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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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Precipitation of toxic megacolon in active flare-up of IBD.
INTERPRETATION
Dolichocolon: axial elongation and tortuosity of the colon.
Megacolon: radial distension of the colon; reference points: 6 cm (1
1
/
2
vertebral heights) in transverse colon, 12 cm
in cecum. Caveat: contrast study contraindicated in acute IBD or megacolon.
Diverticula: distribution, size and number of limited clinical relevance; chronic diverticulotic stricture: smooth mucosal
surface overall preserved (see Figure 4–18D) as opposed to ulceration/apple core in cancer.
Cancer: characteristic "apple core" lesion (Figure 2–4B), mucosal integrity not preserved.
Figure 2–4B.
Apple core lesions.
PITFALLS
Overlapping of contrast-filled colon segments (particularly sigmoid and cecum) missing of relevant pathology.
False positive defects after inadequate cleansing.
Sensitivity of barium: colorectal cancer, 80–85%; large polyps (> 1 cm), 50%.
Test Element: Water-Soluble Contrast Enema
PURPOSE
Nonelective evaluation of colonic anatomy, configuration, search/rule out leak/perforation or point of obstruction (road map).
Elective evaluation of diverted segment (
eliminates risk of contrast impaction).
Therapeutic (and diagnostic) intent: fecal impaction
taking advantage of hyperosmolar, ie, laxative properties to facilitate
bowel movement.
EQUIPMENT AND TECHNIQUE
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Rectal exam. Insertion of rectal tube and insufflation of balloon. Instillation of contrast. Single column: images taken during
inflow of contrast.
RISKS
Radiation exposure: 700 mrem (7.0 mSv).
Colonic distention/rupture from hyperosmolar effect with suction of fluid into closed segment and trapped contrast
(prestenotic).
INTERPRETATION
As above for barium enema, in addition:
– Leak or perforation: extravasation of contrast.
– Intussusception
contrast enema potentially therapeutic.
– Volvulus: "bird's beak," "ace of spades."
PITFALLS
Lower detail and sharpness of contrast (compared with barium).
Overlapping of contrast-filled colon segments (particularly sigmoid and cecum)
risk of missing relevant pathology.
False positive defects from residual stool.
Further Steps
Depending on clinical circumstances and radiologic findings:
Cross-sectional imaging studies: CT scan or MRI.
Ultrasound: abdominal, chest.
PET not typically indicated as next step unless specific circumstances.
Obstruction/leak/perforation
surgical exploration/intervention?
Cross-Reference
Colonoscopy (Ch. 2)
CT colonography ("virtual colonoscopy") (Ch. 2)
Colorectal cancer—colon cancer (153.X) (Ch. 4)
Large bowel obstruction (LBO, 560.9) (Ch. 4)
Colonic volvulus (560.2) (Ch. 4)
Diverticular disease (diverticulosis, diverticulitis, 562.1X) (Ch. 4)
POUCHOGRAM
Overview
Instillation of radiographic contrast material into existing pouch (ileoanal pouch, continent ileostomy) for assessment of
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pouch configuration and functional evaluation. Conversely, endoscopy is preferable for assessment of mucosal pathologies
(eg, pouchitis, ulcers, etc). Precontrast images (scout film) and post-evacuation films are mandatory to rule out unrelated
findings and to assess adequate ability to evacuate.
Expected Benefits
Assessment of pouch anatomy, configuration, size, obstruction, prolapse, in-/outlet, potentially valve segment
(continent ileostomy).
Assessment of integrity (eg, leak, perforation), delineation of nonanatomical communication (fistula).
As guidance for intervention, eg, radiologic drain placement (continent ileostomy).
Limitations
Limited ability to assess the mucosa.
Interference with overlaying bowel loops.
Specific Test: Barium Pouchogram
PURPOSE
Fast, universally available, reasonably reliable examination.
