Endoanal ultrasonography has recently emerged as a popular diagnostic modality for mapping and imaging the anal sphincter. This procedure can be performed as an outpatient procedure; it is relatively quick and virtually painless. The imaging typically is performed in a proximal to distal manner with defining a variety of levels of the anal canal as it progresses. Anal ultrasond can provide a detailed image of the anal sphincter musculature. The internal anal sphincter appears endosonographically as a hypoechoic circular band that is most prominently seen at the level of the mid-anal canal. The external anal sphincter appears as a thicker circular mixed echogenic band outside of the hypoechoic internal sphincter. Anal ultrasond can be used to evaluate patients with anal fistulas with or without abscess. Imaging is performed and the fistulous tracts or abscesses are identified by hypoechogenicity within the external sphincter muscle or the ischiorectal fossa. Its ability to clearly image the anal sphincters has allowed its use for the evaluation of anal fistulas. Moreover, anal ultrasound has emerged as the technique of choice for imaging the anal sphincters and for evaluating incontinence. Each of the individual physiologic tests offers valuable information that is relevant to the continence mechanism, and the ultrasound yields results that are complementary to other tests. Ultrasound serves as a surveillance tool to monitor the results after sphincterplasty. We illustrate the endo-anal sonographic features of various anal diseases and the ultrasound-anatomic correlation for the anus.
Abscess ; Anal Canal ; Fistula ; Humans ; Muscles ; Organothiophosphorus Compounds ; Outpatients ; Rectal Fistula

Over the last decade, anorectal physiologic investigations have emerged as a useful adjunct for patients with functional evacuation disorders. Through application of new sophisticated techniques and armamentarium, it has been possible to find more specific aspects of the colorectal function in patients with refractory defecation disorders. There are three groups of patient's with constipating symptoms. These patients have obstructed defecation, slow transit constipation, or a combination of both. Slow transit constipation is a severe disorder of colonic motility presenting predominantly in women. Obstructed defecation is a clinical problem frequently thought to be due to functional abnormalities of the pelvic floor leading to outlet obstruction. Defecation is an integrated process of colonic and rectal emptying, and has led to the realization that obstructed defecation is more complex than just a simple disorder of the pelvic floor muscles. Anorectal manometry establishes a quantitative measure of the pressure generated by the anal sphincters. Defecography is used to diagnose a variety of anatomical abnormalities of the rectum, including rectocele and intussusception. Tests of motor and sensory conduction in the pudendal nerves may indicate nerve damage, which accompanies chronic straining at stool. Colonic transit is an important variable and should always be considered in the assessment of patients with pelvic floor abnormalities, and measurement of colon transit by radioopaque markers or radioisotope techniques is an essential part of the workup of these patients. For the great majority of patients, dietary adjustment with increased fiber and liquid supplement can resolve these symptoms. Patients with slow transit colon can be expected to have a satisfactory outcome from colectomy and ileorectal anastomosis, but it is now appreciated that these patients form only a small proportion of those with chronic idiopathic constipation. Current management strategies for patients with obstructed defecation should be based on carefully identifying the underlying pathophysiological disorder and the use of conservative nonsurgical methods, including pelvic floor retraining (biofeedback) where appropriate. Surgical intervention should be limited to the very few patients with identifiable, surgically correctable causes of outlet obstruction.
Anal Canal ; Colectomy ; Colon ; Constipation ; Defecation ; Defecography ; Diagnosis* ; Female ; Humans ; Intussusception ; Manometry ; Muscles ; Pelvic Floor ; Pudendal Nerve ; Rectocele ; Rectum