Procedures of Alimentary Canal: Large Intestine

Examination Protocol

• Introduce patient to radiologist

• On request, release clip to allow barium to flow

• Single-Contrast (barium only): flow of barium is suspended periodically to reduce cramping and defecation impulse

• Double-Contrast (barium and air): examinations flow of barium first, then air or other gas after barium is evacuated

• Filling is viewed on fluoroscope

• Radiologist instructs patient to rotate to visualize all portions of bowel

Routine double-contrast procedures

• AP/PA

• LPO/RPO

• PA/AP Axial

• RAO/LPO Axial

• Lateral Rectum

• Rt./Lt. Lateral Decubitus

• Lateral Rectum (ventral decubitus)

• Post -evacuation

Routine single-contrast procedures

• AP/PA

• LPO/RPO

• PA/AP Axial

• RAO/LPO Axial

• Lateral Rectum

• Post-evacuation

AP/PA Large Intestine

• Collimation: 14 x 17"

• SID: 40"

• Prone or supine

• Respiration: suspended

• CR level of iliac crest and MSP

• Most commonly is AP

AP vs PA

SLIDE 5

- See polyps (inpouchings) and diverticulum (outpouchings)

- Barium in term-5transverse colon (PA)/barium in ascending and descending colon (AP)

Structure shown: AP

• The entire contrast-filled large intestine.(the exception to this is the lt. Colic flexure)

• The barium will go to the most posterior parts (air in transverse colon).

• Ascending colon, Descending colon, and Rectum

SLIDE 6

structures shown: PA

• The entire contrast-filled large intestine.

• The barium will go to the most anterior parts. (air in ascending and descending)

• Transverse colon, and Sigmoid colon

SLIDE 7

how much barium is in barium enema bag?

1,500 cc

How long is the alimentary canal?

30 feet

AP or PA axial large intestine

• Collimation: 10 x 12"

• Supine or prone

• Respiration: suspended

• CR• AP: angled 30-40º(ave 35º) cephalic

• PA: angled 30-40º(ave 35º) caudal

Structures shown: AP or PA axial

• An elongated projection of the rectosigmoid region of the large intestine.

• The barium will be located in the rectum (supine) or sigmoid (prone)

• Sigmoid colon superior to rectum

LAO/RAO or LPO/RPO large intestine

• Collimation: 14 x 17"

• SID: 40"

• Semi-prone or semi-supine

• Oblique 35-45º (45 for asthenic and 35 for hypersthenic)

• Respiration: suspended

• CR perpendicular at the level of iliac crest and 1" lateral to the MSP toward the elevated side (LPO/RPO)

• CR perpendicular at the level of iliac crest and 1" lateral to the MSP toward the unelevated side (LAO/RAO)

Structures shown: LPO/RAO

• The Rt. Colic flexure is demonstrated.

• The flexure should be open & free of superimposition

Structures shown: RPO/LAO

• The Left Colic flexure is best demonstrated

• The flexure should be open and free of superimposition

right and left lateral decubitus large intestine

• Collimation: 14 x 17"

• Place the patient in a true recumbent lateral position.

• Body elevated on radiolucent sponge

• Respiration: Suspended

• CR horizontal at the level of iliac crest and MSP

structures shown: left lateral decubitus

• An air-filled Rt. Side of the intestine.

• This projection is helpful in demonstrating polyps

structures shown: right lateral decubitus

• An air-filled Lt. Side of the intestine.

• This projection is helpful in demonstrating polyps

• Medial side of ascending and lateral surface of descending

SLIDE 15

which projections demonstrate air fluid levels

decubitus

lateral rectum large intestine

• Collimation: 10 x 12"

• Left or Right True Lateral (Left lateral commonly performed)

• Respiration: suspended

• CR perpendicular at the level of the ASIS and mid-axillary plane.

SLIDE 16

structures shown: lateral rectum

• Lateral projection of the rectosigmoid region.

• Either left or right laterals may be performed.

• Left is preferred due to the location of the barium

SLIDE 17

ventral decubitus lateral rectum

• Collimation: 10 x 12"

• prone, no rotation

• Respiration: suspended

• CR horizontal at level of the ASIS and mid-axillary plane

SLIDE 18

structures shown: ventral decubitus

• This is usually performed with a double contrast exam.

• This is an excellent projection to demonstrate the rectum

best projection of rectum?

ventral decubitus

what demonstrates rectosigmoid region?

lateral, ventral decubitus, PA/AP Axial

post-evacuation large intestine

- demonstrates haustra

defecography

Performed on Patients with defecation dysfuntion

No patient preparation required

Barium paste inserted with a special injector into the rectum

Patient seated in lateral position on a radiolucent commode

Under fluoroscopic guidance (or videorecording), images are saved during defecation at a rate of 1-2 frames per second (fps)

Measurements are taken of:

The anorectal angle

The angle between the long axis of the anal canal

rectum

Which body positions best demonstrate left colic flexure?

RPO/LAO

which projection best demonstrates haustra?

post evacuation