Bowel Obstruction Handout
Transcript of Bowel Obstruction Handout
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Bowel Obstruction
Borut MarincekInstitute of Diagnostic Radiology
University Hospital Zurich, Switzerland
Nordic Forum – Trauma & Emergency Radiology U
• To illustrate the spectrum of acute obstruction of the small and the large bowel
• To explain how these bowel obstructions may present radiologically, with an emphasis on MDCT
• To discuss complications of acute bowel obstruction
Lecture Objectives
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= 20% of surgical hospital admissions for acute abdomen
Small bowel obstruction (SBO) (80%)• Postoperative adhesions (50-75%)• Primary & metastatic neoplasia (10-15%)• External/internal hernia (8-15%)• Other: Crohn disease, intussusception, hematoma,
gallstone, bezoar
Bowel Obstruction: Etiologies
Large bowel obstruction (LBO) (20%)• Carcinoma (60%, most frequently sigmoid)• Volvulus (10-15%, sigmoid > cecum) • Diverticulitis (10%)• Other: intussusception, fecal impaction, ischemia,
foreign object, extrinsic compression
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1. Is mechanical obstruction present ? DDx: adynamic ileus (laparotomy, pancreatitis, peritonitis, mesenteric ischemia, neuroleptics, opiates)
2. What is the site (small bowel / large bowel) ?3. What is the cause ?4. Any complications ?
Simple (wall viability not compromised) or strangulation obstruction (compromised vascular supply intestinal ischemia) ?
Urgent surgery or conservative management ?
Bowel Obstruction: Four Relevant Questions
U Bowel Obstruction: Traditional Role of Imaging U Abdominal Plain Film (APF) vs CT
Sensitivity (%)
CT(N=188)
APF(N=871)
7549Bowel obstruction
689Urolithiasis
600Pancreatitis
90Intraabdominal foreign body
250Diverticulitis
400Pyelonephritis
500Appendicitis
(Ahn, Radiology 2002)
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APF: Problems• Nondiagnostic or misleading in approx. 50%• Poor predictor of site or cause of obstruction• Frequently fails to demonstrate findings of ischemia or
infarctionAntegrade contrast studies: Problems• Slow transit, prolonged retention of barium • Water-soluble contrast usually diluted by SB fluidCT: Advantages• Demonstrates site & cause of obstruction, extraluminal
abnormalities• Provides information about state of bowel wall (i.e.
strangulation)
Bowel Obstruction: Imaging Modalities U
APF: Problems• Nondiagnostic or misleading in approx. 50%• Poor predictor of site or cause of obstruction• Frequently fails to demonstrate findings of ischemia or
infarctionAntegrade contrast studies: Problems• Slow transit, prolonged retention of barium • Water-soluble contrast usually diluted by SB fluidCT: Advantages• Demonstrates site & cause of obstruction, extraluminal
abnormalities• Provides information about state of bowel wall (i.e.
strangulation
Bowel Obstruction: Imaging Modalities
CT instead of A
FP or
antegrade contrast studies
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• Less common than SBO• Different in other ways:
- etiology: cancer most common- symptoms: insidious- right-sided mimics SBO
• APF:- dilated colon >5-6 cm, cecum largest- rectal gas?
• CT interpretation:- look at scout views- start in pelvis- find cecum and terminal ileum- find transition zone, look for etiology - masses, etc
Large Bowel Obstruction U LBO: Annular Sigmoid Carcinoma
CT confusing ?Rectal contrast= key for LBO
diagnosis
U LBO: Metastasis Breast Carcinoma
Retroperitonealinfiltration
U Fecal Impaction (Coprostasis) ? (61 yo, m)
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U Decompensated LBO (61 yo, m)
Adenocarcinoma transverse colonIschemic distention colitis of cecum
Colon distended >6 cm, cecum largest
U LBO: Fecal Impaction (Coprostasis)
U LBO: Fecal Impaction (Coprostasis)
Most commonly in laxativeabusers, psychiatric patients, severe generalized athero-sclerosis / cerebral sclerosis
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Sigmoid diverticulitis
Findings typical of carcinoma:• Short segment involved • Pericolic lymph nodes
Findings typical of diverticulitis:• Long segment involved (>5 cm)• Pericolic inflammation• Symmetric wall thickening (75%)
High Grade LBO: Diverticulitis or Carcinoma?
