Bladder Stones

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).[2, 3] 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.

The most common factors that promote uric acid stone formations are persistently low urinary pH, dehydration leading to low urinary volume, and high uric acid production. Nitrogen atoms from urate interact with free protons to form uric acid that is 20 times less soluble than urate. Low pH promotes urate conversion to uric acid, which is less soluble and so more prone to forming crystals. At persistently low pH uric acid crystals can form and stabilise even with normal urinary urate concentration.[4]

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.[5] 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).[6, 7, 5]

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.

Two delicate "jack" stones removed before open prostatectomy.

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).[8]

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.[9]

Bladder inflammation secondary to external beam radiation (ie, radiation cystitis) or schistosomiasis can also predispose to vesical calculi.[10] 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.[11]

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.[12] 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.

Iatrogenic foreign bodies include the following[13, 14, 15, 16, 17, 18] :

• Surgical gauze
• Suture material
• Shattered Foley catheter balloons
• Eggshell calcifications that form on a catheter balloon
• Staples
• Ureteral stents
• 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.[19]

Noniatrogenic bodies include objects placed into the bladder by the patients for recreational and various other reasons.[20] Examples include wire, a carrot, and writing implements.[13]

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.[21]

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.[22]

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.[23]

Bladder stones constitute only approximately 5% of all urinary tract calculi, but they are responsible for 8% of urolithiasis-related mortalities in developed nations. The incidence of bladder stones is higher in developing countries where children are subject to a diet deficient in animal protein, poor hydration, and recurrent diarrhea. Bladder stones are more common in males, with male:female ratios between 10:1 and 4:1 reported. The age distribution has two peaks: the first at 3 years, in children in developing countries, and the second at 60 years.[24]

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.[25]

In 1977, Van Reen published a symposium on idiopathic urinary bladder stone disease.[7] 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.

The presentation of vesical calculi ranges from a complete absence of symptoms to the presence of suprapubic pain, dysuria, intermittency, frequency, hesitancy, nocturia, and urinary retention.[3] Parents of children with vesical calculi may notice priapism and occasional enuresis.[10]

Other common signs include terminal gross hematuria and sudden termination of voiding with some degree of associated pain referred to the tip of the penis, scrotum, perineum, back, or hip. The discomfort may be dull or sharp and is often aggravated by sudden movements and exercise. Assuming a supine, prone, or lateral head-down position may alleviate the pain initiated when the stone contacts the bladder neck by causing the stone to roll back into the bladder.

A history of prior pelvic surgery should be sought in all patients, especially when synthetic materials were implanted.[26]

Common physical examination findings include suprapubic tenderness, fullness, and, occasionally, a palpable distended bladder if the patient is in acute urinary retention. Associated findings include cystoceles in women, stomal stenosis (if the patient had undergone prior urinary diversion), and neurologic deficits in patients with neurogenic bladder.

Historically, bladder calculi were diagnosed on the basis of transurethral passage of van Buren sounds. Contact between a van Buren sound and a stone causes transmission of a clicking noise or vibration, which confirms the presence of the stone. Because of advances in cystoscopy, this maneuver is not used today. Currently, imaging studies are used to identify bladder stones (see Workup).

On laboratory studies, less specific signs of vesical calculi include the following:

• Microscopic or gross hematuria
• Pyuria
• Bacteriuria
• Crystalluria
• Urine cultures positive for urea-splitting organisms

Abdominopelvic planar radiography is commonly used to identify radiopaque bladder stones. However, calculi, which are composed predominantly of uric acid, are radiolucent and, unless coated with calcium, are more difficult to visualize on radiographs. Cystoscopy, noncontrast computed tomography (CT), and ultrasonography are other diagnostic methods commonly used to confirm the presence of bladder calculi.[10]

Urinalysis is usually inexpensive and rapid and provides useful information in this setting. On the dipstick, bladder calculi can be associated with test results positive for nitrite, leukocyte esterase, and blood. Because bladder calculi usually cause dysuria and pain, patients may reduce daily fluid intake, which raises urine specific gravity. Adults with uric acid bladder calculi are expected to have an acidic pH. Microscopy usually demonstrates red blood cells (RBCs) and pyuria. Microscopic crystals are usually consistent with the composition of the stone.

Urine culture with sensitivity is indicated. A culture of the urine is helpful for documenting and directing treatment of associated infections.

A complete blood count should be performed. In patients with outlet obstruction and infection, the white blood cell (WBC) count may be elevated, with a left shift.

A comprehensive metabolic panel is ordered. The creatinine level may be elevated in outlet obstruction. Other findings may give a clue to an underlying abnormality.

