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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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Fecal incontinence (787.6) (Ch. 4)
Colorectal cancer—rectal cancer (154.1) (Ch. 4)
Pelvic floor dysfunction (618.X) (Ch. 4)
Functional disorders—chronic constipation (564.0X) (Ch. 4)
Selected colorectal reference values (App. 2)
Fecal incontinence scoring systems (App. 2)
ENDORECTAL ULTRASOUND (ERUS)
Overview
Use of ultrasound waves (2–15 MHz) for imaging of extraluminal structures. Ultrasound pulses are emitted from a
transducer. Reflection/refraction/transmission of the signal depends on tissue composition/impedance and presence/absence
of interfaces: the signals returning to the probe are recorded. The reflected beams are processed to obtain an electronic
reconstruction of the tissue.
Tissue penetration depth is related inversely, and resolution directly, to frequency:
Transcutaneous (eg, abdominal) ultrasound: 3–7 MHz.
Endoluminal ultrasound: 7–10 MHz.
Image optimization also is dependent on:
Focal range (too close need to interpose water-filled layer; too far need to lower frequency).
Artefacts: edge effect, mirror image, interference/reverberation, shadowing, posterior enhancement, refraction, side
lobe.
Adjustment of time gain compensation.
Expected Benefits
Visualization of extraluminal anatomy and pathology.
Limitations
Lesion not in reach of probe, or probe cannot be passed through lesion (eg, obstructing cancer, stricture, etc).
Procedure not tolerated (
alternative: ERUS under anesthesia/sedation).
Operator-dependent examination!
Accuracy/sensitivity/specificity not perfect
clinical and pathologic correlation needed:
Distinction between normal vs scar vs tumor not always possible.
False positive (ie, reactive, noncancerous) lymph node enlargement after recent biopsy.
Preparation
Fleet enema immediately before testing.
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Cancer: rigid sigmoidoscopy.
Incontinence: anophysiology studies (see earlier discussion), questionnaires.
Test Element: Endorectal Ultrasound (ERUS)
PURPOSE
Evaluation and staging of rectal cancer.
Evaluation and staging of anal cancer?
INDICATION
Anorectal tumors: pretreatment evaluation and staging.
Anorectal tumors: post-treatment reassessment, surveillance.
EQUIPMENT AND TECHNIQUE
Ultrasound machine with rotating 10 (7) MHz probe, equipped with water-filled balloon.
RISKS
Direct trauma during insertion of probe, discomfort (balloon distention), perforation.
REFERENCE VALUES
Rectum: 5 layers of rectal wall (Figure 2–2A and 2–2B).
Landmarks: prostate, seminal vesicles, rectovaginal septum, puborectalis muscle/sphincter complex.
Figure 2–2B.
ERUS—normal rectum (left) and anal canal (right).
INTERPRETATION
Primary lesion: distortion of the rectal wall; depth, axial and circumferential size:
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– Noninvasive polyp or T1 cancer: thickening of black-2, intact of white-2.
– T2 cancer: interruption of white-2, no indentation into white-3.
– T3 cancer: interruption of white-2, indentation of tumor fingers into white-3.
– T4 cancer: blurring of the plane toward prostate, distortion of sphincter complex.
Extraluminal structures:
– Lymphadenopathy: reproducible round/oval, nonbranching hypoechogenic extraluminal structures with
measured diameter of 3–20 mm (sometimes even more).
– Recurrent tumor: asymmetric hypoechogenic tissue distortion, often only distinguishable from scar through
observation of interval change on serial exams.
– Blood vessels: branching, can be followed over longer course, occasionally visible pulsations.
– Seminal vesicles: continuation to supraprostatic structure.
PITFALLS
Artefacts, reactive lymphadenopathy (shortly after biopsy) cannot be distinguished from metastatic lymphadenopathy (
overstaging), distinction between scar and tumor. Lymph node metastases may be < 5 mm ( understaging).
