With this article we continue our series of white papers on radiologic patient positioning techniques for x-ray examinations. The monthly series explores each of the major modalities. If you'd like to comment on an article or contribute an installment, please e-mail Show The contrast study of the large bowel, also called the lower gastrointestinal (LGI) series, is commonly performed using a barium enema. It is a valuable diagnostic tool that helps detect abnormalities in the large intestine. The barium enema, along with colonoscopy, remains standard in the diagnosis of colon cancer, ulcerative colitis, and other inflammatory diseases of the colon. There are two basic radiological methods of examining the large intestine by means of contrast enemas: a single-contrast method and a double-contrast method.
Barium sulfate is the most common type of contrast media used for a barium enema. It is important to choose a barium suspension of appropriate density and viscosity for barium enema. If the viscosity of the barium suspension is too high, the examination will be prolonged, the filling of cecum and right colon will be difficult, and the drainage of barium will be inadequate. A standard mixture used for single-contrast barium enemas ranges between 15%-25% weight-to-volume (500 cc of barium sulfate is mixed into 1,500 cc tepid water to produce a 12%-20% solution). A double-contrast barium enema uses a thicker barium with a weight-to-volume (w/v) concentration between 75%-95% or higher. Some patients require glucagon during the examination. Glucagon is a hypotonic drug used to achieve relaxation of colon. Colonic relaxation diminishes patient discomfort, accelerates the examination, and decreases incontinence. Choice of contrast medium and indications for examination The choice between the single- and double-contrast barium enema is the prerogative of the radiologist, and is an educated decision based on the condition of the individual patient and the clinical problem to be solved. The single-contrast barium enema is preferable for the very young, the very old, the seriously ill, or the very disabled patient. Such patients are usually unable to stand on their own or to turn 360º when lying down. The method is often used for suspected obstruction, fistulization, and evaluation of the distal colon after colostomy.
The double-contrast barium enema is preferable in patients with a family or personal history of colon neoplasia, in patients suspected or known to have inflammatory bowel disease, and in the search for the etiology of anemia, weight loss, or hematochezia. The use of biphasic examinations (a double-contrast examination followed immediately after evacuation by low-density barium or a limited double-contrast evaluation of a difficult segment identified in single contrast) should be considered when a given examination is incomplete or equivocal.
Water-soluble contrast medium should be used for patients with suspected perforation and for patients with suspected anastomotic leak. Contraindications Contraindications to the use of any barium enema include:
Patient preparation
Supplies
A scout film is taken of the anteroposterior (AP) abdomen. If sufficient retained stool is visualized on the scout film, consider rescheduling the patient for the following day and repeating the bowel preparation or performing a cleansing enema. Residual stool can obscure small colonic lesions.
Radiation
Rectal tube insertion procedure
Patient positioning, imaging techniques for routine single-contrast barium enema The basic principle for performing an accurate single-contrast barium enema is radiography of the colon so that all segments of the colon are clearly seen without overlapping loops. It is also necessary that each segment of colon be seen at fluoroscopy and on at least two films so that any suspected lesion can be verified. This is accomplished by a combination of fluoroscopy and compression spot films of the entire colon, as well as bucky films of the entire colon. Compression spot filming is employed to thin out the barium column so that a small lesion, such as a polyp, can be easily seen. However, the rectum and the pelvic loops of the sigmoid colon are not amenable to compression. A through examination incorporates the following procedures and film sequences.
Spot films
Overhead films All overhead films must be taken at 110 kVp; suggested films which should be obtained are the following:
Patient positioning, imaging techniques for routine double-contrast barium enema
AuntMinnie.com contributing writer June 27, 2002 Related Reading Patient positioning tips for a premium UGI series, April 17, 2002 Positioning techniques for quality esophagrams, March 20, 2002 Dorsal and lateral decubitus patient positioning for abdominal x-ray exams, February 28, 2002 AP abdominal projection x-ray positioning techniques, January 16, 2002 Tips and techniques for decubitus and oblique chest x-rays, December 21, 2001 Copyright © 2002 AuntMinnie.com Why is the PA projection rather than the AP projection recommended for a small bowel series?The PA projection with the patient in prone projection is preferred over an AP in supine as it results in a more uniform radiographic density of the entire abdomen. The entire colon, including the rectum, should be clearly seen.
Which of the following positions is routine for a small bowel radiograph?Unit test 1, 2, 3, & Midterm. What is the ideal kV range for a double contrast barium enema?The ideal kV range for a double-contrast barium enema is: 90 to 100. Evacuative proctography is most commonly performed on geriatric patients. During a colostomy barium enema, a double-contrast retention enema tip is used.
What are the routine positions in performing barium enema?The patient should be in the left lateral decubitus position at the beginning of the exam, with the knees bent, in preparation for placement of the rectal tube.
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