Alternate Names: Nuclear magnetic resonance - abdomen; NMR - abdomen; Magnetic resonance imaging - abdomen; MRI of the abdomen

How Performed: The MRI scanner is in an area that has been shielded from outside magnetic fields. You are asked to lie on a narrow table that can slide inside a large tunnel-like tube within the scanner. The scanner creates a magnetic field around you, then pulses radio waves at the tissues in question. Several sets of images are usually required, each taking from 2 to 15 minutes. The complete scan takes about 1 hour; some scans take more than 90 minutes.

How To Prepare: No preparatory tests, diets, or medications are usually needed. Occasionally you may be asked to fast for 4 to 6 hours prior to the scan. The colon may need to be cleaned (with preparations such as a laxative or an enema) before MRI of some abdominal structures. You must sign a consent form before the scan.

Because of the strong magnets, no metallic objects are allowed into the room. Items such as jewelry, watches, credit cards, and hearing aids can be damaged by the strong magnets. Pins, hairpins, metal zippers, and similar metallic items can distort the images. Frequent exposure to ferrous metals (such as a sheet-metal worker experiences) may make reading an MRI scan difficult. You may be required to wear a hospital gown, or you may be allowed to wear "sweats" or similar clothing without metal fasteners. You should take out any removable dental work just prior to the scan.

Infants and children:
The physical and psychological preparation you can provide for this or any test or procedure depends on your child’s age, interests, previous experience, and level of trust. For specific information regarding how you can prepare your child, see the following topics as they correspond to your child’s age:

• infant test or procedure preparation (birth to 1 year)
• toddler test or procedure preparation (1 to 3 years)
• preschooler test or procedure preparation (3 to 6 years)
• schoolage test or procedure preparation (6 to 12 years)
• adolescent test or procedure preparation (12 to 18 years)

How It Feels: There is no pain. You do not feel the magnetic field and radio waves. The primary discomfort is the claustrophobic feeling that some people experience from being inside the scanner. The table may be hard or cold, but you can request a blanket or pillow. The machine produces loud thumping and humming noises. Usually you are given ear plugs to reduce the noise. A technologist observes you during the entire procedure, and may enter the room to speak (or may speak through an intercom in the scanner) with you.

Excessive movement can blur MRI images. If you have difficulty lying still or are very anxious, a sedative may be given. Medication may be given to reduce the activity of the intestines and minimize motion artifact (blurring of the images caused by movement, including intestinal peristalsis) during the scan of the abdomen. There is no recovery required (unless you have been sedated). After an MRI scan, you usually can resume normal diet, activity, and medications.

Risks: There is no ionizing radiation, and usually no contrast dye is needed. The procedure is safe in most cases, and there are no documented side effects. However, because the effects of strong magnetic fields on a fetus are not well documented at this time, pregnant women are usually advised to avoid MRI scans.

Because the strong magnets can displace or disrupt the action of implanted metallic objects, people with cardiac pacemakers cannot be scanned and should not enter the MRI scan area. MRI also should not be used for most people with metallic objects in their bodies, such as artificial joints, inner ear (cochlear) implants, brain aneurysm clips, some artificial heart valves, and metallic foreign bodies in the eye or other body areas.

MRI is not usually recommended for acute trauma situations, because traction and life-support equipment cannot enter the scanner area and because of the long scan times.

Why Performed: MRI provides detailed pictures of soft tissues without obstruction by overlying bone. It is used to clarify findings from previous X-rays or CT scans, or may be recommended when the area to be scanned is obstructed by overlying bone or foreign bodies. It can show a wide area of the abdomen from multiple planes. MRI can reflect certain organ functions. It clearly shows lymph nodes and blood vessels, and is a noninvasive procedure that can evaluate blood flow.

MRI may be used in diagnosing abnormal growths. It can distinguish tumors or other lesions from normal tissues and can provide information for the staging (determination of the size, extent, and spread) of abdominal tumors. MRI is sometimes used to avoid the dangers of angiography or repeated exposure to radiation.

Normal Values: The abdominal organs are normal in size and position as viewed from any plane. There are no new growths or lesions, and there is normal organ function (of the organs where MRI can indicate their function).

Abnormal Results: The sensitivity of MRI depends, in part, on the experience of the radiologist. As MRI becomes more common, increasingly detailed diagnoses may be possible.

Abdominal MRI may reveal many disorders, including:

• obstructed vena cava
• renal vein thrombosis
• renal arterial obstruction
• hydronephrosis (kidney enlargement from reflux of urine)
• glomerulonephritis (inflammation of the kidney glomeruli)
• acute tubular necrosis
• extent of tissue damage in organ (kidney) transplant rejection
• pancreatic cancer
• adrenal masses
• mass (tumor) of the gallbladder
• other tumors or masses
• differentiates cancer from other types of lesions
• staging of prostate, uterine, or bladder cancer
• lymphadenopathy (abnormalities of the lymph nodes)
• portal vein obstruction (liver)
• enlarged spleen or liver
• distended gallbladder or bile duct
• gallstones, bile duct stones
• focal diseases such as abscess, hemangiomas, or others

• abdominal aortic aneurysm
• acute renal failure
• adenomyosis
• atheroembolic renal disease
• carcinoma of the renal pelvis or ureter
• chronic renal failure
• cystinuria
• hydatidiform mole
• injury of the kidney and ureter
• insulinoma
• islet of Langerhans’ tumor
• medullary cystic disease
• multiple endocrine neoplasia (MEN) II
• multiple endocrine neoplasia (MEN) I
• nephrolithiasis
• ovarian cancer
• pheochromocytoma
• skin lesion of histoplasmosis

Cost:

Special Considerations: MRI is more accurate than a CT scan or other tests for certain conditions but less accurate for others. The function of the intestines is not readily visible. Disadvantages include the high cost, long duration of the scan, and sensitivity to movement. People with claustrophobia or who are confused or anxious may have difficulty lying still for the relatively long scan times. MRI is not portable (it cannot be taken to the patient, the patient must come to the scanner) and is incompatible with metallic implants, life-support devices, traction apparatus, and similar equipment.

MRI is superior in most cases in which differentiation of soft tissues is necessary. It can view organs that may be obscured by bone or foreign bodies on conventional X-rays or CT scans. It is capable of showing the tissues from multiple viewpoints and is a noninvasive way to evaluate blood flow.