Approach Considerations
On laboratory studies, less specific signs of vesical calculi include the following:
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Microscopic or gross hematuria
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Pyuria
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Bacteriuria
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Crystalluria
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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]
Laboratory Studies
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.
Radiography
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]
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]
Ultrasonography
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]
Computed Tomography
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
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.
Other Tests
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]
Histologic Findings
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.
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Multiple laminated bladder calculi in patient with neurogenic bladder.
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Endoscopic view of spiculated "jack" stone with erythematous bladder mucosa in background.
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Large calculus visible on plain film of intravenous pyelogram performed for hematuria.
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Ex vivo photograph of bladder stone.
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Two delicate "jack" stones removed before open prostatectomy.
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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.
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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.
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Laser destruction of stone. Note small lacuna generated in stone as result of laser energy. At lower power settings, stone can be quickly reduced to dust.
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Layered nature of bladder calculus exposed as laser strips away surface.
