Cholecystography Health Dictionary

Also known as Röntgen rays, these were discovered in 1895 by Wilhelm Conrad Röntgen. Their use for diagnostic imaging (radiology) and for cancer therapy (see RADIOTHERAPY) is now an integral part of medicine. Many other forms of diagnostic imaging have been developed in recent years, sometimes also loosely called ‘radiology’. Similarly the use of chemotherapeutic agents in cancer has led to the term oncology which may be applied to the treatment of cancer by both drugs and X-rays.

The rays are part of the electro-magnetic spectrum; their wavelengths are between 10?9 and 10? 13 metres; in behaviour and energy they are identical to the gamma rays emitted by radioactive isotopes. Diagnostic X-rays are generated in an evacuated tube containing an anode and cathode. Electrons striking the anode cause emission of X-rays of varying energy; the energy is largely dependent on the potential di?erence (kilovoltage) between anode and cathode. The altered tissue penetration at di?erent kilovoltages is used in radiographing di?erent regions, for example in breast radiography (25–40 kV) or chest radiography (120–150 kV). Most diagnostic examinations use kilovoltages between 60 and 120. The energy of X-rays enables them to pass through body tissues unless they make contact with the constituent atoms. Tissue attenuation varies with atomic structure, so that air-containing organs such as the lung o?er little attenuation, while material such as bone, with abundant calcium, will absorb the majority of incident X-rays. This results in an emerging X-ray pattern which corresponds to the structures in the region examined.

Radiography The recording of the resulting images is achieved in several ways, mostly depending on the use of materials which ?uoresce in response to X-rays. CONTRAST X-RAYS Many body organs are not shown by simple X-ray studies. This led to the development of contrast materials which make particular organs or structures wholly or partly opaque to X-rays. Thus, barium-sulphate preparations are largely used for examining the gastrointestinal tract: for example, barium swallow, barium meal, barium follow-through (or enteroclysis) and barium enema. Water-soluble iodine-containing contrast agents that ionise in solution have been developed for a range of other studies.

More recently a series of improved contrast molecules, chie?y non-ionising, has been developed, with fewer side-effects. They can, for example, safely be introduced into the spinal theca for myeloradiculography – contrast X-rays of the spinal cord. Using these agents, it is possible to show many organs and structures mostly by direct introduction, for example via a catheter (see CATHETERS). In urography, however, contrast medium injected intravenously is excreted by the kidneys which are outlined, together with ureters and bladder. A number of other more specialised contrast agents exist: for example, for cholecystography – radiological assessment of the gall-bladder. The use of contrast and the attendant techniques has greatly widened the range of radiology. IMAGE INTENSIFICATION The relative insensitivity of ?uorescent materials when used for observation of moving organs – for example, the oesophagus – has been overcome by the use of image intensi?cation. A faint ?uorographic image produced by X-rays leads to electron emission from a photo-cathode. By applying a high potential di?erence, the electrons are accelerated across an evacuated tube and are focused on to a small ?uorescent screen, giving a bright image. This is viewed by a TV camera and the image shown on a monitor and sometimes recorded on videotape or cine. TOMOGRAPHY X-ray images are two-dimensional representations of three-dimensional objects. Tomography (Greek tomos

– a slice) began with X-ray imaging produced by the linked movement of the X-ray tube and the cassette pivoting about a selected plane in the body: over- and underlying structures are blurred out, giving a more detailed image of a particular plane.

In 1975 Godfrey Houns?eld introduced COMPUTED TOMOGRAPHY (CT). This involves

(i) movement of an X-ray tube around the patient, with a narrow fan beam of X-rays; (ii) the corresponding use of sensitive detectors on the opposite side of the patient; (iii) computer analysis of the detector readings at each point on the rotation, with calculation of relative tissue attenuation at each point in the cross-sectional plant. This invention has enormously increased the ability to discriminate tissue composition, even without the use of contrast.

The tomographic e?ect – imaging of a particular plane – is achieved in many of the newer forms of imaging: ULTRASOUND, magnetic resonance imaging (see MRI) and some forms of nuclear medicine, in particular positron emission tomography (PET SCANNING). An alternative term for the production of images of a given plane is cross-sectional imaging.

While the production of X-ray and other images has been largely the responsibility of radiographers, the interpretation has been principally carried out by specialist doctors called radiologists. In addition they, and interested clinicians, have developed a number of procedures, such as arteriography (see ANGIOGRAPHY), which involve manipulative access for imaging – for example, selective coronary or renal arteriography.

