Bowel Obstruction Handout

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Transcript of Bowel Obstruction Handout

U Nordic Forum Trauma & Emergency Radiology

U Lecture Objectives

Bowel Obstruction 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

Borut Marincek Institute of Diagnostic Radiology University Hospital Zurich, Switzerland

U Bowel Obstruction: Etiologies = 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 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

U Bowel Obstruction: Four Relevant Questions 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 ?

U Bowel Obstruction: Traditional Role of Imaging

U Abdominal Plain Film (APF) vs CTSensitivity (%) APF (N=871) Bowel obstruction Urolithiasis Pancreatitis Appendicitis Pyelonephritis Diverticulitis Intraabdominal foreign body 49 9 0 0 0 0 90(Ahn, Radiology 2002)

CT (N=188) 75 68 60 50 40 25

U Bowel Obstruction: Imaging Modalities APF: Problems Nondiagnostic or misleading in approx. 50% Poor predictor of site or cause of obstruction Frequently fails to demonstrate findings of ischemia or infarction Antegrade contrast studies: Problems Slow transit, prolonged retention of barium Water-soluble contrast usually diluted by SB fluid CT: Advantages Demonstrates site & cause of obstruction, extraluminal abnormalities Provides information about state of bowel wall (i.e. strangulation)

U Bowel Obstruction: Imaging Modalities APF: Problems Nondiagnostic or misleading in approx. 50% Poor predictor of site or cause of obstruction Frequently fails to demonstrate findings of ischemia or infarction Antegrade contrast studies: Problems Slow transit, prolonged retention of barium Water-soluble contrast usually diluted by SB fluid CT: Advantages Demonstrates site & cause of obstruction, extraluminal abnormalities Provides information about state of bowel wall (i.e. strangulation

or s P die AF t u of st s a d ra te ont s c in T ade C r eg nt a

U Large Bowel Obstruction 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

U LBO: Annular Sigmoid Carcinoma

CT confusing ? Rectal contrast = key for LBO diagnosis

U LBO: Metastasis Breast Carcinoma

U Fecal Impaction (Coprostasis) ? (61 yo, m)

Retroperitoneal infiltration

U Decompensated LBO (61 yo, m) Colon distended >6 cm, cecum largest

U LBO: Fecal Impaction (Coprostasis)

Adenocarcinoma transverse colon Ischemic distention colitis of cecum

U LBO: Fecal Impaction (Coprostasis) Most commonly in laxative abusers, psychiatric patients, severe generalized atherosclerosis / cerebral sclerosis

U High Grade LBO: Diverticulitis or Carcinoma? Findings typical of diverticulitis: Long segment involved (>5 cm) Pericolic inflammation Symmetric wall thickening (75%) Findings typical of carcinoma: Short segment involved Pericolic lymph nodes

Sigmoid diverticulitis

U LBO: Sigmoid Volvulus (= Closed Loop Obstruction) Northern exposure sign(Javors, AJR 1999)

U LBO: Cecal Volvulus (= Closed Loop Obstruction)

Coffee bean sign (inverted U-configuration)

CT whirl sign indicative of volvulus

U LBO: Cecal Volvulus with Ischemic Complication 58 yo, f: ischemic necrosis cecum

U LBO: Ischemic Radiation Colitis

Torsion of involved colon around mesocolon = whirl sign on CT: stretching and engorgement of ileocecal artery & vein in cecal volvulus (in sigmoid volvulus IMA & IMV)

Ovarian carcinoma, surgery & radiotherapy 23 yrs ago: ischemic radiation colitis of rectosigmoid

U LBO: Ischemic Radiation Colitis

U LBO: Sigmo-Sigmoid Intussusception

Cervical carcinoma, surgery & radiotherapy 10 yrs ago: ischemic radiation colitis of rectum and sigmoid

Bowel within bowel mesenteric fat, enhancing mesenteric vessels Lead point = polyp (adenocarcinoma T2N0)

U LBO: Colo-Colic Intussusception

U LBO: Endometriosis 40 yo, f: rectosigmoid & cecum

Submucosal lipoma of ileocecal valve

Cecal perforation

U Small Bowel Obstruction 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

U SBO: Multiple Postoperative Adhesions Kidney-TPL 1 month ago SB: distended (>2.5 cm) & collapsed loops No mass at transition zone adhesive SBO: adhesive bands unidentified on CT (diagnosis of exclusion)

U SBO: Multiple Postoperative Adhesions Ventral incisional hernia; SB faeces sign (phytobezoar) = indicator of SBO when associated with SB dilatation

U SBO: Neoplasia Circumferential adenocarcinoma distal ileum

curved MPR

U Hernias: External & Internal 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

U SBO: Incarcerated Femoral Hernia

Incarceration irreducible hernia (irreducible sac of jejunal loop) Incacerated hernia may strangulate, clinical diagnosis difficult in obese patients

U SBO: Incarcerated Obturator Hernia

U SBO: Incarcerated Ventral (Paraumbilical) Hernia

Obturator hernia f:m = 5:1 7th-8th decade of life

Paraumbilical hernia: Related to diastasis of rectus abdominis muscle Risk factors: multiple pregnancies, obesity High prevalence for incarceration & strangulation

U SBO: Incarcerated Ventral Incisional Hernia 10 days after abdominal hysterectomy

U SBO: Ventral Incisional Hernia Multiple laparotomies after resection of sigmoid colon

Incarceration?

U SBO: Ventral Incisional Hernia

U SBO: Internal Hernias A paraduodenal B foramen of Winslow C intersigmoid D pericecal E transmesenteric F retroanastomotic

(Martin, AJR 2006)

No incarceration (reducible hernia)

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)

U SBO: Pericecal Hernia

U SBO: Retroanastomotic Hernia After Gastric Bypass

Mesenteric swirl best single predictor(Lockhart, AJR 2007)

U SBO: Crohn Disease

U SBO: Intussusception Mesenteric fat & vessels in bowel lumen (bowel-within-bowel appearance) Lead point: jejunal melanoma metastasis Crohn disease: typically partial obstruction

Terminal ileum: wall thickening & layering enhancement active disease

Subdiaphragmatic melanoma metastasis, left renal cyst

U SBO: Diagnosis?

U SBO: Impacted Gallstone

Rigler Triad: SBO, pneumobilia, ectopic gallstone

U SB Strangulation Obstruction

U SB Strangulation Obstruction

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 blood flow compromised first, causing increasing vascular pressure and vessel engorgement with continuing arterial influx; hemorrhage into bowel wall and lumen can occur; finally arterial supply ceases, due to arterial spasm following increasing vascular resistance

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

U SBO: Strangulation Ischemia Appendectomy & cholecystectomy 54 yrs ago

U SBO: Strangulation Ischemia

Segmental ischemia & infarction of jejunum secondary to adhesive band

Appendectomy 1 yr ago Venous ischemia of ileum secondary to adhesive band

U SBO: Strangulation Ischemia Appendectomy & cholecystectomy several yrs ago

U Bowel Obstruction: Summary

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 obst