MRI Defecography, ODS Clinical Trial
Official title:
Role of MRI Defecography in Diagnosis of Obstructed Defecation Syndrome
The aim of the study was to assess the advantages of dynamic magnetic resonance imaging defecography to elucidate the underlying anatomic and pathophysiologic background in obstructed defecation patients to guide physicians in patient management.
Obstructed defecation syndrome (ODS) is a term used to describe the whole complex of
mechanical and functional disorders leading to difficult or inadequate rectal emptying.
obstructed defecation syndrome has prevalence rate 3.4 % in general population, In obstructed
defecation feces do reach the rectum, but rectal emptying is extremely difficult. These
patients have a feeling that defecation is blocked. Despite repetitive attempts, complete
evacuation of rectal contents is not possible. The patients may also complain of prolonged
and unsuccessful straining at stools, feelings of incomplete evacuation, digital removal of
feces, and laxative abuse.
Constipation caused by obstructed defecation is of two basic types: functional and
mechanical. The functional type includes anismus (pelvic floor dys-synergy), and descending
perineal syndrome, whereas the mechanical type includes rectocele, enterocele, internal
intussusception and overt rectal prolapse.
All of these conditions represent either a defect of pelvic support or abnormal function of
the pelvic floor musculature. The etiology of ODS is controversial. It is presumed that in
childbearing women damage to the innervation and soft tissues of the pelvis may occur as a
direct consequence of vaginal childbirth. Trauma to the pelvic soft tissues can result in
endopelvic fascial and pelvic support defects. Cumulative nerve damage from stretching of
pelvic floor due to childbirth and activities that cause chronic and repetitive increases in
intra-abdominal pressure such as obesity and chronic cough have been suggested to play a role
in the development of symptomatic defects.
Although patients frequently complain of constipation, symptoms such as fruitless straining
and incomplete evacuation are rather subjective and unreliable. Nevertheless, an
international team of experts included these symptoms in the definition of constipation.This
Rome III guidelines, for a patient to be labeled as suffering from functional constipation,
which also includes obstructed defecation, following criteria should be present for at least
3 months:
1. Must include two or more of the following:
1. Straining during at least 25% of defecations,
2. Lumpy or hard stools in at least 25% of defecations,
3. Sensation of incomplete evacuation for at least 25% of defecations,
4. Sensation of ano-rectal obstruction/ blockage for at least 25% of defecations,
5. Manual maneuvers to facilitate at least 25% of defecations (e.g., digital
evacuation, support of the pelvic floor),
6. Fewer than three defecations per week.
2. Loose stools are rarely present without the use of laxatives.
3. Insufficient criteria for irritable bowel syndrome. The same criteria define
dys-synergic defecation as inappropriate contraction of the pelvic floor or less than
20% relaxation of basal resting sphincter pressure with adequate propulsive forces
during attempted defecation .
On physical examination, the paradoxical contraction of the pelvic floor can be assessed by
palpation of the puborectalis muscle while the patient is straining . Perineal descent >3 cm,
mucous discharge or mucosal prolapse may also be seen when the patient is asked to strain for
stools . However, most clinicians do not rely on palpation and advocate the use of specific
tests to diagnose ODS . Electromyography (EMG) of the pelvic floor, the balloon expulsion
test (BET), and defecography are the most frequently used tests. Other radiologic methods for
the dynamic evaluation of the ODS include magnetic resonance imaging and ultrasonography,
each of which has its advantages and limitations.
The development of fast Magnetic Resonance Imaging sequences provides a new alternative to
study all pelvic visceral movements in a dynamic fashion. MR defecography has several
important advantages over conventional defecography. Its non-ionic nature, multiplanar
capacity, dynamic evaluation and good temporal resolution along with its high-resolution
soft-tissue contrast makes it an ideal modality in the assessment of ODS patients. Imaging in
the mid-sagittal plane allows evaluation of the anal canal, anorectal angle, levator muscle
and hiatus and the vaginal disposition as well as their relationship to a consistent
electronically designated pubo-coccygeal Line (PCL). Diagnostic parameters for pelvic
dys-synergy include an indented impression of the pubococcygeus muscle on the rectum with
excessive obtuse anorectal angulation accompanied by very prolonged rectal emptying on
T2-weighted MR images.
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