Key points � Portable bladder ultrasound scanners are of sufficient clinical accuracy in estimating PVR urine volume in most patients.

� Studies however report conflicting results regarding the use of the device in children aged less than 36 months and postnatal women.

� There was insufficient evidence available to conclude that any of the models of PBUS compared demonstrated superior clinical accuracy.

� Evidence suggests that adopting standard protocols, including staff training and identifying appropriate patients, for the use of PBUS is associated with reduced risk of unnecessary catheterisation, reduced UTIs and fewer adverse events, as well as improved patient satisfaction, when compared with catheterisation.

� No relevant economic evidence was identified, thus it was not possible to comment on the cost effectiveness of PBUS.

� Further research is required on the accuracy and suitability of newer PBUS so that NHS purchasing can be evidence based.

In response to an enquiry from the Scottish Health Technologies Group

Number 32 September 2010

Portable bladder ultrasound scanners

Portable bladder ultrasound scannersThis Evidence Note reviews the best available published evidence relating to whether or not the use of portable bladder ultrasound scanners (PBUS) can reduce the need for urinary catheterisation and hence avoid catheter associated urinary tract infections (CAUTIs). The note examines the accuracy of PBUS and also their impact on health outcomes such as urinary tract infections (UTIs). It further examines evidence around implementing bladder scanning protocols in healthcare facilities. The management and/or monitoring of catheterisations by healthcare professionals were not considered.

Health technology descriptionThere are two methods for assessing post-void residual (PVR) urine volume: sterile catheterisation (direct measurement of urine volume) and bladder ultrasound (indirect estimation of urine volume)1. Bladder ultrasound scanning offers a non-invasive alternative to catheterisation. The scanner is used, primarily as a diagnostic aid, to non-invasively identify incomplete bladder emptying and determine bladder volume2,3 in adults and children with urinary problems of varying aetiologies, such as4:

� postoperative patients at risk of urinary retention (UR);

� patients with UTIs, urinary incontinence (UI), enlarged prostate, urethral stricture, neurogenic bladder and other lower urinary tract dysfunctions; and

� patients with conditions that interfere with voiding, such as spinal cord injuries, stroke and diabetes.

Due to its non-invasive nature, the use of ultrasound technology may reduce the risk of urethral trauma and urinary infection associated with catheterisation. Stationary and portable ultrasound machines are available in both 3-dimensional (3D) and 2-dimensional (2D) versions. The PBUS offer potential benefits that the stationery machines do not due to their portability and ease of use2,5 which permits the use of the

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device in community settings outside of the hospital environment.

The portable, battery-powered, ultrasound scanner utilises automated technology to digitally register bladder volume, including PVR urine volume, while providing images of the bladder area2,6-8. It consists of a base component with a display screen and a hand-held ultrasound transducer (scan head) which is usually positioned on the patient’s abdomen and pointed towards the bladder. The base component employs ultrasound technology, through electrical connection to the scan head, to automatically create an image of the bladder and calculate bladder and PVR measurements2,9. Use and interpretation of results of PBUS can be complex, particularly in patients who are morbidly obese2, have irregular bladder shapes or in postnatal women (immediately after childbirth) as the device records the volume of cystic structures within the pelvis10 and so interpretation of results requires specific knowledge and high levels of clinical competence11. Some authors have however suggested that although training is required to interpret results, only minimal technical skills are required to use the device3.

In the past, the BladderScan® series, manufactured by Verathon Medical, were the most common PBUS6,12. However, a number of alternatives have recently been launched on the United Kingdom (UK) market. These include the Bardscan®, Cubescan® and different Sonosite®

models. Some of these portable scanners, like the Bardscan® and Cubescan® provide real-time ultrasound imaging. There are however other scanners that provide only numeric bladder volumes with no image of the bladder shape.

EpidemiologyAs detailed above, PBUS may find application in a number of bladder problems of varying aetiologies. Often the problem can manifest as either UI, UR or in women more commonly as recurrent UTIs.

