Elsevier

Disease-a-Month

Volume 61, Issue 2, February 2015, Pages 45-59
Disease-a-Month

Urinary tract infections

https://doi.org/10.1016/j.disamonth.2014.12.002Get rights and content

Introduction

Urinary tract infections (UTIs) account for nearly 7 million office visits and 1 million emergency department visits, resulting in 100,000 hospitalizations annually.1 UTIs are more common in women with 33% requiring antimicrobials for at least 1 episode by the age of 24. With an estimated annual cost of community-acquired UTIs being around 1.6 billion dollars, the financial burden is significant.1

A UTI is a microbial infection in any part of the urinary tract including the kidneys, ureters, bladder, and urethra. Certain conditions that predispose patients to UTIs are listed in Table 1. UTIs can be categorized anatomically. If it is localized to the bladder it is called cystitis; if there is renal involvement it is called pyelonephritis. Cystitis and pyelonephritis can both be subcategorized into being either an uncomplicated or complicated infection. Factors that classify complicated UTIs include:

  • Diabetes

  • Pregnancy

  • Symptoms for seven or more days before seeking care

  • Renal failure

  • Urinary tract obstruction

  • Presence of indwelling urethral catheter stent or nephrostomy tube

  • Recent urinary tract procedure or instrumentation

  • Functional or anatomic abnormalities of the urinary tract

  • Renal transplant

  • Immunosuppression

  • History of urinary tract infections in childhood

In addition to cystitis and pyelonephritis there are several other conditions that can affect the urinary tract. These include:

  • Chronic pyelonephritis

  • Emphysematous pyelonephritis

  • Recurrent UTIs

  • Catheter-associated UTIs (CAUTI)

  • Candiduria/funguria

  • Prostatitis

Section snippets

Cystitis

Basis of diagnosis

  • Dysuria

  • Frequency of urination

  • Urgency

  • Suprapubic or low back pain

  • No fevers

  • Positive UA

Pyelonephritis

Basis of diagnosis

  • Fevers ≥38°C

  • Rigors and chills

  • Flank pain or costovertebral angle tenderness

  • Positive urine cultures

  • Leukocytosis

Patients with pyelonephritis will present with similar symptoms and laboratory findings seen in cystitis, but will also have signs of systemic inflammation and flank pain. In such patients, a Gram stain can be useful in guiding immediate empiric antimicrobial selection. It is important to quickly and aggressively treat these patients to prevent severe complications that

Emphysematous pyelonephritis

Basis of diagnosis

  • Presence of gas within the kidney parenchyma

  • Sepsis

  • Leukocytosis

  • Cultures positive for gas-forming bacteria

Emphysematous pyelonephritis (EPN) is a life-threatening complication of poorly controlled diabetes, characterized by bacterial production of gas within the kidney parenchyma. Up to 90% of patients who develop EPN have poorly controlled diabetes mellitus. Early diagnosis and treatment may help avoid emergency nephrectomy. There is a 21% mortality rate from EPN, which is

Pyonephrosis

Urinary tract obstruction in the presence of pyelonephritis may result in pyonephrosis. Pyonephrosis is the presence of pus within the urological system. Patients with pyonephrosis can decompensate rapidly due to obstruction. Thus, early recognition and treatment is of paramount importance.

Similar to an abscess, pyonephrosis is typically associated with fever and chills. It may be caused by a broad spectrum of pathologic conditions involving either an ascending infection of the urinary tract or

Chronic pyelonephritis

Basis of diagnosis

  • Symptoms of acute pyelonephritis except with low-grade fevers

  • Costovertebral angle tenderness which is less severe as compared to acute pyelonephritis

  • Recurrent and inadequately treated pyelonephritis

  • Ultrasound or CT scan shows renal scarring

  • Underlying urinary tract obstruction

Chronic pyelonephritis is characterized by renal inflammation and fibrosis induced by recurrent or persistent renal infection, vesicoureteral reflux, or other causes of urinary tract obstruction such as

Asymptomatic bacteriuria

Asymptomatic bacteriuria (AB) is defined as 2 consecutive clean-catch midstream bacterial cultures with colony counts >105 CFU/mL in females consisting of the same organism. It is also defined as a single clean-catch specimen in men or a single catheterized specimen in all patients. Treatment is only warranted in all pregnant women, men undergoing urological procedures that include mucosal bleeding, and all renal transplant patients. Treatment includes the same doses and regimens as seen in

Catheter-associated urinary tract infections

Basis of diagnosis

  • Presence of indwelling Foley catheter

  • Costovertebral angle tenderness

  • Rigors and chills

  • Delirium

  • Encephalopathy

  • Polymicrobial etiology

Catheter-associated UTI (CAUTI) is the most common healthcare-associated infection in the world. Most cases of CAUTI are usually preventable by avoiding inappropriate use of Foley catheters. The most effective means to decrease the incidence of CAUTI is to reduce the use of Foley catheters or to discontinue them as soon as possible. CAUTI is seen in

Recurrent UTIs and chemoprophylaxis

Women with more than 3 recurrent UTIs yearly should be considered for more aggressive prophylactic regimens in addition to behavioral modification. Women whose recurrent UTIs are associated with sexual intercourse should be offered postcoital prophylaxis. Affective regimens include a single dose of postcoital Nitrofurantoin 100 mg, Trimethoprim–Sulfamethoxazole 80/400 mg mg, or Cephalexin 500 mg. Alternative regimens include Trimethoprim–Sulfamethoxazole 40/200 mg every night or 3 times weekly or

Funguria

Funguria is a common phenomenon encountered in hospitalized patients especially those in an ICU/long-term care setting. Funguria is generally a benign condition. Among healthy adults, yeast are encountered in <1% of urine specimens but account for 5–10% of positive urine culture results in hospital and tertiary care patients. The majority of cases occur in patients with indwelling bladder catheters.17 The majority of these infections are due to Candida species. There are multiple predisposing

Prostatitis

Prostatitis is an inflammatory condition that affects the prostate. Nearly 15% of all men will experience prostatitis like symptoms during their lifetime.20 Although some cases of prostatitis are clearly infectious, most men who are diagnosed with this will have no evidence of bacterial infections. Currently, prostatitis remains more prevalent in men less than 50 years old. Other risk factors include functional or anatomical abnormalities, urogenital instrumentation, chronic indwelling bladder

Conclusion

Urinary tract infections constitute a multitude of disease processes seen in patients. The first and most important question is if the patient is symptomatic. This ranges from having increased frequency and dysuria in cystitis to acutely septic patients in pyelonephritis and acute prostatitis. Workup should include a urinalysis looking for evidence of pyuria followed by urine cultures and Gram stains. If acute bacterial prostatitis is suspected, gentle palpation should be done to verify one׳s

Acknowledgements

The authors would like to acknowledge Dr. Amar Chadaga and Dr. Armand Krikorian for their insightful review of this manuscript.

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