Tag: Washington University School of Medicine

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Introduction:
An abdominal CT scan is an imaging method that uses x-rays to create cross-sectional pictures of the belly area. CT stands for computed tomography.
CT scans are pictures taken by a specialized x-ray machine. The machine circles your body and scans an area from every angle within that circle. The machine measures how much the x-ray beams change as they pass through your body. It then relays that information to a computer, which generates a collection of black-and-white pictures, each showing a slightly different “slice” or cross-section of your internal organs. Because these “slices” are spaced only about a quarter-inch apart, they give a very good representation of your internal organs and other structures. Doctors use CT scans to evaluate all major parts of the body, including the abdomen, back, chest, and head.

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CT stands for computerized tomography. In this procedure, a thin X-ray beam is rotated around the area of the body to be visualized. Using very complicated mathematical processes called algorithms, the computer is able to generate a 3-D image of a section through the body. CT scans are very detailed and provide excellent information for the physician.

A CT scan is an excellent way to view the organs inside your abdomen. It is especially useful for looking at solid organs, such as the liver, pancreas, spleen, kidneys, and adrenal glands. It is also excellent for viewing the large blood vessels that pass through the abdomen (the aorta and vena cava) and for finding lymph nodes in the abdomen. Organs that can change their shape when they are empty or full, such as stomach and intestines, are harder for a CT scan to evaluate well, because it is sometimes difficult for a doctor to tell for sure if they are abnormal. Often the CT can give some information about these organs, though. Abdominal CT scans are often used to look for signs of inflammation or infection inside the abdomen in different organs, to look for cancer, or to look for injury to one or another internal organ.

A CT scan provides a better picture of internal organs than traditional x-rays. The benefits of an abdominal CT scan usually far outweigh the risks of radiation exposure.

How the Test is Performed
You will be asked to lie on a narrow table that slides into the center of the CT scanner. Usually, you will lie on your back with your arms raised above the head.

The health care provider may inject a dye into one of your veins. This helps certain diseases and organs show up better on the images.

Once inside the scanner, the machine’s x-ray beam rotates around you. Small detectors inside the scanner measure the amount of x-rays that make it through the abdomen. A computer takes this information and creates several individual images, called slices.

You must be still during the exam, because movement causes blurred images. You may be told to hold your breath for short periods of time.

The actual scan time only takes a few minutes, although the entire procedure usually takes much longer.
A CT scan is an excellent way to view the organs inside your abdomen. It is especially useful for looking at solid organs, such as the liver, pancreas, spleen, kidneys, and adrenal glands. It is also excellent for viewing the large blood vessels that pass through the abdomen (the aorta and vena cava) and for finding lymph nodes in the abdomen. Organs that can change their shape when they are empty or full, such as stomach and intestines, are harder for a CT scan to evaluate well, because it is sometimes difficult for a doctor to tell for sure if they are abnormal. Often the CT can give some information about these organs, though. Abdominal CT scans are often used to look for signs of inflammation or infection inside the abdomen in different organs, to look for cancer, or to look for injury to one or another internal organ.

Why the Test is Performed
An abdominal CT rapidly creates detailed pictures of the belly area. The test may be used to:

*Study blood vessels
*Identify masses and tumors, including cancer
*Look for infections, kidney stones, or appendicitis
.How to Prepare for the Test
If you are having an abdominal CT scan, you might have to fast 2–4 hours before your test. You also may have to drink a large quantity of oral contrast, a fluid that will show up on the CT scan and help define the lining of some internal organs.

Tell your doctor if you’re allergic to x-ray contrast dyes, may be pregnant, or have diabetes and take insulin. Insulin can cause hypoglycemia after missing a meal. or have had difficulty with previous CT scans.

If contrast or sedation is used, you may also be asked not to eat or drink anything for 4-6 hours before the test.

Since x-rays have difficulty passing through metal, you will be asked to remove jewelry and wear a hospital gown during the study.

What happens when the test is performed?
The test is done in the radiology department of a hospital or in a diagnostic clinic. You wear a hospital gown and lie on your back on a table that can slide back and forth through the donut-shaped CT machine. A technician or other health care professional inserts an IV and injects more contrast dye through it. This dye outlines blood vessels and soft tissue to help them show up clearly on the pictures.

The technologist moves the table with a remote control to enable the CT machine to scan your body from all of the desired angles. You will be asked to hold your breath for a few seconds each time a new level is scanned. The technologist usually works the controls from an adjoining room, watching through a window and sometimes speaking to you through a microphone. A CT scan takes about 30–45 minutes. Although it’s not painful, you might find it uncomfortable if you don’t like to lie still for extended periods.

