Table 3. Comparative studies: transvaginal ultrasound versus endoanal ultrasound.
| Aim | Cohort assessed | Probe characteristics | Technique | 2D/3D | Outcome | Difficulties noted/limitations |
| Frudinger et al [30]Transvaginal versus anal endosonography for detecting damage to the anal sphincter | 47 parous and 1 nulliparous (75% complained of faecal incontinence) | Anal and vaginal ultrasound with B&K rectal endoprobe,a 10-MHz | Position: supine left lateral position? | 2D | TVUS: sensitivity and specificity for detection of IAS defects were 44% and 96%, and for EAS defects were 48% and 88%, respectively | Limited anatomical information on TVUS due to axial plane imaging only |
| Modified vaginal probe in 5 patients, B&K,a 10 MHz transducer | Probe: Inserted 3cm into vagina and gradually withdrawn | |||||
| Poen et al [22] | 56 females (36 patients with faecal incontinence, 20 patients with perianal sepsis) | Anal and vaginal ultrasound with B&K,a 7 MHz rotating endoprobe, probe inserted into vagina until rectum was visualised | Patient position not stated | 2D | TVUS increased the diagnostic yield in 25% (added important information—location of abscess and fistulae tracts) | Limited focal range of the vaginal probe in viewing the dorsolateral part of the EAS |
| Evaluate TVUS in the diagnosis of faecal incontinence and perianal sepsis | Probe: inserted into the vagina until the rectum was visualised and gradually withdrawn while images of the PR and anal sphincters were taken | |||||
| Stewart et al [23] | 50 patients of which 32 were referred for faecal incontinence and rest for other anorectal problems; 44 had both EAUS and TVUS | EAUS: B&K,a with 10 MHz rotating endoprobe | Position: EAUS—left lateral decubitus position | 2D | TVUS is accurate as EAUS for sphincter evaluation | TVUS and EAUS performed by same radiologist |
| TVUS: with 7.5 MHz biplane side-fire transrectal probe | TVUS—supine position | |||||
| Validate the use of TVUS for sphincter evaluation | Probe: For TVUS, special attention to depression of the probe towards the perineal body as the probe is withdrawn | |||||
| Ramirez et al [24] | 30 females with faecal incontinence (3 sepsis from episiotomy,4 previous anal surgery, 3 complained of rectal prolapse) | Both EAUS and TVUS; B&K,a 7 MHz endoprobe | Patient position not stated | 2D | TVUS more valuable in a group of patients with a “doubtful” EAUS study | TVUS is difficult to perform and 1 in 4 patients could be adequately scanned (reason not stated), but TVUS clarified doubts in 10% of cases arising from findings on EAUS |
| The value of TVUS as compared with EAUS | Probe: Inserted into the vagina until the rectum was visualised and gradually withdrawn while images of the PR and anal sphincters were taken |
2D, two-dimensional; 3D, three-dimensional; EAS, external anal sphincter; EAUS, endoanal ultrasound; IAS, internal anal sphincter; TVUS, transvaginal ultrasound.
aBruel & Kjaer, Naerum, Denmark.