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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_1499_Библиотеки_им_академика_М_И_Перельмана.pdf
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Direct visualization of small bowel mucosa.
Limitations and Risks
Pathology missed (inadequate visibility).
Obstruction.
Technique is time-consuming, expensive, and not universally available.
Characteristic Features
Pathology: varices, portal hypertension, erosions, areas of Crohn disease, small bowel tumors/polyps.
Cross-Reference
Small bowel follow-through (SBFT) (Ch. 2)
CT enterography ("virtual small bowel follow-through") (Ch. 2)
Familial adenomatous polyposis (FAP; 211.3, 235.2, V84.09) (Ch. 4)
IBD—Crohn disease (555.X) (Ch. 4)
Acute lower GI bleeding (578.9) (Ch. 4)
ANOPHYSIOLOGY STUDIES
Overview
Series of elective tests to assess the function and morphology of the anorectum. Common indications are workup of fecal
incontinence, obstructed defecation, complex perianal fistulae, assessment and staging, as well as surveillance of anorectal
tumors. Test results are not absolute, but always require correlation with patient's individual history, severity of complaints,
clinical findings, and unrelated test results.
Typical test combinations:
Fecal incontinence: "triple studies"—PNTML, manometry/anorectal sensation, ultrasound.
Obstructed defecation: EMG, manometry/anorectal sensation, balloon expulsion test.
Anal/rectal tumor: ultrasound, potentially with ultrasound-guided biopsy; rarely triple studies are needed if anorectal
function is an important parameter for decision-making.
Ruling out Hirschsprung disease: RAIR.
Expected Benefits
Obtain objective and reproducible evaluation of anorectal function for assessment and documentation (liability) of patient's
symptoms, patient counseling, assessment of treatment effect.
Limitations
Patient cooperation required false pathologic results possible.
Lack of 1:1 correlation of test results and symptoms
test interpretation and correlation within context of other elements of
information necessary.
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Latex allergy.
Preparation
Fleet enema right before testing.
Questionnaires: CCFIS (Wexner score) and FIQL.
Test Element: Pudendal Nerve Terminal Motor Latency (PNTML)
PURPOSE
Assessment of transmission time within pudendal nerve from site of stimulus to site of sphincter contraction.
INDICATION
Evaluation of fecal incontinence: evidence for neuromuscular component of sphincter dysfunction?
Evaluation of possible preexisting autonomic nerve damage prior to pelvic or sphincter-reconstructive surgery.
EQUIPMENT AND TECHNIQUE
Medtronic Duet Encompass (or comparable) machine with integrated/compatible software component. St. Marks Electrode.
A grounding probe is attached to the patient's leg, and the test electrode connected and attached to the gloved finger.
Insertion into posterolateral quadrants. Sequential stimulation with 50 mA until an adequate curve is reproducible.
RISKS
Discomfort from electrical stimulus.
Electrical shock if improper setup (eg, too high mA, lack of grounding).
REFERENCE VALUES
Normal PNTML 2.5 ms (Figure 2–1A).
Figure 2–1A.
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Anophysiology—PNTML.
INTERPRETATION
Prolonged PNTML (if reading and stimulation curve adequate) is evidence of pudendal neuropathy.
Normal PNTML: can either be true normal, or false normal if significant nerve damage present is masked by sufficient
number of intact and transmitting nerve fibers.
Absent PNTML reading: either related to complete absence of pudendal nerve function, or false negative (see below).
PITFALLS
False negative: related to inadequate technique or stimulation, scar tissue, extraluminal pathology.
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False positive: direct electrical stimulation of the sphincter muscle.
COMMENT
Majority of patients with idiopathic fecal incontinence have prolonged PNTML.
Controversy in literature about value of PNTML in predicting success of overlapping sphincteroplasty: half the reports show
correlation and the other half, no relationship. Nonetheless, PNTML test is recommended prior to sphincteroplasty to protect
surgeon in case of insufficient success or recurrent incontinence.
Test Element: Anal Manometry
PURPOSE
Objective (reproducible?) assessment of sphincter strength and sphincter tone at rest and squeeze (ie, obtain numbers for
subjective impression on digital rectal exam). Definition of high-pressure zone.
INDICATION
Evaluation of fecal incontinence, pelvic floor and levator ani spasms, outlet obstruction, rarely in setting of anal fissure
(before/after sphincterotomy).
Objective evaluation of treatment success after nonsurgical and surgical management.
EQUIPMENT AND TECHNIQUE
Medtronic Duet Encompass (or comparable) machine with integrated/compatible data recording and analysis software.
Multichannel catheter with a defined and oriented number of water-perfused channels. Pressure-sensitive pizo-electrodes are
arranged around a central channel which is connected to the balloon at the catheter's end. These pressure sensors measure
the pressure needed to overcome the outflow resistance. Calibration of catheter to room air pressure with probe held
externally at the level of the anus. Correct orientation of the catheter with separate recording of 4–8 positional pressures:
anterior, posterior, R lateral, L lateral.