UI is defined as any involuntary urinary leakage13

that may occur due to a number of abnormalities in the lower urinary tract function or as a result of other illnesses14. Risk factors for UI include age,

female gender, obesity, lower urinary tract symptoms, functional and cognitive impairment, pregnancy, childbirth, diet, smoking, genetics and family history2,14. UI is under-diagnosed14. The Leicestershire Medical Research Council (MRC) Incontinence Study15 reported that 33.6% of individuals over 40 years of age have significant urinary symptoms. Of these, 6.2% found the condition bothersome while 2.4% found it both bothersome and socially disabling15. Data from Information Statistics Division (ISD) Scotland estimate the prevalence of current UI in adults as 9%16.

UR is defined as the inability to pass urine despite persistent effort17. The definition of UR, based on PVR urine volume, is influenced by the population and clinical condition of interest2. There is no clear consensus regarding what constitutes a normal or abnormal residual volume; clinically significant volumes could vary between a lower limit of 50 ml and upper limit of 300 ml2,14,18.

UTIs are a common complication of urinary catheters that can extend hospital stays. It has been reported that approximately 40% of all hospital-acquired (nosocomial) infections can be attributed to UTIs and about 80% of UTIs (32% of nosocomial infections) are associated with both indwelling and intermittent catheterisation2,19. Catheterisation is associated with a 5% risk of urinary infection in long-term care patients5. CAUTI surveillance is not mandatory in Scotland. The Scottish National Healthcare Associated Infection Prevalence Survey20, conducted between 2005 and 2006, estimated the percentage of urology patients with catheters as 40.3%. The greatest proportion of patients catheterised were identified in surgical, medical and elderly specialties20.

Clinical effectivenessThe literature available for PBUS is variable in methodological quality (mostly non-experimental designs involving small numbers of participants and varying requirements for staff training), thus limiting generalisability and the confidence which can be placed in any conclusions drawn.

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Accuracy of PBUS

A National Institute for Health and Clinical Excellence (NICE) guideline14, published in 2006, on the management of UI in women was identified. Based on three studies (with residual urine volumes cut-offs ranging between 50– 200 ml) that assessed the accuracy of PBUS compared with catheterisation in men and women, the guideline concluded that the bladder scanner is less invasive with lower adverse effects. The sensitivity (range 67–95%) and specificity (range 63–99%) of ultrasound in detecting PVR volumes were found to be within clinically acceptable limits. However, one study showed a much lower sensitivity at residuals >100 ml. The findings led the guideline to recommend that a bladder scan should be used in preference to catheterisation in the measurement of PVR volumes, on the grounds of acceptability and reduced rate of adverse events. However, due to lack of evidence for what constitutes a clinically significant residual, this recommendation may be limited only to women with signs and symptoms suggestive of voiding dysfunction.

Similar to the NICE guideline14, there was general consensus amongst other secondary evidence2,9,21-24 that although PBUS are not as accurate as catheterisation and require training, they offer acceptable levels of clinical utility and reduced risk of UTIs and improved patient satisfaction due to their non-invasive nature. Results of the studies suggest that the benefits resulting from the use of PBUS outweigh the risks and exceed the benefits of catheterisation. Based on a review of 17 non-randomised controlled trials (RCT) (prospective, observational studies with contemporaneous control), a health technology assessment (HTA) conducted in 2006 by the Ontario Medical Advisory Secretariat reported significant results regarding the negative health outcomes that were avoided due to the use of the PBUS2. Catheterisations avoided ranged from 16–47% whilst UTIs were reduced by 38–72%. Subgroup analysis showed that PBUS are less accurate for women than men. Higher levels of accuracy were demonstrated in patients with spinal cord injuries compared with other acute care and rehabilitative patients. There was

variability in the type and model of PBUS used in the studies2. A recent primary study25 of 101 women with an indication for PVR measurement concluded that the BladderScan BVI 3000® is an accurate alternative to catheterisation. Results from this ultrasound scanner were highly reproducible and correlated significantly with catheterised volumes, with a mean difference of 12.9 ml (p<0.001)25.

