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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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Colorectal cancer—colon cancer (153.X) (Ch. 4)
Gastrointestinal stromal tumor (GIST; 171.9) (Ch. 4)
Carcinoid tumors (235.2) (Ch. 4)
Rare tumors (Ch. 4)
Follow-up for colorectal cancer (Ch. 6)
CEA monitoring for colorectal cancer (Ch. 6)
ANGIOGRAPHY WITH POSSIBLE EMBOLIZATION
Overview
Selective mesenteric (visceral) angiography remains an important tool in the management of acute severe GI bleeding.
Diagnostic value: extravasation of contrast material to identify bleeding site. Potentially therapeutic value through direct
intervention (eg, embolization).
Mesenteric angiography (Figure 2–9): sequential injection of contrast into IMA, SMA, celiac trunk.
Figure 2–9.
Angiogram SMA (left) and IMA (right).
False negative examinations due to intermittent nature of hemorrhage, transient vasospasms, intermittent clotting.
Pharmacologic agents that actively trigger bleeding (eg, heparin, urokinase/streptokinase, etc) may improve sensitivity, but
also lead to increased bleeding complications.
Expected Benefits
Direct visualization of arterial perfusion, identification of pathologic lesion and bleeding site (30–50%), possible intervention
with superselective embolization.
Limitations
Intermittent bleeding: most bleeding will have stopped before initiation of diagnostic imaging or intervention.
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Active bleeding > 1.0 mL/min.
Venous bleeding source may escape detection.
Specific Test: Angiography with Pharmacologic Intervention
PURPOSE
After identification of bleeding site induction of vasoconstriction with selective vasopressin drip ability for hemodynamic
stabilization, bridge to surgery rather than final treatment.
EQUIPMENT AND TECHNIQUE
Intravascular injection of contrast via transfemoral access catheter, phased fluoroscopic visualization.
RISKS
Radiation exposure: 750–5000 mrem (7.5–50.0 mSv).
Procedure-related complication: 2%.
30–50% false negative findings; risk of rebleeding; risk of myocardial or peripheral vascular ischemia
contraindicated in
coronary artery or peripheral vascular disease.
INTERPRETATION
Cessation of extravasation at identified bleeding site, decreased hemodynamic instability.
PITFALLS
Vasopressin infusion successful in 70–90%, but high risk of rebleeding after cessation of drip.
Test Element: Angiography with Superselective Embolization
PURPOSE
After identification of bleeding site superselective embolization with gel foam, microcoils, or polyvinyl alcohol particles
decreased perfusion pressure to stop hemorrhage without causing segmental devascularization.
More durable than pharmacologic intervention, avoidance of systemic side effects.
EQUIPMENT AND TECHNIQUE
Intravascular injection of contrast via transfemoral access catheter, phased fluoroscopic visualization insertion of 3-F
microcatheter.
RISKS
Radiation exposure: 750–5000 mrem (7.5–50.0 mSv).
Procedure-related complication: 2%.
Thirty to fifty percent false negative findings; recurrent bleeding; with modern technique only 5–10% risk of intestinal
ischemia/infarction.
INTERPRETATION
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Superselective embolization of identified bleeding site: 75–85% successful.
PITFALLS
Intestinal ischemia/infarction need for repeated clinical monitoring and surgery if evidence of deterioration.
Further Steps
Identified bleeding site and successful intervention monitoring for possible complication surgery.
Identified bleeding site and intervention not successful surgery, eg, segmental resection.
Bleeding site not identified, but bleeding stopped and patient stable watchful waiting, colonoscopy, repeat tests if
bleeding recurs, etc.
Bleeding site not identified and ongoing bleeding with patient instability surgery, ie, subtotal colectomy.
Cross-Reference
Colonoscopy (Ch. 2)
Magnetic resonance imaging (MRI) (Ch. 2)
Nuclear scintigraphy (Ch. 2)
Ischemic colitis (557.X) (Ch. 4)
Diverticular disease (diverticulosis, diverticulitis, 562.1X) (Ch. 4)
Acute lower GI bleeding (578.9) (Ch. 4)
NUCLEAR SCINTIGRAPHY
Overview
Nuclear scintigraphic provides noninvasive functional imaging based on dynamic changes within a target tissue or organ
compared with the surrounding environment. Examples increased metabolic tissue activity, changes in passage,
extravasation. Substrates are generally gamma-emitting radioisotopes linked to a carrier. The change in activity is captured
by serial images with a whole body gamma camera. Radioactivity half-life is dependent on the physical half-life of the
radioisotope and the biologic half-life of the whole substrate (excretion, metabolism, etc).