The initial imaging study of choice is plain radiography of the kidneys, ureters, and bladder (KUB), which is the least expensive and easiest radiologic test to obtain. Alone or as the first film of intravenous pyelography (IVP), KUB detects radiopaque stones. Pure uric acid and ammonium urate stones are radiolucent but may be coated with a layer of opaque calcium sediment. Laminations are common, with the layers stratified according to metabolic and infectious status and the degree of periodic hematuria (see the images below).[10]

Multiple laminated bladder calculi in patient with neurogenic bladder.

Large calculus visible on plain film of intravenous pyelogram performed for hematuria.

If the clinical suspicion remains high and the initial KUB reveals no stones, the next step is bladder ultrasonography, which may be able to differentiate a calculus from tumor or clot. Cystography or IVP demonstrates the stone as a filling defect in the bladder.

If the filling defect moves when the patient is repositioned, the presence of a stone is highly likely (the differential diagnosis includes clot, fungal ball, and papillary urothelial carcinoma on a stalk). Nonmobile filling defects could be calculi attached to the bladder wall via a stitch or in a diverticulum (the differential diagnosis include urothelial carcinoma, clot, and calculus). IVP may also be used to identify associated abnormalities (eg, upper urinary tract calculi, ureterocele, cystocele, enlarged prostate, and bladder diverticula).[10]

With the increasingly widespread availability of ultrasonography, it is reasonable to use this relatively inexpensive and rapid modality more extensively in the diagnosis of bladder calculi. Sonograms typically show a classic hyperechoic object with posterior shadowing, and they are effective in identifying both radiolucent and radiopaque stones.[27]

CT scanning is usually performed for other reasons (eg, abdominal pain, pelvic mass, or suspected abscess) but may demonstrate bladder calculi when performed without intravenous (IV) contrast material. Unenhanced spiral CT scanning is highly sensitive and specific in diagnosing calculi along the urinary tract. Even pure urate calculi can be detected with this method. The stone may be obscured if contrast has been administered.[10]

Low dose (LD) and ultra-low dose (ULD) CT has been shown to have high diagnostic accuracy, sensitivity, and specificity for identifying urinary tract stones with a significant radiation dose reduction in comparison to standard dose CT.[28]

Cystoscopy remains the most commonly used test for confirming the presence of bladder stones and planning treatment. This procedure allows the examiner to visualize the stones and assess their number, size, and position (see the images below). Additionally, examination of the urethra, prostate, bladder wall, and ureteral orifices allows identification of strictures, prostatic obstruction, bladder diverticula, and bladder tumors.[10]

Endoscopic view of spiculated "jack" stone with erythematous bladder mucosa in background.

Bladder stone accretion on matrix. Patient had history of urinary tract infections and presented with irritative voiding symptoms and microscopic hematuria. Upper-tract evaluation findings were normal, but cystoscopy demonstrated calculus. Upon laser treatment of stone, soft matrix core was encountered beneath glistening outer core. Exposed matrix core is visible in crevices.

Bladder stone accretion on matrix. Patient had history of urinary tract infections and presented with irritative voiding symptoms and microscopic hematuria. Upper-tract evaluation findings were normal, but cystoscopy demonstrated calculus. Upon laser treatment of stone, soft matrix core was encountered beneath glistening outer core. Exposed matrix core is visible in crevices.

Pelvic magnetic resonance imaging (MRI) is an expensive imaging modality that yields poor resolution of calculi. It is not recommended in the evaluation of bladder calculi. If performed, MRI may show an incidental black hole of low water content, corresponding to a calculus, in an otherwise full bladder.

Like MRI, technetium-99m MAG-3 renal scanning is a poor imaging modality in the setting of vesical lithiasis. It may demonstrate the incidental finding of focal photopenia within the bladder resulting from calculus formation.[29]

The presence of long-standing untreated bladder calculi is associated with dysplasia and squamous cell carcinoma of the bladder. Occasionally, a calculus is found to be adhering to a transitional cell carcinoma. If a suspicious area does not clear after successful removal of the calculus and treatment of any associated infection, biopsy is performed to rule out malignant degeneration.

Because a bladder stone is in itself a sign of an underlying problem, both removal of the stone and treatment of the underlying abnormality are nearly always indicated. Management of the underlying cause of stone formation (eg, bladder outlet obstruction, infections, foreign body, or diet) is integral to prevention of recurrence. The only contraindication to bladder stone removal would be existence of the stone in a medically unstable or near-terminal asymptomatic patient.