The use of X-rays, ultrasound or computerised tomography to control the direction and position of needles has made possible guided biopsies (see BIOPSY) – for example, of pancreatic, pulmonary or bony lesions – and therapeutic procedures such as drainage of obstructed kidneys (percutaneous nephrostomy), or of abscesses. From these has grown a whole series of therapeutic procedures such as ANGIOPLASTY, STENT insertion and renal-stone track formation. This ?eld of interventional radiology has close a?nities with MINIMALLY INVASIVE SURGERY (MIS).

Radiotherapy, or treatment by X-rays The two chief sources of the ionising radiations used in radiotherapy are the gamma rays of RADIUM and the penetrating X-rays generated by apparatus working at various voltages. For super?cial lesions, energies of around 40 kilovolts are used; but for deep-seated conditions, such as cancer of the internal organs, much higher voltages are required. X-ray machines are now in use which work at two million volts. Even higher voltages are now available through the development of the linear accelerator, which makes use of the frequency magnetron which is the basis of radar. The linear accelerator receives its name from the fact that it accelerates a beam of electrons down a straight tube, 3 metres in length, and in this process a voltage of eight million is attained. The use of these very high voltages has led to the development of a highly specialised technique which has been devised for the treatment of cancer and like diseases.

Protective measures are routinely taken to ensure that the patient’s normal tissue is not damaged during radiotherapy. The operators too have to take special precautions, including limits on the time they can work with the equipment in any one period of time.

The greatest value of radiotherapy is in the treatment of malignant disease. In many patients it can be used for the treatment of malignant growths which are not accessible to surgery, whilst in others it is used in conjunction with surgery and chemotherapy.... x-rays

The gall-bladder rests on the underside of the LIVER and joins the common hepatic duct via the cystic duct to form the common BILE DUCT. The gall-bladder acts as a reservoir and concentrator of BILE, alterations in the composition of which may result in the formation of gallstones, the most common disease of the gallbladder.

Gall-stones affect 22 per cent of women and 11 per cent of men. The incidence increases with age, but only about 30 per cent of those with gall-stones undergo treatment as the majority of cases are asymptomatic. There are three types of stone: cholesterol, pigment and mixed, depending upon their composition; stones are usually mixed and may contain calcium deposits. The cause of most cases is not clear but sometimes gall-stones will form around a ‘foreign body’ within the bile ducts or gall-bladder, such as suture material. BILIARY COLIC Muscle ?bres in the biliary system contract around a stone in the cystic duct or common bile duct in an attempt to expel it. This causes pain in the right upper quarter of the abdomen, with nausea and occasionally vomiting. JAUNDICE Gall-stones small enough to enter the common bile duct may block the ?ow of bile and cause jaundice. ACUTE CHOLECYSTITIS Blockage of the cystic duct may lead to this. The gall-bladder wall becomes in?amed, resulting in pain in the right upper quarter of the abdomen, fever, and an increase in the white-blood-cell count. There is characteristically tenderness over the tip of the right ninth rib on deep inhalation (Murphy’s sign). Infection of the gall-bladder may accompany the acute in?ammation and occasionally an EMPYEMA of the gall-bladder may result. CHRONIC CHOLECYSTITIS A more insidious form of gall-bladder in?ammation, producing non-speci?c symptoms of abdominal pain, nausea and ?atulence which may be worse after a fatty meal.

Diagnosis Stones are usually diagnosed on the basis of the patient’s reported symptoms, although asymptomatic gall-stones are often an incidental ?nding when investigating another complaint. Con?rmatory investigations include abdominal RADIOGRAPHY – although many gall-stones are not calci?ed and thus do not show up on these images; ULTRASOUND scanning; oral CHOLECYSTOGRAPHY – which entails a patient’s swallowing a substance opaque to X-rays which is concentrated in the gall-bladder; and endoscopic retrograde cholangiopancreatography (ERCP) – a technique in which an ENDOSCOPE is passed into the duodenum and a contrast medium injected into the biliary duct.

