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Bladder ultrasound: avoiding unnecessary catheterizations.

Because urethral catheterization is associated with infection, patient discomfort, and increased treatment costs, unnecessary catheterizations should be avoided. Portable bladder ultrasound devices can be used to assess bladder volumes and protocols established to guide the decision to use catheterization.


More than 1 million patients in acute and long-term care facilities are estimated to acquire nosocomial urinary tract infections (UTIs) each year in the United States (Tambyah & Maki, 2000). The majority of these infections are associated with urethral catheterization. Though they may seem harmless and easily remedied with antibiotic therapy, nosocomial UTIs have been estimated to cause 1 death in every 1,000 episodes of catheterization, adding up to 6,500 U.S. deaths yearly (Gokula, Hickner, & Smith, 2004). With a better understanding of alternative strategies and more thorough assessment of urinary retention, nurses can avoid many catheterizations.

One responsibility of all health care providers is to protect patients from hospital-acquired infection and its associated risks. Nurses use skills of inspection, palpation, percussion, and catheterization to evaluate and treat suspected urinary retention. Although it is still appropriate to apply these skills when they are needed, an additional tool is now available to guide the assessment. Portable bladder ultrasound devices have been available since the early 1980s; they are easy to use, and their accuracy and reliability have been proven in many studies (Borrie et al., 2001; Chan, 1993; Coombes & Millard, 1994; Marks, Dorey, Macairan, Park, & DeKernion, 1997; O'Farrell et al., 2001; Ouslander et al., 1994; Schnider, Birner, Gendo, Ratheiser, & Auff, 2000). Although they also may spare patients the discomfort and risks of catheterization, they are still underutilized and nurses on many hospital units do not have access to these devices (Smith, 2002).

The literature on nosocomial urinary infection rates, catheterization, and urinary retention is reviewed. Recent clinical trials involving portable bladder ultrasound devices and the effect of bladder ultrasound protocols on catheterization and infection rates are discussed. Additionally, a guideline for completing cost comparisons and a description of bladder ultrasound protocols to guide care providers in their decision to use invasive catheterizations are provided.

Urinary Catheterization and Infections of the Urinary Tract

Urinary catheterization is an invasive procedure that compromises the body's natural defense against infection. Normal bacteria flora surrounding the meatus or distal urethra can be introduced into the bladder during catheter insertion. Additionally, microorganisms can travel to the bladder along the outside or the inside of the catheter (Maki & Tambyah, 2004; Wong & Hooton, 2002). Bacteria from the hands of health care personnel and from contaminated drainage bags also can lead to infection (Maki & Tambyah, 2004). Catheterizations can be uncomfortable, embarrassing, and risky for the patient; time consuming for the nurse; and costly for the institution. One of the major risks of urethral catheterization is urinary tract infection (Sparks et al., 2004). Catheter-associated urinary tract infections have been identified as the second most common cause of bacteremia linked to increased institutional death rates (Maki & Tambyah, 2004). Catheters have been associated with gram-negative sepsis (Gokula et al., 2004). However, catheterization has long been the gold standard for assessing urinary retention. Whether intermittent or indwelling, catheters are used to relieve obstruction of the urinary tract, drain the bladder of patients with neurogenic dysfunction and urinary retention, aid in surgical procedures, perform bladder irrigation, and monitor fluid status closely in the critically ill (Gokula et al., 2004; Wang & Hooton, 2002). Catheterization should be avoided for purposes of collecting specimens and for urinary incontinence that poses no risk to the patient (Wang & Hooton, 2002).

Studies have estimated that 40% of all hospital-acquired infections are of the urinary tract, and that the majority of these followed urinary catheterization (Maki & Tambyah, 2004; Wang & Hooton, 2002). These infections can add 1 to 4 days to a patient's hospital stay and from $676 to $2,836 to hospitalization costs (Gokula et al., 2004). The risk of developing a nosocomial UTI is estimated to be 5% per day, with approximately 4% of these infections resulting in bacteremia (Gokula et al., 2004). Two recent studies have confirmed that infections of the urinary tract continue to compose the majority of hospital-acquired infections worldwide. A 5-year French study of 1,764 patients in intensive care units found that the urinary tract was the most common site of nosocomial infection, with a rate of 17.2 per 1,000 procedure days (Misset et al., 2003). A large Norwegian study of nosocomial infection rates in long-term care facilities also found that approximately 50% of nosocomial infections were of the urinary tract (Eriksen, Iversen, & Aavitsland, 2004).

