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Ins and Outs of Bowel USStephanie G. Cohen MD
Assistant Professor of Medicine and PediatricsEmory University School of Medicine
Overview
• Discuss the use of ultrasound for evaluating abdominal pain
• Review relevant anatomy and pertinent findings
• Describe technique and pitfalls of sonographic evaluation
General Concepts
• Transducer selection• High vs Low
frequency
• Graded-compression• Displace bowel gas
• Obtain images in 2 planes
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Case
• 75 yo woman presents to the ED feeling unwell for 1 day
• Vomited x 2, BM yesterday
• HR BP
• Right abdo pain
Decreased bowel gas
Imaging for SBO
Sensitivity 50-60% 92-96% 88%
Specificity 50-55% 93% 96%
AXR CT
Abdominal Imaging; 2005; 30:160-178
US
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Small Bowel Obstruction
• Dilated bowel > 2.5 CM
• Peristalsis (To/fro)
• Bowel wall thickening >3 mm
• Keyboard sign
• Tanga sign
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Tanga Sign
Technique: Lawn Mower
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• Sensitivity 46% 91%
• Specificity 67% 84%
Emerg Med J 2011;28:676-678
AXR US
Limitations
• Miss “dilated” bowel loop
• Ileus vs SBO
• Cause of obstruction
• Decreased peristalsis is a late finding
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Characteristics
• 2nd common cause of acute abdominal emergency in children
• Hyperplasia of Lymphoid tissue
• Typical age 5 mos-3 yrs • 50% < 1 year• > 5 years concern for PLP
Pathologic Lead Points
• Meckel Diverticulum
• Duplication cyst
• Polyp
• Tumor (lymphoma)
• HSP
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• Intussusceptum: Donor loop
• Intussuscipiens:Receiving loop
• 90% ileocolic
Intussusceptum
Intussuscipiens
Clinical Features• Vomiting: bilious or non-bilious
• Colicky abdominal pain
• Irritable or lethargic
• RLQ mass
• “Currant jelly” stool or guaiac positive• Late finding
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AXR: Intussusception
• Findings• No bowel gas in RLQ• Target sign• Meniscus sign
• Accuracy 40-90%• Misses 30% of cases
• Detect Pneumoperitoneum
US: Intussusception
• US is the imaging modality of choice• Sensitivity: 97-100% • Specificity 88-100%
• Ileocolic intussusceptions • Subhepatic• Size> 2.5 cm
Transverse Orientation
Target or Donut
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Longitudinal Orientation
Sandwich or Pancake Sign
Pseudo-kidney Sign
https://i.ytimg.com/vi/1zonru8G0M4/hqdefault.jpg
https://classconnection.s3.amazonaws.com/944/flashcards/1224944/jpg/pseudokidney1344048300884.jpg
https://sonokids.wordpress.com
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Small-bowel Intussusception
• Smaller
• Transient
• Asymptomatic
Scanning Technique
https://sonokids.wordpress.com
Novice sonographers can diagnose intussusception
• Physicians received 1-hr didactic session (6 PEM)
• 82 patients were enrolled, 16% diagnosed with ileocolic intussusception
• Performance characteristics• Sensitivity 85%, Specificity 97%• PPV 85%, NPV 97%
• POCUS can be used as a rule in test; negative findings may warrant further imaging or observation
Riera, A, et. al. Ann Emerg Med. 2012; 60(3) 264-268
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Pearls/Pitfalls• Scan in a systematic fashion
• Lawn mower vs follow the colon
• Repeat US if there is a high clinical suspicion• Intussusception may be intermittent
• Recognize pseudo-kidney sign
• Mimics• Bowel wall thickening: IBD, Intramural hematoma • Psoas muscle, Stool
Case
• 9 yo boy presents with fever, HA, and abd pain
• Nausea and anorexia, Vomited x 1
• Abdomen firm, but no focal tenderness
Appendicitis
• Most common surgical emergency in children• 60-80K cases annually
• Diagnosis in young children is often delayed with higher rates of perforation
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Clinical Symptoms• Periumbilical pain
• Migratory pain
• Nausea
• Anorexia
Less than 50% of patients present with classic symptoms
US for Appendix• Study characteristics
• Sensitivity 44-90%• Specificity 88-100%
• Limitations• Operator dependent• Body habitus• Difficulty visualizing a normal appendix• Location is not fixed
Location
• Attaches at base of the cecum
• Tip can be found in different positions