Stationary pull-through method: sequential recording of alternating 10 second periods of resting/squeeze at 6 static
levels of 1-cm intervals.
Continuous pull-through method: motor-driven extraction of the probe and continuous pressure recording: two
separate drive-throughs with one at rest and one during maximal squeeze.
RISKS
Discomfort from probe/balloon placement.
REFERENCE VALUES
Variation of normal anal canal pressures according to gender, age, measurement technique.
INTERPRETATION
Radial pressures: more commonly reported pressure values, recorded with circumferential measuring ports: resting
pressure 50–100 mm Hg, squeeze pressure 100–350 mm Hg.
Axial pressures: less frequently reported pressure values, recorded along longitudinal spiral of the catheter lumina.
Volume manometry:
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–High-pressure zone: length and maximal amplitude, defining the physiologic anal canal.
–Area under the curve: integration of pressure values of the pressure profile over the length of the anal canal;
better summative information of the total outlet resistance than just a single maximal resting and squeeze
pressure.
PITFALLS
False normal pressures (despite sphincter weakness): compensatory use of gluteal muscles this pitfall can be
avoided/reduced by repeat testing after period of lasting gluteal contraction: while skeletal muscles become tired, sphincter
muscle function is relatively resistant to fatigue.
COMMENT
Ongoing controversy about value and best interpretation of manometry in predicting severity of fecal incontinence. Single
values likely are insufficient; pressure profile potentially is more meaningful. Continued lack of an incontinence score that
incorporates physiologic data.
Test Element: Rectoanal Inhibitory Reflex (RAIR)
PURPOSE
The RAIR is a physiologic relaxation of the internal sphincter muscle upon sudden distention of the rectum. Believed to play a
role in anorectal sampling. Reflex may be absent in Hirschsprung disease, Chagas disease, 50% of ileoanal or coloanal
anastomoses (ie, RAIR can recover in up to 50% after colo-anal or ileo-anal pullthrough procedure). Presence of RAIR
reliably rules out Hirschsprung disease.
INDICATION
Evaluation of fecal incontinence: neurogenic component?
Evaluation of constipation
rule out Hirschsprung disease.
EQUIPMENT AND TECHNIQUE
Same as before continuation after previous test.
Catheter advanced such that pressure sensors in anal canal and balloon in the rectum. Await steady state pressure
undulations > 0. Short insufflation of 15–40 mL of room air.
RISKS
Discomfort, otherwise negligible.
REFERENCE VALUES
RAIR present at 15–40 mL insufflation (Figure 2–1B).
Figure 2–1B.
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Anophysiology—RAIR.
INTERPRETATION
RAIR present: normal high negative predictive value, ie, if RAIR present Hirschsprung disease ruled out.
RAIR absent: consistent with Hirschsprung disease, Chagas disease, 50% of ileoanal or coloanal anastomoses
further
evaluation depending on context.
PITFALLS
RAIR falsely absent: due to inadequate technique, large rectocele, megarectum, or underlying neuromuscular disease.
Test Element: Anorectal Sensation and Rectal Compliance
PURPOSE
Evaluation of somatic and visceral anorectal sensation.
INDICATION
Evaluation of fecal incontinence.
Evaluation of IBS.
Evaluation of constipation.
EQUIPMENT AND TECHNIQUE
Somatic sensation: perianal wiping with Q-tip to assess sensation (symmetry?) and to trigger anocutaneous reflex,
ie, reflectory sphincter contraction.
Visceral sensation: manometry equipment as before, but exchange of balloon into one with high material compliance:
catheter advanced into rectum, followed by slow instillation of body-temperature water (maximum 450 mL) with
continuous pressure measurement
recording of the following steps:
– First sensation: patient feels balloon in the rectum (not just at the anal verge).
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– First urge: patient notices first urge to move bowels.
– Maximally tolerable volume: patient starts to feel discomfort/pain.
– Rectal compliance =
volume/ pressure.
RISKS
Discomfort, balloon rupture, internal balloon loss ( always secure balloon edge externally).
REFERENCE VALUES
First sensation: 10–50 mL.
First urge: 50–100 mL.
Maximally tolerable volume: 140–320 mL (F), 170–440 mL (M).
Rectal compliance: 2–6 mL/mm Hg.
INTERPRETATION
Normal: normal sensation and compliance.
IBS: reduced volume tolerance, normal compliance.
IBD or rectal stricture: reduced volume tolerance, reduced compliance.
Neurologic dysfunction: reduced sensation, increased volume tolerance, normal (or increased) compliance.
PITFALLS
Patient cooperation needed. False normal compliance if balloon distends more axially (lower resistance) than radially (high
resistance). External loss of balloon (incontinence) before meaningful volume instilled.
Test Element: EMG
PURPOSE
Evaluation of neuromuscular integrity and coordination.
INDICATION
Evaluation of pelvic floor dyssynergia or anismus (nonrelaxing puborectalis muscle).