A large study by Tambyah and Maki (2000) found that catheter-associated UTIs are rarely symptomatic, often go untreated, and are associated with a large reservoir of antibiotic-resistant bacteria and yeasts. In their study of 1,497 catheterized patients, 235 nosocomial UTIs developed with one case of bacteremia. Another recent study of catheter use in a mid-western hospital found that less than half of catheterizations performed were indicated (Gokula et al., 2004). With an estimated 4 to 5 million patients catheterized yearly, it is imperative that unnecessary catheterizations be avoided (Maki & Tambyah, 2004; Wang & Hooton, 2002).

Urinary Retention

Urinary retention (UR) is an incomplete emptying of the bladder leaving a residual urine volume. It also has been identified as post-void residual (PVR) urine in individuals who are able to void. A clear definition of UR, in terms of actual volumes of residual urine, has not been established and has varied from study to study. The incidence of UR increases with age and occurs in one in three men over the age of 80 (Borrie et al., 2001). Conditions precipitating UR can include a history of urinary problems, such as enlargement of the prostate, urethral strictures, cystocele, and neuropathic bladder (Ouslander et al., 1994). UR also has been associated with anticholinergic medications, analgesics, and pain (Jolley, 1997). Cognitive impairment, stroke, and a lower functional status also may precipitate UR (Kong & Young, 2000).

Studies on varied populations have yielded no consensus regarding normal and abnormal post-void residuals. A study by Grosshans, Passadori, and Peter (1993) of urinary retention in hospitalized older adult patients cited 16 different references, all offering different normal values for PVR; of the studies cited, normal post-void residual urine volumes ranged from 0 ml to 250 ml. In their study of 100 patients, the prevalence of PVR volumes greater than 50 ml was 34%.

According to an extensive literature review by Borrie et al. (2001), clinically significant post-void volumes varied between 50 ml and 300 ml. Most authors accepted volumes between 100 ml and 150 ml as normal. This group studied urinary retention in a geriatric rehabilitation setting. They used the BVI 2500+[R] (Diagnostic Ultrasound) scanner to assess PVR urine in 167 patients. In their study, catheterization was indicated for two consecutive PVR volumes greater than 150 ml. Only 11% of their sample met this criterion.

A recent study by Dromerick and Edwards (2003) observed the relationship between post-void residuals and UTIs in 101 stroke rehabilitation patients. Authors confirmed that few data exist to distinguish between normal and abnormal residual urine volumes. They concluded that the patient's risk of UTI increases only after two consecutive bladder ultrasound readings of greater than 150 ml. They recommended using a threshold for catheterization of 50 ml to 200 ml.

Kong and Young (2000) defined urinary retention as two consecutive PVRs greater than 100 ml. In their study of 80 post-stroke patients, 29% had urinary retention by these study parameters. This was associated significantly with the development of a UTI.

While not all urethral catheterizations are unnecessary, many catheterizations can be avoided. Urinary retention can be assessed noninvasively by portable ultrasound (Borrie et al., 2001; Coombes & Millard, 1994; Marks et al., 1997). The implementation of bladder ultrasound protocols will help caregivers determine when catheterization is necessary. More research is required in order to better define pathologic urinary retention.

Bladder Ultrasound Devices

Portable bladder ultrasound devices are accurate, reliable, and noninvasive (Chan, 1993; Coombes & Millard, 1994; Marks et al., 1997; Ouslander et al., 1994; Schnider et al., 2000). They are easy to use and cost effective. The use of a bladder ultrasound device is appropriate when there is urinary frequency, absent or decreased urine output, bladder distention, or inability to void after catheter removal, and during the early stages of intermittent catheterization programs (Lewis, 1995). McCliment (2002) discussed use of bladder ultrasound devices to help manage incontinence in nursing home patients. By monitoring fluid intake habits and using the scanner for 3 days, staff members customized "continence care schedules" for each patient. This has helped patients to recognize the sensations associated with bladder volumes and establish voiding patterns. It has been the author's experience that bladder ultrasound devices have been used to assess the patency of indwelling catheters. When urine output from an indwelling catheter decreases, or when a patient has signs of urinary retention with a catheter in place, the bladder scan device can be used to determine bladder volume. In theory, there should be minimal urine in the bladder if an indwelling catheter is in place. High urine volumes may suggest that the catheter is occluded or positioned improperly.

