Bladder Stone

Bladder stones, also called vesical calculi or cystolithiasis, are hard deposits of crystallised minerals that form inside the urinary bladder. They occur when urine that has pooled in the bladder is not fully expelled, allowing its mineral content to concentrate and eventually crystallise around a nucleus of debris, bacteria, or foreign material.

Bladder stones are most common in older men, primarily because the most frequent underlying cause is bladder outlet obstruction from benign prostatic hyperplasia (BPH). They can, however, affect women, children, and any patient with conditions that impair complete bladder emptying -- including neurogenic bladder and bladder diverticula.

What is a Bladder Stone?

The urinary bladder stores urine between voidings. Under normal circumstances, the bladder empties fully each time urine is passed. When emptying is incomplete -- for any reason -- residual urine remains in the bladder between voidings. Over time, the minerals naturally present in urine (calcium, oxalate, phosphate, uric acid, and others) become increasingly concentrated in this pooled urine.

As concentration rises, these minerals begin to crystallise around a tiny piece of debris -- a fragment of mucus, a clump of bacteria, or even a suture material from a prior procedure. The initial crystal acts as a seed, attracting further mineral deposition and gradually growing into a stone. Bladder stones range from a few millimetres to several centimetres in diameter. They may be single or multiple, smooth or jagged, and vary in colour and hardness depending on their composition.

Types of Bladder Stone

Bladder stones are classified by their mineral composition. Knowing the type guides decisions about prevention, diet modification, and -- for certain stone types -- medical dissolution therapy.

Calcium Oxalate / Calcium Phosphate

The most common type overall. In the bladder, calcium stones typically arise secondary to urinary stasis -- the prolonged pooling of calcium-rich urine allows crystallisation. Associated with high dietary calcium or oxalate intake, dehydration, and bladder outlet obstruction. Appear dense and clearly visible on plain X-ray.

Uric Acid Stones

Form when urine is persistently acidic (low pH). More common in men, patients with gout, and those with a high-purine diet (red meat, organ meat, shellfish). Importantly, pure uric acid stones are radiolucent -- they may not be visible on plain X-ray but are clearly seen on CT and ultrasound.

Struvite (Infection) Stones

Also called magnesium ammonium phosphate or 'triple phosphate' stones. Form in the presence of urea-splitting bacteria (most commonly Proteus, Klebsiella, Pseudomonas) that alkalinise the urine. Associated with recurrent UTIs and indwelling catheters. Can grow rapidly. Treatment of the underlying infection is essential alongside stone removal.

Symptoms of Bladder Stones

Small bladder stones may cause no symptoms and be discovered incidentally on imaging performed for another purpose. As stones grow larger or become lodged near the bladder outlet, they produce increasingly disruptive and often distinctive symptoms.

Classic Bladder Stone Symptoms

Dysuria: Pain or burning during urination, often worsening at the end of voiding as the contracting bladder presses against the stone
Interrupted urine stream: The stone rolls into the bladder outlet during voiding, blocking flow; the stream stops and may restart when the stone rolls away. This intermittent obstruction is characteristic of bladder stones and differs from the continuous poor stream of BPH alone.
Terminal haematuria: Blood appearing at the end of urination, as the contracting bladder scrapes against the stone. Blood visible throughout the stream can also occur.
Urinary frequency and urgency: The stone irritates the bladder wall, triggering persistent urgency even with a partially empty bladder
Incomplete bladder emptying: A persistent sensation that the bladder has not emptied, often because the stone is resting at the bladder outlet

Symptoms warranting urgent assessment

Complete inability to pass urine despite a full and painful bladder: Acute urinary retention caused by a stone obstructing the urethra
Severe sudden lower abdominal pain: May indicate a large stone suddenly impacting the bladder outlet
High fever with urinary symptoms: Suggests urinary tract infection complicating the stone

Causes and Underlying Conditions

Bladder stones are almost always secondary to an underlying condition that impairs bladder emptying or alters urine composition. Treating the stone without identifying and managing this underlying cause leads to recurrence.