Expected Benefits
Noninvasive detection of pathology.
Limitations
Generally unspecific information, anatomic uncertainty (2-dimensional image), indirect evidence need for careful
interpretation and potentially for follow-up tests.
Specific Test: Tagged Red Blood Cell Scan ("Bleeding Scan")
PURPOSE
Sensitive diagnostic tool (50–90%) to detect bleeding > 0.1–0.5 mL/min: it is therefore the test of choice for first evaluation
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of significant lower GI bleeding.
INDICATION
Lower GI bleeding.
EQUIPMENT AND TECHNIQUE
Technetium-99m scanning: sensitivity 50–90%.
Technetium-99m–labeled red blood cells: allows late scanning after 24 hours.
Indium-111–labeled red cells: more expensive and labor-intensive technology, long half-life causing blurring of
images; advantage: detection of intermittent bleeding.
Sulfur-99m colloid: immediately available.
Cinematic technetium-99m red blood cell scintigraphy for real-time scanning.
RISKS
Radiation exposure: > 570 mrem (5.7 mSv).
INTERPRETATION
Immediate blush (within 10 min): highly predictive for accurate identification of bleeding segment (Figure 2–10). Late
images less reliable (cumulative effect, diffusion).
Figure 2–10.
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Bleeding scan.
PITFALLS
Low specificity (50%), limited anatomic resolution false localization of bleeding site in 10–60%. Pathology in hepatic and
splenic flexure potentially obscured if substrate (eg, sulfur-99m colloid) phagocytosed in reticuloendothelial system (liver,
spleen).
Specific Test: Meckel Scan
PURPOSE
Detection of ectopic gastric mucosa in a Meckel diverticulum: IV technetium-99m (
99m
Tc) pertechnetate is secreted by
gastric mucosa tissue, both in the stomach and in ectopic locations.
INDICATION
Lower GI bleeding: suspicion for Meckel diverticulum, lack of other bleeding source.
EQUIPMENT AND TECHNIQUE
IV
99m
Tc pertechnetate. Gamma camera.
RISKS
Radiation exposure: 635 mrem (6.35 mSv).
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INTERPRETATION
Early abdominal images with localized activity in RLQ in addition to the gastric activity (which serves as positive control).
PITFALLS
False negative, if no functioning gastric mucosa in Meckel diverticulum: however, this is clinically not relevant because of low
risk of bleeding in absence of gastric mucosa.
Test Element: Octreotide Scan
PURPOSE
Detection of neuroendocrine tumor activity with specific uptake of indium-111–labeled somatostatin-analogue octreotide:
80–90% sensitivity.
EQUIPMENT AND TECHNIQUE
Indium-111–labeled somatostatin-analogue octreotide. Gamma camera.
RISKS
Radiation exposure: 1810 mrem (18.1 mSv).
INTERPRETATION
Detection of foci of increased activity: suspicious for metastatic carcinoid.
PITFALLS
Lack of anatomic resolution cross-sectional imaging needed.
Test Element: Scintigraphic Emptying and Transit Studies
PURPOSE
Ingestion/delivery of carrier-linked isotope and observation of material progression through stomach, small intestine, colon
and eventually anorectal evacuation: quantitative measurement of gastric, small bowel, and colonic transit time.
EQUIPMENT AND TECHNIQUE
Indium-111, technetium-99m, iodine-131 linked to carrier (eg, diethylene-triamine pentaacetic acid [DTPA]).
RISKS
Radiation exposure: 100–500 mrem (1.0–5.0 mSv).
INTERPRETATION
Measurement of active transit time.
Further Steps
Depending on the results (positive/negative) and the clinical circumstances:
Further radiologic studies: PET, CT/MRI, etc.
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Surgical planning or exploration without further imaging.
No immediate action necessary, watchful waiting.
Cross-Reference
Colonic transit study (Sitzmark) (Ch. 2)
Computed tomography (CT scan) (Ch. 2)
Magnetic resonance imaging (MRI) (Ch. 2)
Positron emission tomography (PET/PET-CT) (Ch. 2)
Carcinoid tumors (235.2) (Ch. 4)
Acute lower GI bleeding (578.9) (Ch. 4)
"Incidentalology"—approach to incidental findings (Ch. 4)
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McGraw-Hill Manual: Colorectal Surgery > Chapter 3. Anatomy and Physiology >
EMBRYOLOGIC COLORECTAL DEVELOPMENT
Overview
Knowledge of embryologic development facilitates the understanding of congenital malformations and many other disease
processes.
