What are the causes of focal calcification in the urinary bladder?

Etiology of Focal Calcification in Urinary Bladder

The most common causes of focal calcification in the urinary bladder include urinary tract infections (particularly schistosomiasis and tuberculosis), bladder tumors, urinary calculi, and radiation or cyclophosphamide-induced cystitis. Understanding these etiologies is crucial for proper diagnosis and management to reduce morbidity and mortality.

Infectious Causes

Schistosomiasis

• Most common cause of bladder wall calcification worldwide 1
• Produces mural calcification with a typical thin arcuate pattern
• May be associated with calcification in other portions of the urinary tract
• Endemic in certain regions, particularly Africa and the Middle East

Tuberculosis

• Can cause focal calcification in the bladder wall
• Usually associated with other signs of genitourinary tuberculosis
• Less common than schistosomiasis as a cause of bladder calcification

Chronic Urinary Tract Infections

• Urease-producing organisms (Proteus, Klebsiella) can lead to struvite stone formation
• Encrustation cystitis may develop with chronic infections
• Positive association between history of urinary calculi and bladder cancer 1

Neoplastic Causes

Bladder Tumors

• Account for approximately 8% of calcified bladder lesions 2
• Different patterns based on histology:
  • Transitional cell carcinoma: surface nodular calcifications
  • Mucinous adenocarcinoma: multiple fine punctate calcifications within the mass
  • Urachal carcinoma: calcification typically at the dome of the bladder 3
• Pure central calcification in renal masses usually indicates malignancy 3

Urinary Calculi

Bladder Stones

• Account for 5% of all urinary calculi 4
• Usually contain calcium components
• May appear laminated, faceted, spiculated, or seedlike
• Risk factors include:
  • Bladder outlet obstruction
  • Neurogenic bladder
  • Foreign bodies (including sutures from previous surgery)
  • Indwelling catheters

Migrated Renal/Ureteral Calculi

• Can become trapped in the bladder
• Usually have uniform radiopacity compared to phleboliths which are often less opaque centrally 3

Iatrogenic and Medication-Related Causes

Radiation Cystitis

• Late complication of pelvic radiation
• Can lead to dystrophic calcification in the bladder wall

Cyclophosphamide-Induced Cystitis

• Direct toxic effect on bladder mucosa
• Can lead to hemorrhagic cystitis and subsequent calcification

Post-Surgical Changes

• Suture materials can serve as nidus for calcification
• Higher risk after prostate surgery or anti-incontinence procedures 4
• Bladder augmentation using ileum or colon (not gastric tissue) increases risk 4

Other Causes

Amyloidosis

• Rare cause of bladder wall calcification
• Usually part of systemic disease

Anatomical Abnormalities

• Urachal remnants may calcify and mimic bladder calculi 5
• Important to use multi-planar reformatted images to distinguish from true bladder stones

Foreign Bodies

• Can serve as nidus for stone formation
• Common in patients with indwelling catheters

Diagnostic Approach

1. CT urography is the imaging procedure of choice for evaluating hematuria and suspected bladder abnormalities 6
2. Consider patient risk factors:
   • History of recurrent UTIs
   • Travel to endemic areas for schistosomiasis
   • Previous pelvic radiation or cyclophosphamide treatment
   • Neurogenic bladder or outlet obstruction
3. Cystoscopy with biopsy is almost always necessary for confirmation and to rule out bladder neoplasia 7

Clinical Implications

• Patients with spinal cord injury and indwelling catheters have significant association between bladder calculi and development of malignant bladder tumors 4
• Patients who undergo bladder augmentation with gastric tissue appear protected from stone formation due to acidic environment, while ileum and colon tissues promote stone formation 4
• Complete removal of stones is important to eradicate causative organisms, relieve obstruction, and prevent further stone growth 1

Understanding the specific etiology of focal bladder calcification is essential for proper management and prevention of complications, including malignancy, recurrent infections, and renal deterioration.