Treatment Biliary colic is treated with bed rest and injection of morphine-like analgesics. Once the pain has subsided, the patient may then be referred for further treatment as outlined below. Acute cholecystitis is treated by surgical removal of the gall-bladder. There are two techniques available for this procedure: ?rstly, conventional cholecystectomy, in which the abdomen is opened and the gall-bladder cut out; and, secondly, laparoscopic cholecystectomy, in which ?breoptic instruments called endoscopes (see FIBREOPTIC ENDOSCOPY) are introduced into the abdominal cavity via several small incisions (see MINIMALLY INVASIVE SURGERY (MIS)). Laparoscopic surgery has the advantage of reducing the patient’s recovery time. Gall-stones may be removed during ERCP; they can sometimes be dissolved using ultrasound waves (lithotripsy) or tablet therapy (dissolution chemotherapy). Pigment stones, calci?ed stones or stones larger than 15 mm in diameter are not suitable for this treatment, which is also less likely to succeed in the overweight patient. Drug treatment is prolonged but stones can disappear completely after two years. Stones may re-form on stopping therapy. The drugs used are derivatives of bile salts, particularly chenodeoxycholic acid; side-effects include diarrhoea and liver damage.... gall-bladder, diseases of

A severe pain in the upper right quadrant of the abdomen that is usually caused by the gallbladder’s attempts to expel gallstones or by the movement of a stone in the bile ducts. The pain may be felt in the right shoulder (see referred pain) or may penetrate to the centre of the back. Episodes of biliary colic often last for several hours and may recur, particularly after meals.

Injections of an analgesic drug and an antispasmodic drug may be given to relieve the colic.

Tests such as cholecystography or ultrasound scanning can confirm the presence of gallstones, in which case cholecystectomy (surgical removal of the gallbladder) is possible.... biliary colic

Lumps of solid matter found in the gallbladder, or in the bile ducts. Gallstones are composed mainly of cholesterol and bile pigments from the breakdown of red blood cells. They develop when there is a disturbance in the chemical composition of bile.

Gallstones are rare in childhood and become increasingly common with age. Women are affected more than men. Risk factors include a high-fat diet and being overweight.

Most gallstones cause no symptoms. When symptoms do occur, they often begin when a stone gets stuck in the duct leading from the gallbladder, causing biliary colic and nausea. Gallstones may cause indigestion and flatulence. Possible complications are cholecystitis and bile duct obstruction.Diagnosis is by ultrasound scanning, X-ray oral cholecystography, or cholangiography.

Stones that are not causing symptoms are usually left alone.

In other cases, the gallbladder and stones may be removed by cholecystectomy.

Ultrasonic shock waves (see lithotripsy) are sometimes used to shatter stones; the fragments pass into the bowel and cause no further problems.

Drugs such as chenodeoxycholic acid or ursodeoxycholic acid can dissolve some stones if given over a period of months.... gallstones

Techniques that produce images of the liver, gallbladder, bile ducts, and blood vessels supplying the liver, to aid the detection of disease.

Ultrasound scanning, CT scanning, and MRI are commonly used.

Radionuclide scanning may reveal cysts and tumours and show bile excretion.

X–ray techniques include cholangiography, cholecystography, and ERCP (endoscopic retrograde cholangiopancreatography).

In these procedures, a contrast medium, which is opaque to X-rays, is introduced to show abnormalities in the biliary system.

Angiography reveals the blood vessels in the liver.... liver imaging

the normal radiological appearance of the tip of the gall bladder, seen in a minority of cholecystograms (see cholecystography). Its name is derived from its resemblance to the characteristic Balkan headgear.... phrygian cap

A distorted sensation based on misinterpretation of a real stimulus (for example, a pen is seen as a dagger). It is differs from a hallucination, in which a perception occurs without any stimulus.Usually, illusions are brief and can be understood when explained. They may be due to tiredness or anxiety, to drugs, or to forms of brain damage. Delirium tremens is a classic inducer of illusions. imaging techniques Techniques that produce images of structures within the body. The most commonly used and simplest techniques are X-rays (to view dense structures such as bone) and contrast X-rays, in which a medium, such as barium, that is opaque to X-rays is introduced into the body. Contrast X-ray techniques include barium X-ray examinations (used to examine the oesophagus, the stomach and the small intestine); cholecystography (used to visualize the gallbladder and common bile duct); bronchography (to view the airways connecting the windpipe to the lungs); angiography and venography (to provide images of the blood vessels); intravenous urography (to visualize the kidneys and urinary tract); and ERCP (by which the pancreatic duct and biliary system are examined).

Many X-ray imaging techniques have been superseded by newer procedures. These include ultrasound scanning, MRI (magnetic resonance imaging), PET scanning, and radionuclide scanning. However, X-rays are used in CT scanning. Some of these techniques use computers to process the raw imaging data and produce the actual image. Others can produce images without a computer, although one may be used to enhance the image. imipramine A tricyclic antidepressant drug most commonly used as a longterm treatment for depression. Possible adverse effects include excessive sweating, blurred vision, dizziness, dry mouth, constipation, nausea, and, in older men, difficulty passing urine.... illusion