Bladder outlet obstruction: The most common cause in men

Benign prostatic hyperplasia (BPH): The enlarged prostate compresses the urethra, causing incomplete bladder emptying. BPH is responsible for the majority of bladder stones in men over 50. The prevalence of bladder stones in men with BPH increases significantly with prostate size and residual urine volume.
Urethral stricture: Scarring within the urethra that narrows the passage and obstructs urine flow
Bladder neck contracture: Narrowing of the bladder outlet, sometimes occurring after prostate surgery

Neurogenic bladder

Conditions that damage the nerves controlling the bladder -- including spinal cord injury, multiple sclerosis, Parkinson's disease, diabetes, and stroke -- may cause the bladder to contract poorly (acontractile) or to retain significant residual urine. Long-term catheterisation to manage neurogenic bladder is itself a risk factor for stone formation.

Bladder diverticula

Diverticula are outpouchings of the bladder wall that develop as a consequence of chronic high-pressure voiding against obstruction, or congenitally. Urine that enters a diverticulum does not drain during normal voiding -- it pools indefinitely, providing an ideal environment for stone formation. Stones within diverticula are particularly difficult to treat endoscopically and may require open surgery.

Urinary catheters and foreign material

An indwelling urethral or suprapubic catheter provides a surface on which mineral encrustation can accumulate, gradually building a stone. Suture material from prior bladder surgery, staples, and other foreign bodies can also serve as a nidus. Calcified catheter balloons and encrusted catheters are a specific and serious complication.

Kidney stones migrating to the bladder

A kidney stone that passes from the kidney through the ureter can become lodged in the bladder rather than passing out through the urethra. Once in the bladder, further mineral deposition can cause the stone to grow beyond the size at which spontaneous passage is possible. These 'secondary' bladder stones may be of a different composition from primary bladder stones.

Dehydration and dietary factors

Chronic dehydration concentrates urine and accelerates mineral crystallisation
High dietary sodium increases urinary calcium excretion
High dietary animal protein increases urinary calcium, oxalate, and uric acid
Low dietary citrate -- citrate is a natural inhibitor of stone formation; diets low in fruit and vegetables reduce citrate excretion

Complidations of Untreated Bladder Stones

Bladder stones that are left untreated will continue to grow and cause progressive complications:

Recurrent urinary tract infections: The stone provides a surface for bacterial colonisation. Infections in the presence of a stone are difficult to eradicate with antibiotics alone and tend to recur until the stone is removed.
Bladder wall damage: The stone abrades the bladder mucosa, causing chronic inflammation, haematuria, and over time, thickening and fibrosis of the bladder wall. Longstanding bladder stone irritation has been associated with an increased risk of squamous cell carcinoma of the bladder.
Acute urinary retention: A stone that impacts the bladder outlet can completely block urine flow, causing acute urinary retention. This is a urological emergency requiring immediate catheterisation.
Bladder dysfunction: Chronic obstruction from a large stone, combined with the underlying cause (typically BPH), can cause progressive detrusor muscle damage and eventual loss of bladder contractility.
Ureteric obstruction: A stone near the ureteric orifice can obstruct the flow of urine from the kidney into the bladder, causing hydroureter and hydronephrosis with risk of renal impairment.