The largest portion of studies that evaluated the accuracy and reliability of bladder scan devices used a model of the BladderScan BVI[R] (Diagnostic Ultrasound). Several models have demonstrated acceptable levels of accuracy and reliability, including the BVI 2000[R] (Ouslander et al., 1994; Sparks et al., 2004), BVI 2500[R] (Coombes & Millard, 1994; Frederickson et al., 2000; Marks et al., 1997; Moore & Edwards, 1997), BVI 2500+[R] (Borrie et al., 2001; Coombes & Millard, 1994), BVI 3000[R] (Kong & Young, 2000), and the BVI 5000[R] (O'Farrell et al., 2001). Other acceptable devices include a French device, the Massiot-Philips SDR 120 Suresne (Grosshans et al., 1993), and the MK 100 (Chan, 1993).

Portable bladder ultrasound devices are easy to use and well tolerated by patients. Smith (1999) offered step-by-step instructions for use of the BVI 3000, as one example of the bladder ultrasound. First, after the machine is turned on, the operator indicates whether the patient is male or female. After explaining the procedure, the operator applies ultrasound gel to the hand-held transducer. Next, with the patient supine, the transducer is placed 1 inch above the symphysis pubis pointing toward the bladder. There is an icon of a person on the transducer and the head of the icon should be pointing toward the head of the patient. Finally, the transducer button is pressed to scan the bladder. The device signals when the scan is complete and a picture of the bladder and an estimated volume appears on the screen. Several scans can be done in order to obtain the best picture and most accurate assessment of the bladder's volume.

Cost Comparisons

In the literature, bladder ultrasound devices have been estimated to cost from $8,300 to $10,000 (Frederickson et al., 2000; Moore & Edwards, 1997; Smith, 2002). Considering the additional $680 in hospital costs per incidence of hospital-acquired UTI, and the costs of supplies and nursing time, the expense of the device would be recovered (Moore & Edwards, 1997). Recent studies have outlined cost-benefit analyses used when considering the purchase of a portable bladder ultrasound device by an institution.

Philips (2000) described one facility's attempt to decrease nosocomial urinary tract infections and the associated cost analysis. Prior to implementing their UTI Reduction Project, they estimated the yearly cost of nosocomial UTIs to be $1.7 million. A portion of this program encouraged the use of a bladder ultrasound protocol after indwelling catheter removal. In the month prior to the introduction of the bladder ultrasound protocol, 118 intermittent catheterizations were performed in the rehabilitation unit. One month after the protocol, only two intermittent catheterizations were performed. Supply savings alone were estimated at $2,784 yearly. If 1,392 catheterizations were avoided yearly, then approximately 27 nosocomial UTIs may also be avoided; potential savings were estimated at $45,900 for 1 year.

Frederickson et al. (2000) also offered a brief cost analysis in their study of a bladder ultrasound protocol in orthopedic and surgical units. They estimated the BVI 2500[R] to cost $8,300 and treatment costs for nosocomial UTIs to be $680 for each incident. They concluded that the supply cost saved after 2,280 avoided catheterizations would recover the cost of the device in about 2.9 years. However, when considering the cost of UTIs, it would take only 12 avoided infections to recover the cost of the device.

Wooldridge (2000) clearly outlined the information required for a comprehensive cost analysis when comparing intermittent catheterizations and bladder ultrasound devices. Data to be considered for intermittent catheterization included the number of catheterizations yearly, number of times a measurement of bladder volume is required, time required for catheterizations, associated labor costs, supply costs, UTI rates, and UTI treatment and medication costs. However, Wooldridge directed this information to long-term care facilities and did not include the costs of extended hospital stays, which would need to be considered in acute care settings. According to Wooldridge, these costs should be compared to the costs associated with bladder ultrasound use which include the number of times a measurement of bladder volume is required, time spent scanning, and labor costs associated with scanning. She also noted that catheterization labor costs must be calculated using licensed personnel wages, whereas ultrasound can be performed by nursing assistants. After calculating the savings associated with ultrasound use, the final step would be to compare approximate savings to the cost of the device. Training to use a scan involves a 10-minute video, which describes operation. Training videos are available online from Diagnostic Ultrasound.

Clinical TriMs

Resnick (1995) conducted a small bladder scan trial in a geriatric rehabilitation setting. The BVI 2000[R] device was used on 16 patients over the age of 65. A post-void residual volume of 300 ml was used as the threshold for catheterization. She found that catheterization could be avoided in almost half of her sample, as 47% of scans revealed a bladder volume of less than 300 ml.