Test Element: Ultrasound-Guided Biopsy
PURPOSE
Evaluation of extraluminal pathology ~2–8 cm proximal to anal verge.
INDICATION
Cancer surveillance: evaluation of possible recurrence.
Lymphadenopathy: confirmation of stage III disease.
EQUIPMENT AND TECHNIQUE
Endosonic multiplane transducer with channel for needle insertion.
Automatic-release TruCut biopsy needles. Visualization of pathology with conventional ultrasound
biplanar verification with
biopsy probe positioning of pathologic lesion in target plane/beam.
RISKS
Direct trauma during insertion of probe, pain/discomfort (size of the probe, needle through anoderm), bleeding, infection,
rectourethral fistula.
REFERENCE VALUES
Obtained tissue adequate and reflective of the true nature of the problem.
INTERPRETATION
Positive biopsy proof of tumor spread.
Negative biopsy
possibility of false negative (sampling error).
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PITFALLS
Sampling error. Limitation of probe insertion.
Test Element: Endoanal Ultrasound
PURPOSE
Evaluation of structural integrity and pathology in the anal canal.
INDICATION
Evaluation of fecal incontinence: sphincter defect, sphincter attenuation?
Fistula/abscess: location, course.
EQUIPMENT AND TECHNIQUE
Ultrasound machine with rotating 10 (7) MHz hardcap probe.
RISKS
Direct trauma during insertion of probe, discomfort.
REFERENCE VALUES
Anal canal (Figure 2–2B):
IAS: hypoechogenic (ie, black) ring: does not extend as far distal as EAS.
EAS: thicker hyperechogenic (ie, white) ring.
Puborectalis muscle: hyperechogenic (ie, white) parabolic muscle.
INTERPRETATION
Sphincter morphology (IAS, EAS): segmental gap/defect of internal or external sphincter (need to be assessed
separately); assessment of sphincter thickness and architecture (scarring? atrophy?).
Fistula: hypoechogenic tract, positive identification if whitening (hyperechogenicity) of the tract results from peroxide
injected into external fistula opening.
Abscess: extrasphincteric localized hypoechogenicity.
PITFALLS
Artefacts, rectocele/short anal canal mistaken for anterior sphincter defect.
Further Steps
Correlation with other clinical, radiologic, intraoperative, and pathologic data.
Cross-Reference
Fecal incontinence (787.6) (Ch. 4)
Colorectal cancer—rectal cancer (154.1) (Ch. 4)
Recurrent rectal cancer (789.3, 154.1) (Ch. 4)
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Follow-up for colorectal cancer (Ch. 6)
Tumor staging in TNM system (App. 2)
CONVENTIONAL X-RAYS (PLAIN FILMS)
Overview
Despite the rapid evolution of sophisticated diagnostic imaging techniques, conventional x-rays (plain films) remain an
important evaluation tool because of their universal availability, simplicity, and low cost. The radiation exposure of a single
test is moderate (compared with, eg, natural background radiation exposure of 300 mrem [3 mSv]), but the cumulative dose
of medical imaging is significant.
Expected Benefits
Baseline imaging studies in many instances are sufficient, or they give a clue to serve as guidance for targeted ordering of
subsequent, more specific tests. Serial images for assessment of evolution/resolution of a particular pathologic process (eg,
bowel distention).
Limitations
Generally unspecific; lack of anatomical detail; 2-dimensional image of 3 dimensions results in superimposed structures;
magnification effects for structures farther away from the x-ray film; blurring of contact zones (silhouette signs).
Specific Tests: Chest X-Ray
PURPOSE
1. Cardiopulmonary and mediastinal assessment.
2. Search for pneumoperitoneum (upright chest x-ray), eg, hollow viscus perforation or anastomotic leak.
3. Evaluation of chest skeleton.
EQUIPMENT AND TECHNIQUE
Posteroanterior (potentially lateral) upright chest x-ray; if patient mobility limited: perform anteroposterior supine chest x-
ray.