• Retro-cecal and extra-peritoneal locations have less abdominal pain
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Normal Sono-anatomy
• Ovoid
• Aperistaltic
• Blind ending
• Central echogenicity• Air-filled• Apposition of mucosal
layer
Sono:Appendicitis
• Diameter > 6 mm
• Non-compressible
• Target or round
• +/-appendicolith
• Periappendiceal inflammation
Appendicitis
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Choosing your approach
• Point of maximal pain
• Follow the ascending colon to the cecum
• Landmark
• Retrocecal appendix• Left lateral decubitus position• Interrogate the right flank
Choosing your approach
• Point of maximal pain
• Follow the ascending colon to the cecum
• Landmark
• Retrocecal appendix• Left lateral decubitus position• Interrogate the right flank
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Sono-anatomy RLQ
P
Choosing your approach
• Point of maximal pain
• Follow the ascending colon to the cecum
• Landmark
• Retrocecal appendix• Left lateral decubitus position• Interrogate the right flank
Secondary Signs
• Free fluid• Echogenic fat• Hyperemia• Abnormal LN• Abnormal bowel• Bowel wall edema• Appendicolith
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• Assess accuracy of EP performed POCUS
• Sensitivity 65% (52-76%)
• Specificity 90% (81-95)
• Trained PEM physicians can accurately diagnose acute appendicitis
• Sensitivity 85% (75-95%)
• Specificity 93% (85-100%)
• Similar accuracy to radiology studies
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Pearls• Provide appropriate analgesia prior to scanning
• Scan in systematic fashion
• Image entire length of the appendix
• Perforated appendix may not be visualized
• Look for secondary signs of appendicitis• FF, Peri-appendiceal fat, Phlegmon
Pitfalls• Appendix > 6 mm with normal anatomy
• Other inflammatory process• IBD, PID
• Mimics: LN, TI
• Not visualizing the complete appendix • Tip appendicitis 10%
Case
• 26-day-old male vomiting after feeds
• Episodes described as projectile with vomitus coming out of mouth and nose
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HPS:Background
• Most common cause of gastric outlet obstruction in infants
• 3/100 live births• Males (first born) are 5 x more affected• 2nd-6th week of life
• Non-bilious emesis with each feed eventually becomes projectile
Clinical Characteristics
• Physical exam • Palpable olive• Peristaltic wave
• Metabolic abnormalities• Hypokalemic, hypochloremic metabolic alkalosis• Paradoxical aciduria
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Peristaltic Wave
NEJM video January 14, 2014
Imaging for HPS
• US introduced by Teele in 1977
• Study Characteristics• Sens 95%; Spec 95%
• Fixed abdominal location
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Sonographic Features• Muscle wall thickness
• > 3 mm (4 mm)
• Channel length • > 14 mm (17 mm)
• Absent peristalsis of pyloric muscle
• Little or no movement of stomach contents into duodenum
TARGET
HOT DOG
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Scanning Technique
• High frequency linear transducer
• Positioning• Supine or right-lateral decubitus position
• Graded compression
• Feed during study• Acoustic window to visualize the pylorus
Locating the Pylorus
• Trained PEM physicians can accurately assess for presence of pyloric stenosis
• Sensitivity 100%, Specificity 100%
• Similar measurements with radiology studies
Acad Emerg Med. 2013; 20:646–651
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Pearls• Place in right lateral decubitus and feed while
scanning
• No fluid passes through the channel and no muscle relaxation
• HPS is an evolving process and should warrant re-examination if typical symptoms persist
• Measure in perpendicular plane
Probe Orientation
Pitfalls• False-negative
• Gastric overdistention: displaces pylorus posteriorly
• False positive • Gastric decompression: pseudo-thickening
of the pylorus muscle • Probe orientation • Pylorospasm
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Take home points…• US can evaluate undifferentiated abdominal pain
• Decrease use of plain radiographs• Expedite care of patients with US findings• Avoid CT in low risk patients
• Scan in a systematic fashion
• Repeat US study if there is a high clinical suspicion
Questions?