Occasionally for evaluation of fecal incontinence: loss of muscular contractile capacity?
EQUIPMENT AND TECHNIQUE
Surface anal electromyography: bilateral placement of electrodes at anal verge plus additional grounding electrode
recording of summative electric sphincter muscle activity at rest, at squeeze, at straining, and during coughing.
Needle EMG: insertion of concentric needle electrode into the muscle (
discomfort!).
RISKS
Surface EMG: no risks.
Needle EMG: discomfort, infection, bleeding.
REFERENCE VALUES
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Potential > 100 mV, fiber density.
INTERPRETATION
Normal sequence: normal pattern at rest, followed by adequate increase during squeeze and coughing, but decrease during
straining.
Dyssynergia: normal or increased pattern at rest, increase during squeeze, coughing, but also during straining.
PITFALLS
Surface EMG is relatively inaccurate as it represents summation potential of all fibers and is buffered by skin and
subcutaneous tissue.
Test Element: Balloon Expulsion Test
PURPOSE
Simple screening evaluation to rule out pelvic floor dyssynergia: ability to expel balloon is a complex activity that requires
proper coordination of the rectum, pelvic floor, and anal sphincter muscle.
INDICATION
Constipation, obstructed defecation, pelvic floor dyssynergia (anismus, paradoxical puborectalis contraction).
EQUIPMENT AND TECHNIQUE
Balloon is inserted into rectum and insufflated with 100–200 mL of water patient is asked to expel balloon: (1) on
examination table; (2) if not possible in lateral decubitus position, transfer to restroom and attempt in sitting position.
Variation of the test: addition of defined external weight.
RISKS
Discomfort, balloon rupture, internal balloon loss ( always secure balloon edge externally).
REFERENCE VALUES
Normal: balloon expelled (any position).
Abnormal: balloon cannot be expelled (not even in sitting position).
INTERPRETATION
Normal test: no evidence for pelvic floor dyssynergia further tests not needed.
Abnormal test: false pathologic (patient not cooperating) vs true dyssynergia
further tests (eg, defecating proctogram).
PITFALLS
Test dependent on patient cooperation.
Test Element: Balloon Retention Test
PURPOSE
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Simple screening evaluation to assess functional and coordinative ability to prevent fecal accident: ability to retain balloon
against external traction force is a complex activity that requires proper coordination of the rectum, pelvic floor, and anal
sphincter muscle.
INDICATION
Fecal incontinence.
EQUIPMENT AND TECHNIQUE
Balloon is inserted into rectum and insufflated with 100 mL of water patient is asked to retain balloon while examiner
exerts increasing external traction. Recording of extraction force.
RISKS
Discomfort, balloon rupture, internal balloon loss ( always secure balloon edge externally).
REFERENCE VALUES
Normal: balloon can be retained against significant external traction (> 0.5 kg).
Abnormal: balloon lost under minimal to moderate external traction (< 0.5 kg).
INTERPRETATION
Normal balloon retention capacity: pseudo-incontinence vs seepage due to anal disconfiguration (eg, keyhole
deformity).
Abnormal balloon retention capacity: true morphologic-functional neuromuscular incontinence
PITFALLS
Test dependent on patient cooperation.
Test Element: Endoanal Ultrasound (See Also Next Section Endorectal
Ultrasound (ERUS))
PURPOSE
Evaluation of structural integrity and pathology in the anal canal and the rectum.
INDICATION
Evaluation of fecal incontinence: sphincter defect, sphincter attenuation?
Anorectal tumors: evaluation and staging.
Extraluminal pathology: ultrasound-guided biopsy.
Fistula/abscess: location, course.
EQUIPMENT AND TECHNIQUE
Ultrasound machine with rotating 10 (7) MHz probe.
RISKS
Direct trauma during insertion of probe, discomfort (balloon distention); biopsy risk of bleeding, infection, rectourethral
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fistula.
REFERENCE VALUES
Anal canal: IAS = hypoechogenic (black) ring, EAS = hyperechogenic (white) ring, puborectalis muscle = hyperechogenic
(white) parabolic muscle.
Rectum: 5-layer model of rectal wall (Figure 2–2A), prostate and seminal vesicles, rectovaginal septum.
Figure 2–2A.
ERUS—5-layer model of rectal wall.
INTERPRETATION
Sphincter defect (IAS, EAS).
Anorectal tumor:
staging (size, penetration, invasion, lymph nodes).
Other pathology: fistula showing as hypoechogenic tract that become hyperechogenic upon injection of peroxide into external
fistula opening.
Abscess: hypoechogenic pocket.
PITFALLS
Artefacts, rectocele/short anal canal mistaken for anterior sphincter defect.
Further Steps
Defecating proctogram vs dynamic MRI.
Colonic transit studies (Sitzmark study).
Cross-Reference
Defecating proctogram (defecography) (Ch. 2)
Fecal control (continence) (Ch. 3)