Defecography (also known as proctography, defecating/defecation proctography, evacuating/evacuation proctography or dynamic rectal examination) is a type of medical radiological imaging in which the mechanics of a patient's

defecation Defecation (or defaecation) follows digestion, and is a necessary process by which organisms eliminate a solid, semisolid, or liquid waste material known as feces from the digestive tract via the anus. The act has a variety of names ranging f ...

are visualized in real time using a

fluoroscope Fluoroscopy () is an imaging technique that uses X-rays to obtain real-time moving images of the interior of an object. In its primary application of medical imaging Medical imaging is the technique and process of imaging the interior of a ...

. The anatomy and function of the anorectum and pelvic floor can be dynamically studied at various stages during defecation.

History

Defecating proctography was pioneered in 1945, during

World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the World War II by country, vast majority of the world's countries—including all of the great power ...

. The procedure gained popularity at this time in the midst of an outbreak of whipworm, which is known to cause rectal prolapse. It has since become used for diagnosis of various anorectal disorders, including anismus and other causes of obstructed defecation. It has fallen out of favor due to inadequate training in the technique. It is now only performed at a few institutions. Many radiology residents refer to the procedure as the "Def Proc", "Defogram", or "Stool Finale".

Indications

Defecography may be indicated for the following reasons: * Evaluation of rectal outlet obstruction (obstructed defecation) symptoms * Evaluation of all types of rectal (fecal) incontinence. * Suspected conditions such as

internal rectal intussusception A rectal prolapse occurs when walls of the rectum have prolapsed to such a degree that they protrude out of the anus and are visible outside the body. However, most researchers agree that there are 3 to 5 different types of rectal prolapse, depend ...

enterocele An enterocele is a protrusion of the small intestines and peritoneum into the vaginal canal. It may be treated transvaginally or by laparoscopy. An enterocele may also obstruct the rectum, leading to symptoms of obstructed defecation. Enteroceles ...

, anismus,

rectocele In gynecology, a rectocele ( ) or posterior vaginal wall prolapse results when the rectum bulges ( herniates) into the vagina. Two common causes of this defect are childbirth and hysterectomy. Rectocele also tends to occur with other forms of pe ...

sigmoidocele Sigmoidocele (also known as Pouch of Douglas descent) refers to a condition where the sigmoid colon descends (prolapses) into the lower pelvic cavity. This can obstruct the rectum and cause symptoms of obstructed defecation. Pathophysiology Th ...

. * To compare pre- and post-surgical repair of rectal outlet obstruction (obstructed defecation). Specifically, defecography can differentiate between anterior and posterior

. Also, in external rectal prolapse that was not directly visualized during examination, this radiographic projection will demonstrate its presence.

Technique

In females, pre-procedural preparation involves smearing a small amount of

barium Barium is a chemical element with the symbol Ba and atomic number 56. It is the fifth element in group 2 and is a soft, silvery alkaline earth metal. Because of its high chemical reactivity, barium is never found in nature as a free element. Th ...

contrast agent in the vagina, which will help to identify if anterior rectocele, enterocele or sigmoidocele is present. The technique itself involves the insertion of a caulking gun device into the rectum with a subsequent manual infusion of barium paste until there is adequate distension. The patient is then transferred to a portable plastic commode which is situated next to a fluoroscope which records the defecation. Positioning of the X-ray camera is of paramount importance as visualization of the buttocks, rectal vault, and lower pelvis is critical.

Diagnostic yield and interpretation

Anatomical and physiological parameters that can be objectively measured by this investigation include: Anorectal angle This is the "mid-axial longitudinal axis of the rectum and the anal canal", created by the anterior pull of the puborectalis sling at the level of the anorectal junction. At rest, it is held at 90 - 100°. This becomes more acute (70 - 90°) when the patient contracts the anal sphincters and pelvic floor muscles, and more obtuse (110 - 180°)during defecation. Perineal descent This is "the caudad movement of the pelvic floor uringstraining". Defecation normally involves a relaxation of the pelvic floor (

levator ani The levator ani is a broad, thin muscle group, situated on either side of the pelvis. It is formed from three muscle components: the pubococcygeus, the iliococcygeus, and the puborectalis. It is attached to the inner surface of each side of the ...

), leading to descent of the perineum. After straining, the opposite occurs, the perineum rises. From the proctogram, descent is calculated by drawing an imaginary line (the pubococcygeal line) between the most inferior point on the

pubic bone In vertebrates, the pubic region ( la, pubis) is the most forward-facing ( ventral and anterior) of the three main regions making up the coxal bone. The left and right pubic regions are each made up of three sections, a superior ramus, inferior ...

and the tip of the

coccyx The coccyx ( : coccyges or coccyxes), commonly referred to as the tailbone, is the final segment of the vertebral column in all apes, and analogous structures in certain other mammals such as horses. In tailless primates (e.g. humans and othe ...

. Normal perineal descent or elevation is less than 4 cm from the pubococcygeal line in either direction (

superior Superior may refer to: *Superior (hierarchy), something which is higher in a hierarchical structure of any kind Places *Superior (proposed U.S. state), an unsuccessful proposal for the Upper Peninsula of Michigan to form a separate state *Lake ...

or inferior). Efficiency of emptying/evacuation Normally, there is 90-100% evacuation of rectal contents.