Lewis (1995) analyzed the outcome of 72 catheterizations for PVR. She found that 67% of catheterizations yielded retained volumes of less than 100 ml. The BVI 2500[R] was introduced with a protocol and 6 months later the use of catheterization was reviewed again. Lewis (1995) found that 95% of PVR assessments were done using the bladder scan device and that only 21% of those scanned required catheterization.

Moore and Edwards (1997) reviewed one hospital's attempt to decrease nosocomial UTI rates. They reported that of 57 catheterized patients, 19% developed UTIs. After the introduction of the BVI 2500[R], an evaluation study conducted on two units found a 50% reduction in UTIs and only 22% of patients requiring catheterization.

Implementing a Bladder Ultrasound Protocol

Inpatient units and long-term care facilities that serve populations affected with urinary retention and incontinence should consider implementing a bladder ultrasound protocol. As there is no agreed upon distinction between normal and abnormal post-void residual, care providers must determine this based on the population and the institution. To maximize adherence, nurses should be involved in the development and dissemination of these protocols. Based on the literature review, the author recommends using a PVR of greater than 150 ml as indication for catheterization. This recommendation is based on the more recent study by Dromerick and Edwards (2003) that associated residual urine volumes of greater than 150 ml with development of urinary tract infections.

For patients with known or suspected urinary retention, bladder ultrasound should be performed as soon as possible after voiding. It is important to remember that the bladder is continuously filling (Marks et al., 1997). Bladder ultrasound readings should be taken immediately after voiding to get a more accurate assessment of residual volume. Moore and Edwards (1997) stated that bladder ultrasound measurements should be obtained within 10 to 15 minutes after voiding. The measurement should be confirmed with a second reading. Consecutive readings should be taken until a full view of the bladder is obtained on the scanner. This is done each time when checking for residual. If the volume falls below the protocol threshold and the patient is asymptomatic, catheterization is not indicated. Implementing such a protocol can decrease the number of catheterizations performed and the associated risks.

In the UTI Reduction Project described by Philips (2000), a protocol was established for using bladder ultrasound assessment after indwelling catheter removal. It included bladder scanning 4 hours after the catheter was removed. If the bladder volume was greater than 300 ml, a straight catheterization was performed. The bladder scanner was used again 4 hours later and the patient catheterized for urine volumes over 300 ml. If two catheterizations were required, replacing the indwelling catheter was considered. In this UTI reduction project an algorithm was developed to guide nurses' assessment of the patient's need for continual indwelling catheterization. The indwelling urinary catheter guideline data collection tool provided a daily score for the patient. Scores were based on hemodynamics, possibility of spinal injury, incontinence, urologic requirements, mental status, mobility, and skin assessment. Continued indwelling catheters were indicated in patients scoring 5 and above. Alternatives such as intermittent catheterization or external catheter use should be considered in patients with scores of 3 to 4. Patients scoring less than 2 should have catheters removed. An estimated 27 UTIs and 1,392 catheterizations were avoided related to use of the bladder ultrasound device. The author's institution estimated savings at $45,900 (Phillips, 2000).

Frederickson et al. (2000) described a bladder ultrasound protocol implemented for surgery and orthopedic patients. This protocol addressed two issues, patients who were "due to void" and patients who "voided with residual" volume. In the "due to void" group, urine volumes greater than 400 ml or urine volumes greater than 300 ml with symptoms required catheterization. Volumes less than 400 ml were checked again with ultrasound in 1 hour. On recheck, patients with volumes less than 300 ml had their hydration status assessed. In the "voided with residual" group, patients with an ultrasound-determined post-void residual volume greater than 150 ml were catheterized. Three consecutive volumes greater than 150 ml required consultation with the physician, and three volumes less than 150 ml required no further assessment. With these guidelines, the "due to void" surgical patients required 38% fewer catheterizations and the "voided with residual" group required 81% fewer. The orthopedic patients required 20% fewer catheterizations.


The nurse's responsibility to provide the highest quality of care includes protection from hospital-acquired infection. Research has shown that nosocomial infections are costly for the patient and the hospital. With regard to urinary retention, noninvasive portable bladder ultrasound devices can assess bladder volumes accurately and reliably. When bladder ultrasound protocols are implemented, many catheterizations can be avoided. This evidence should be integrated into practice to improve quality of care.


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Elizabeth Stevens, BSN, RN, ARNP, was a Staff Nurse, James A. Haley Veterans Hospital, Tampa, FL, at the time this article was written.
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Title Annotation:Clinical Practice
Author:Stevens, Elizabeth
Publication:MedSurg Nursing
Geographic Code:1USA
Date:Aug 1, 2005
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