Embryonic period: first 8 weeks; fetal period: from 9th week to birth.
Landmarks
Ectoderm epidermis, nervous system.
Mesoderm mesenchymal tissues: muscular and connective tissue component of intestinal tract.
Endoderm GI tube to form epithelia and parenchymatous tissues of visceral/thoracic organs.
Fusion zones:
– Cephalad endo-/ectoderm: stomatodeum.
– Caudad endo-/ectoderm: proctodeum.
Developmental Details
WEEKS 2–4 (EMBRYONIC DISC EARLY ORGAN LAYOUT)
Three germ layers: ectoderm, mesoderm, endoderm.
Notochord: primordial axis of the embryo axial skeleton and inductor of neural plate ( neuroectoderm).
Day 21: heart begins to beat circulation.
Craniocaudal and lateral folding of 3 layers formation of cranial and caudal ends head fold (stomatodeum), tail
fold (proctodeum).
WEEKS 4–8 (MORPHOGENESIS/ORGANOGENESIS)
Week 4: formation of primordial gut: foregut, midgut, hindgut cloacal membrane.
Formation of cloaca urinary, genital, and rectal tracts empty through the same opening.
Week 5: migration of neural crest cells along spinal cord sympathetic ganglia; proximal to distal migration of
neural crest cells to internal organs.
Week 6: formation of levator ani.
Week 7: fusion of urorectal septum with cloacal membrane (perineal body) partitioning of cloaca into dorsal and
ventral part; division of cloacal sphincter into posterior (external anal sphincter) and anterior (bulbocavernosus,
transverse perinei muscles) parts.
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Week 8: rupture of anal membrane communication of hindgut with amniotic cavity; formation of internal anal
sphincter (hindgut).
WEEKS 9–12 (TISSUE AND ORGAN DIFFERENTIATION)
Midgut small intestine including most of duodenum, colon from cecum to splenic flexure: arterial supply by SMA.
– Week 9: physiologic umbilical herniation
90-degree counter-clockwise rotation.
– Week 10: return of intestines to the abdomen
180-degree counter-clockwise rotation, 90-degree horizontal
rotation of duodenum/pancreas to the right.
Hindgut colorectum from splenic flexure to anus, bladder, most of the urethra: arterial supply by IMA.
– Formation of anal canal: proctodeum = fusion zone between hindgut (proximal) and ectoderm (distal)
dentate line, separate blood supply above/below.
Clinical Focus and Pathology
Remnant of primitive streak sacrococcygeal teratoma.
Remnants of notochord chordoma.
Intestinal malrotations incomplete rotation, incomplete fixation (eg, mobile cecum), volvulus.
Incomplete return of intestines omphalocele, umbilical hernia.
Persistent yolk stalk Meckel diverticulum, omphaloenteric fistula.
Failure of recanalization intestinal duplication.
Failure of neural crest cells to migrate to distal bowel Hirschsprung disease.
Abnormal partitioning of urorectal septum anorectal malformations.
Cross-Reference
Vascular anatomy (Ch. 3)
Anorectal landmarks (Ch. 3)
Pediatrics—congenital aganglionic megacolon (Hirschsprung disease, 751.3) (Ch. 4)
Pediatrics—congenital malformations (751.2) (Ch. 4)
VASCULAR ANATOMY
Overview
Knowledge of the vascular anatomy is prerequisite for the performance of safe and oncologically correct surgery. Vascular
anatomy to the colorectal organs is characterized by 3 circulatory systems: systemic arterial network, systemic venous
network, and portal venous network.
Landmarks
SMA/SMV: at duodenum part III.
IMA: at the aorta.
IMV: at the inferior edge of the pancreas.
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Splenic flexure: transition from superior to inferior mesenteric vessels.
Dentate line: border between visceral and systemic circulation.
Anatomic Details
SMALL INTESTINE
Arterial:
Supply mostly from SMA, partly from celiac trunk, some proximal collateralization, but end arteries at the level of the
bowel.
SMA: 1st
branch: pancreaticoduodenal artery, 2nd: mid-colic artery, 3rd:
vascular arcades to small bowel.
Venous:
Paralleling the arterial supply SMV portal vein.
COLON (FIGURE 3–1)
Figure 3–1.
Vascular anatomy of the colon.
Arterial: