Bladder (vesical) calculi are stones or calcified materials that are present in the bladder (or in a bladder substitute that functions as a urinary reservoir). They are usually associated with urinary stasis but can form in healthy individuals without evidence of anatomic defects, strictures, infections, or foreign bodies. The presence of upper urinary tract calculi is not necessarily a predisposition to the formation of bladder stones.
Bladder calculi are an uncommon cause of illness in most Western countries, but they result in specific symptoms and are a significant source of discomfort. This article discusses the diagnosis and current management techniques for vesical calculus disease.
The incidence of bladder stones in children is slowly declining, even in endemic areas. This is mostly due to improved nutrition, better prenatal and postnatal care, and improved awareness of the problem in the endemic areas. In the 21st century, the incidence of this disease in children will probably continue to decline, and the disease will largely become a disease of adults.
Aggressive treatment of lower urinary tract symptoms with alpha-blockers and 5-alpha-reductase inhibitors should further decrease the overall incidence of bladder stones by improving bladder emptying. Removal of bladder stones will continue to progress toward minimally invasive techniques, thus decreasing hospital stay and recovery times. Continued advances in surgical equipment and the ability to downsize without the sacrifice of effectiveness could eventually render open surgery for stones obsolete.
In addition, continued aggressive management of neurogenic bladder, specifically in the pediatric neurogenic bladder population, may lead to a rise in both the incidence of struvite stones and the development of creative and minimally invasive surgical techniques for augmented bladders.
In men, the main anatomic problem that leads to vesical obstruction is prostatic enlargement. The prostate forms a ringlike growth around the vesical neck and, when hypertrophic, can significantly impede the flow of urine. Stasis due to this blockage is responsible for the deposition of layer upon layer of new stone material.
In women, voiding dysfunction and urinary stasis can occur but are less commonly associated with calculi. Typical anatomic findings include cystoceles, enteroceles, or findings of previous urethral surgery, all of which contribute to elevated residuals. With rare exceptions, any foreign body that cannot escape the bladder becomes calcified and eventually forms a stone.
Most vesical calculi formed de novo within the bladder, but some initially may have formed within the kidneys as a dissociated Randall plaque or on a sloughed papilla and subsequently passed into the bladder, where additional deposition of crystals causes the stone to grow.
However, most renal stones that are small enough to pass through the ureters are also small enough to pass through a normally functioning bladder and an unobstructed urethra. In older men with bladder stones composed of uric acid, the stone most likely formed in the bladder. Stones composed of calcium oxalate usually originate in the kidney.
In adults, the most common type of vesical stone (seen in more than 50% of cases) is composed of uric acid. Less frequently, bladder calculi are composed of calcium oxalate, calcium phosphate, ammonium urate, cysteine, or magnesium ammonium phosphate (when associated with infection). [1, 2] Perhaps surprisingly, patients with uric acid bladder calculi rarely ever have a documented history of gout or hyperuricemia. In many cases, the core consists of one chemical, and layers of different chemicals form around this core.
In children, stones are composed mainly of ammonium acid urate, calcium oxalate, or an impure mixture of ammonium acid urate and calcium oxalate with calcium phosphate.  The common link among endemic areas relates to feeding infants human breast milk and polished rice. These foods are low in phosphorus, ultimately leading to high ammonia excretion. These children also usually have a high intake of oxalate-rich vegetables (increased oxalate crystalluria) and animal protein (low dietary citrate). [4, 5, 3]
In patients with spinal cord injuries, bladder stones are often composed of struvite or calcium phosphate.
Vesical calculi may be single or multiple, especially in the presence of bladder diverticula, and can be small or large enough to occupy the entire bladder. They range from soft to extremely hard, with surfaces ranging from smooth and faceted to jagged and spiculated (“jack” stones; see the image below). In general, most vesical calculi are mobile within the bladder, though some stones are fixed when they form on a suture, on the intravesical portion of a papillary tumor, or on retained stents.
In regions where vesical lithiasis is endemic in children, stone formation is more common among boys younger than 11 years and among people from low socioeconomic backgrounds, is not usually associated with renal calculi, and is relatively less likely to recur after treatment (in comparison with upper urinary tract calculi). 
