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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