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Contrast Media

The hospital and/or physician protocol will determine if the patient will be receiving contrast for the scheduled study, depending on the anatomy being imaged.  The type of imaging modality and body part to be visualized dictates which contrast given and how it will be administered.  The technologist may administer oral contrast, intravenous contrast or both.

All patients will complete a Contrast Screening form (or data equivalent in the departmental documentation). Any questions or concerns the patient has will be addressed prior to the procedure by the administering technologist. Pre-procedural instructions will be provided.  In addition, patient health history is reviewed and medications reconciled by the physician, nurse or registered technologist prior the administration of any contrast to a patient.

All patients with known allergy to iodinated contrast will need premedication 12 hours prior to the procedure as per department protocol.  The ordering  physician should be familiar w/ the hospital protocol, or can call and obtain it and provide you with the medication necessary for the patient to have their test.

Oral Contrast:
Oral Contrast is usually recommended for all studies of the abdomen in Diagnostic X-ray and CT.  Oral Contrast enhances the digestive tract allowing it to be visualized.  The patient should follow the preparation instructions provided by their physician for the test they are to have.  If the patient is unsure of the preparation for a test, contact your physician office or the Wentworth-Douglass Imaging Department at 740-2670.  Preparation instructions for all studies are listed on the WDH website at www.wdhospital.com

In Diagnostic X-ray and some CT studies, a white chalky substance is used, called Barium.  Barium blocks the passage of x-rays, so barium-filled organs stand out better on x-ray exams. For an examination of the esophagus or stomach, patients drink a mixture of barium sulfate and water. This mixture usually is thick and white and can vary in texture.  It is inert and will not harm most patients.  It is important to drink plenty of fluids (water and juice) after any barium test.

CT, patients must arrive in the Imaging Department one hour prior to their scheduled time to drink the contrast allowing it to fill the entire digestive system for the scan.  Generally this takes about one to one and a half hours.  At Wentworth Douglass Hospital a water soluble contrast is added to crystal light so the taste is tolerable. We will also mix it with plain filtered/chilled tap water, if you prefer and you do not have to gulp down the contrast all at once.  It is best to drink it over a 30-45 minute period.

Intravenous Contrast:
Intravenous contrast is used to highlight blood vessels and to enhance the structure of organs like the brain, spine, liver, and kidney. For CT and diagnostic X-ray, the contrast agent, usually an iodine compound (OmniPaque® or Visipaque®) is clear, with a water-like consistency. Typically the contrast is contained in a special injector, which injects the contrast through an IV taped in place (usually the bend of the elbow, or on the back of the hand) during a specific period in the exam.  Some exams require hand injection, as in Intravenous Pyelograms in diagnostic x-ray, or in CT when injecting through a port that is not specified for power injectors.

Once the contrast is injected into the bloodstream, it circulates throughout the body. The x-ray beam is weakened as it passes through the blood vessels and organs that have "taken up" the contrast. These structures are enhanced by this process and show up as white areas on the images. When the test is finished, the kidneys and liver quickly eliminate the contrast from the body.

Iodine is considered to be a safe contrast agent. It has been used for many years without serious side effects. Because iodine contrast increases the visibility of target tissues on the images, the benefits are considered to outweigh the risks.

The most common side effect of iodine is a warm or "flushed" sensation during the actual injection of the iodine, followed sometimes by a metallic taste in the mouth that usually lasts for less than a minute. No treatment is necessary for this sensation, if experienced and it should pass quickly.

Diabetics maybe told to withhold some medications for a few days following a procedure where iodinated contrast was injected.  Usually this is the case for patients taking any kind of diabetes medications containing Metformin or Glucophage.  The technologist will work with the patient to determine if medication withholding is necessary.

MRI uses a different type of contrast which works differently than that in X-ray or CT. Contrast agents may be injected intravenously to enhance the appearance of blood vessels, tumors or inflammation. In addition, contrast agents may also be directly injected into a joint in the case of arthrograms, MR images of joints.

MRI contrast works by altering the local magnetic field in the tissue being examined. Normal and abnormal tissue will respond differently to this slight alteration, giving us differing signals. These varied signals are transferred to the images, allowing us to visualize many different types of tissue abnormalities and disease processes better than we could without the contrast.

Your blood filters out the contrast through you urinary system naturally, so it is crucial that the kidneys are functioning properly.  Creatinine levels/GFR's (Glomerular Filtration Rate) are required for all patients receiving intravenous contrast and meet any of the following criteria:  50 years of age or older or diabetic and/or with known kidney insufficiency/compromise.  Lab results must be within 30 days prior to the procedure. Patients currently receiving dialysis will not receive Gadodiamide (Omniscan®) for MRI.

Rarely, a mild reaction can occur when a patient is allergic to imaging contrast.  This consists of itching over various parts of the body and possibly the development of hives.  This reaction lasts from several minutes to a few hours after the injection. When this reaction occurs, medication is usually administered to counteract the itching.  More serious allergic reactions, while uncommon, include difficulty breathing and swelling of the throat or other parts of the body. These reactions, if experienced, are treated immediately.

After the procedure, each patient is observed for at least 10 minutes post injection and discharged with follow-up instructions if there is no evidence of complications. The IV must remain in place until discharge. Patients with a known contrast reaction will be monitored for 30 minutes in the event that there is a delayed reaction.

Creatinine is an element produced by the body and excreted in urine.  IV contrast filters out through the urinary system so it is important that the kidneys are functioning properly prior to contrast administration.  A simple blood test used to measure kidney function. Therefore, if the procedure requires IV contrast, the patient may need to have labs drawn.  Creatinine is needed for all patients 50 years of age or older, diabetics, or patients with known renal insufficiency.  The creatinine must be drawn within 30 days prior to the scheduled exam.

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Wentworth-Douglass Hospital
789 Central Avenue, Dover, NH 03820
Phone: (603) 742-5252
Toll free: 1 (877) 201-7100