EQUIPMENT AND TECHNIQUE
Limited bowel cleansing/evacuation prior to exam.
– Ileoanal pouch: rectal exam, insertion of rectal tube and gentle insufflation of balloon, instillation of contrast
images in multiple projections, particularly lateral view.
– Continent ileostomy: insertion of Foley catheter into stoma/valve segment, instillation of contrast
images in
multiple projections, particularly tangential to skin surface.
RISKS
Radiation exposure: 300–700 mrem (0.3–7.0 mSv).
Barium peritonitis: contraindicated if concern about perforation/leak.
INTERPRETATION
Ileoanal pouch:
– Intact pouch of normal size, no extravasation; lateral projection: pouch follows sacral curvature.
– Pathology: leak, stricture, fistula; lateral projection: pouch does not follow sacral curvature suspicion of
presacral pathologic lesion or process (hematoma, abscess).
Continent ileostomy:
– Size, configuration of pouch reservoir, leak, etc.
– Valve segment (negative imprint to pouch reservoir): assessment of length, course (kinking?), fistula?
desintussusception, ie, valve outside reservoir (see Figure 4–15A).
PITFALLS
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Radiologist often inexperienced with pouches surgeon's presence helpful.
Overlapping of contrast-filled small bowel segments
risk of missing relevant pathology.
Suboptimal projections.
Covering of relevant pathology with catheter or balloon
false negative.
Test Element: CT-Pouchogram
PURPOSE
To assess 3-dimensional (3D) configuration and correlation to surrounding structures.
EQUIPMENT AND TECHNIQUE
Enteral CT-contrast: instilled into pouch high-resolution CT scan with 3D reconstruction.
RISKS
Radiation exposure: 1000 mrem (10.0 mSv).
INTERPRETATION
As above.
PITFALLS
Radiologist often inexperienced with pouches surgeon's presence helpful.
Further Steps
Depending on clinical circumstances and radiologic findings:
Pouchoscopy.
Small bowel follow-through.
Obstruction/leak/perforation
surgical exploration/intervention?
Cross-Reference
Pouchoscopy (Ch. 2)
Familial adenomatous polyposis (FAP; 211.3, 235.2, V84.09) (Ch. 4)
IBD-ulcerative colitis (556.9) (Ch. 4)
"Pouchology"—the science of pouches (Ch. 4)
Pouchitis—ileoanal dysfunction (569.60) (Ch. 4)
Kock pouch dysfunction (Ch. 4)
SMALL BOWEL FOLLOW-THROUGH (SBFT)
Overview
Instillation of radiographic contrast material to the upper GI tract (oral ingestion or via NGT), followed by sequential x-rays
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to observe the progression of the contrast through the small into the large bowel (Figure 2–5).
Figure 2–5.
Small bowel follow-through.
Expected Benefits
Assessment of anatomy, configuration, diameter, length (eg, after previous resections), strictures, fistulae, mucosal
abnormalities, etc.
Assessment of functional integrity: passage time, delayed contrast progression.
Identification of site of obstruction.
Limitations
Limited ability to assess the mucosa due to overlay of loops.
Specific Test: Barium SBFT
PURPOSE
Evaluation of the small bowel with best contrast (elective setting).
EQUIPMENT AND TECHNIQUE
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Scout film. Administration of 2 bottles of liquid barium serial images in appropriate time intervals (Figure 2–5). If colon is
not reached within 4 hours late films (eg, 24 hours later).
RISKS
Radiation exposure: 300 mrem (3 mSv).
Barium peritonitis:
barium contraindicated if concern about perforation/leak.
Impaction of contrast precipitates in static bowel may result in functional bowel obstruction.
INTERPRETATION
Crohn disease: potentially visible mucosal alteration, presence and number of strictures, presence/characterization or
absence of fistula.
Enterocutaneous fistula: characterization of fistula-bearing bowel segment, identification of distal obstruction.
Partial bowel obstruction: evidence and nature of transition point, additional distal obstructive sites.
