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

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

Small Bowel Obstruction

• Dilated bowel > 2.5 CM

• Peristalsis (To/fro)

• Bowel wall thickening >3 mm

• Keyboard sign

• Tanga sign

Tanga Sign

Technique: Lawn Mower

• 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

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

• 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

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

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

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

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

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

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

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

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

• 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

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

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

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

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

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

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

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?