In general, most vesical calculi procedures are performed via endoscopy. However, if the stone is too large or too hard or if the patient’s urethra is too small (eg, in children) or has been surgically altered in such a way as to complicate access to the bladder, an open or percutaneous suprapubic surgical approach is preferable. The presence of bladder calculi in patients with benign prostatic hyperplasia (BPH) is an absolute indication for surgery.[30]

The only potentially effective medical treatment for bladder calculi is urinary alkalization for the dissolution of uric acid stones. Stone dissolution may be possible if the urinary pH can be raised to 6.5 or higher. Potassium citrate 60 mEq/day is the treatment of choice. However, overly aggressive alkalization may lead to calcium phosphate deposits on the stone surface, making further medical therapy ineffective.[10]

Other agents for stone dissolution, such as Suby G or M solution, are rarely used. Renacidin can be used to dissolve phosphate or struvite calculi, but treatment is slow and invasive because it must be used in conjunction with indwelling irrigating catheters. Patients must also be monitored closely for signs of sepsis or hypermagnesemia. Further measures include irrigation of the bladder or continent diversions with saline for mechanical flushing of debris or with one of the above solutions for prevention of stone formation.[25]

When underlying errors of metabolism are discovered during 24-hour urine evaluation of stone disease, various treatments are available to prevent further calculus development. However, discussion of these treatments is beyond the scope of this article.

Currently, 3 different surgical approaches to this problem are used:

• Transurethral cystolitholapaxy
• Percutaneous suprapubic cystolitholapaxy
• Open suprapubic cystotomy

A systematic review and meta-analysis concluded that a transurethral approach, when feasible, is the intervention of choice for bladder stones in adults and children, because of shorter procedure duration and hospital stay. The evidence suggested that endoscopic surgery is as effective as open surgery.[31]

Transurethral cystolitholapaxy

In transurethral cystolitholapaxy, cystoscopy is performed to visualize the stone, an energy source is used to fragment it, and the fragments are then removed through the cystoscope. The energy sources may be a mechanical device (ie, a lithoclast [pneumatic jack hammer]), an ultrasonic device, an electrohydraulic device, a manual lithotrite, or a laser.

Unlike renal and most ureteral calculi, bladder calculi have not been effectively treated with electrohydraulic shock-wave lithotripsy (ESWL) in most centers[32] ; however, some studies suggest that ESWL performed with the patient in the prone position can be considered.[33] The pulsed-dye and other wavelength-specific light sources (eg, holmium laser) fracture the stone through direct absorption, vaporization, water absorption, and pressure-wave generation.[34] A case report describes successful transurethral cystolitholapaxy of a 4-cm bladder stone with the EMS LithoClast Trilogy lithotripter (EMS Electro Medical Systems SA, Amherst, MA), a device that combines an electromagnetic impactor with ultrasonic energy and suction in a single probe.[35]

Because of ongoing advances in instrumentation, the smaller caliber of the pediatric urethra can be accommodated. Thus, these approaches are now applicable to selected children.[36]

Percutaneous suprapubic cystolitholapaxy

In percutaneous suprapubic cystolitholapaxy (which now is often the primary approach in the pediatric population), the percutaneous route allows the use of shorter- and larger-diameter endoscopic equipment (usually with an ultrasonic lithotripter), thereby permitting rapid fragmentation and evacuation of calculi.[37]

Often, a combined transurethral and percutaneous approach can be used to aid in stone stabilization and to facilitate irrigation of the stone debris. The authors favor a combined approach with the use of the ultrasonic lithotripter or the pneumatic lithoclast. The holmium laser is also effective but is generally slower, even with the 1000-µm fiber.[38]

The electrohydraulic lithotripsy (EHL) unit has been associated with a higher incidence of bladder mucosal injury.[39] Options for accessing the bladder may be challenging in certain circumstances, such as in patients who have undergone prior bladder reconstruction or prior bladder neck procedures for improved continence.

Paez et al, in a study of percutaneous removal of bladder stones via ultrasound-assisted access of the bladder through prior suprapubic tube tracts (a Mitrofanoff catheterization channel with a 30-French Amplatz sheath was used in 1 case) reported no complications and concluded that percutaneous treatment was a safe alternative in this population subset.[40] This same procedure has also been described in continent diversions with urethral closure.[41]

First described in 1963 by Barnes et al and supported by numerous subsequent articles, transurethral lithotripsy combined with transurethral resection of the prostate (TURP) or transurethral incision of the prostate (TUIP) can be accomplished easily and safely.[42, 43] It is advisable to complete the stone ablation before carrying out these prostatic interventions; hemorrhage and excess fluid absorption are potential complications when the procedures are performed in the reverse order.

In a study by Tugcu et al, 64 patients underwent TURP in addition to concomitant bladder calculi surgery.[44] Participants were treated with either (1) a percutaneous suprapubic approach with a 30-French access sheath or (2) transurethral cystolitholapaxy with a 23-French sheath and pneumatic lithotripter; those who underwent percutaneous stone removal had a statistically significantly larger stone burden, and the mean operating time for the percutaneous approach was nearly half that for transurethral removal.