RISKS
Radiation exposure: 6 mrem (0.06 mSv)
INTERPRETATION
Free air (Figure 2–3A): after preceding abdominal exploration most commonly absorbed within 7–10 days; increase
of free air after previously documented disappearance suggestive of perforation/leak.
Pulmonary lesions: inflammatory vs neoplastic.
Mediastinum: air, widening, lymphadenopathy.
Atelectasis, pulmonary consolidations, pleural effusion, vascular congestion, pulmonary edema, pneumothorax, etc.
Figure 2–3A.
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Free air.
PITFALLS
Chilaiditi syndrome: suprahepatic colon loop mimicking free subdiaphragmatic air.
False negative for free air: small/early hollow viscus perforation may not show.
False positive (for perforation): benign causes of pneumoperitoneum.
Specific Tests: Abdominal Series
PURPOSE
Assessment of bowel gas pattern and diameter, extraintestinal air (eg, pneumobilia, hollow viscus perforation or anastomotic
leak with local diffuse pneumoperitoneum), extraintestinal fluid (enlarged interloop space). Opacifications (gallstones,
urolithiasis, pancreas calcifications, vascular, foreign bodies). At the same time, assessment of visible skeletal and soft tissue
structures (eg, osteolysis, subcutaneous emphysema, etc).
EQUIPMENT AND TECHNIQUE
Supine and upright abdominal views extending from diaphragm to pelvis. If patient mobility limited: perform supine and left
lateral decubitus abdominal x-ray.
RISKS
Radiation exposure: 70 mrem (0.7 mSv); 20–30% false negative findings.
INTERPRETATION
Free peritoneal air: left lateral decubitus position (upright chest x-ray better if possible). Retroperitoneal air.
Subcutaneous or subfascial gas.
Fluid levels and bowel dilation (Figure 2–3B): consistent with obstruction; transition point suggestive of mechanical
obstruction; air visible throughout to rectum suspicious for pseudoobstruction or enteritis.
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"Double bubble" sign (two air-filled structures in epigastrium, while little or no air is seen distally): duodenal
obstruction, intestinal malrotation, obstruction produced by midgut volvulus or by Ladd bands.
Colonic dilation with coffee-bean sign: volvulus of sigmoid colon (axis to LLQ) or cecum (axis to RLQ).
Diffuse colonic dilation: maximum 6 cm (1
1
/
2
vertebrae) for transverse colon, 12 cm for cecum. Critical diameter
depending on speed of evolving dilation.
Pneumatosis: intestinal ischemia vs pneumatosis cystoides intestinalis.
Air in the hepatic area:
– Portal venous gas (liver periphery): ominous for intestinal necrosis or severe infection.
– Pneumobilia (liver hilum): contact of intestinal lumen with biliary tree, eg, post-ERCP, gallstone ileus,
hepaticojejunal anastomosis.
Negative colonic contrast: limited intestinal air except for the colon occasionally allows clear visualization of colonic
configuration.
Displacement of intestinal gas: mass effect?
Calcifications: gallstones, kidney stones, arteriosclerosis, phleboliths, appendicolith, mesorectal calcifications
hemangioma.
Foreign bodies.
Figure 2–3B.
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Air-fluid levels in SBO.
PITFALLS
Normal abdominal x-ray does not exclude possibility of pathologic lesion or process, eg, bowel obstruction or viscus
perforation.
Air-fluid levels: consistent with but not pathognomonic for bowel obstruction; can also be found in enterocolitis (diarrhea),
postoperative ileus.
Rectal air after preceding rectal examination.
Specific Tests: Skeletal X-Rays
PURPOSE
Evaluation of skeletal anatomy and integrity. Not typically needed for colorectal questions but incidental findings when
ordered for other indications.
EQUIPMENT AND TECHNIQUE
Depending on target, x-ray in 2 separate projections.
RISKS
Radiation exposure: skull, 3 mrem (0.03 mSv); limb, 6 mrem (0.06 mSv); pelvis, 70 mrem (0.7 mSv); spine, 30–70 mrem
(0.3–0.7 mSv).