How the Test Will Feel
The x-rays are painless. Some people may have discomfort from lying on the hard table.

Contrast give through an IV may cause a slight burning sensation, a metallic taste in the mouth, and a warm flushing of the body. These sensations are normal and usually go away within a few seconds.

Risk Factors:-
There are a few small risks. The contrast dye used in the test can damage your kidneys, especially if they are already impaired by disease.However, some newer dyes are less likely to cause kidney injuries. If kidney damage does occur, this is usually temporary, although in some rare cases it becomes permanent. If you are allergic to the dye used in the procedure, you may get a rash or your blood pressure may drop enough to make you feel faint until you get treatment. As with x-rays, there is a small exposure to radiation. The amount of radiation from a CT scan is greater than that from regular x-rays, but it’s still too small to be likely to cause harm unless you’re pregnant.

An abdominal CT scan is usually not recommended for pregnant women, because it may harm the unborn child. Women who are or may be pregnant should speak with their health care provider to determine if ultrasound can be used instead.

CT scans and other x-rays are strictly monitored and controlled to make sure they use the least amount of radiation. CT scans do create low levels of ionizing radiation, which has the potential to cause cancer and other defects. However, the risk associated with any individual scan is small. The risk increases as numerous additional studies are performed.

In some cases, a CT scan may still be done if the benefits greatly out weigh the risks. For example, it can be more risky not to have the exam, especially if your health care provider thinks you might have cancer.

The most common dye used is iodine based. A person who is allergic to iodine may have nausea, sneezing, vomiting, itching, or hives. Rarely, the dye may cause anaphylaxis (a life-threatening allergic response).

Results:-
What Abnormal Results Mean

The CT scan may show the following:

*Abdominal aortic aneurysm
*Abscesses
*Acute bilateral obstructive uropathy
*Acute cholecystitis
*Acute unilateral obstructive uropathy
*Addison’s disease
*Amebic liver abscess
*Appendicitis
*Bilateral hydronephrosis
*Bowel wall thickening
*Carcinoma of the renal pelvis or ureter
*Cholangiocarcinoma
*Choledocholithiasis
*Cholelithiasis
*Chronic bilateral obstructive uropathy
*Chronic cholecystitis
*Chronic pancreatitis
*Chronic unilateral obstructive uropathy
*Complicated UTI (pyelonephritis)
*Cystinuria
*Cysts
*Echinococcus
*Enlarged lymph nodes
*Enlarged organs
*Gastrointestinal or bowel obstruction
*Glucagonoma
*Hairy cell leukemia
*Hepatocellular carcinoma
*Histoplasmosis; disseminated
*Hodgkin’s lymphoma
*Islet of Langerhans’ tumor
*Multiple endocrine neoplasia (MEN) II
*Nephrocalcinosis
*Nephrolithiasis
*Non-Hodgkin’s lymphoma
*Ovarian cancer
*Pancreatic abscess
*Pancreatic carcinoma
*Pancreatic pseudocyst
*Pancreatitis
*Pheochromocytoma
*Primary hyperaldosteronism
*Pyelonephritis – acute
*Pyogenic liver abscess
*Renal cell carcinoma
*Retroperitoneal fibrosis
*Sclerosing cholangitis
*Stones (bladder, kidney, liver, gall bladder)
*Testicular cancer
*Tumors
*Unilateral hydronephrosis
*Ureterocele
*Wilms’ tumor
*Wilson’s disease
*Zollinger-Ellison syndrome

Additional conditions under which the test may be performed include the following:-
*Acute renal failure
*Alcoholic liver disease (hepatitis/cirrhosis)
*Atheroembolic renal disease
*Chronic glomerulonephritis
*Chronic renal failure
*Cushing syndrome
*Cushing syndrome caused by adrenal tumor
*Injury of the kidney and ureter
*Medullary cystic kidney disease
*Multiple endocrine neoplasia (MEN) I
*Polycystic kidney disease
*Reflux nephropathy
*Renal artery stenosis
*Renal vein thrombosis
*Skin lesion of histoplasmosis

How long is it before the result of the test is known?
The radiologist can probably give you preliminary results within a day. The formal reading of your CT scan might take another day.

Resources:
https://www.health.harvard.edu/fhg/diagnostics/abdominal-ct-scan.shtml
http://www.nlm.nih.gov/medlineplus/ency/article/003789.htm