Post on 12-Jan-2017
Many Faces of Bowel Obstruction
Prof. Raju SharmaAll India Institute of Medical Sciences, New
Delhi
Bowel Obstruction Wide variety of causes Non-specific clinical manifestations: pain, vomiting,
distension, decreased passage of stool & flatus Pain out of proportion to exam. findings s/o strangulation Imaging plays a vital role Time is critical Reliance on imaging has steadily increased Qs: Sx or not? Expectations are very high!
IMAGING MODALITIES
Plain radiograph (supine/erect) Ultrasonography- children, pregnant women Computed Tomography- modality of choice CT Enterography in low grade obstruction Magnetic Resonance Imaging – seldom used
Computed Tomography
Modality of choice Global perspective of entire abdomen Uninhibited by bowel gas & fat Transition point, cause, vascular compromise MDCT: thin collimation, MPRs Oral contrast: not useful in emergent situation I.V contrast mandatory unless CI CT Angiography: bowel ischemia Radiation concern: ASIR, low dose protocols
Bowel Obstruction
Accounts for 20% of acute abdominal surgical condition Small bowel obstruction 4 to 5x more common than large Common causes: adhesions, hernia, volvulus,
inflammatory strictures, neoplasms, intussusception, ischemic
Intraluminal/ Intramural/ Extrinsic Acute/Subacute/Chronic Simple/Strangulated Complete/Incomplete Open/Closed loop
Plain Radiographs
Supine, erect, chest radiographs Utility of erect radiograph? If severely ill- lateral decubitus abdominal radiograph Moderate sensitivity 40-80% Dilated loops > 3cm Air fluid levels: >2.5 cm, at disparate levels Transition point is important D/D: Paralytic ileus
Plain Radiographs
Mechanical Obstruction
Paralytic IleusPseudo-
obstruction
Small BowelProximal/
DistalLarge Bowel Acute/Subacute
Partial/CompleteSimple/
StrangulatedOpen/Closed loop
Ischemia/ Perforation
Etiology
CT
Causes of Small Bowel Obstruction
External hernias Adhesions Malrotation, bands Internal hernias Peritoneal Carcinomatosis Gall stone ileus Parasites Foreign body
Ulcero-constrictive lesions Intussusception Tumors
Carcinoma Carcinoid
Radiation Ischemia
Extrinsic
Intra-luminal
Intrinsic
Small Bowel Obstruction Large Bowel Obstruction
Large Bowel Obstruction
• Cecum has the widest diameter – develops the maximum tension in the wall
• Risk of perforation ↑ when diameter > 9 cm
Pneumoperitoneum
• CT has sensitivity of 81-94% & specificity of 96% for high grade obstruction
• Dilated bowel with transition point
• Small bowel faeces sign close to transition point
• Evaluate for hernia, volvulus, ischemia
Closed Loop Obstruction
2 points along the course of bowel are obstructed at single location
More than one transition zone Affected loops are markedly dilated
(>4cm) with fluid Fusiform tapering at point of twist Stretched mesenteric vessels
converging to a point Vascular supply may get
compromised: prompt surgery
MRI
Signs of Vascular Compromise
Clinical signs like fever, tachycardia, acidosis are not reliable
Meta-analysis found CT sensitivity of 83% and specificity 92%
Bowel wall edema or hemorrhage Altered bowel wall enhancement: ↑ enhancement then ↓ Mesenteric fluid & stranding Vascular engorgement Pneumatosis, free intraperitoneal air, portal venous gas Certain causes have higher likelihood of vascular
compromise: closed loop, volvulus, hernia, obstructing mass
Bowel Ischemia
58 yr male with acute pain abdomen
Mesenteric Venous Ischemia
Usually a diagnosis of exclusion, kinking or tethering of loops
Form in 90% abdominal surgeries but only 5% complicated by SBO
Highest incidence after colo-rectal surgery 1% of patients develop obstruction in immediate post-op
period -90% of are due to adhesions Signs for predicting need for surgery:
Free intra-peritoneal fluid Mesenteric fat stranding High grade obstruction Absent small bowel feces sign
Adhesive Obstruction
Adhesive Obstruction
Ileo-Cecal Tuberculosis
Inflammatory Stricture
Duodenal Tuberculosis
• 2% of GI TB• 3rd part most common• Ulcerative type or hyperplastic• Healing with fibrosis may lead to
duodenal obstruction
Crohn’s Disease
Chronic Fibro-stenotic Disease
Hernia Causing Obstruction Internal/ External Inguinal (80%)/ Femoral (5%)/ Obturator/ Ventral/
Spigelian Hernial sites should be included on plain radiographs Inferior epigastric artery is landmark to differentiate
indirect/ direct IH Femoral hernia is seen anteromedial to femoral vein, more
common in women, more prone to strangulation Obturator hernia: more common in elderly women,
between the pectineus and obturator externus
Obstructed Right Inguinal Hernia
80 yr lady: Obturator hernia
Intussusception
70 yr old male patient with vomiting & abdominal distension
Small Bowel Obstruction due to Intussusception Caused by GIST
Intussusception Causing Obstruction & Ischemic Bowel
Adenocarcinoma
• Duodenal/ Jejunal location• Annular/ Polypoidal/ Asymm. wall thickening• Obstruction is common
25 year male with recurrent pain abdomen
Midgut Volvulus
Sclerosing Encapsulating Peritonitis
Ascariasis
Gall Stone Ileus: Riggler Triad
Post-Gad
Mesenteric Lymphangioma causing SBO due to Volvulus
Mesenteric lymphangioma causing volvulus
Causes of Large Bowel Obstruction
Sigmoid volvulus Cecal Volvulus Tumors: 55% Diverticulitis: 12%
Intussusception Tuberculosis Ischemic strictures Stercoral colitis/ulcer
10%
Large Bowel Obstruction
Volvulus
Caecal Sigmoid
70 year old man with constipation and vomiting
Adenocarcinoma Sigmoid Colon
Diverticulitis
• Bowel wall thickening, peri-colonic inflammation, diverticulosis
• Inflamed diverticuli may be hyperdense on CT
• Sigmoid colon: most often involved
• Hinchey’s classification• Perforated malignancy may
mimic perforated diverticulitis
Sigmoid Perforation
Conclusion Confirm bowel obstruction Small bowel or large bowel Likely etiology Is strangulation / perforation present Increasing shift towards conservative management in
uncomplicated SBO If CT features point towards vascular compromise –
urgent surgery In conjunction with clinical signs guide management Early diagnosis is critical
www.aiims-mamc-pgi-imagingcourse.com
Thank you for your attention!