[Progress in diagnostics of anorectal disorders. Part I: anatomic background and clinical and neurologic procedures]

Before and after Anorectal Surgery: Which Information Is Needed from the Functional Laboratory?

Background

Anorectal surgery covers a wide spectrum of surgery. Diagnostic workup of anorectal disease is based on clinical examination with basic functional tests followed by more elaborate diagnostic tests. Since the incidence of anorectal disorders increases with age, more patients will present in outpatient clinics, thus underlining the relevance of this topic.

Methods

A PubMed literature search was performed using the terms 'anal incontinence', 'anal and rectal surgery', 'functional diagnostics', and combinations of these terms. No restriction regarding publication year or publication type was applied but randomized trials, 'metanalyses', or guidelines were ranked higher. Only articles in English or German were included.

Results

The diagnostic value of digital rectal examination, anal manometry and endosonography, the water holding procedure, contrast enema, and incontinence scores is summarized.

Conclusion

The article focusses on basic clinical and functional diagnostic tests which can be easily applied in the pre- and postoperative setting to evaluate the postoperative outcome.

Three-dimensional anal endosonography in depicting anal-canal anatomy

PURPOSE

This report describes the advantages of 3D anal endosonography in depicting the normal anatomy of the anal canal in relation to sex and age.

MATERIALS AND METHODS

A retrospective study was performed of 85 patients, 33 men and 52 women, previously examined with 3D anal ultrasound (US) for clinically suspected anorectal disease but found to be negative. The examinations were performed with a Bruel and Kjaer US system with a 2050 transducer, scanning from the anorectal junction to the subcutaneous portion of the external anal sphincter (EAS). The 3D reconstructions provided an estimation of sphincter length in the anterior and posterior planes, and axial 2D images enabled calculation of the thickness of the internal anal sphincter (IAS) and EAS in the anterior, posterior and lateral transverse planes.

RESULTS

Distribution of the sphincter complex is asymmetric in both sexes: the EAS and IAS are significantly shorter in females, especially in the anterior longitudinal plane (p=0.005 and p<0.001, respectively). EAS and IAS thickness increases with age, especially the lateral IAS (R(2)=0.37, p<0.001) and the posterior EAS (R(2)=0.29, p=0.01).

CONCLUSIONS

A good knowledge of anal-canal anatomy is essential to detect sphincter abnormalities when assessing pelvic floor dysfunction.

Intraoperative pelvic nerve stimulation performed under continuous electromyography of the internal anal sphincter

PURPOSE

The aim of this animal study was to investigate the effect of intraoperative pelvic nerve stimulation on internal anal sphincter electromyographic signals in order to evaluate its possible use for neuromonitoring during nerve-sparing pelvic surgery.

METHODS

Eight pigs underwent low anterior rectal resection. The intersphincteric space was exposed, and the internal (IAS) and external anal sphincter (EAS) were identified. Electromyography of both sphincters was performed with bipolar needle electrodes. Intermittent bipolar electric stimulation of the inferior hypogastric plexus and the pelvic splanchnic nerves was carried out bilaterally. The recorded signals were analyzed in its frequency spectrum.

RESULTS

In all animals, electromyographic recordings of IAS and EAS were successful. Intraoperative nerve stimulation resulted in a sudden amplitude increase in the time-based electromyographic signals of IAS (1.0 (0.5-9.0) μV vs. 4.0 (1.0-113.0) μV) and EAS (p < 0.001). The frequency spectrum of IAS in the resting state ranged from 0.15 to 5 Hz with highest activity in median at 0.77 Hz (46 cycles/min). Pelvic nerve stimulation resulted in an extended spectrum ranging from 0.15 to 20 Hz. EAS signals showed higher frequencies mainly in a range of 50 to 350 Hz. However, after muscle relaxation with pancuronium bromide, only the low frequency spectrum of the IAS signals was still present.

CONCLUSIONS

Intraoperative verification of IAS function by stimulation of pelvic autonomic nerves is possible. The IAS electromyographic response could be used to monitor pelvic autonomic nerve preservation.