Acute cystitis is defined as the acute infectious inflammation of the urinary bladder. Uncomplicated acute cystitis means that the patient does not have any structural abnormalities and is not immunocompromised. Patients usually present with dysuria, urinary urgency, urinary frequency and suprapubic pain/tenderness. Urine analysis usually reveals pyuria. Trimethoprim-sulfamethoxazole is the treatment of choice for uncomplicated cases while ciprofloxacin should be preserved for complicated cases.
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Escherichia coli: Gram negative rod off a culture plate from a patient with urinary tract infection

Image: “Escherichia coli: Gram negative rod of a culture plate from a patient with urinary tract infection” by Bobjgalindo – Own work. License: GFDL


Definition of Acute Cystitis

Acute cystitis is one form of urinary tract infections that are usually more common among women. The term “uncomplicated acute cystitis” indicates a form of confined urinary tract infection to the urinary bladder without ascending infection. The term also implies that the patient is a premenopausal nonpregnant woman who does not have any preexisting urologic structural abnormalities.

Epidemiology of Acute Cystitis

Acute cystitis is a very common condition especially among sexually active women. The most common identified causative organism is Escherichia coliStaphylococcus saprophyticus, Klebsiella species, and Proteus are responsible for most of the remaining cases.

Most common etiology: Escherichia coli

  • Only a few serogroups cause most infections , e.g. “uropathogenic E. coli”

Approximately, 7 million people present to the outpatient clinic due to acute cystitis. This is associated with tremendous costs on the health care system, up to $1.6 billion. Therefore, the notion to diagnose acute uncomplicated cystitis on the phone is becoming more commonly acceptable among physicians and patients.

The condition, even though not life threatening, can be associated with significant morbidity. Approximately, half of the cases report severe pain that they have to miss work or school. The symptoms usually last for one week and during this week half of the patients abstain from sexual intercourse.

Pathophysiology of Acute Cystitis

E. coli bacteria

Image: “Low-temperature electron micrograph of a cluster of E. coli bacteria, magnified 10,000 times. Each individual bacterium is oblong shaped.” by Eric Erbe, digital colorization by Christopher Pooley, both of USDA, ARS, EMU. License: Public Domain

Cystitis means bladder mucosal invasion by enteric bacteria. Escherichia coli inhabit the periurethral vaginal opening and can ascend to the bladder and colonize the bladder. The urinary tract system should be sterile; therefore, the presence of pathologic E. Coli would result in inflammation of the bladder and the initiation of the symptoms of acute cystitis.

Adhesins that are expressed on the bacterial surfaces play an important role in facilitating E coli adhesion to the cellular membranes in the urinary epithelium.

Host resistance also plays a role in the pathophysiology of urinary tract infections predisposition. Sexual intercourse, urinary tract obstruction, and instrumentation for instance by urethral catheterization puts the patient at risk of developing urinary tract infections and cystitis.

  • Shorter urethra in women; closer to anus and colon flora
  • Causative organisms colonize vaginal introitus and periurethral area.
  • Massage of urethra in women during sexual intercourse forces bacteria into bladder.
  • Motile bacteria can ascend urinary tract against urinary stream.

Lactobacilli are nonpathogenic bacteria that colonize the vagina in healthy premenopausal women. Recent use of antibiotics for any indication can eradicate this bacterium, allowing room for uropathogenic bacteria to grow and colonize the urinary and genital tracts.

Therefore, recent use of antibiotics, sexual intercourse, abnormal urinary tract anatomy, urethral instrumentation, and urinary tract obstruction by stones or other disease processes are the most common risk factors for developing acute cystitis.

Clinical Presentation of Acute Cystitis

Patients with acute cystitis complain of dysuria, urinary urgency and increased urinary frequency. Urinary frequency is different from polyuria. In urinary frequency, the patient goes many times to the bathroom to urinate because of the feeling to do so but the total volume of urinary output is usually not increased.

Polyuria, which can be caused by diabetes insipidus, diabetes mellitus, or nephrotic syndrome is associated with an actual increase in the amount of urine produced per day.

Lower abdominal pain is also commonly found in patients with cystitis. Patients can also complain of lower back and flank pain even though they do not have ascending pyelonephritis. Bloody urine can complicate the picture in about 10% of the cases. Patients might develop fevers and chills but these signs are usually more common with ascending urinary tract infections.

