UTI Uncomplicated vs. UTI Complicated

Urinary tract infections (UTIs) start with the colonization of uropathogens in the vaginal introitus or the urethral meatus. The colonization then moves up through the urethra into the bladder. This infection of the bladder and lower urinary tract is called cystitis. When an infection ascends into the upper urinary tract and the kidneys, it is called pyelonephritis. A UTI that extends beyond the bladder and includes a fever or other systemic symptoms is a complicated UTI. Complicated UTIs can lead to sepsis.

UTIs can be clinically categorized as either acute uncomplicated UTIs or acute complicated UTIs based on the extent and severity of the infection. This categorization directs the management of care and differs from other conventions.

Let’s compare:

Genitourinary abnormalities may be associated with an acute complicated UTI (See Table 1). Blockage to a normal stream of urine decreases the flushing action of bacteria. Mechanisms of infection include (Hooton & Gupta, 2021):

• Genitourinary tract instrumentation increasing introduction of organisms
• Obstruction with incomplete urinary drainage
• Persistence of bacteria in biofilm on stones or indwelling devices 

The risk of infection varies with different abnormalities. 

An acute complicated UTI occurs in people of any age group (Hooton & Gupta, 2021):

• Men are not generally considered to have acute complicated UTI without concerning symptoms. However, the possibility of prostatic involvement should always be considered. Because uncomplicated UTI is rare in men, any male urinary infection is usually considered to be complicated.
• Increased residual urine volume, cystoceles, and a history of genitourinary surgery associated often times with postmenopausal women are issues consistent with a complicated infection.
• Cystitis or pyelonephritis in a nonpregnant, premenopausal woman without risk factors is considered an acute uncomplicated UTI.

The typical presentation of UTI encompasses both cystitis with complicating features and pyelonephritis.

Signs and symptoms of cystitis include (Hooton & Gupta, 2021; McLellan & Hunstad, 2017):

• Dysuria
• Urinary frequency
• Urinary urgency
• Suprapubic pain
• Hematuria

Signs and symptoms of acute complicated UTI which suggest that infection has extended beyond the bladder include (Hooton & Gupta, 2021; McLellan & Hunstad, 2017):

• Fever
• Other features of systemic illness such as:
  • Chills
  • Marked fatigue or malaise beyond the baseline
  • Rigors

Signs and symptoms of pyelonephritis classically include (Hooton & Gupta, 2021; McLellan & Hunstad, 2017):

• Fever/chills/rigors
• Flank pain
• CVA tenderness
• Nausea/vomiting
• Symptoms of cystitis are often but not always present
• Atypical symptoms may occur, including:
  • Pain in the epigastrium
  • Pain in the lower abdomen
• For men, the presentation of recurrent UTI with pelvic or perineal pain can include prostatitis

Not all patients with acute complicated UTI present with clear symptoms localized to the urinary tract. For example (Hooton & Gupta, 2021; McLellan & Hunstad, 2017):

• Patients with neurological illnesses may have atypical presentations:
  • Spinal cord injuries and neurogenic bladder patients may have autonomic dysreflexia and increased bladder and leg spasms.
  • Patients with multiple sclerosis may have deterioration in neurological function and increased fatigue.
• Elderly or debilitated patients may present with more generalized signs or symptoms of infection without clear symptoms of UTI.
  • Patients and caregivers often interpret cloudy or foul-smelling urine as a UTI. This finding may accompany bacteriuria; it is not diagnostic.
• Patients with chronic symptoms or impaired communication are more problematic.
• For patients with indwelling catheters, clinical deterioration without genitourinary symptoms is seldom due to UTI.
  • Fever without genitourinary symptoms is a common presentation of UTI in patients with indwelling catheters.

Patients with acute complicated UTI may be associated with severe morbidities, such as septic shock or death. However, patients may also present with (Hooton & Gupta, 2021):

• Acute renal failure
  • Acute renal failure is more likely to occur in patients with:
    • Diabetes mellitus
    • Increased age
    • Recent urinary tract instrumentation
    • Urinary tract abnormalities
    • Urinary tract obstruction(s)
  • When renal failure occurs in patients with an acute complicated UTI, deterioration in renal function is usually caused by the underlying urological defect rather than infection.
• Bacteremia
• Multiple organ system dysfunctions
• Sepsis
• Shock
• Acute or chronic infection is occasionally associated with suppurative complications, such as:
  • Metastatic infection, including bone and joint infection or endocarditis
  • Paraurethral abscesses
  • Renal abscesses
  • Perirenal abscess

Acute pyelonephritis can also be complicated (Hooton & Gupta, 2021):

• Emphysematous pyelonephritis
• Papillary necrosis
• Perinephric abscess
• Progression of the upper urinary tract infection to renal corticomedullary abscess 

Massive destruction of the kidney by granulomatous tissue, usually due to obstruction by renal stones, is xanthogranulomatous (Hooton & Gupta, 2021). Nonspecific signs and symptoms like malaise, fatigue, nausea, or abdominal pain may persist for weeks or months before presentation.

It is important to be able to differentiate uncomplicated from complicated UTIs. Remember to always consider the atypical presentations as well.

• Flores-Mireles, A., Walker, J., Caparon, M., & Hultgren, S. (2015). Urinary tract infections: Epidemiology, mechanisms of infection, and treatment options. Nature Reviews Microbiology. 13 (5): 269-284. Visit Source.
• Hooton, T., & Gupta, K. (2021). Acute complicated urinary tract infection (including pyelonephritis) in adults. UpToDate. Visit Source.
• McLellan, L., & Hunstad, D. (2017) Urinary tract infection: Pathogenesis and outlook. Trends in Molecular Medicine. 22 (11): 946-957. Visit Source.