REF012 - DMSA Kidney Imaging

The purpose of this document is to assist clinicians in deciding on the appropriateness of a Nuclear Medicine DMSA scan for static renal imaging and to give guidance on the mechanism of referral.

Static renal images are obtained using technetium-99m labelled DMSA. This radiopharmaceutical is taken up by the proximal renal tubules and fixed there. As rapid loss of tracer does not occur, several views of the kidneys can be obtained. This is of particular relevance in paediatrics, where it may be important to identify sites of cortical scarring, for example in children with recurrent urinary tract infection or reflux.

Static renal images provide good definition of the cortical outline and, in addition, show the relative distribution of functional tissue. The ratio of radiopharmaceutical uptake between the kidneys provides a measure of divided renal function. By selecting regions of interest within an individual kidney, it is also possible to measure the relative function at these sites, which may be of relevance when a duplex system is present.

• The referrer may be any clinician holding a current valid medical qualification and currently employed in Secondary Care.
• Referrals from Primary Care will be accepted if the investigation has been suggested by a Consultant Radiologist in a report from a previous investigation, following discussion with a Consultant Radiologist, or recommended by a Secondary Care Specialist. Details of such suggestions or discussions should be included on the request form.

Referring clinicians are reminded of the requirement to avoid unnecessary exposure to ionising radiation. The investigation may already have been requested at this hospital or elsewhere and clinicians are asked to be particularly vigilant to ensure that their request is not a double request.

Requests will only be accepted if the diagnostic question fulfills one of the referral criteria detailed in section 'Referral Criteria'. Appropriate clinical information must be supplied to allow the investigation to be justified. It is not acceptable to simply request the investigation without appropriate clinical information. Requests will be returned to the referrer if:

• The diagnostic question is unclear.
• The diagnostic question cannot be answered by the investigation.
• Insufficient clinical information is supplied to justify the investigation.

Requests should be submitted on the orange stripe NUCLEAR MEDICINE (ISOTOPE SCAN) request form. 'Patient details', 'Investigation required' and 'Reason for Test/Diagnostic Question' should be fully and appropriately completed and the form signed.

Sufficient clinical information must be provided to justify the investigation proceeding.

As there are other nuclear medicine kidney imaging procedures, which provide different information, the diagnostic question needs careful consideration.

The clinical indications are detailed below

From NICE guidance^[1]

4-6 months after acute episode in patients with atypical or recurrent UTI.

4-6 months after acute episode in recurrent UTI ONLY.

Atypical UTI includes:

• Seriously ill (for more information, refer to the NICE guideline on fever in under 5s: assessment and initial management)
• Poor urine flow
• Abdominal or bladder mass
• Raised creatinine
• Septicaemia
• Failure to respond to treatment with suitable antibiotics within 48 hours
• Infection with non-E. coli organisms

Recurrent UTI:

• Two or more episodes of UTI with acute upper UTI (acute pyelonephritis), or
• One episode of UTI with acute upper UTI plus 1 or more episodes of UTI with lower UTI (cystitis), or
• Three or more episodes of UTI with lower UTI

There are no specific contraindications. Assessment for scarring should be delayed 4-6 months from last urinary tract infection to avoid a possible false positive scan.

There is no specific patient preparation.