What can defecography reveal

Defecography is a type of medical radiography that uses a fluoroscope to visualize a patient's bowel movements in real time. The anatomy and function of the anorectum and pelvic floor can be studied dynamically during different phases of the defecation process. Many patients do not know much about defecography and often have questions about why this examination should be done. Defecation radiography is a method of performing a combination of dynamic and static examinations on the anal canal and rectum when the patient is "defecating", with an emphasis on functional examinations. So what can defecography reveal?

Advantages of defecography

1. Able to observe the contraction, emptying and movement of the anorectal canal under fluoroscopy.

2. Observation of the anal canal and rectum is clearer and more accurate than enema, and the chance of detecting lesions is higher.

Applicable certificate

Mainly for patients with constipation

How to operate

1. Perform barium enema first, usually into the descending colon, requiring 300-400ml of barium.

2. The patient sits on the fecal bucket, and the lateral rectal position is photographed when sitting still, lifting the anus, and forcing the stool to pass.

3. A frontal view is also required to show the condition of the rectum and its relationship with the small intestine and sigmoid colon.

Measurement items

1. Anal angle

2. Distance from pubocaudal line to anus

3. Distance between the two

4. Anal canal length

5. Sacral-rectal distance

6. Sacrum and sacrococcygeal curvature

7. Make corresponding measurements for various abnormalities

Diagnosis of diseases by changes in anal angle

The anal angle changes mainly with the movement of the puborectalis muscle and anal sphincter.

Static close to right angle (70～140°)

The force displacement is an obtuse angle (110-180°)

The levator ani is an acute angle (75-80°)

Pelvic floor spasm syndrome

A functional disorder in which the pelvic floor muscles contract and do not relax when straining to defecate. During forced evacuation, the anal angle does not increase, but remains at about 90° or less, and pressure marks due to puborectalis muscle spasm are often seen.

Pelvic floor spasm syndrome combined with rectocele causes "goose disease".

Abnormal contraction or relaxation of the internal sphincter

The pressure mark of the puborectalis muscle disappears, the anorectal junction descends, and the anal angle increases. The anal canal is narrow and difficult to open, defecation is laborious, the movements are short and discontinuous, and the barium flow is trickle, resulting in prolonged defecation time.

Puborectalis achalasia

The anal angle of patients with this disease does not increase significantly when they force to defecate, and remains at around 90° or less. The length of the puborectalis muscle does not increase significantly, and puborectalis muscle pressure marks are often seen.

Puborectalis achalasia

The anal angle is small, the anal canal becomes longer, and little or no barium is excreted.

Shelf sign

PRMH can be diagnosed by seeing the "shelf sign", while the small anal angle and elongated anal canal can serve as reference.

The "shelf sign" refers to the fact that the anorectal junction remains straight or slightly changes upward when sitting still or exerting force, shaped like a shelf.

Puborectalis achalasia

The distance from the puborectalis muscle impression behind the anorectal junction to the pubic bone.

Static 14～16cm

Force displacement 15～18cm

Anal levator 12～15cm

Diagnosing diseases by changes in the distance above the anus

The supraanal distance reflects the position of the rectal anal junction, that is, the changes in the perineum during defecation. The supraanal distance is mainly affected by the movement of the levator ani muscles and will increase during defecation.

Abnormal perineal descent

When a normal person strains to defecate, the perineum will drop. The reason for this is that the levator ani muscles contract to lower and open the anus during defecation. For a normal person, the distance above the anus does not exceed 30mm when straining to defecate.