Preventing Bladder Stone Recurrence

Without attention to the underlying cause and lifestyle modification, bladder stones recur at a high rate. The following measures significantly reduce the risk of new stone formation:

Address the root cause

Treat BPH effectively: Alpha-blockers, 5-alpha reductase inhibitors, or surgical treatment (TURP, HoLEP) reduce residual urine and eliminate the primary environment for stone formation in most men
Manage neurogenic bladder with a structured intermittent catheterisation programme to ensure regular and complete bladder emptying
Change urinary catheters at regular intervals and ensure the balloon is fully deflated before removal

Fluid intake and diet

Drink at least 2.5-3 litres of fluid daily: Water is the most effective. Aim for pale yellow urine throughout the day.
Distribute fluid intake evenly: Avoid going many hours without drinking, particularly in Singapore's warm climate
Reduce dietary sodium: High salt intake increases urinary calcium excretion. Target below 5-6 grams of sodium per day.
Moderate animal protein: High meat intake increases urinary calcium, oxalate, and uric acid. Replace some animal protein with plant protein.
For uric acid stones: Reduce purine-rich foods (red meat, organ meats, shellfish, anchovies). Increase fruit and vegetable intake to alkalinise urine naturally.

Specific prevention based on stone type

Calcium stones: Contrary to intuition, a normal dietary calcium intake is recommended -- very low calcium diets increase oxalate absorption. Reduce dietary oxalate (spinach, nuts, chocolate) and sodium.
Uric acid stones: Potassium citrate to alkalinise urine. Allopurinol if uric acid levels are elevated (gout).
Struvite stones: Complete treatment of urinary infection. Long-term low-dose antibiotics in selected patients with recurrent infection stones.

How Are Bladder Stones Diagnosed?

Diagnosis combines the clinical history -- particularly the characteristic interrupted urine stream -- with imaging and direct visualisation of the bladder interior.

Urine Dipstick and Microscopy: First-line investigation. Detects haematuria (common with bladder stones), pyuria (white cells suggesting infection), and crystalluria. Urine culture excludes or identifies concurrent urinary tract infection.
Ultrasound (KUB Ultrasound): Safe, non-invasive, radiation-free imaging of the kidneys, ureters, and bladder. Identifies bladder stones as echogenic (bright) foci with posterior acoustic shadowing. Also measures post-void residual urine volume -- a key indicator of bladder outlet obstruction. Misses very small stones or those in diverticula.
CT KUB (Computed Tomography Kidney-Ureter-Bladder): Non-contrast CT is the most sensitive imaging investigation for urinary tract stones, including bladder stones. Identifies all stone types including radiolucent uric acid stones. Measures stone size and density, maps the entire urinary tract, and identifies the underlying cause. The preferred investigation when ultrasound is inconclusive.
Plain Abdominal X-ray (KUB X-ray): Simple, quick, and widely available. Identifies calcium-containing and struvite stones as opacities in the bladder region. Will miss uric acid stones (radiolucent). Useful for monitoring known calcified stones. Often performed as a first-line image when bladder stone is suspected.
Cystoscopy: Direct visualisation of the bladder interior through a cystoscope. Definitively identifies stones, their number, size, and location. Assesses the bladder wall, ureteric orifices, and bladder outlet. Can be performed under local anaesthetic as an outpatient procedure. Also the first step of cystolitholapaxy when treatment is planned.
Post-Void Residual (PVR) Measurement: Ultrasound measurement of urine remaining in the bladder immediately after voiding. Elevated residual volume confirms incomplete emptying as the cause of stone formation. Essential for identifying bladder outlet obstruction. A PVR above 150-200 ml is clinically significant.
Uroflowmetry: Measures the rate and pattern of urine flow. Identifies the reduced peak flow rate characteristic of bladder outlet obstruction. The flow curve shape helps distinguish obstruction from detrusor dysfunction. Used alongside PVR to assess the severity of the underlying condition.
Blood Tests: Full blood count to identify infection (elevated white cell count). Renal function tests (creatinine, urea) to assess kidney function, particularly if ureteric obstruction is suspected. Calcium, uric acid, and parathyroid hormone levels to identify metabolic causes of stone formation.
Stone Analysis: When a stone is retrieved during cystolitholapaxy, it is sent for biochemical analysis. Determining the stone composition guides dietary and medical advice to prevent recurrence -- different stone types require different prevention strategies.