USMLE Guide: Bladder Infection

Introduction

Bladder infection, also known as cystitis, is a common condition characterized by inflammation of the urinary bladder. It is primarily caused by bacterial infection, most commonly escherichia coli (E. coli). This USMLE guide aims to provide essential information on the etiology, clinical presentation, diagnosis, and management of bladder infections.

Etiology

• Bacterial infection: E. coli accounts for approximately 80-90% of bladder infections. Other bacteria such as Staphylococcus saprophyticus, Klebsiella pneumoniae, and Proteus mirabilis can also cause bladder infections, but they are less common.

Clinical Presentation

• Dysuria: Pain or burning sensation during urination.
• Frequency and urgency: Increased frequency of urination and a strong urge to urinate.
• Hematuria: Blood in the urine, which may appear pink or red.
• Lower abdominal discomfort: Mild to moderate pain or pressure in the lower abdomen.
• Cloudy or foul-smelling urine: Urine may appear turbid and emit an unpleasant odor.

Diagnosis

• Urinalysis: Presence of leukocytes (pyuria) and nitrites (indicating bacterial metabolism of nitrates) in the urine supports the diagnosis.
• Urine culture: Identifies the causative organism and determines its susceptibility to antibiotics.
• Imaging studies: In recurrent or complicated cases, renal ultrasound or computed tomography (CT) scan may be performed to evaluate the urinary tract for any abnormalities.

Management

• Antibiotics: Empirical treatment with antibiotics is initiated based on the most likely causative organism, prior antibiotic use, and local resistance patterns. Commonly used antibiotics include:
  • Trimethoprim-sulfamethoxazole (TMP-SMX)
  • Nitrofurantoin
  • Ciprofloxacin
  • Ceftriaxone
• Fluid intake: Encourage increased fluid intake to help flush out bacteria from the urinary tract.
• Urinary analgesics: Phenazopyridine may be used to provide symptomatic relief by alleviating pain and burning during urination.
• Prevention: Advise patients to practice good hygiene, urinate before and after sexual intercourse, and avoid irritants like bubble baths and spermicides.

Complications

• Pyelonephritis: If not promptly treated, bladder infection can ascend into the kidneys, causing a more severe infection known as pyelonephritis.
• Sepsis: In rare cases, the infection can spread to the bloodstream, leading to sepsis, a life-threatening condition.
• Recurrent infections: Some individuals may experience recurrent bladder infections, which may require further evaluation and tailored management.

Conclusion

Bladder infection is a common condition primarily caused by bacterial infection, most commonly E. coli. It presents with dysuria, frequency, urgency, hematuria, and lower abdominal discomfort. Diagnosis is confirmed through urinalysis and urine culture. Management includes antibiotics, increased fluid intake, and urinary analgesics. Complications such as pyelonephritis, sepsis, and recurrent infections may arise if left untreated.