NB: this literature25 was not included in the identified secondary evidence.

Accuracy of PBUS in specific population groups

Additional primary literature studies which investigated the clinical utility and user satisfaction of PBUS in specific population groups were also identified. Assessment of residual urine in postpartum women

Three observational studies10,26,27, including one UK-based study10 assessed the reliability of PBUS compared with catheterisation in postpartum women. The residual urine volume indicative of a positive result ranged from 100 ml to 400 ml. Two studies26,27 concluded that the BladderScan™ BVI 3000®27 and BVI 6100®26

were reliable and non-invasive screening methods for detecting postpartum urinary retention after vaginal delivery and for reducing the number of unnecessary catheterisations, when used by trained nurses. Using a 400 ml threshold, one study26 estimated the sensitivity and specificity of the BVI 6100® as 76% and 96% respectively. Despite obtaining clinically irrelevant differences in measured volumes, the UK-based study10 reported that the BVI 3000® is not as accurate as urethral catheterisation for determining residual urine volume in the puerperium. Volumes measured by PBUS were overestimated (by 9 ml) and underestimated (by 33 ml) compared with volumes measured by standard real-time ultrasound and catheterisation respectively.

Accuracy of PBUS in specific population groups

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Assessement of bladder volume in children

Four randomised studies28-31 and four non-randomised observational studies32-35, published between 2005 and 2008, evaluated the accuracy of PBUS (different BVI® models and Sonosite 180®) in children in various settings. All four fairly large studies28,30-32 investigating the clinical utility of the Sonosite 180® found that first-attempt urine collection success rates (collection of 2– 2.5 ml) in children 36 months or younger were significantly improved by the bladder ultrasound device (range 92–100%) compared with the conventional use of catheters without imaging (range 67–78%). This reduction in unsuccessful urethral catheterisation was also deemed clinically meaningful.

Conflicting findings however were reported in other studies29,33-35, including one RCT29, that utilised various BVI® models in children. The studies29,33-35 found that the portable bladder scanner was not reliable in assessing bladder volume in children aged under 36 months. Compared with catheterisation, the BVI 6200® and BVI 3000® underestimated bladder volumes in two studies29,34 while the BVI 3000® failed to detect significant volumes in a small study with neonatal cases (n=10)35. Furthermore, volumes were overestimated in a study comparing the BVI 2500® with standard ultrasound33. Nonetheless, reliability was found to be within the acceptable limits in children older than 36 months33,34 and those with bladder volumes greater than 20% of the expected bladder capacity for age33. The authors of the studies concluded that although the PBUS could be used as a diagnostic aid for assessment of bladder filling (as there is currently no better alternative which reduces the risk of UTIs associated with unnecessary catheterisation), it needs to be used with caution in children less than 36 months33-35, particularly neonates with complex problems35, and should not replace current clinical assessment using catheters29.

Greater satisfaction and a higher likelihood of using volumetric bladder ultrasound compared with conventional catheterisation were reported by both caregivers and healthcare providers in a prospective RCT36. Using a seven-point Likert scale

(1=‘none’, 7=‘a great deal’), caregivers in the catheterisation group rated the children’s discomfort higher (4.4 versus 3.4; p=0.02) and were less satisfied (4.5 versus 6.4; p <0.0001) than those in the ultrasound group36. However, another randomised study found no significant difference in caregiver satisfaction between the use of ultrasound and catheterisation in a paediatric population31. It is likely that this study was underpowered to detect a difference in satisfaction scores31.

