Bladder calculus (vesical calculus) is a mineral deposit that forms within the bladder lumen or migrates from the upper urinary tract. In adults, it most commonly develops on the background of bladder outlet obstruction (BPH, urethral stricture), while in the pediatric population, nutritional deficiencies and endemic stone disease are predominant. Based on composition, stones are classified as uric acid, calcium oxalate, calcium phosphate, struvite (infection stone), and cystine stones. Stones are generally mobile and change position within the bladder with positional changes — this feature is known as the 'rolling stone' sign and is confirmed by supine/prone comparison on CT. On ultrasound, bladder stones appear as posterior hyperechoic foci with clean posterior acoustic shadowing; on Doppler US, twinkling artifact (rapid color change at the stone surface on color Doppler) is a pathognomonic finding aiding diagnosis. On CT urography, stones are detected as high-density structures in the bladder lumen; uric acid stones show relatively low density (200-500 HU), while calcium-containing stones are markedly hyperdense (>700 HU). On MRI, stones appear as signal void (hypointense) on all sequences. Treatment is planned based on stone size: small stones (<2 cm) are managed with cystolithotripsy or laser lithotripsy, while large stones (>3 cm) require open/percutaneous cystolithotomy. Treatment of the underlying obstructive pathology is mandatory to prevent recurrence.
Age Range
40-85
Peak Age
65
Gender
Male predominant
Prevalence
Common
Bladder stones form through two main mechanisms: (1) primary stone formation — crystallization and stone growth in the bladder lumen due to stasis; (2) secondary migration — descent of a kidney or ureteral stone into the bladder and continued growth within the bladder. Primary formation is most commonly related to bladder outlet obstruction (BPH, urethral stricture, neurogenic bladder): obstruction → incomplete bladder emptying → residual urine accumulation → urinary stasis → mineral supersaturation → crystal nucleation → stone growth. Uric acid stones form in acidic urine (pH <5.5) and may be radiolucent — they show low-to-moderate density (200-500 HU) on CT because uric acid crystals consist of elements with lower atomic numbers than calcium. Calcium oxalate and phosphate stones appear markedly hyperdense (>700 HU) on CT due to high calcium content — calcium's high atomic number (Z=20) increases X-ray attenuation. Struvite stones form through alkalinization of urine pH (pH >7.0) by urease-producing bacteria (Proteus, Klebsiella), resulting in magnesium ammonium phosphate crystallization; they are often large, potentially staghorn-shaped, and show moderate density on CT. On ultrasound, all stone types appear hyperechoic due to high acoustic impedance mismatch and produce 'clean acoustic shadow' posteriorly — this shadow results from near-complete reflection of sound waves at the stone surface. Twinkling artifact occurs when irregular microstructures on the stone surface (crystal facets, cracks) scatter ultrasound waves in multiple directions (diffuse scattering), creating phase instability in the Doppler signal — this instability appears as a rapidly changing colored pixel pattern on color Doppler and does not mimic true blood flow.
Rapid color change at the calculus surface on color Doppler ultrasound (twinkling artifact) is a pathognomonic finding of bladder stone, caused by microstructures on the crystal surface disrupting Doppler phase. On CT, the stone that displaces gravity-dependently with positional change (rolling stone sign) distinguishes free intraluminal calculus from immobile wall calcification.
Appears as a high-density structure in the bladder lumen on non-contrast CT. Calcium oxalate stones show the highest density (>1000 HU), calcium phosphate stones range 800-1200 HU, struvite stones 600-900 HU, and uric acid stones show the lowest density (200-500 HU). Cystine stones show homogeneous density in the 600-800 HU range. Stone morphology varies by composition: calcium oxalate monohydrate stones have smooth surface and homogeneous density, calcium oxalate dihydrate stones show spiculated/mulberry surface. Stone size can range from a few mm to >5 cm. Large stones may completely fill the bladder lumen and show 'jack-stone' (spiked ball) morphology.
Report Sentence
An intraluminal calculus measuring __ mm with density of __ HU is seen in the bladder lumen; density is consistent with __ composition.
Gravity-dependent displacement of the bladder stone on CT sections obtained in supine and prone positions. In supine position the stone is seen in the posterior (dependent) portion of the bladder, while in prone position it moves anteriorly. This finding proves the stone is free intraluminal and not adherent to the bladder wall — distinguishing from immobile calcification in wall lesions (e.g., calcified tumor). It also helps differentiate from impacted stone at the ureterovesical junction — impacted stones do not change position.