A case report by Wilhelm and colleagues describes successful treatment of a patient who had undergone lower urinary tract reconstruction, with creation of an ileal pouch and a continent umbilical stoma, and had developed pouch urolithiasis in the urinary reservoir. The stone was extracted through the stoma via a modified access sheath, using flexible ureteroscopy and laser lithotripsy. No analgesia was needed, and the procedure was performed in an outpatient setting.[45]

Open suprapubic cystotomy

In open suprapubic cystotomy, stones are not fragmented but are removed intact. This approach can be used with larger and harder stones and in cases where open prostatectomy or bladder diverticulectomy is indicated. Open prostatectomy is generally indicated when the prostate volume exceeds 80-100 g.

The advantages of suprapubic cystolithotomy include rapidity, easy removal of several calculi in a single procedure, the ability to extract calculi that are adherent to bladder mucosa, and the ability to remove large stones that are too hard or dense to fragment expeditiously via transurethral or percutaneous techniques. The major disadvantages include postoperative pain, longer hospital stay, and longer bladder catheterization times.

Typical follow-up is 3-4 weeks postoperatively with kidney-ureter-bladder (KUB) radiography or bladder ultrasonography to document clearing of all the fragments. Thereafter, metabolic evaluation may be pursued as indicated, and KUB radiography may be done at 6- to 12-month intervals as warranted. A metabolic stone profile analysis is indicated in patients with uric acid stones, concurrent upper tract calculi, a strong family history of stone disease, calculi without obstruction, and recurrent calculi.

In 2019, the European Association of Urology (EAU) and/or cystoscopy are the optimum imaging modalities for detection of bladder stones.

• Asymptomatic migratory bladder stones in adults may be left untreated, especially if stones are small.
• Primary and secondary bladder stones are usually symptomatic and unlikely to pass spontaneously. Active treatment of such stones is usually indicated.
• Stones composed of uric acid or struvite can be dissolved by chemolysis. Uric acid stones can be dissolved by oral urinary alkalinization when a pH > 6.5 is consistently achieved, typically using an alkaline citrate or sodium bicarbonate. Careful monitoring is required during therapy. Irrigation chemolysis is possible for struvite or uric acid stones; a two-way or three-way Foley catheter can be used.
• Bladder stones can be treated with open, laparoscopic, robotic assisted laparoscopic, or endoscopic (transurethral or percutaneous) surgery or extracorporeal shock wave lithotripsy (SWL).
• Open suprapubic cystolithotomy is successful, but is associated with a need for catheterization and longer hospital stay in both adults and children, compared with all other stone removal modalities.
• In both adults and children, transurethral cystolithotripsy provides similar, high stone-free rates (SFR) and appears to be safe.
• Bladder stones in men aged over 40 years are typically related to benign prostatic hyperplasia (BPH), the management of which should also be considered.
• Bladder stones formed after bladder augmentation may be removed via open cystolithotomy or endoscopically. Daily bladder irrigation with 250 mL of saline solution significantly reduces the incidence of recurrent stone formation and bacterial colonization compared with lower- volume bladder irrigations. 
• For bladder stones formed after urinary diversion, a percutaneous approach or open procedure may be required if the caliber of the nipple is too small to allow the safe insertion of an appropriately sized endoscopic instrument without risking damage to the continence apparatus.

Specific EAU treatment recommendations are as follows[24] :

• Offer adults and children transurethral cystolithotripsy where feasible.
• In adult men with bladder outlet obstruction (BOO) and bladder stones, preferably treat the underlying BOO simultaneously with stone removal.
• Offer adults and children percutaneous cystolithotripsy where transurethral is not possible or is associated with a high risk of urethral stricture (eg, young children, patients with previous urethral reconstruction, patients with spinal cord injury).
• Discuss open cystolithotomy for very large bladder stones (there is no evidence to suggest a size cut-off).
• Open, laparoscopic, robotic, and extracorporeal shock wave lithotripsy are alternatives where endoscopic treatment is not feasible.
• Perform transurethral cystolithotripsy with a continuous flow instrument (eg, nephroscope or resectoscope) where possible in adults.
• In children with primary stones, perform open cystolithotomy preferably without placing a catheter or drain in uncomplicated cases (ie, those with no prior infection, surgery, or bladder dysfunction).
• Recommend regular irrigation therapy with saline solution to patients with a bladder augmentation or continent cutaneous urinary reservoirs.

The goals of pharmacotherapy are to dissolve the stone, reduce morbidity, and prevent complications. In patients with uric acid stones, urinary alkalinization may help dissolve the stone.

Class Summary

The only potentially effective medical treatment for bladder calculi is urinary alkalization for the dissolution of uric acid stones. However, overly aggressive alkalization may lead to calcium phosphate deposits on the stone surface, making further medical therapy ineffective.[10]

Potassium citrate (Urocit K)

Stone dissolution may be possible if the urinary pH can be made greater than or equal to 6.5. Potassium citrate 60 mEq/day is the treatment of choice.