Anal canal The anal canal is the part that connects the rectum to the anus, located below the level of the pelvic diaphragm. It is located within the anal triangle of the perineum, between the right and left ischioanal fossa. As the final functional segme ...

length This is measured during maximal evacuation. Anal canal width Again measured during maximal evacuation, this is usually less than 2.5 cm. Conditions which may be demonstrated include: * Anismus (pelvic floor dyssynergia) It has been suggested that some patients may be embarrassed by this procedure, which give findings of abnormal defecation. For example, the patient may not be able to relax under the conditions, leading to relaxation failure of puborectalis and false positive diagnosis of anismus. It has also been reported that there is a high false positive rate of anismus diagnosis with

anorectal manometry Anorectal manometry (ARM) is a medical test used to measure pressures in the anus and rectum and to assess their function. The test is performed by inserting a catheter, that contains a probe embedded with pressure sensors, through the anus and in ...

for similar reasons. *

Rectocele In gynecology, a rectocele ( ) or posterior vaginal wall prolapse results when the rectum bulges ( herniates) into the vagina. Two common causes of this defect are childbirth and hysterectomy. Rectocele also tends to occur with other forms of pe ...

This is the most common finding with this type of imaging. Almost always, this is an anterior rectocele where the anterior rectal wall bulges forward, into the vagina in females. In males, the prostate gland gives more support in this area compared to the vaginal cavity, so rectoceles, especially anterior rectoceles are uncommon in males. Less commonly and in males, there may be posterior rectoceles, where the rectum bulges posteriorly. Both the size and the efficiency of emptying can be assessed with proctography. Since many rectoceles are asymptomatic, this may only be a significant finding if there are symptoms of obstructed defecation. Usually rectoceles greater than 3 cm and those that do not empty are clinically significant. *

Enterocele An enterocele is a protrusion of the small intestines and peritoneum into the vaginal canal. It may be treated transvaginally or by laparoscopy. An enterocele may also obstruct the rectum, leading to symptoms of obstructed defecation. Enteroceles ...

and

Sigmoidocele Sigmoidocele (also known as Pouch of Douglas descent) refers to a condition where the sigmoid colon descends (prolapses) into the lower pelvic cavity. This can obstruct the rectum and cause symptoms of obstructed defecation. Pathophysiology Th ...

Enterocele is a prolapse of peritoneum that contains a section of

small intestine The small intestine or small bowel is an organ (anatomy), organ in the human gastrointestinal tract, gastrointestinal tract where most of the #Absorption, absorption of nutrients from food takes place. It lies between the stomach and large intes ...

. Sigmoidocele is a prolapse of peritoneum that contains a section of

sigmoid colon The sigmoid colon (or pelvic colon) is the part of the large intestine that is closest to the rectum and anus. It forms a loop that averages about in length. The loop is typically shaped like a Greek letter sigma (ς) or Latin letter S (thus ' ...

. In females, these prolapses usually descend between the rectum and the vagina. They are most likely to be seen during straining. * Rectal prolapse/

Internal rectal intussusception A rectal prolapse occurs when walls of the rectum have prolapsed to such a degree that they protrude out of the anus and are visible outside the body. However, most researchers agree that there are 3 to 5 different types of rectal prolapse, depend ...

The rectum may be seen to prolapse, whether internally or externally. There can be difficulty differentiating between internal intussusception and a normal rectal fold. The thickness of the intussusception is half the width of the intussusception (the intussusception is a doubled over layer of rectal wall). This is most likely to be seen during straining. * Megarectum This is excessive width (>9 cm) of the rectum at the level of the distal sacrum and incomplete evacuation. * Descending perineum syndrome If the perineum descends >4 cm, descending perineum syndrome may be diagnosed. *

Fecal incontinence Fecal incontinence (FI), or in some forms encopresis, is a lack of control over defecation, leading to involuntary loss of bowel contents, both liquid stool elements and mucus, or solid feces. When this loss includes flatus (gas), it is referre ...

If the barium paste does not stay in the rectum.

Cinedefecography and MRI defecography

Cinedefecography is a technique that is an evolution of defecography. The defecation cycle is recorded as a continuous series rather than individual still radiographs. More recent techniques involve the use of advanced, cross-sectional imaging modalities such as

magnetic resonance imaging Magnetic resonance imaging (MRI) is a medical imaging technique used in radiology to form pictures of the anatomy and the physiological processes of the body. MRI scanners use strong magnetic fields, magnetic field gradients, and radio wave ...

.MRI Defecating Proctogram
/ref> This is known as dynamic pelvic MRI, or MRI proctography. The MRI proctography also called MRI defecography is not as efficient as conventional X-ray defecography for some problems.

References

External links

Dynamic rectal examination on "the Radiology Assistant"
many example defecating proctograms with interpretation. {{Digestive system procedures Diagnostic obstetrics and gynaecology Digestive system imaging Fluoroscopy Colorectal surgery