Comparative effectiveness of different portable bladder ultrasound scanners

A UK study12 investigated the accuracy of four commonly used portable bladder scanners (BVI 3000®, BVI 6100®, Sonosite iLook 15® and Bardscan®) in 28 healthy volunteers. Relative to the average of all four scanners, the iLook 15® and Bardscan® under-predicted bladder volumes by 34 ml and 21 ml respectively, while the BVI 3000® and BVI 6100® over-predicted bladder volumes by 17 ml and 38 ml respectively (p<0.05). Volumes obtained from the iLook 15® and Bardscan® were about 50 ml lower than both BVI® models. Although not statistically significant (p=0.051), the BVI 3000® had a slightly greater error variability compared with the other scanners. The authors concluded that no scanner could be classed as being the most accurate. The BVI 6100® was however found to be the fastest and lightest scanner with a markedly less variable error12.

Another UK study37 comparing the BVI 3000®, Bardscan® and another 3D-ultrasound system (HDI 4000®), in a random sequence, concluded that the HDI 4000® is the most accurate of all three scanners. Estimated volumes from all three ultrasound scanners were found to be significantly correlated to voided volumes (p <0.001). The Bardscan® and BVI 3000® underestimated and overestimated respectively, large bladder volumes. Voided volumes were significantly underestimated by 21 ml by the Bardscan® (p=0.008). This finding led the authors to also conclude that the Bardscan® is not as accurate as the BVI 3000® despite having the advantage of producing real-time images

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and instantaneous volume calculation.

Three studies25,38,39 that compared BVI® models with catheterisation25,38 and other ultrasound devices38,39 found the accuracy of the BVI® scanners ‘sufficient’ for clinical practice. In a population of 89 men and women with lower urinary tract symptoms, Choe et al.38 found no significant difference in the accuracy and precision in estimating residual volumes between the BME-150A® (S & D Medicare Co., Seoul, Korea) and BVI 3000®. Both devices were found to be clinically acceptable alternatives to urethral catheterisation. The portable 3D (BVI 2500®) and stationary 2D (Vingmed CFM 800®) ultrasound scanners also demonstrated sufficient accuracy for clinical practice in a study involving patients with permanent bladder catheters39.

One study40 that assessed the accuracy of the BVI 6100® in measuring volumes ≤150 ml concluded that, compared with existing ultrasound methods, the 3D ultrasound device provides significantly greater accuracy for estimating lower bladder volume when appropriate patients are selected and examiner measurement error is reduced.

Implementing portable bladder ultrasound scanning protocols

Several authors3-5,21,41,42 have recommended the development of protocols, in emergency hospitals and radiology departments, for the use of ultrasound scanners in the management of urinary retention. These should include training requirements, documentation, clinical indications for use and quality evaluation (results and outcomes tracking). Sparks et al.23 however posit that good quality research which documents the effectiveness of PBUS on clinical outcomes is required prior to adopting the use of the technology over catheterisation.

A rapid response report by NHS National Patient Safety Agency43 stated that ultrasound devices should be made available in acute and community hospitals, and training should be provided to staff in their use. Healthcare providers have also been advised to complement knowledge gained from training with clinical judgement when using PBUS to measure PVR volumes and total residual volumes21.

Successful adaptation of bladder scanning ultrasound programmes that provided staff training in facilities have been reported in a number of studies8,24,44-47. These programmes resulted in easy identification of individuals at risk of developing UTIs45, reduced unnecessary catheterisation24,46,47 and reduced UTIs46. Continuous quality assurance and additional training for staff demonstrating inaccurate measurements were however recommended44.

SafetyGenerally, there are no complications associated with PBUS. One study reported potential adverse effects including skin irritation, allergic reaction to the ultrasound gel and padding and pressure sore formation at the site where the sensor is placed2.

Cost effectivenessNo relevant economic evaluations (based on or generalisable to UK costs) were identified.

Equality and Diversity NHS QIS is committed to equality and diversity in respect of the six equality groups defined by age, disability, gender, race, religion/belief and sexual orientation.

