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abstract

122 - ANAL SPINCHTER IMAGING: AT REST OR ON PFMC?

122

ANAL SPINCHTER IMAGING: AT REST ORON PFMC?

N. SUBRAMANIAM, H. DIETZ;
Sydney Med. Sch. Nepean, Sydney, Australia.

Introduction: In the quest for anon-invasive, patient-acceptable and low cost imaging modality,transperineal ultrasound (TPUS) is increasingly used to evaluate theanal sphincter (1). Imaging is usually undertaken on pelvic floormuscle contraction (PFMC) as this seems to enhance tissuediscrimination and aids in the crucial step of identifyingthe fascial plane between levator ani and external anal sphincter(EAS) and hence the cranial termination of the EAS (2). For variousreasons some women are unable to achieve a satisfactory PFMC, and inthis situation the sphincter is assessed at rest.
Objective:To determine whether sphincter imaging at rest is inferior to imagingon PFMC.
Methods: In a retrospective study, we analyseddata obtained at a tertiary urodynamic center in 2015. All womenunderwent a standardized interview including St Mark’s incontinencescore (SMIS), clinical examination and 4D TPUS. Tomographicultrasound imaging (TUI) was used to obtain volume data at rest andon PFMC to evaluate EAS and IAS trauma as described previously(3).The first author, blinded against all clinical data, analysedarchived sphincter volume data at a later date, using proprietarysoftware. Individual slices were rated positive if there was a defectof at least 30o of the EAS and/or IAS circumference in 4/6slices at rest and on PFMC (Figure 1). The correlation between bothmethods and their association with anal incontinence (AI) symptoms,bother score and SMIS were examined using non-parametric analysis andcross tabulation.


Figure 1: A comparison of 3Dtomographic imaging at rest (A) and on PFMC (B). There is an externalanal sphincter defect in all 6 slices which is evident both at restand on PFMC.
Results: 463 women were seen during the studyperiod. Ultrasound examinations and anal sphincter volumes weremissing in 4 and 14 patients respectively. Two patients were excludeddue to insufficient quality images and another 2 for absent PFMC ondemand. The final data set comprises 441 patients.
Mean age was56.5 (20.4-87.8) years, the mean BMI 29.3 (15.7-64.4) kg/m2. Medianparity was 2 (0-8), 88 % (n=389) were vaginally parous and 26%(n=114) had a history of forceps. AI was reported in 56 (13%)patients, with a median St Mark’s score of 11 (IQR, 2-22).
Whenthe diagnoses of sphincter defect at rest and defect on PFMC weretested against all measures of AI, neither of the two seemedobviously superior in terms of predicting AI (Table 1).

Table1:Anal incontinence and significant EAS and IAS trauma

Measuresof anal incontinence

EASOR (CI 95%), (p value)

IASOR (CI 95%), (p value)

Rest

PFMC

Rest

PFMC

AI(yes/no)

2.50(1.27-4.9)(p=0.007)

2.94(1.48-5.86)(p=0.001)

6.44(2.76-15.05)(p<0.001)

7.56(3.15-18.13)(p<0.001)

AI Bother(0-10)

1.12(1.02-1.23)(p=0.023)

1.17(1.06-1.28)(p=0.002)

1.26(1.13-1.41)(p<0.001)

1.28(1.14-1.43)(p<0.001)

SMIS(0-24)

1.08(1.02-1.13)(p=0.005)

1.09(1.04-1.15)(p=0.001)

1.14(1.07-1.20)(p<0.001)

1.15(1.08-1.22)(p<0.001)


On cross tabulation, the agreementbetween rest and PFMC for EAS and IAS significant defects was 96.6%and 98.3% respectively, if discrepancy by one slice was accepted.Table 2 suggests a slight tendency to over-diagnosis when sphinctersare assessed at rest.

Table2: Cross tabulation of sum of abnormal EAS slices at rest and onPFMC

EASAbnormal Slices
(n=441)

Rest

0

1

2

3

4

5

6

PFMC
Agreement:82.5%
1 Slice Discrepancy: 14.1%
Total: 96.6%

0

302

18

5

1




1

2

9

13

3

1



2


2

12

7

3



3




7

5

2


4





11

6


5





1

5

6

6






2

18


Conclusions: Allassociations between the diagnosis of 'significant anal sphincterdefect' and AI were stronger when imaging was performed on PFMCcompared to imaging at rest. This may be due to a tendency toover-diagnose defects when imaging is undertaken at rest. However,the difference is likely to be of limited clinicalsignificance.
References:
1. Pelvic floor ultrasound:Atlas and textbook. Sydney 2016; 71-82
2. Ultrasound ObstetGynecol 2013; 42: 461-66
3. Ultrasound Obstet Gynecol 2015; 46:363-66