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Infectious Disease and Microbiology – Cystitis
Cystitis is a lower urinary tract infection (UTI) involving the bladder and occurs in both women and men. It is one of the most common bacterial infections encountered in clinical practice. In the United States, approximately 7 million cases of UTI occur annually. About one-third of women up to 24 years of age will experience at least one episode requiring antibiotic treatment. Furthermore, nearly half of women whose uncomplicated UTIs resolve spontaneously will develop a recurrence within one year. Cystitis is significantly more prevalent in young women than in young men (approximately 20% vs. 0.5% between ages 16–35 years).
Risk factors vary by population. In premenopausal women, risk factors include prior UTI, congenital urinary tract abnormalities, frequent or recent sexual activity, use of spermicides, diaphragm contraception, increasing parity, diabetes mellitus, pregnancy, obesity, neurologic disease, and conditions requiring indwelling or repetitive bladder catheterization. In postmenopausal women, vaginal atrophy, incomplete bladder emptying, pelvic organ prolapse (rectocele, cystocele, urethrocele, uterovaginal prolapse), diabetes, and prior UTIs increase risk. In men, prostatic hypertrophy, urethral obstruction, catheterization, urinary incontinence, and prior urologic surgery are important risk factors.
The most common etiologic agent is Escherichia coli, responsible for more than 80% of cases. Other Enterobacteriaceae include Proteus mirabilis, Klebsiella pneumoniae, Enterobacter species, Citrobacter species, Serratia species, Salmonella species, and Morganella morganii. Non-Enterobacteriaceae such as Pseudomonas aeruginosa may also be involved, particularly in healthcare-associated infections. Among gram-positive organisms, Staphylococcus saprophyticus is a notable cause, especially in young sexually active women. The emergence of extended-spectrum β-lactamase (ESBL)-producing E. coli and other resistant uropathogens is a growing concern in both community and hospital settings.
Clinically, patients typically present with dysuria, urinary frequency, urgency, abrupt onset of symptoms, and sometimes turbid, foul-smelling, or bloody urine. Suprapubic tenderness may be present, and approximately 10% report low back discomfort. Children may present with nonspecific symptoms such as fever, vomiting, or diarrhea. Elderly patients often exhibit minimal or atypical symptoms.
Physical examination may reveal suprapubic tenderness but is otherwise often unremarkable. Diagnosis is supported by laboratory evaluation. Urinary dipstick testing may detect leukocyte esterase and nitrites. Urine microscopy can demonstrate pyuria and bacteriuria. Urine culture confirms the diagnosis and guides antimicrobial therapy. Pregnancy testing should be considered in women of childbearing age. Imaging is generally unnecessary in uncomplicated cases but ultrasonography may be indicated in men, in women who fail to respond to therapy, or in cases of recurrent infection not clearly related to sexual activity.
The differential diagnosis includes infectious conditions such as pyelonephritis (upper UTI), urethritis, vaginitis, and asymptomatic bacteriuria, as well as noninfectious causes including interstitial cystitis, urolithiasis, bladder tumor, and chronic prostatitis or chronic pelvic pain syndrome.
Acute uncomplicated cystitis is treated with short-course antimicrobial therapy. Common regimens include trimethoprim-sulfamethoxazole for three days, trimethoprim alone for three days, fluoroquinolones such as ciprofloxacin or levofloxacin for three days, fosfomycin as a single oral dose, or nitrofurantoin for five to seven days. Selection should be guided by local resistance patterns. In pregnancy, amoxicillin, nitrofurantoin (avoided near term due to risk of neonatal hemolysis), cefpodoxime, or fosfomycin may be used. Recurrent cystitis may be managed with continuous low-dose prophylaxis using agents such as trimethoprim, trimethoprim-sulfamethoxazole, nitrofurantoin, or fluoroquinolones, though this strategy must be individualized due to increasing antimicrobial resistance.
Complementary approaches have been studied. Certain probiotics (e.g., Lactobacillus strains) may reduce recurrence rates. Cranberry products have been suggested to reduce bacterial adherence and may modestly lower recurrence in women with recurrent UTIs. Methenamine salts may be beneficial in short-term prophylaxis in patients without structural urinary abnormalities. Phenazopyridine may relieve dysuria but does not treat infection and carries potential adverse effects such as hemolytic anemia.
The prognosis for acute uncomplicated cystitis is excellent with appropriate antibiotic therapy. However, recurrent episodes are common, especially in patients with underlying risk factors. Complications may include urethritis, progression to pyelonephritis, and psychological distress associated with recurrent infection. Preventive measures include good hygiene, avoidance of spermicides and diaphragms, careful monitoring during pregnancy, and glycemic control in patients with diabetes.
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