REF014 HIDA

The purpose of this document is to assist clinicians in deciding on the appropriateness of the Nuclear Medicine procedure and to give guidance on the mechanism of referral.

The radiopharmaceutical used for hepatobiliary imaging is a technetium-99m labelled iminodiacetic acid (IDA) derivative usually referred to as HIDA (hepatic IDA). This is cleared from the circulation by hepatocytes and then secreted into bile by carrier mechanisms identical to bilirubin. It is used for imaging the gall bladder and visualising the major ducts in the biliary tree. In a normal subject, the liver, common bile duct, gall bladder and duodenum should be visualised within 90 minutes of administration. If this is not the case, delayed images should be obtained at 4 hours.

Once gall bladder filling has been demonstrated, contraction efficiency can be shown by imaging the gall bladder after the patient consumes a fatty meal. The approximate ejection fraction can be calculated from the counts in the gall bladder pre- and post- fatty meal.

Absence of gall bladder visualisation indicates cystic duct obstruction and supports the diagnosis of acute cholecystitis. Occasionally the gall bladder is not visualised when chronic disease is present, but it will usually be seen on delayed images. The technique may provide evidence of obstruction in the biliary tree when this is present.

Good biliary visualisation can be consistently achieved when bilirubin levels are normal or slightly elevated. As hepatic function deteriorates and bilirubin levels progressively rise, however, a greater proportion of the radiopharmaceutical is excreted via the kidneys and less via the hepatobiliary route.

Once the radiopharmaceutical is in the bowel, it is possible to assess bile reflux from the duodenum into the stomach and further reflux into the oesophagus. Bile reflux studies are usually undertaken in patients who have had ulcer surgery. Symptoms of bile vomiting, epigastric pain and heartburn may occur, especially in patients who have had gastric resections, and it is important to establish the presence of reflux before corrective surgery is undertaken. Oesophageal reflux of bile tends to cause severe symptoms and is rare in patients without gastric resection.

NB: It may be necessary to use an unlicensed version of the radiopharmaceutical for this test which will be supplied pre-prepared and tested by another Trust (currently Sheffield Teaching Hospitals). By referring a patient for this test you are agreeing that this is acceptable for your patient.

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 or following discussion with a Consultant Radiologist or 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 fulfils one of the referral criteria detailed below. 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.

The patient should have had an ultrasound of the gall bladder to ensure the normal appearance initially. If the patient has biliary calculi the referral must be discussed with the ARSAC licence holder

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

The clinical indications are detailed below:

• Assessment of gall bladder function/dysfunction

Referral for the following studies must be discussed with the ARSAC liecence holder

• Functional biliary pain syndromes in adults and paediatric patients (NEEDS NORMAL ULTRASOUND FIRST)
• Acute/chronic cholecystitis
• Right-upper-quadrant pain variants
• Biliary system patency
• Bile leakage
• Neonatal hyperbilirubinemia (biliary atresia vs. neonatal hepatitis “syndrome”)
• Assessment of biliary enteric bypass (e.g., Kasai procedure)
• Assessment of liver transplant
• Afferent loop syndrome
• Assessment of choledochal cysts
• Calculation of gallbladder ejection fraction (GBEF)
• Functional assessment of the liver before partial hepatectomy
• Demonstration of anomalous liver lobulation
• Enterogastric (duodenogastric) reflux assessment
• Oesophageal bile reflux after gastrectomy
• Biliary Dyskinesia and Sphincter of Oddi dysfunction

• Pregnancy – Discuss with ARSAC licence holder
• A theoretic possibility of allergic reactions should be considered in patients who receive multiple doses of hepatobiliary compound^[1]

• Adults: Fast for a minimum of 2 hours but preferably 6 hours before the appointment time^[1][2]
• Children: Fast for 2-4 hours before the appointment time^[2]
• Infants: Fast for 2 hours before the appointment time. Clear fluids are allowed if medically necessary^[2]
• Patients fasting for longer than 24 h (including those on total parenteral nutrition), can cause the gallbladder not to fill with radiotracer within the normally expected time frame. In these cases, pretreatment with sincalide might be necessary^[2]. Discuss with the ARSAC licence holder
• For patients being investigated for suspected biliary atresia, pre-treat with 5mg/kg/day of Phenobarbitone for 5 days before the appointment.