Report Sentence
The calculus in the bladder lumen demonstrates gravity-dependent displacement between supine and prone positions (rolling stone sign), consistent with free intraluminal stone.
Appears as a posteriorly located markedly hyperechoic focus in the bladder lumen on B-mode ultrasound. A 'clean' acoustic shadow forms behind the stone — this shadow is a sharply marginated homogeneous hypoechoic/anechoic band. Clean acoustic shadow differs from 'dirty' shadow: dirty shadow is seen in gas-containing structures (reverberation artifact) and contains internal echogenicities. When stone size >5 mm, US sensitivity exceeds 90%; sensitivity decreases for <5 mm stones. Examination should be performed with a full bladder (as acoustic window) — stone detection is difficult in an empty bladder. Multiple stones may be seen clustered or separately.
Report Sentence
A __ mm hyperechoic focus is seen in the bladder lumen with clean posterior acoustic shadowing; consistent with bladder calculus.
Appears as a rapidly changing colored pixel pattern (blue-red mixture) at the stone surface on color Doppler ultrasound — does not represent true blood flow, it is an artifact. Twinkling artifact is a particularly helpful additional finding in small stones (<5 mm) and when acoustic shadow is not clearly delineated. It is seen in all calculus types but is more prominent in rough-surfaced stones (calcium oxalate dihydrate, struvite). When a suspicious hyperechoic focus is detected on B-mode, Doppler should be activated to search for twinkling artifact — its presence strengthens the calculus diagnosis. Twinkling artifact is also used in renal stones and can increase calculus detection rate by 20-30%.
Report Sentence
Twinkling artifact is seen on color Doppler over the hyperechoic focus; this finding supports the diagnosis of calculus.
In the delayed (excretory) phase of CT urography, the stone appears as a filling defect in the contrast-opacified bladder lumen. The stone maintains its own hyperdense density while the surrounding opaque urine increases contrast, clearly delineating the stone margins. This phase is particularly useful for detecting small stones (<5 mm) and differentiating from bladder wall lesions. The triad of non-enhancing filling defect + gravity-dependent position + movement (rolling stone) confirms the diagnosis. Blood clot (coagulum) can also create filling defects but clot density (40-70 HU) is much lower than stone density.
Report Sentence
A non-enhancing filling defect is seen in the opacified bladder lumen on excretory phase CT urography, consistent with bladder calculus.
On MRI, bladder stones appear as signal void (markedly hypointense) on T2-weighted sequences. The contrast between hyperintense urine signal (free water in bladder lumen appears bright on T2) and hypointense stone facilitates stone detection. On T1-weighted sequences, the stone is also hypointense but contrast is less compared to T2 because urine signal is also low. On DWI, the stone remains signal void — shows no diffusion restriction because there are no free water molecules in the crystalline structure. MRI is less commonly used than CT and US for bladder stone diagnosis but may serve as an alternative when CT is contraindicated (pregnancy, radiation avoidance). Small stones (<3 mm) may not be detected on MRI.
Report Sentence
Signal void is seen in the bladder lumen on T2-weighted sequence creating conspicuous contrast against hyperintense urine signal; consistent with bladder calculus.
Signs of bladder outlet obstruction are frequently seen with bladder calculus: (1) Bladder wall thickening and trabeculation — irregular inner wall contour due to detrusor muscle hypertrophy; (2) Bladder diverticula — pockets forming at areas of wall thickening due to mucosal herniation; (3) Increased bladder volume — post-void residual; (4) Bilateral ureterhydronephrosis — reflection to upper urinary system in prolonged obstruction; (5) Prostatic hypertrophy (in males) — prostatic indentation at the bladder base. These findings indicate the underlying obstructive pathology and explain the etiology of stone formation. The triad of trabeculation + diverticulum + stone is pathognomonic for chronic bladder outlet obstruction.
Report Sentence
Bladder wall trabeculation and thickening are seen, consistent with chronic bladder outlet obstruction; the intraluminal calculus has formed on this background.