Bladder outlet obstruction remains the most common cause of bladder calculi in adults. Prostatic enlargement, elevation of the bladder neck, and high postvoid residual urine volume cause stasis, which leads to crystal nucleation and accretion. This ultimately results in overt calculi. In addition, patients who have static urine and develop urinary tract infections are more likely to form bladder calculi.
In a study of patients with spinal cord injuries (SCIs) (newly acquired neurogenic bladders) who were monitored for more than 8 years, 36% developed bladder calculi. Subsequent reports indicated that as a consequence of better care of SCI patients, this rate has dropped to less than 10%. In a retrospective study of 93 SCI patients with bladder stones, Bartel and colleagues found that indwelling catheters were associated with a higher risk of developing bladder stones and a higher risk of recurrence of bladder stones than intermittent catheterization or reflex micturition. 
Bladder inflammation secondary to external beam radiation (ie, radiation cystitis) or schistosomiasis can also predispose to vesical calculi.  The dystrophic calcifications that develop from radiotherapy-related bladder and prostate damage may serve as a nidus for stone formation. Congenital or acquired vesical diverticula may produce localized urinary stasis, leading to stone formation. Other rare anatomic abnormalities implicated as contributors to stasis and stone formation include sliding inguinal hernias containing the urinary bladder. 
Multiple risk factors predispose to bladder stones in pediatric patients undergoing bladder augmentation. Mathoera et al, in a study of 89 pediatric patients who had undergone bladder augmentation and presented with bladder calculi, found that cloacal malformations, vaginal reconstructions, ureteral reimplantations, and bladder neck surgery were all associated with higher risk for stone formation.  Antibiotic prophylaxis for recurrent infections decreased struvite stone formation but did not significantly reduce overall stone formation.
Other etiologic factors for bladder stone formation include foreign bodies in the bladder that act as a nidus for stone formation. These may be iatrogenic or noniatrogenic in origin.
Shattered Foley catheter balloons
Eggshell calcifications that form on a catheter balloon
Migrating contraceptive devices
Erosions of surgical implants
Prostatic urethral stents
Stones on suture material may have an early presentation if sutures were originally placed within the bladder lumen. They may have a delayed presentation if they are caused by erosion through the bladder wall. 
Metabolic abnormalities are not a significant cause of stone formation in patients with urinary diversions. In this group of patients, the stones are primarily composed of calcium and struvite. In rare cases, medications (eg, viral protease inhibitors) may be the source for bladder calculus formation. 
In a prospective, comparative analysis of 57 men undergoing surgery for bladder outlet obstruction secondary to benign prostatic hyperplasia, 27 of whom had bladder calculi, Childs and colleagues found that patients with calculi were more likely to have a history of renal stone disease and gout and were more likely to have lower urinary pH and magnesium level and higher uric acid supersaturation on 24-hour urine studies, suggesting that multiple factors, including metabolic abnormalities, may contribute to the pathogenesis of bladder calculi. 
In general, if an otherwise healthy person in the United States or Europe is found to have a bladder stone, a complete urologic evaluation must be undertaken to find a cause for urinary stasis. Potential causes include benign prostatic hyperplasia, urethral stricture, neurogenic bladder, diverticula, and congenital anomalies such as ureterocele and bladder neck contracture. In females, examples include an incontinence repair that is too tight, cystoceles, and bladder diverticula. 
Since the 19th century, the incidence of primary bladder calculi in the United States and Western Europe has been steadily and significantly declining as a consequence of improved diet, better nutrition, and infection control. In these countries, vesical calculi principally affect adults, with a steadily declining frequency in children. In the Western hemisphere, vesical calculi primarily affect men who are usually older than 50 years and have associated bladder outlet obstruction.
However, the incidence of bladder calculi in less developed countries and areas such as Thailand, Burma, Indonesia, the Middle East, and North Africa remains relatively high. Although vesical lithiasis is becoming less common in these populations, it remains a disorder that affects children and it is far more common in boys than in girls. 
In 1977, Van Reen published a symposium on idiopathic urinary bladder stone disease.  Unfortunately, the worldwide data are insufficient to provide a definitive and accurate picture of the frequency of bladder calculi, mostly because of poor hospital records in developing regions of the world. Although several studies have been done in countries with a high incidence of the disease, the reporting is not uniform.
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