The Evidence Note process has been assessed and no adverse impact across any of these groups is expected. The completed equality and diversity checklist is available on www.nhshealthquality.org

About Evidence NotesFor further information about the Evidence Note process, see www.nhshealthquality.org

To propose a topic for an Evidence Note, email evidencenotes.qis@nhs.net

References can be accessed via the internet (where addresses are provided), via the NHS Knowledge Network (formally eLibrary) http://www.knowledge.scot.nhs.uk, or by contacting your local library and information service.

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References

1. Kelly CE. Evaluation of voiding dysfunction and measurement of bladder volume. Rev Urol. 2004;6 Suppl 1:S32-7.

2. Medical Advisory Secretariat. Portable bladder ultrasound: an evidence-based analysis. 2006 [cited 2010 Sep 20]; Available from: http://www.health.gov.on.ca/english/providers/program mas/tech/reviews/pdf/rev_pbu_040106.pdf

3. Rigby D, Housami FA. Using bladder ultrasound to detect urinary retention in patients. Nurs Times. 2009;105(21):34,36-7.

4. Krapp K. Bladder ultrasound. 2002 [cited 2010 Sep 20]; Available from: http://www.enotes.com/ nursing-encyclopedia/bladder-ultrasound

5. Wooldridge L. Ultrasound technology and bladder dysfunction. Am J Nurs. 2000;June Suppl:3-14.

6. Verathon Inc. BladderScan® bladder volume instruments: noninvasive, accurate, reliable and easy to use. 2008 [cited 2010 Sep 20]; Available from: http://www.verathon.com/BladderScan.htm

7. ECRI Institute. Portable non-invasive ultrasound measurement of bladder volume. US: ECRI Institute; 2006.

8. Newman DK. Using the BladderScan® for bladder volume assessment. 2007 [cited 2010 Sep 20]; Available from: http://www.seekwellness.com/incontinence/using_the_bladderscan.htm

Acknowledgements

NHS Quality Improvement Scotland would like to acknowledge the helpful contribution of the following, who gave advice on the content of this Evidence Note:

• Dr Lucia Dolan, Consultant Gynaecologist & Subspecialist Urogynaecology, NHS Lothian• Mr Christopher Driver, Consultant Paediatric Surgeon and Urologist, NHS Grampian • Dr Fiona Murdoch , Epidemiologist, NHS National Services Scotland• Dr Michael Palmer, Consultant Urologist, NHS Greater Glasgow and Clyde• Ms Allison Robertson, Lead CNS Urology, NHS Tayside• Ms Lorna Thompson, Programme Manager, SIGN• Members of the Working Group for SHTG

And also Bard Limited, Mcube-Europe Ltd and Verathon Medical UK Ltd

NHS QIS Development Team

• Ms Hilda Emengo, Author/Health Services Researcher• Ms Jenny Harbour, Information Scientist• Mrs Susan Downie, Medical Writer• Ms Doreen Pedlar, Project Co-ordinator• Ms Marina Logan, Team Support Administrator

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References continued

9. Croatian P. Bladder ultrasound scanning for the measurement of post-void residual urine volume. 1996 [cited 2010 Sep 20]; Available from: http://www.unc.org/publications/publications. php?id=13

10. Mathew S, Horne AW, Murray LS, Tydeman G, McKinley CA. Are portable bladder scanning and real-time ultrasound accurate measures of bladder volume in postnatal women? J Obstet Gynaecol. 2007;27(6):564-7.

11. Addison R. Assessing continence with bladder ultrasound. Nurs Times. 2007;103(19):44-5.

12. Small DR, Watson A, McConnachie A. A quantitative comparison of four current portable ultrasound bladder scanners. Br J Med Surg Urol. 2008;1(1):35-40.

13. Abrams P, Cardozo L, Fall M, Griffiths D, Rosier P, Ulmsten U, et al. The standardisation of terminology of lower urinary tract function: report from the Standardisation Sub-committee of the International Continence Society. Am J Obstet Gynecol. 2002;187(1):116-26.