Criteria
Hyperdense >700-1000 HU on CT; monohydrate form has smooth surface, dihydrate form has spiculated/mulberry surface; most common stone type (60-70%); forms on background of hypercalciuria and hyperoxaluria.
Distinct Features
Identified as calcium stone material on DECT (dual-energy CT) — shows minimal density change between low and high energy (unlike uric acid stones). Always radiopaque on radiograph and CT. Jack-stone morphology is specific to calcium oxalate dihydrate stones.
Criteria
Low-moderate density 200-500 HU on CT; radiolucent on plain radiograph (invisible); forms in acidic urine (pH <5.5); associated with gout, metabolic syndrome, myeloproliferative diseases; specifically identifiable on DECT.
Distinct Features
Uric acid stones show significant density increase at low energy (80 kVp) on DECT — this feature is specific to uric acid and indicates treatability with medical litholysis (alkaline citrate, allopurinol). Dissolution with urine alkalinization (pH >6.5) is possible — may not require surgery.
Criteria
Moderate density 600-900 HU on CT; associated with urease-producing bacteria (Proteus mirabilis, Klebsiella); alkaline urine (pH >7.0); usually large, rapidly growing; more common in women; history of recurrent UTI; magnesium ammonium phosphate composition.
Distinct Features
Laminar/concentric layered structure may be visible on CT — reflects alternating deposition of bacterial biofilm and mineral layers. Staghorn configuration is classic in the kidney but in the bladder usually appears as a large single stone. Recurrence rate after surgery without antibiotic treatment is high (>50%).
Criteria
Homogeneous density 600-800 HU on CT; forms on background of cystinuria (autosomal recessive); usually at young age (<30); bilateral and recurrent; 'ground-glass' internal structure; hexagonal crystals on urine microscopy are diagnostic.
Distinct Features
Homogeneous 'ground-glass' internal structure on CT is quite specific for cystine stones — other stone types usually appear homogeneously hyperdense or heterogeneous. Shows different attenuation profile from calcium and uric acid stones on DECT. Medical treatment (D-penicillamine, tiopronin, urine alkalinization) is possible but surgery is also usually required.
Distinguishing Feature
Urothelial carcinoma shows enhancement and continuity with the wall; does not move with positional change (immobile); bladder calculus does not enhance and moves gravity-dependently (rolling stone). Calcified tumor may mimic stone but presence of enhancing solid component is distinguishing.
Distinguishing Feature
Diverticulum is a fluid-filled structure extending outward from the bladder wall; stone within diverticulum (diverticular stone) may not move — rolling stone sign may be lost due to narrow neck. Diverticulectomy should be considered due to risk of coexisting stone + tumor within diverticulum.
Distinguishing Feature
Cystitis is characterized by diffuse wall thickening and mucosal enhancement; no intraluminal calculus present. However, infected stone (struvite) may coexist with cystitis — in this case both wall thickening and stone are seen. Absence of stone in isolated cystitis is distinguishing.
Distinguishing Feature
Ureterocele appears as a cystic structure in the bladder lumen (cobra-head sign); may contain stone but is surrounded by ureterocele membrane. Free bladder stone has no membrane/cyst structure. Ureterocele stone is localized at the orifice and immobile.
Urgency
urgentManagement
surgicalBiopsy
Not NeededFollow-up
3-monthBladder stone treatment is planned based on stone size and underlying pathology. Small stones (<2 cm) are treated with transurethral cystolithotripsy (laser, pneumatic, or ultrasonic lithotripsy), while large stones (>3 cm) may require percutaneous or open cystolithotomy. The underlying obstructive pathology (BPH, urethral stricture) must be treated simultaneously — otherwise recurrence rate is high. Medical litholysis (urine alkalinization + allopurinol) may be attempted for uric acid stones. Follow-up imaging (US or low-dose CT) at 3 months post-treatment is recommended for recurrence surveillance. Metabolic stone analysis (24-hour urine, stone composition analysis) is mandatory for recurrence prophylaxis.
Bladder stones usually develop secondary to bladder outlet obstruction (BPH). Symptoms include suprapubic pain, dysuria, hematuria, and stream interruption. Small stones may pass spontaneously. Cystolithotomy or lithotripsy is performed for large stones. Treatment of underlying obstruction (BPH) is important for recurrence prevention. Chronic bladder stone irritation may create risk of squamous metaplasia and SCC.