GI bleeding of unknown source: identification of altered bowel segment, tumor.
PITFALLS
Overlapping of contrast-filled colon segments risk of missing relevant pathology.
False positive defects (air bubbles, enteric content).
Specific Test: Water-Soluble Contrast SBFT
PURPOSE
Evaluation of the small bowel while avoiding negative barium impact (subacute/nonelective setting).
Taking advantage of the cathartic (laxative) effect of the water-soluble contrast, the study may potentially result in opening
up a partial bowel obstruction.
EQUIPMENT AND TECHNIQUE
Scout film. Administration of 2 bottles of water-soluble contrast with serial images in appropriate time intervals. Late films
not revealing due to dilution of the contrast.
RISKS
Radiation exposure: 300 mrem (3 mSv).
Osmotic effect of hyperosmolar contrast
risk of perforation in closed loop (eg, colonic obstruction and competent ileocecal
valve).
INTERPRETATION
Partial bowel obstruction: evidence and nature of transition point, additional distal obstructive sites.
Enterocutaneous fistula: characterization of fistula-bearing bowel segment, identification of distal obstruction.
PITFALLS
Water-soluble contrast significantly diluted in the course of the small bowel suboptimal resolution of structural details.
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Overlapping of contrast-filled colon segments risk of missing relevant pathology.
False positive defects (air bubbles, enteric content).
Specific Test: 50–50 SBFT
PURPOSE
Evaluation of the partially obstructed small bowel with a mixture of 50% water-soluble contrast and 50% barium. Goal:
obtaining better contrast than with water-soluble contrast alone, but avoiding too much barium in partially obstructed bowel;
taking advantage of the cathartic (laxative) effect of the water-soluble contrast that may potentially open up a partial bowel
obstruction.
EQUIPMENT AND TECHNIQUE
Scout film. Administration of 2 bottles of water-soluble contrast and barium mixed in a 1:1 ratio with serial images in
appropriate time intervals. If colon is not reached within 4 hours late films.
RISKS
Radiation exposure: 300 mrem (3 mSv).
Osmotic effect of hyperosmolar contrast
risk of perforation if hyperosmolar contrast trapped in functionally closed loop.
Negative impact of barium.
INTERPRETATION
Partial bowel obstruction: evidence and nature of transition point, additional distal obstructive sites.
PITFALLS
This combination is of relatively limited value, not good enough to allow an accurate evaluation, but essentially carrying the
same risks as a barium SBFT.
Further Steps
Depending on clinical circumstances and radiologic findings:
Cross-sectional imaging studies: CT scan or MRI.
Ultrasound: abdominal, chest.
Surgical exploration, depending on the circumstances.
Cross-Reference
Small bowel obstruction (SBO) (Ch. 1)
CT enterography ("virtual small bowel follow-through") (Ch. 2)
IBD—Crohn disease (555.X) (Ch. 4)
Enterocutaneous fistula (569.81) (Ch. 4)
COLONIC TRANSIT STUDY (SITZMARK)
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Overview
Qualitative and (semi-)quantitative assessment of unassisted colonic transit time. Useful tool for evaluation of patients with
constipation and abdominal bloating to distinguish between etiopathogenetic subtypes and serve as guidance for further
diagnostic and treatment options.
Classical method: ingestion of radiopaque markers (commercial: Sitzmarks, or hand-made: cut radiopaque tubes) with
scheduled x-rays: inexpensive, safe, and simple, does not require infrastructure.
Alternative method: scintigraphy with oral radioisotope markers.
Expected Benefits
Assessment of colonic transit function in patients with chronic constipation for distinction between:
Slow transit constipation (colonic inertia).
Pelvic floor dysfunction/fecal outlet obstruction.
Normal transit constipation, eg, IBS.
Limitations
Noncooperative patients: continuation of laxatives, lack of fiber supplementation.
