Catheter-associated urinary tract infection: Clinical sciences

Catheter-associated urinary tract infection, or CAUTI for short, is a urinary tract infection in the presence of an indwelling urinary catheter or after the recent removal of the catheter, typically in the last 48 hours. So to decrease the chances of patients developing CAUTIs, you should try to avoid urinary catheters if possible, or remove them as soon as they are no longer needed. When they arise, CAUTIs are most commonly caused by Escherichia coli and Klebsiella pneumoniae, which can colonize the catheter and use it to gain access to the urinary tract.

Now, CAUTIs can be symptomatic or asymptomatic. Symptomatic UTI, or SUTI, is the more commonly diagnosed type because the patient will have symptoms. On the other hand, asymptomatic UTIs are often discovered incidentally when blood and urine cultures are ordered during the workup for other conditions like sepsis. Asymptomatic bacteriuria, or ASB, is when pathogens are found in the urine but not the blood. Asymptomatic bacteremic urinary tract infection, or ABUTI, is when the pathogen is found in both the urine and blood.

Now, if you suspect CAUTI, first, you should obtain a focused history and physical examination, and order labs, such as CBC, CMP, and urinalysis. Based on the findings, we can either suspect ABUTI or CAUTI.

First, let’s take a look at a patient who might have an ASB or catheter-associated ABUTI. The patient might have a history of a current or recently removed indwelling catheter, and although they have no history of UTI symptoms and no findings on physical exam, their labs reveal pyuria and bacteriuria, meaning that their urine cultures are positive.

These findings are often consistent with ASB. However, if blood and urine cultures were ordered as workup of another condition, such as fever or sepsis, and both come back positive for the same pathogen, meaning that they match, this is catheter-associated ABUTI. In that case, you should start antibiotics, and if indicated, remove or replace any indwelling catheter.

Now let’s take a look at how to assess the culture results. If the urine and blood cultures come back negative, or grow different pathogens, consider an alternative diagnosis. On the flip side, if the urine and blood cultures are positive for the same pathogen, the diagnosis is catheter-associated ABUTI, so don’t forget to tailor antibiotics based on culture results. Finally, if the urine culture is positive, but the blood culture is negative, the diagnosis is ASB.

If this is the case, assess indications for antibiotic therapy, like pregnancy, scheduled urologic intervention, or renal transplantation within the past 3 months. If the patient has any of these indications, start tailored antibiotic therapy based on culture results. However, if there are no indications, then no treatment is needed.

Alright, now let’s go back and take a look at individuals who might have catheter-associated SUTI. They present with a history of a current or recently removed urinary catheter and a history of UTI symptoms. These usually include fever, suprapubic discomfort, dysuria, as well as urinary frequency and urgency. Common physical exam findings include suprapubic and costovertebral angle tenderness. In severe cases, especially in older patients, you might detect altered mental status, like confusion or lethargy. Finally, when it comes to labs, they usually reveal elevated WBC count, pyuria, and bacteriuria.

At this point, you can suspect catheter-associated SUTI. But, to confirm the diagnosis, again, you need to obtain a urine sample for culture. While waiting for results, don’t forget to start empiric antibiotics and remove or replace the indwelling catheter if indicated.