History of recent sexually transmitted diseases, and multiple current sexual partners put the patient at an increased risk of developing acute cystitis. Recent history of hospital admission, urinary catheterization, or use of antibiotics should be sought to evaluate for possible risk factors.

Patients with acute cystitis are not toxic or severely ill. If the patient has fever, chills and severe costovertebral angle tenderness, the possibility of acute pyelonephritis should be excluded. Suprapubic tenderness is common in patients with acute cystitis. Because of the overlap of the symptoms with pelvic inflammatory disease, pelvic examination is indicated.

Patients with acute cystitis in contrast to pelvic inflammatory disease should not have cervical tenderness, or vaginitis.

Diagnostic Workup for Acute Cystitis

Urine analysis is indicated to provide evidence for the presence of white blood cells in the urine. The presence of more than 10rimethoprim-sulfamethoxazole white blood cells per mL of urine is indicative of infectious acute cystitis.

Pyuria presence is a very good sign of acute cystitis but the specificity is usually low. Nitrate tests detect the presence of uropathogens by detecting the byproducts of the nitrate reductase enzyme which is present in them. The specificity of this test can be as high as 100%.

The golden standard for the diagnosis of urinary tract infections remains urine culture. Patients with more than 1000 colony-forming units per mL on urine culture are diagnosed with acute cystitis.

Patients with uncomplicated acute cystitis rarely have elevated white blood cells in the blood, therefore, a complete blood count is not useful. Immobilized patients, those with spinal cord injuries or those with severe urinary tract obstruction should undergo diagnostic catheterization which allows for the collection of a urine sample for culture and sensitivity testing.

Presumptive diagnosis: presence of pyuria

  • >10 WBCs/µl of mid-stream urine in counting chamber
  • >5-10 WBCs/high-power microscopic field in centrifuged urine sample
  • Dipstick leukocyte esterase test
    • Sensitivity: 75-96 %
    • Specificity: 94-98 %
  • Microscopic hematuria
  • Urine culture: >105   bacteria/mL (most patients)
    • <105/mL in some symptomatic patients
  • Gram stain of uncentrifuged, mid-stream urine
    • Presence of 1 organism/microscopic field ≈ 105 organisms/mL

Treatment of Acute Cystitis

Treatment of acute cystitis usually includes antibiotics but more recent data are showing that symptoms can resolve without any specific treatment. Therefore, some experts are recommending allowing for a 48 hour delay of antibiotic treatment if the patient agrees to see if their symptoms would improve on their own.

Trimethoprim and sulfamethoxazole

Image: “Structural formulae of dihydrofolate reductase inhibitor trimethoprim and sulfonamide antibiotic sulfamethoxazole. Both are components of a combination drug trimethoprim/sulfamethoxazole (BAN—co-trimoxazole), sold under the brand names Septra and Bactrim.” by Vaccinationist – Own work. License: Public Domain

If antibiotics are going to be used, the first-line therapy is usually trimethoprim-sulfamethoxazole. Ciprofloxacin should not be used in uncomplicated cases of acute cystitis to lower the risk of developing resistant organisms. Once antibiotic therapy is started, symptoms usually take six days to resolve.

Patients who cannot receive trimethoprim-sulfamethoxazole for some reason, such as allergic reactions to sulfonamides can receive fosfomycin or ciprofloxacin.

Patients with complicated acute cystitis due to history of recurrent urinary tract infections, being pregnant or having diabetes mellitus should receive ciprofloxacin as first line therapy.
More sick patients who cannot tolerate oral antibiotics should receive intravenous ciprofloxacin or ampicillin plus gentamicin.

Patients with asymptomatic bacteriuria who are not pregnant should not receive any specific treatment. On the other hand, pregnant women with asymptomatic bacteriuria might benefit from antibiotic therapy.

Antibacterial agent choices

  • Good activity against offending pathogen while least effect on vaginal and intestinal flora
    • Nitrofurantion (5 days), fosftomycin (1 day), TMP/SMX (3 days), pivmecillinam (3-7 days)
    • Fluoroquinolones (3 days) – held in reserve

Management of recurrent cystitis

  • Trimethoprim/sulfamethoxazole (TMP/SMX) (single strength), nitrofurantoin, or fluoroquinolone after intercourse
  • Long-term prophylaxis
    • Nightly nitrofurantoin 50 mg, TMP/SMX (half tablet), or fluoroquinolone
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