MRI Scan of the Rectum
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This InsideRadiology item deals with the large number of treatment procedures that use catheter angiography requiring the ‘direct’ injection of contrast into a diseased artery or vein. This is in contrast to diagnostic angiography (which is obtained by ‘indirect’ imaging techniques) such as CT, MRI and duplex ultrasound.
Outlined below is a sample of conditions where angiography may be used (generally by means of angioplasty, stent insertion or embolisation).
Prerequisites vary depending on the specific type of angiography carried out and the indication. Fasting before an angiogram is not required in all cases, but might be appropriate in certain circumstances. In general, patients should be well hydrated before angiography in order to minimize the risk of contrast medium-induced nephrotoxicity.
Several groups of patients should have special attention:
Patient weight that exceeds the angiography table limit (150 kg mostly). Overweight patients might prohibit the use of angiography equipment because of technical safety concerns
Angiography is an invasive procedure that might incur complications.
Angiography suites have exacting protocols that aim to limit the possibility of bleeding complications after angiography. These include instructions to patients regarding periods where they must lie flat, when they can sit up, gently mobilise etc. On occasion, a patient will develop a delayed groin haematoma or bleed after having left the angiography suite. The treatment involves lying the patient flat, compression to the puncture site and communication with the angiography suite or on-call emergency (radiology) service. Occasionally, hospital admission to limit the bleeding and to correct any associated hypotension, blood loss etc. might be required.
Referrers should watch out for worsening symptoms post-angiography e.g. worsening limb ischaemia post-angioplasty. If that happens, contact the emergency department of the local hospital, and if possible contact the radiologist who carried out the angiogram. Emergency re-intervention (e.g. percutaneous thrombectomy or thrombolysis) might be required.
Delayed onset rash can occur usually within 24 hours of the procedure. It is usually self-limiting, and requires symptomatic treatment only.
There are other forms of non-invasive imaging for the integrity of the blood vessels, which include ultrasound, CT and MRI.
The best form of imaging for your patient will depend on the indications and contraindications, and in many cases this choice is best discussed with a radiologist.
Depending on the clinical problem, other investigations might be appropriate: see Diagnostic Imaging Pathways below.
Angiography is not contraindicated by the above.
Angiography is not contraindicated by the isolated development of a rash previously.
Angiography is not contra-indicated by vomiting after prior contrast medium administration. Vomiting does not indicate an allergic reaction.
There is no good evidence to support routine fasting before angiography – the risk of vomiting leading to aspiration during angiography in a conscious, normally sentient patient is very small. In certain circumstances, fasting is desirable e.g. complex angiographic procedures might require emergency anaesthetic support/transfer to an operating theatre.
Fluids should be encouraged, because the risk of contrast medium nephrotoxicity is far greater than any risk of aspiration during a routine angiographic procedure.
Society of Interventional Radiology: www.sirweb.org/medical-professionals
Diagnostic Imaging Pathways: www.imagingpathways.health.wa.gov.au
Page last modified on 29/3/2017.
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