INTERPRETATION
Mandibular osteoma, dental abnormalities (number, form) Gardner syndrome.
Sacral destruction/malfusion (pelvic scimitar sign) meningomyelocele, chordoma.
Ankylosing spondylitis, sacroiliitis IBD.
PITFALLS
None.
Further Steps
Depending on clinical circumstances and radiologic findings:
Cross-sectional imaging studies: CT scan or MRI.
Ultrasound: abdominal, chest.
Specific contrast studies.
PET not typically indicated as next step unless specific circumstances.
Immediate surgical exploration without further imaging: eg, free peritoneal air.
Cross-Reference
Contrast enemas (Ch. 2)
Small bowel follow-through (SBFT) (Ch. 2)
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Computed tomography (CT scan) (Ch. 2)
CONTRAST ENEMAS
Overview
Instillation of radiographic contrast material (with air = double contrast (Figure 2–4A), without air = single-column contrast)
into hollow viscus or cavity to obtain anatomic road map and functional assessment. Evaluation of mucosal pathologies
limited, contrast enema therefore only indicated if endoscopy is not possible, not successful, or because of patient
preference.
Figure 2–4A.
Barium air double contrast enema.
Precontrast images (scout film) and postevacuation films mandatory. Particularly for evaluation of colon: bowel cleansing
mandatory (screening), desirable (elective test for specific symptom), even though not always possible (emergency, eg, large
bowel obstruction).
Different types of contrast agents:
Barium sulfate:
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– Pro: better image quality, better tolerability if aspirated.
– Con: potentially fatal barium peritonitis (
contraindicated if perforation/leak suspected, confirmed, or
imminent, or if surgery planned shortly after study), barium impaction in the colon (particularly if stasis
(diverted/unused segments and contrast not washed out, prestenotic segments).
Water-soluble contrast, eg, diatrizoate meglumine (Gastrografin), diatrizoate sodium (Hypaque):
– Pro: no risk of contrast-induced peritonitis
contrast of choice for perforation/leak; cathartic effect.
– Con: poorer image quality (less mucosal details, rapid dilution along the course of the intestines); aspiration
risk of chemical pneumonitis; hyperosmolar dehydration and risk of rupture of closed segment with trapped
contrast.
Caveat: Patients with "contrast allergy" are allergic to iodine-based contrast agents, but not to the above-mentioned barium!
Expected Benefits
1. Assessment of colonic anatomy, configuration (eg, haustration, tortuosity/redundancy, rigid pipe of burned out
colitis), diameter, length of target pathology (eg, stricture), diverticula, malrotation, residual length after previous
resections, etc.
2. Assessment of integrity (eg, leak, perforation), delineation of nonanatomic communication (fistula).
3. As guidance prior to or during intervention, eg, colonic stent placement.
Limitations
Limited ability to assess the mucosa.
Inability to perform therapeutic intervention for findings
subsequent colonoscopy (or surgery) may be necessary.
Lower sensitivity for small and even larger polyps.
False positive findings in inadequate colon cleansing.
Specific Test: Barium Enema
PURPOSE
Evaluation of colon polyps, cancer, diverticulosis double-contrast study.
Evaluation of fistula or sinuses tracts, colonic obstruction
single-contrast enema.
EQUIPMENT AND TECHNIQUE
Bowel cleansing. Rectal exam. Insertion of rectal tube and insufflation of balloon. Instillation of contrast by means of rectal
tube. Single column study: images during in-flow and contrast distention; double contrast study: images after evacuation of
contrast and insufflation of air until cecum dilated.
RISKS
Radiation exposure: 700 mrem (7.0 mSv).
Barium peritonitis: contraindicated if concern about perforation/leak, and within 5–7 days after incomplete colonoscopy with
biopsy.
Impaction of contrast precipitates in static or diverted colon may cause functional bowel obstruction.