Is it an asymptomatic bacteriuria or a urinary tract infection?

July 6, 2017

Contributed by Dr. Philip Chan

Case

JR is a 92-year-old woman who lives at a long-term care (LTC) facility. She complains of not feeling well for the last two days with some lower abdominal discomfort. She has no burning on voiding, but her urine is cloudy and has a strong odor. She has also had recent falls. Her vitals were within normal limits. Her comorbidities include mild-to-moderate stage dementia, hypertension, atrial fibrillation on anticoagulant therapy, osteoarthritis and coronary artery disease.

Background

Urinary tract infections (UTIs) are commonly suspected in older adults in LTC facilities. This often results in antibiotic prescription, even when the patients are asymptomatic.^{1, 2} Asymptomatic bacteriuria (ASB) is quite common in the elderly population and the use of antibiotics in this setting can lead to increased antibiotic resistance and possible harm.¹ Cognitive impairment, difficulties with communicating symptoms, chronic genitourinary problems and comorbidities often pose a challenge to accurate diagnosis of a UTI. Urine cultures are often requested as a first investigation in those with increased confusion, falls or functional decline, and/or increased urine cloudiness or odor. Age-related changes and indwelling catheters often lead to ASB consequently complicating the interpretation of the urinalysis and urine culture. It is important to recognize these challenges and to have a systematic approach for this patient population.^{1, 3}

Loeb et.al.⁴ developed a list of minimum criteria for initiation of antibiotics for LTC residents. They showed a reduction in the number of antibiotics prescribed for suspected UTI, without significant difference in hospitalizations or mortality between treatment and control.⁴ Numerous UTI protocols have been developed based on these criteria. Examples include protocols found online at Toward Optimized Practice³ and Do Bugs Need Drugs.⁵ Although these guidelines should not replace clinical judgment, they do offer a systematic approach for investigating patients with a potential UTI.

Assessment

UTIs should be diagnosed using a history of localized genitourinary tract symptoms and a significant urinary culture. There are many possible genitourinary tract symptoms and signs, aside from dysuria, frequency/urgency and fever, which front-line staff should seek. New back or flank pain may indicate an upper UTI and can be missed in the dementia patient with absent or masked fever. Checking the patient for suprapubic tenderness, hematuria, urinary retention and worsening frequency or urinary incontinence can be helpful, and site staff can provide useful collateral history. An exception is seniors with chronic urinary catheters and fever in which typical UTI symptoms may not be present and critical evaluation is needed.^{1, 3, 6} Those who are insensate (e.g., high level spinal trauma or multiple sclerosis) often do not have localized symptoms, and early investigations and treatments should be considered if there is increasing fatigue and new or worsening neurological symptoms.³

The clinical history is important given the high rate of asymptomatic bacteriuria in LTC seniors.^{1, 4} Residents with an indwelling Foley catheter for more than 14 days can have a 100% rate of ASB⁷ so should be changed prior to sample collection to limit contamination by biofilm.¹

Significance of urine culture results depends on the clinical history, method of urine collection, colony count and organism(s) isolated. The practitioner should look for a colony count of greater than or equal to 10 ^ 8 cfu/L with a single organism, but lower counts can be significant in patients with high clinical suspicion of a UTI,⁸ since urinary frequency or fluid rehydration can limit bacterial incubation time in the bladder.³ Proteus and M. Morganii organisms may be associated with renal or ureteric stone formation. If organisms are confirmed then urology consultation should be considered.³

Pyuria alone cannot differentiate a UTI from ASB,^{1, 3} although a negative urine microscopy and culture can help exclude a UTI. For the elderly, there is no benefit for antibiotic treatment for asymptomatic bacteriuria in terms of recurrent symptomatic infections.^{1, 7} Antibiotic prophylaxis is recommended for ASB if there will be urologic instrumentation causing mucosal bleeding.^{3, 9}

Management

In the low-risk stable patient, oral or subcutaneous fluid rehydration should be considered for 24 hours with monitoring of vital signs and development of UTI symptoms. In those with symptoms of a UTI as described above, they should have a urine sample sent for analysis and culture. Antibiotics should be guided by results of urine culture results.⁵ For recommended antibiotic regimens and durations, please refer to the online Bugs and Drugs Treatment recommendations.⁵

Special considerations for LTC patients include renal dosing of antibiotics based on calculated creatinine clearance and reviewing interactions with medications (e.g., warfarin and checking INR earlier).

Back to case.

JR was assessed and felt to be clinically dehydrated so no urine analysis or culture was done. The plan was to push oral fluids to 1.5L per day, and by day two, her urine color and odor had improved and her lower abdominal pain had resolved. There was also an improvement in her mental status.

ASB is common in older adults in LTC facilities. A systematic approach to diagnosing UTIs in this population is crucial to avoiding inappropriate antibiotic use and reducing the risk of multi drug resistant antibiotics.

References

1. 1. Genao L, Buhr GT. Urinary tract infections in older adults residing in long-term care facilities. The annals of long-term care: the official journal of the American Medical Directors Association. 2012;20(4):33.
   2. Trautner BW. Asymptomatic bacteriuria: when the treatment is worse than the disease. Nature Reviews Urology. 2012;9(2):85-93.
   3. Toward Optimized Practice [available here].
   4. Loeb M, Bentley DW, Bradley S, Crossley K, Garibaldi R, Gantz N, et al. Development of minimum criteria for the initiation of antibiotics in residents of long-term–care facilities: results of a consensus conference. Infection Control & Hospital Epidemiology. 2001;22(02):120-4.
   5. Do Bugs need Drugs [Available here].
   6. Hooton TM, Bradley SF, Cardenas DD, Colgan R, Geerlings SE, Rice JC, et al. Diagnosis, prevention, and treatment of catheter-associated urinary tract infection in adults: 2009 International Clinical Practice Guidelines from the Infectious Diseases Society of America. Clinical infectious diseases. 2010;50(5):625-63.
   7. Nicolle LE, Bradley S, Colgan R, Rice JC, Schaeffer A, Hooton TM. Infectious Diseases Society of America guidelines for the diagnosis and treatment of asymptomatic bacteriuria in adults. Clinical Infectious Diseases. 2005:643-54.
   8. Long Term Care. Choosing wisely Canada [available here].
   9. Canadian Geriatrics Society. Choosing wisely Canada [Available here].