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Taking a midstream specimen of urine

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Collecting midstream specimens of urine (MSU) is a common nursing activity. 

Abstract

VOL: 102, ISSUE: 18, PAGE NO: 22

Rachel Gilbert, RN, BSc, DipHE, is continence nurse specialist, Kingston NHS Primary Care Trust, Surrey

It is indicated for adults and children who are continent and can empty their bladder on request. The general principle is to collect the midstream or middle part of a void if a urinary tract infection (UTI) is suspected.

Since this is one of the most frequently occurring infections, an MSU may be required in many areas of clinical practice. Yet despite being a regular nursing activity, the procedure is often undertaken incorrectly.

Underpinning theory

An MSU is obtained using a clean technique to reduce the risk of bacterial contamination. The theory is that midstream urine accurately represents the urine in the bladder. Since urine is sterile in the absence of a UTI it should not be contaminated (Baillie and Arrowsmith, 2005).

However, urine is a good culture medium and will support the multiplication of any bacteria introduced when the specimen is obtained (Higgins, 2000). Consequently, a falsely raised bacteriuria can lead to misdiagnosis (Wilson, 2005).

Contamination

Bacterial contamination is likely to result from incorrect collection. Higgins (2000) identifies the purpose of an MSU as washing away any bacteria present in the urethra with the flushing action of the first part of the void. Wilson (2005) points out how the reliability of urine testing is dependent upon specimen quality. MSU contamination can originate from:

- The distal urethra because this is usually colonised with bacteria;

- External influences such as hand or genital contamination.

Skin cleansing

Research does not support routine washing of the genitals or perineum before the procedure. Cleansing appears to make no difference to contamination rates (Mousseau, 2001).

The strength of the urine stream appears more important, so the urine volume in the bladder should be considered. In the absence of pathology preventing a strong stream, such as prostatic enlargement or bladder hypoactivity, higher bladder volumes may increase the strength of the stream (Mousseau, 2001). This means the best time to collect MSU is when the bladder is at least half full.

Cleansing may be appropriate when personal hygiene is poor or if faecal contamination is known. Wilson (2005) advises on the importance of removing all traces of cleanser and drying the skin.

Patient education

The patient needs to understand the principles of MSU collection, and informed consent should be obtained. Baillie and Arrowsmith (2005) discuss how the procedure must be explained carefully and confidentially to increase the likelihood of success. A patient information leaflet (Prodigy, 2006) can help support verbal instructions and a practical demonstration.

The procedure

The practitioner may need to assist depending on the patient’s independence and understanding. The following is an outline of the procedure for a patient who can produce a specimen with little or no assistance:

- Ensure a suitable location and that all equipment is at hand (suitable receptacle, sterile laboratory container, personal protective clothing);

- Wash hands using warm soapy water (practitioner and patient). Alcohol solution may be used to disinfect visibly clean hands

(Fig 1). The practitioner should wear standard personal protective clothing (clean gloves and apron);

- Wash the perineum and genitals if indicated with warm soapy water and dry thoroughly. Uncircumcised males should retract the foreskin and cleanse the glans penis (Figs 2-3);

- The patient begins voiding into the toilet (or alternative facility, for example a commode or urinal) (Fig 4). Encourage females to separate and keep open the labia during voiding (Fig 5) (Royal Marsden Hospital, 2005) although this is not essential;

- Place a sterile receptacle, preferably a wide-necked sterile container used for laboratory specimens, in the urine stream without the patient interrupting the void (Fig 6);

- Remove the receptacle so the patient can finish the void into the toilet or alternative facility;

- If necessary transfer the specimen to a sterile container used for laboratory specimens. Refer to local policy regarding suitable containers;

- Remove personal protective equipment and disinfect hands;

- Complete the labelling on the container and accompanying laboratory forms and enter details in the patient’s notes;

- Dispatch the MSU to the laboratory immediately or refrigerate according to local policy if this is not possible.

Professional responsibilities

All nurses who carry out clinical procedures must have received approved training, undertaken supervised practice and demonstrated competence in the clinical area. The onus is also on the individual to ensure that knowledge and skills are maintained from both a theoretical and a practical perspective. Nurses should also undertake this role in accordance with an organisation’s protocols, policies and guidelines.

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