Bladder lithiasis is believed to make up 5% of all urinary calculi. Since the 19th century, the incidence of bladder calculi in the developed world has steadily decreased secondary to improvements in diet, nutrition and antimicrobial therapy. The majority of bladder calculi occur in adults, particularly in elderly men with bladder outlet obstruction. However, groups at risk for urinary stasis and infection are also at risk for bladder stone formation. Additionally, multiple case reports have documented a myraid of foreign bodies (sutures, staples, Foley catheters, ureteral stents, intrauterine devices, hair, etc) found in the bladder that may act as a nidus for stone formation. Essentially any foreign body, either iatrogenic or otherwise, which makes its way into the bladder may act as a scaffolding for stone formation. In contrast to developed areas, bladder calculi remain a relatively common problem in underdeveloped nations and occur most commonly in the pediatric population.
Unlike the rapid clearance rates of urine in the renal tubules, the bladder is a reservoir for relatively stagnant urine and its precipitates. The presence of infection or poor bladder emptying may allow for the supernaturation and heterogeneous nucleation around a nidus. Subsequent aggregation results in crystal and stone formation. The composition of bladder calculi depends on the urinary pH and degree of urine saturation.
In the United States most stones are of mixed composition, with struvite being a major component if infection is present.
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Vesical calculi can be classified as migrant, primary idiopathic, or secondary calculi, which include calculi related to urinary stasis, infection, and foreign bodies.
Migrant Calculi
Migrant bladder calculi are formed in the upper tracts, pass into the bladder, and are retained there. Most calculi that migrate out of the ureter into the bladder are smaller than 1 cm and, in adults, are easily passed per urethra. Calculi that are retained are associated with a small bladder outlet (children) or bladder outlet obstruction.
Retained upper tract stones may grow to a large size in the bladder. The primary etiology of the calculus is related to the metabolic factors associated with renal calculi formation.
Primary Idiopathic (Endemic) Calculi
Endemic bladder stones form in children in the absence of obstruction, local disease, neurologic lesion, or known primary infection. it is rare in developed countries.
However, endemic bladder calculi remain common in infants and children of lower socioeconomic background in North Africa and the Middle and Far East. Stone formation results from dietary and nutritional deficiencies. Compared with cow's milk, human breast milk and foods such as polished rice and cereals are low in phosphorus . This dietary phosphate deficiency leads to low urine phosphate excretion and high peaks of ammonia excretion . Chronic dehydration, excessive protein or oxalate consumption, high endogenous oxalate production, and deficiencies in vitamins A, B
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, and B
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and magnesium have been associated with stone formation.
Children younger than 10 years are typically affected, with the peak incidence around
3 years. This accounts for the male-to-female ratio of 10:1.
Secondary Bladder Calculi
Progress in nutrition and diet has decreased the incidence of bladder calculi; it is now predominantly a disease of adults and accounts for approximately 5% of urinary calculi . These secondary bladder calculi are most often related to urinary stasis or recurrent urinary tract infection due to bladder outlet obstruction or neurogenic bladder dysfunction. Patients with foreign bodies in the urinary tract are also at risk for development of calculi.
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The clinical presentation of bladder calculi varies depending on stone size and location, as well as patient characteristics. While they may be found incidentally in an asymptomatic patient during imaging for other reasons, calculi typically present with classic findings, which may include dysuria, frequency, nocturia, suprapubic pain, terminal gross hematuria, intermittency and urinary retention
These symptoms may be relieved with a supine or head-down position, which may change the position of an obstructing stone at the bladder neck.
Physical examination may reveal a palpable bladder in cases of retention secondary to an obstructing stone or in patients with poor bladder emptying. In addition, large bladder calculi may be palpable on abdominal or bimanual examination in thin patients.
: may reveal microscopic hematuria, pyuria, bacteriuria and crystalluria, with urine cultures demonstrating urea- splitting organisms.
is typically the first step in confirming the diagnosis of a bladder calculus. Radiographic imaging with plain abdominal films has been demonstrated to be inaccurate for diagnosing bladder calculi.
Stone composition and size were the main determinants of whether radiographic imaging was able to detect stones.
Due to the inaccuracies of plain film radiographs, sonography and computerized tomography are the imaging studies of choice for the diagnosis of bladder calculi. Additionally, there have been cases of bladder stones found incidentally during routine bone scintigraphy.
Finally, cystoscopy can be performed to confirm radiographic findings, help determine causative factors and plan for future operative intervention .
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