as a consequence of dehydration associated with life in a hot climate or work in a hot environment
#impairment of inhibitors that prevent crystallization in normal urine.


Causes of urinary stone formation:

Hypercalcaemia
If the GFR is normal, hypercalcaemia almost invariablyleads to hypercalciuria. The common causes of hypercalcaemia leading to stone formation are:

primary hyperparathyroidism
vitamin D ingestion
sarcoidosis.

The other causes of stone formation are:

Dehydration
Hypercalciuria
Hyperoxaluria
Hyperuricaemia and
hyperuricosurea
Infection
Cystinuria
Renal tubular acidosis
Primary renal disease(polycystic kidneys, medullary sponge kidneys)
Drugs

Causes of Urinary stone formations
Symptoms of urinary stones
Investigations and treatment of urinary stones