Common Knowledge: Scans not full-proof for detecting gallstones

"I would still like to see the proof of this. Being that I know quite a bit about these scans I seriously doubt your claim."

1)Imaging and Diagnostic Techniques

Ultrasound of the Abdomen. Ultrasound is a simple, rapid, and noninvasive imaging technique. It is the diagnostic method most frequently used to detect Gallstones and is the method of choice for detecting acute cholecystitis. If possible, the patient should not eat for 6 or more hours before the test, which takes only about 15 minutes. During the procedure, the doctor can check the liver, bile ducts, and pancreas, and quickly scan the gallbladder wall for thickening (characteristic of cholecystitis).

How well ultrasound can help in the diagnosis varies based on the patient's situation:

* Ultrasound accurately detects Gallstones as small as 2 mm in diameter. Some experts recommend that the test be repeated if an ultrasound does not detect stones, but the health care provider still strongly suspects gallstones.
* Air in the gallbladder wall may indicate gangrene.
* Ultrasound does not appear to be very useful for identifying cholecystitis in patients who have symptoms but do not have gallstones.
* Ultrasound is also not as accurate for identifying common bile duct stones or imaging the cystic duct. Nevertheless, normal ultrasound results, along with normal bilirubin and liver enzyme tests are very accurate indications that there are no stones in the common bile duct.

Endoscopic Ultrasound. In an ultrasound variation called endoscopic ultrasound (EUS), the physician places an endoscope (a thin, flexible plastic tube containing a tiny camera) into the patient's mouth and down the esophagus, stomach, and then the first part of the small intestine. The tip of the endoscope contains a small ultrasound tranducer, which provides "close-up" ultrasound images of the anatomy in the area. EUS is useful when the health care provider suspects common bile duct stones, but they are not seen on a regular ultrasound and the patient is not clearly ill. However, if common duct stones are detected, they cannot be removed using this method.

X-Rays. Standard x-rays of the abdomen may detect calcified Gallstones and gas. Variations include oral cholecystography or cholangiography.

* In oral cholecystography, the patient takes a tablet containing a dye the night before the test. The dye fills the gallbladder, and x-ray images are taken the next day. The test has largely been replaced by ultrasound; however, it may be useful in some cases for determining the structural and functional status of the gallbladder, often before nonsurgical procedures.
* In cholangiography, a dye is injected into the bile duct and x-rays are used to view the duct. It is typically used during operations to provide a clear image of the biliary tract.

Cholescintigraphy (Also Called Gallbladder Radionuclide Scan or HIDA scan). Cholescintigraphy, a nuclear imaging technique, is more sensitive than ultrasound for diagnosing acute cholecystitis. It is noninvasive but can take 1 - 2 hours or longer. The procedure involves the following steps:

* A tiny amount of a radioactive dye is injected intravenously. This material is excreted into bile.
* The patient lies on a table under a scanning camera, which detects gamma (radioactive) rays emitted by the dye as it passes from the liver into the gallbladder.
* The test can take up to 2 hours, because each image takes about a minute, and images are taken every 5 -15 minutes.

If the dye does not enter the gallbladder, the cystic duct is obstructed, indicating acute cholecystitis. The scan cannot identify individual gallstones or chronic cholecystitis.

Occasionally, the scan gives false positive results (detecting acute cholecystitis in people who do not have the condition). Such results are most common in alcoholic patients with liver disease or patients who are fasting or receiving all their nutrition intravenously.

Endoscopic Retrograde Cholangiopancreatography (ERCP). Endoscopic retrograde cholangiopancreatography (ERCP) has been the gold standard for detecting common bile duct stones, particularly because stones can be removed during the procedure. (See "Surgery" section below for a description of the procedure.)

However, this technique is invasive and carries a risk for complications, including pancreatitis. With the advent of noninvasive imaging techniques, ERCP is now generally limited to patients who have a high likelihood of common bile ducts stones, which would need to be removed. It may also be used to diagnose biliary dyskinesia.

Computed Tomography. Computed tomography (CT) scans may be a valuable additional imaging technique if the doctor suspects complications, such as perforation, common duct stones, or other problems such as cancer in the pancreas or gallbladder. Helical (spiral) CT scanning is an advanced technique that is faster and obtains clearer images. With this process, the patient lies on a table while a donut-like, low-radiation x-ray tube rotates around the patient.

Magnetic Resonance Cholangiography (MRCI), or Magnetic Resonance Cholangiopancreatography (MRCP). These imaging techniques may be very useful for detecting common bile duct stones and other abnormalities of the biliary tract. A dye is injected into the patient's veins that helps visualize the biliary tract. MRCP is extremely sensitive in detecting biliary tract cancer. This imaging procedure may not detect very small stones or chronic infections in the pancreas or bile duct. It is most likely to be useful in a small subset of patients who have unclear symptoms that suggest gallbladder or biliary tract problems, but ultrasound and other routine tests have been negative. For these patients, performing a MRCP can eliminate the need for ERCP and its side effects.


Virtual Endoscopy. Virtual endoscopy is an experimental technique that uses data from CT and MRI scans to generate a three-dimensional view of various body structures. The images resemble those used in endoscopy (an invasive procedure), but the procedure is noninvasive. Virtual endoscopy may be able to detect smaller stones in the common bile duct than MRI.

http://www.umm.edu/patiented/articles/how_gallstones_gallbladder_disease_diag...


2)"Acute cholecystitis is associated with gallstones in approximately 95% of cases, thus it is possible to see gallstones on plain radiograph. (Only 20% of gallstones, however, contain sufficient calcium to be seen on a plain radiograph)."

http://www.meddean.luc.edu/lumen/meded/Radio/curriculum/Surgery/cholecystitis...
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