TECHNIQUE and METHODS:

Imaging of the anorectum involves static and dynamic images

The procedure is performed following 150-200 cc of sonographic gel administrated per rectum.(Fig1).

Static images inculde high resolution axial and coronal  T2WI with and without fat-suppression of the anal canal.

Static images are obtained  to exclude perianal fistulas, sinus tracts and  anal sphincter defects which might cause pain during defecation.

Functional images include mid sagittal dynamic steady state free precision obtained at rest, squeeze and evacuation.(Fig 2). It should depict the anotectum, coccyx and pubis in one plane with a temporal resolution of 1 to 3 images per second. to recieive good SNR, the slice thickness could be between 8 to 12 mm.  A matrix around 200 x 256 would be sufficent.

INTERPRETATION:

A reference line representing pelvic floor called pubococcygeal line (PCL) would be drawn between inferior border of the symphysis pubis to the last coccygeal joint as demonstrated in (Fig 3) rather than the tip of the coccyx because of the mobilty of coccyx during defecatioin in some patient.⁽³⁾

Estimation of the anorectal junction descent (organ prolapse)  by drawing a prependicular line to PCL during maximum strain or evacuation as shown in (Fig 4). Staging  of organ prolapse could be mild , moderate or severe as graded in (Table 1).⁽⁴⁾

The obstructive defecography signs that should be reported during the dynamic images  would include rectoceles(Fig 5), enterocele (Fig 6), peritoneaocele (Fig 6 and 7), abnormal anorectal descent, internal rectal prolapse (intussusception) (Fig 7), external rectal prolapse (Fig 8) and dyssynergic defecation (Fig 9).