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“Coffee bean” sign (inverted U-configuration)
“Northern exposure” sign (Javors, AJR 1999)
LBO: Sigmoid Volvulus (= Closed Loop Obstruction) U
CT „whirl sign“ indicative of
volvulus
LBO: Cecal Volvulus (= Closed Loop Obstruction)
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Torsion of involved colon aroundmesocolon = „whirl sign“ on CT:stretching and engorgementof ileocecal artery & vein in cecalvolvulus (in sigmoid volvulus IMA & IMV)
58 yo, f: ischemic necrosis cecum
LBO: Cecal Volvulus with Ischemic Complication U
Ovarian carcinoma, surgery & radiotherapy 23 yrs ago:
ischemic radiation colitis of rectosigmoid
LBO: Ischemic Radiation Colitis
U LBO: Ischemic Radiation Colitis
Cervical carcinoma, surgery & radiotherapy 10 yrs ago:
ischemic radiation colitis of rectum and sigmoid
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Bowel within bowel mesenteric fat, enhancing
mesenteric vessels
Lead point = polyp(adenocarcinoma T2N0)
LBO: Sigmo-Sigmoid Intussusception
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Submucosal lipoma of ileocecal valve
LBO: Colo-Colic Intussusception U
Cecal perforation
LBO: Endometriosis
40 yo, f:rectosigmoid
& cecum
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• More common than LBO• APF:
- multiple gas-fluid levels unequal heights• CT technique:
- oral contrast not necessary- iv contrast critical
• CT diagnosis:- dilated SB >2.5 cm- transition zone, maybe hard to find- small bowel feces sign- coronal & sagittal MPRs can help
Small Bowel Obstruction U
Kidney-TPL 1 month ago
No mass at transition zone adhesive SBO: adhesive bands unidentified on CT (diagnosis of exclusion)
SB: distended (>2.5 cm) & collapsed loops
SBO: Multiple Postoperative Adhesions
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Ventral incisional hernia; SB faeces sign (phytobezoar) =
indicator of SBO whenassociated with SB dilatation
SBO: Multiple Postoperative Adhesions U
curved MPR
Circumferential adenocarcinomadistal ileum
SBO: Neoplasia
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External: herniation of viscera through defect (congenital weakness or previous surgery) in abdominal or pelvic wall (inguinal, femoral, ventral, lumbar, obturator, incisional) in most cases visible or palpable, CT for detection of unsuspected sites, in obese patients
Internal: less common, herniation of viscera through developmental or surgically created defect of peritoneum or mesentery into a compartment within peritoneal cavity diagnosis always based on radiology
Hernias: External & Internal U
• Incarceration irreducible hernia (irreducible sac of jejunal loop)
• Incacerated hernia may strangulate, clinical diagnosisdifficult in obese patients
SBO: Incarcerated Femoral Hernia
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U SBO: Incarcerated Obturator Hernia
Obturator hernia• f:m = 5:1• 7th-8th decade
of life
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Paraumbilical hernia:• Related to diastasis of rectus abdominis muscle• Risk factors: multiple pregnancies, obesity• High prevalence for incarceration & strangulation
SBO: Incarcerated Ventral (Paraumbilical) Hernia
U SBO: Incarcerated Ventral Incisional Hernia
10 days after abdominalhysterectomy
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Incarceration?
SBO: Ventral Incisional Hernia
Multiple laparotomies after resection of sigmoid colon
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No incarceration(reducible hernia)No incarceration
SBO: Ventral Incisional Hernia U
A paraduodenalB foramen of WinslowC intersigmoidD pericecalE transmesentericF retroanastomotic
SBO: Internal Hernias
(Martin, AJR 2006)
• Classic older literature: paraduodenal most common, pericecal second most common
• Increasing incidence of transmesenteric, transmesocolic& retroanastomotic new surgical procedures (Roux-en-Y loop in liver TPL & gastric bypass)
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U SBO: Pericecal Hernia U SBO: Retroanastomotic Hernia After Gastric Bypass
Mesenteric swirl best single predictor (Lockhart, AJR 2007)
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Terminal ileum:wall thickening &
layering enhancement active disease
Crohn disease: typically partial
obstruction
SBO: Crohn Disease U
Mesenteric fat & vessels in bowel lumen(„bowel-within-bowel appearance“)
Lead point: jejunal melanoma metastasis
Subdiaphragmatic melanoma metastasis, left renal cyst
SBO: Intussusception
U SBO: Diagnosis? U SBO: Impacted Gallstone
Rigler Triad: SBO, pneumobilia, ectopic gallstone
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Our most important job in SBO is answer to the question:Simple or strangulation obstruction? Is ischemia present?
Strangulation obstruction (10% of SBO):- most are closed loop (= bowel loop occluded at two adjacent points along its course)- vascular compromise venous mesenteric bloodflow compromised first, causing increasing vascularpressure and vessel engorgement with continuingarterial influx; hemorrhage into bowel wall and lumencan occur; finally arterial supply ceases, due to arterialspasm following increasing vascular resistance
SB Strangulation Obstruction U
CT findings:• Bowel wall thickening >3 mm (non-specific)• Abnormal bowel wall enhancement ( or )• “Target sign”: alternating hypo- / hyperdense layers submucosal edema / hemorrhage
• Pneumatosis intestini & portomesenteric gas• Mesenteric edema• Ascites
SB Strangulation Obstruction
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Appendectomy & cholecystectomy 54 yrs ago
Segmental ischemia & infarction of jejunumsecondary to adhesive band
SBO: Strangulation Ischemia U SBO: Strangulation Ischemia
Appendectomy 1 yr agoVenous ischemia of ileum
secondary to adhesive band
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CT „whirl sign“: strangulating SB volvulus ischemia & infarction of jejunum
secondary to adhesive band
Appendectomy & cholecystectomy several yrs ago
SBO: Strangulation Ischemia U
• Remember 4 questions
• MDCT instead of APF for accurate diagnosis
• MDCT: MPRs improve visualization of transition zone prestenotic / poststenotic bowel better determination of site and cause of obstruction
• MDCT: improved visualization of ischemia in suspected small bowel strangulation obstruction
Bowel Obstruction: Summary