14. National Institute for Clinical Excellence, National Collaborating Centre for Women’s and Children’s Health. Urinary incontinence: the management of urinary incontinence in women. London; RCOG Press; 2006. NICE clinical guideline 40.

15. Perry S, Shaw C, Assassa P, Dallosso H, Williams K, Brittain KR, et al. An epidemiological study to establish the prevalence of urinary symptoms and felt need in the community: the Leicestershire MRC Incontinence Study. J Public Health Med. 2000;22(3):427-34.

16. Information Services Division. Measuring long-term conditions in Scotland. 2008 [cited 2010 Sep 20]; Available from: http://www.isdscotland.org/isd/servlet/FileBuffer?namedFile=2008_08_14_LTC_full_report.pdf&pContentDispositionType=inline

17. Haylen BT, De Ridder D, Freeman RM, Swift SE, Berghmans B, Lee J, et al. An International Urogynecological Association (IUGA)/International Continence Society (ICS) joint report on the terminology for female pelvic floor dysfunction. Int Urogynecol J Pelvic Floor Dynsfunct. 2010;21(1):5-25

18. Darrah DM, Griebling TL, Silverstein JH. Postoperative urinary retention. Anesthesiol Clin. 2009;27(3):465-84.

19. Wagner ML, Schmid MM. Exploring the research base and outcome measures for portable bladder ultrasound technology. Medsurg Nurs. 1997;6(5):304-14.

20. Reilly J, Stewart S, Allardice G, Noone A, Robertson C, Walker A, et al. NHS Scotland national HAI prevalence survey: final report. Glasgow: Health Protection Scotland; 2007.

21. Bee TS. Review: determining the volume of urine by portable ultrasonography for the neurological patients. Singapore Nurs J. 2006;33(1):7-13.

22. NHS Quality Improvement Scotland. Urinary catheterisation & catheter care: best practice statement. 2004 [cited 2010 Sep 20]; Available from: http://www.nhshealthquality.org/nhsqis/files/CATHURIN_BPS_JUN04.pdf

23. Sparks A, Boyer D, Gambrel A, Lovett M, Johnson J, Richards T, et al. The clinical benefits of the bladder scanner: a research synthesis. J Nurs Care Qual. 2004;19(3):188-92.

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References continued

24. Stevens E. Bladder ultrasound: avoiding unnecessary catheterizations. Medsurg Nurs. 2005;14(4):249-53.

25. Al-Shaikh G, Larochelle A, Campbell CE, Schachter J, Baker K, Pascali D. Accuracy of bladder scanning in the assessment of postvoid residual volume. J Obstet Gynaecol Can. 2009;31(6):526-32.

26. Lukasse M, Cederkvist HR, Rosseland LA. Reliability of an automatic ultrasound system for detecting postpartum urinary retention after vaginal birth. Acta Obstet Gynecol Scand. 2007;86(10):1251-5.

27. Van Os AF, Van Der Linden P. Reliability of an automatic ultrasound system in the post partum period in measuring urinary retention. Acta Obstet Gynecol Scand. 2006;85(5):604-7.

28. Baumann BM, McCans K, Stahmer SA, Leonard MB, Shult J, Holmes WC. Volumetric bladder ultrasound performed by trained nurses increases catheterization success in pediatric patients. Am J Emerg Med. 2008;26(1):18-23.

29. Koomen E, Bouman E, Callewaerdt P, Vos GD, Prins MH, Anderson BJ, et al. Evaluation of a non-invasive bladder volume measurement in children. Scand J Urol Nephrol. 2008;42(5):444-8.

30. Tanabe P, Gilboy N. Research to practice: can the use of ultrasound technology or bladder scanning prevent unnecessary pediatric urethral catheterizations? Adv Emerg Nurs J. 2007;29(4):289-96.

31. Witt M, Baumann BM, McCans K. Bladder ultrasound increases catheterization success in pediatric patients. Acad Emerg Med. 2005;12(4):371-4.

32. Chen L, Hsiao AL, Moore CL, Dziura JD, Santucci KA. Utility of bedside bladder ultrasound before urethral catheterization in young children. Pediatrics. 2005;115(1):108-11.

33. De Gennaro M, Capitanucci ML, Di Ciommo V, Adorisio O, Mosiello G, Orazi C, et al. Reliability of bladder volume measurement with BladderScan in paediatric patients. Scand J Urol Nephrol. 2006;40(5):370-5.

34. Rosseland LA, Bentsen G, Hopp E, Refsum S, Breivik H. Monitoring urinary bladder volume and detecting post-operative urinary retention in children with an ultrasound scanner. Acta Anaesthesiol Scand. 2005;49(10):1456-9.

35. Wyneski HK, McMahon DR, Androulakakis V, Nasrallah PF. Automated bladder scan urine volumes are not reliable in complex neonatal cases. J Urol. 2005;174(4 pt 2):1661-2.

36. Baumann BM, McCans K, Stahmer SA, Leonard MB, Shults J, Holmes WC. Caregiver and health care provider satisfaction with volumetric bladder ultrasound. Acad Emerg Med. 2007;14(10):903-7.

37. Ghani KR, Pilcher J, Rowland D, Patel U, Nassiri D, Anson K. Portable ultrasonography and bladder volume accuracy: a comparative study using three-dimensional ultrasonography. Urology. 2008;72(1):24-8.

38. Choe JH, Lee JY, Lee KS. Accuracy and precision of a new portable ultrasound scanner, the BME-150A, in residual urine volume measurement: a comparison with the BladderScan BVI 3000. Int Urogynecol J Pelvic Floor Dysfunct. 2007;18(6):641-4

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References continued

39. Schnider P, Birner P, Gendo A, Ratheiser K, Auff E. Bladder volume determination: portable 3-D versus stationary 2-D ultrasound device. Arch Phys Med Rehabil. 2000;81(1):18-21.

40. Oh-Oka H, Fujisawa M. Study of low bladder volume measurement using 3-dimensional ultrasound scanning device: improvement in measurement accuracy through training when bladder volume is 150ml or less. J Urol. 2007;177(2):595-9.

41. Committee for Evaluation and Diffusion of Innovative Technologies (CEDIT). Portable ultrasound devices. France: CEDIT; 2004.

42. Betsy Lehman Center for Patient Safety and Medical Error Reduction, JSI Research and Training Institute, Massachusetts Department of Public Health. Prevention and control of healthcare associated infections in Massachusetts. Part 1: final recommendations of the expert panel. 2008 [cited 2010 Sep 20]; Available from: http://www.mass.gov/Eeohhs2/docs/dph/patient_safety/haipcp_final_report_pt1.pdf

43. National Patient Safety Agency (NPSA). Minimising risks of suprapubic catheter insertion (adults only): rapid response report. 2009 [cited 2010 Sep 20]; Available from: http://www.npsa.nhs.uk/EasySiteWeb/GatewayLink.aspx?alId=59453

44. Baumann BM, Welsh BE, Rogers CJ, Newbury K. Nurses using volumetric bladder ultrasound in the pediatric ED. Am J Nurs. 2008;108(4):73-6.

45. Boyer DR, Steltzer N, Larrabee JH. Implementation of an evidence-based bladder scanner protocol. J Nurs Care Qual. 2009;24(1):10-6.

46. Lee YY, Tsay WL, Lou MF, Dai YT. The effectiveness of implementing a bladder ultrasound programme in neurosurgical units. J Adv Nurs. 2007;57(2):192-200.

47. Lewis NA. Implementing a bladder ultrasound program. Rehabil Nurs. 1995;20(4):215-7.