Tests
1st tests to order
examination plus endoscopy
Test
Inspection of the perineum may show scarring or fistulae. Straining down, particularly if on a commode, will identify rectal prolapse. Digital examination is helpful to assess both resting and squeeze tone (including maintenance of squeeze pressure) and will identify fecal impaction. A rectal mass may be due to impaction from a fecal bolus or a rectal malignancy. A patulous anus is a sign of low resting sphincter pressure. Reduced perianal sensation with a relevant history may indicate acute disk prolapse or cauda equina syndrome. Endoscopy will identify hemorrhoids or inflammatory bowel disease or a polyp/cancer.
Result
diagnosis is clinical
Tests to consider
anorectal manometry
Test
Resting and squeeze pressures reflect internal and external sphincter function, respectively. Sensation and reflexes reflect neurologic competence. Rectal capacity and compliance reflect rectal reservoir function.
Procedure requires a pressure transducer (water perfused or solid-state) as well as a balloon, which can be inflated in increments to assess sensitivity. Normal ranges for each parameter vary between laboratories.
Result
increased sensitivity may be seen in irritable bowel syndrome; rectal capacity and compliance may be reduced in inflammatory bowel disease and after rectal resection surgery
endoanal ultrasound
Test
Procedure requires a specific endoprobe and a transducer, which allows evaluation of 360° of the anal canal.
Defects in the internal and external sphincter may be detected by the lack of symmetry of the "ring" configuration of the sphincter complex, with defects often represented by a hypoechoic pattern coupled with changes in the thickness of the muscle wall.
Developments in technology including 3D imaging have improved accuracy and understanding of sphincter pathology, and have allowed for calculation of sphincter volumes.[33][34]
Result
may reveal defect in the external ± internal sphincter
endoanal MRI
Test
MRI has been advocated by some authors to delineate the anal sphincter complex as an alternative to endoanal ultrasound. The external sphincter is seen clearly and defects are easily identified. The clarity of the external sphincter does not mean that this is a superior test to endoanal ultrasound, but it does allow a more accurate diagnosis of atrophy, which may be a predictor of sphincter repair success.[35][36][37]
Result
may reveal defect in the external ± internal sphincter
pudendal motor nerve latency test
Test
Procedure involves a specially adapted device worn on the finger. The tip of the finger is placed on the ischial spine inside the anal canal and a stimulus is detected at the base of the finger in the anal canal. This gives a latency of the pudendal nerve, as fibers travel between these two points.
Prolonged latencies may indicate a poor outcome after sphincter repair.[38][39][40] Due to operator/laboratory variability and overlap of normal and abnormal values, this test has limited clinical value. This test is not recommended routinely.[26]
Result
prolonged in neuropathy (>2.1 ms)
proctography
Test
Specialist test ordered after initial conservative therapy has been unsuccessful and only if there is a suspicion that there is a problem with the dynamics of defecation (e.g., intussusception or rectocele). Configuration of the rectal wall and the adequacy of evacuation can be recorded.
The rectum is filled with a mixture of liquid and solid barium with a consistency reflecting a normal stool. Defecation is then recorded and several parameters such as anorectal angle, pelvic floor descent, presence of rectocele, or intussusception can be assessed.
Result
dynamics of defecation; may reveal abnormal anorectal angle or perineal descent; inadequate evacuation may be seen
stool culture
Test
Not routinely performed. Necessary only if incontinence is thought to be due to diarrhea.
Result
normal or positive for growth if infectious cause of diarrhea
rectal biopsy
Test
Not routinely performed. Necessary only if incontinence is thought to be due to diarrhea.
Result
may show evidence of inflammatory bowel disease
CBC
Test
Not routinely performed. Necessary only if incontinence is thought to be due to diarrhea.
Result
usually normal; elevated WBC count if infection is present
CRP
Test
Not routinely performed. Necessary only if incontinence is thought to be due to diarrhea.
Result
usually normal; elevated if infection or inflammation is present
Emerging tests
transvaginal/transperineal ultrasound
Test
Transvaginal and transperineal ultrasound are techniques in development that may allow more detailed assessment of the anal sphincter, particularly if other pathology of the pelvic floor compartment exists.[33]
Result
may reveal sphincter defect
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