Urinary tract infection (UTI)

Internal Medicine Rapid Refreshers is a series of concise information-packed videos refreshing your knowledge on key medical issues that general practitioners may encounter in their daily practice. This episode guides you through the management of urinary tract infections.

Contents

1. Definitions
2. Approach
3. Investigations
4. Management
5. Credits and references

Useful links

• Chapter on urinary tract infections (UTIs) from the McMaster Textbook of Internal Medicine
• Podcast on urinary tract infections from The Intern at Work
• 2010 practice guidelines for the treatment of acute uncomplicated cystitis and pyelonephritis in women by the Infectious Diseases Society of America (IDSA)

Transcript

Introduction

I’m Hosay Said, a senior medical resident at McMaster University. In this video we will go through a practical approach to the assessment and management of patients with urinary tract infections (UTIs). This video is intended for physicians returning to general internal medicine during the coronavirus disease 2019 (COVID-19) pandemic.

Definitions

A UTI is defined as the presence of microorganisms in the urinary tract above the bladder sphincter with associated symptoms of infection. Cystitis is involvement of the bladder only. If the infection goes above the bladder to involve the kidney, this is called pyelonephritis.

Approach

When seeing a patient and assessing for a possible UTI, ask yourself:

1. Are they really symptomatic?
2. Is it an upper versus a lower tract infection?
3. Is this a complicated or an uncomplicated UTI?
4. What is the most likely microbiology?
5. What alternative diagnoses should I consider?

1. Does the patient truly have symptoms of a UTI? One important distinction to make is whether your patient truly has symptoms of a UTI, because we don’t manage asymptomatic bacteriuria in the same way we manage a UTI. We treat asymptomatic bacteriuria in pregnant women and patients who have upcoming urologic instrumentation. I want to emphasize that foul-smelling or cloudy urine is not a symptom of a UTI.

2. Upper or lower urinary tract infection (cystitis vs pyelonephritis): Patients with involvement of the lower tract (cystitis) usually complain of dysuria or pain and burning when they pee, frequency, urgency, and possible hematuria. It’s also important to ask about symptoms of obstruction and review the patient’s medications to see if they’re on any anticholinergic agents, for example, which may cause urinary retention. If the patient has urinary retention or you’re suspecting it, a bladder scan is helpful to confirm that.

Patients with involvement of the upper tract (pyelonephritis) may have flank pain, costovertebral angle (CVA) tenderness on examination, and nausea or vomiting.

Patients with cystitis or pyelonephritis can have systemic symptoms (fevers, chills, rigors), but they’re typically more common in pyelonephritis.

3. Complicated or uncomplicated UTI: A complicated UTI is characterized by the presence of specific risk factors that increase the risk for treatment failure or lead to higher risk for resistant organisms. Factors that suggest a complicated UTI are age >55 years; male sex; current pregnancy; indwelling foley or instrumentation; functional or anatomical abnormality; urinary tract obstruction; symptoms lasting >7 days; diabetes mellitus; recurrent UTIs; and spinal cord injury.

Uncomplicated UTIs are in patients with cystitis and none of the above risk factors or underlying conditions.

4. Likely microbiology: The most common causative organisms responsible for causing UTIs are the “KEEPS” organisms: Klebsiella pneumoniae; Escherichia coli (90%); enterococci; Proteus mirabilis, Pseudomonas aeruginosa (the latter typically in hospitalized patients); and Staphylococcus saprophyticus (in young, otherwise healthy women).

Review your patient’s prior urine cultures to see if they have a history of resistant organisms or if they might have risk factors for having developed resistant organisms. This can help you decide on your antibiotic choices, particularly if the patient has a history of extended-spectrum beta-lactamase (ESBL)-producing bacteria.

5. Alternative diagnoses: A patient coming in with lower urinary tract symptoms or abdominal pain does not necessarily have a UTI. Things to think about include urethritis from a sexually transmitted infection (STI), atrophic vaginitis, nephrolithiasis (renal stones), and prostatitis.

Investigations

When investigating a patient for a suspected UTI, you should do a complete blood count (CBC) looking for evidence of leukocytosis, electrolytes, as well as the creatinine (Cr), with Cr showing whether the patient has acute kidney injury (AKI). That AKI could be secondary to sepsis and organ failure or it could be from a postrenal cause, specifically urinary retention.