Specific Test: Sequential Sitzmark Study (3-Day Variant)
PURPOSE
Qualitative and semi-quantitative assessment of colonic transit time.
EQUIPMENT AND TECHNIQUE
General patient instructions:
Temporary discontinuation of any laxatives or enemas for the duration of the study.
Daily fiber supplement 4 times per day.
At least six 8-ounce glasses of water every day.
Otherwise regular diet (no special adjustments).
Sitzmark capsules: 1 capsule in the morning on days 1, 2, and 3.
Abdominal x-rays: on days 4 and 7.
RISKS
Radiation exposure: 140 mrem (1.4 mSv).
Fecal impaction.
INTERPRETATION
Three distribution patterns:
1. All markers accumulating in the pelvis: pelvic outlet obstruction defecating proctogram.
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2. Markers diffusely distributed throughout colon: slow transit constipation (see Figure 4–24).
3. All markers disappeared: normal-transit, constipation-predominant IBS.
Semi-quantitative calculation of total and segmental transit times.
PITFALLS
False negative test: noncompliant patient cheating (eg, not taking pills, taking laxatives) normal-appearing study with all
markers eliminated.
False positive: too-short interval between tablet ingestion and abdominal x-ray.
Test Element: Simplified Sitzmark Study (1-Day Variant)
PURPOSE
Qualitative assessment of colonic transit time.
EQUIPMENT AND TECHNIQUE
General patient instructions:
Temporary discontinuation of any laxatives or enemas for the duration of the study.
Daily fiber supplement 4 times per day.
At least six 8-ounce glasses of water every day.
Otherwise regular diet (no special adjustments).
Sitzmark capsules: 1 capsule in the morning on day 1.
Abdominal x-rays: on day 5.
RISKS
Radiation exposure: 70 mrem (0.7 mSv).
Fecal impaction.
INTERPRETATION
Three distribution patterns: as above.
PITFALLS
As above.
Further Steps
Defecating proctogram.
Anophysiology studies.
Decision-making about treatment options, eg, subtotal colectomy?
Cross-Reference
Defecating proctogram (defecography) (Ch. 2)
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Pelvic floor dysfunction (618.X) (Ch. 4)
Functional disordes—chronic constipation (564.0X) (Ch. 4)
Functional disorders—irritable bowel syndrome (IBS, 564.1) (Ch. 4)
Selected colorectal reference values (App. 2)
DEFECATING PROCTOGRAM (DEFECOGRAPHY)
Overview
Evaluation of patients with defecation disorders: ie, outlet obstruction, pelvic floor dysfunction, rectal or pelvic organ
prolapse, distal marker distribution on Sitzmark study. Instillation of radiographic contrast paste with viscosity that more
closely resembles stool than regular contrast. Imaging with static images or video defecography while the patient sits on a
special toilet chair and attempts to evacuate the contrast. Assessment includes dynamic observation of structural and
functional alterations in the process as well as rate and completeness of the defecation.
Normal sequence (Figure 2–6): correct anorectal position above pubococcygeal line; puborectalis muscle tone with anterior
traction causes anorectal angle (normal: 90–110 degrees at rest); squeezing results in elevation of pelvic floor and the
anorectal angle becomes more acute; conversely, straining results in widening of anorectal angle (relaxation of puborectalis
muscle), evacuatory force, opening of anal canal, and complete evacuation.
Figure 2–6.
Defecating proctogram with anorectal angle at rest and during straining.
Expected Benefits
Continuous assessment of dynamic interaction between rectum and rectal content during evacuation effort proves useful to
identify rectal intussusception, rectocele with retention of stool, pelvic floor dyssynergia, and extent of rectal emptying.
Limitations
Generally unspecific information, indirect evidence. Interobserver variability of different parameters, particularly
measurement of anorectal angles or agreement for intussusception and anismus.
Lack of information about extraluminal pathology
MRI defecography or dynamic pelvic MRI.