What are the common causes of bladder cystitis in an adult female patient with no underlying medical conditions?

Causes of Bladder Cystitis

Escherichia coli is the causative organism in approximately 75% of all bladder cystitis cases, with the remaining infections primarily caused by Enterococcus faecalis, Proteus mirabilis, Klebsiella, or Staphylococcus saprophyticus. 1

Bacterial Pathogens

The microbial etiology of bladder cystitis is dominated by a narrow spectrum of uropathogens:

• E. coli accounts for more than 75% of all bacterial cystitis in all patient groups 1
• Other common organisms include Enterococcus faecalis, Proteus mirabilis, Klebsiella species, and Staphylococcus saprophyticus 1
• These organisms typically ascend from the periurethral area when normal flora are replaced by uropathogenic bacteria 1

Mechanism of Infection

Cystitis occurs when uropathogenic bacteria from the periurethral area ascend into the bladder, causing an inflammatory response of the bladder mucosa. 1

• UPEC (uropathogenic E. coli) can invade urothelial cells and form intracellular bacterial communities (IBCs), which contribute to both acute and recurrent infections 2
• Type 1 pili are required for bacterial invasion and IBC formation 2
• The urothelial barrier represents a critical mucosal defense that bacteria must bypass to establish infection 2

Risk Factors and Contributing Causes

Behavioral and Hygiene Factors

• Sexual activity, particularly in women using diaphragms and/or spermicides 1
• Inadequate hydration leading to infrequent urination 1
• Delayed post-coital voiding 1
• Use of spermicidal-containing contraceptives 1

Anatomical and Structural Causes

When cystitis recurs rapidly (within 2 weeks) or persists despite treatment, structural abnormalities should be considered:

• Bladder or urethral diverticula 1
• Calculi (stones) 1
• Foreign bodies 1
• Cystoceles 1
• Infected urachal cysts 1
• Fistulae 1
• Urinary tract obstruction 1

Host-Related Factors

Postmenopausal women face increased risk due to:

• Atrophic vaginitis 1
• Urinary incontinence 1
• High postvoid residual urine volumes 1

Other host factors include:

• Immunosuppression 1
• Diabetes 1
• Pregnancy 1
• Voiding dysfunction 1

Iatrogenic Causes

• Catheterization (most important risk factor for catheter-associated UTI, with 3-8% daily incidence of bacteriuria) 1
• Prior urinary tract surgery or instrumentation 1
• Prolonged catheterization duration 1

Non-Infectious Causes

While bacterial infection is the primary cause, interstitial cystitis/bladder pain syndrome represents a non-infectious etiology characterized by bladder pain, frequency, urgency, and nocturia 3, 4. Proposed mechanisms include:

• Bladder wall/urothelial defects 3, 4
• Autoimmune disorders 3, 4
• Neurogenic inflammation 3, 4
• Chronic or subclinical infection 4

Clinical Pearls

A clean-catch or catheterized urine specimen typically reveals >100,000 organisms per milliliter for significant bacteriuria. 1, 5

Important distinction: Reinfection (occurring >2 weeks after treatment with a different pathogen) versus relapse/persistent infection (same organism within 2 weeks) helps guide further evaluation for structural abnormalities 1.