You want your patient to perform a urine collection. It needs to be a midstream urine and a clean catch. Clean catch means the patient has cleaned the area prior to collection to avoid contamination.

Urinalysis is generally not helpful in making the diagnosis of a UTI. Patients can often have evidence of leukocytes and nitrates, which can be found in asymptomatic bacteriuria. However, urinalysis is helpful if there’s an absence of pyuria or bacteriuria, because that suggests an alternative diagnosis, especially in patients with nonspecific symptoms, such as delirium.

You want to obtain a urine culture to see what the causative organism is and blood cultures if your patient is systemically unwell or septic.

Imaging can be considered if you’re suspecting the patient may have upper tract involvement.

Additional testing can be guided based on the patient’s history.

Management

As always, check airway, breathing, and circulation (ABC). Obtain intravenous (IV) access. If the patient is hypotensive, start fluid resuscitation. Always ask about allergies. If there is evidence of urinary retention, the patient should have a foley catheter inserted to relieve that. If the patient already has a chronic indwelling foley, it should be changed.

Patients who are systemically well and have uncomplicated cystitis, the first-line treatment in women is nitrofurantoin (brand name Macrobid) 100 mg orally 2 times a day (bid) for 5 days.

Other reasonable empiric treatment options include:

• Trimethoprim/sulfamethoxazole (TMP/SMX; brand name Septra) 1 double-strength tablet bid (check for allergies and if the patient has normal renal function).
• Cephalexin 500 mg orally 4 times a day (qid) or amoxicillin/clavulanate 875/125 mg orally bid.
• Fosfomycin 3 g × 1 dose.
• Ciprofloxacin 500 mg orally bid (if there are contraindications to all the other options).

In women, treatment duration is typically 3 or 5 days. In men, treatment duration is 7 days, irrespective of the antibiotic choice.

In patients who are systemically well but could have complicated cystitis, all of the mentioned antibiotics are reasonable treatment options. The main difference is the duration of treatment, which typically is 7 days but can also be 7 to 14 days if the patient has an underlying anatomical abnormality or a catheter in place.

There is one caveat in patients coming in with a complicated cystitis. There is limited evidence for the use of fosfomycin in complicated cystitis, and it would be an off-label treatment.

In patients who are systemically unwell or have suspected pyelonephritis, use ceftriaxone 1 to 2 g IV every 24 hours if they have no history of resistant organisms. Look back at the patient’s prior urine cultures. If there’s a history of resistant organisms, tailor your empiric antibiotic choice based on those organisms that were resistant in the past. If there is a history of ESBLs, start ertapenem 1 g IV every 24 hours.

Adjust antibiotics based on new culture results and step down to oral therapy when appropriate. Reasonable oral therapy options include TMP/SMX, ciprofloxacin, cephalexin, and amoxicillin/clavulanate. Treatment duration can range from 7 to 14 days, depending on the antibiotic choice, but it will typically last 10 to 14 days in patients with underlying urologic abnormalities.

As always, circle back to your patient and reassess your treatment intervention. See if there’s resolution of symptoms, including pain, as well as systemic features. If the symptoms are persisting or the clinical condition is deteriorating, obtain imaging studies to exclude a perinephric abscess or underlying urologic obstruction. If there is obstruction, urology service should be urgently consulted for intervention. Another thing to remember if your patient is not improving is a bug-drug issue, particularly if your culture results aren’t back yet and the patient has deteriorated.

There are a few pearls that I want you to take away. Remember that nitrofurantoin cannot be used for pyelonephritis because it won’t reach therapeutic concentrations in the upper urinary tract. If S aureus grows on urine culture, blood cultures should be obtained to rule out S aureus bacteremia and find the source.

Credits and references

I’d like to thank Doctor Heather Bannerman (postgraduate year 3 [PGY3] internal medicine resident; editor for this video) and Doctor Dominik Mertz (Division of Infectious Diseases; consultant for this video).

Resources used to create this Rapid Refresher include the chapter on UTI from the McMaster Textbook of Internal Medicine, The Intern at Work podcast on UTIs, and the 2010 Infectious Diseases Society of America (IDSA) practice guidelines for the treatment of acute uncomplicated cystitis and pyelonephritis in women.