eMedicine Specialties > Radiology > Pediatrics

Hypertrophic Pyloric Stenosis: Imaging

Author: Janet R Reid, MD, FRCP(C), Associate Professor of Radiology, Section Head of Pediatric Radiology, Children's Hospital of Cleveland Clinic
Contributor Information and Disclosures

Updated: Aug 3, 2009

Radiography

Findings

Abdominal radiographs may show a fluid-filled or air-distended stomach, suggesting the presence of gastric outlet obstruction. A markedly dilated stomach with exaggerated incisura (caterpillar sign) may be seen, which represents increased gastric peristalsis in these patients (see Image 1). If the patient has recently vomited or has a nasogastric tube in place, the stomach is decompressed and the radiographic findings are normal.

Supine radiograph in an infant with vomiting demo...

Supine radiograph in an infant with vomiting demonstrates the caterpillar sign.

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Supine radiograph in an infant with vomiting demo...

Supine radiograph in an infant with vomiting demonstrates the caterpillar sign.

A UGI study was once considered the test of choice for hypertrophic pyloric stenosis (HPS). Findings on UGI studies include the following:

  • Delayed gastric emptying (if severe, this may prevent barium from passing into the pylorus and severely limit the study)
  • Cephalic orientation of the pylorus
  • Shouldering (ie, filling defect at the antrum created by prolapse of the hypertrophic muscle)
  • Mushroom or umbrella sign (ie, thickened muscle that indents the duodenal bulb; the name refers to the impression made by the hypertrophic pylorus on the duodenum)
  • Double-track sign (ie, redundant mucosa in the narrowed pyloric lumen, which results in separation of the barium column into 2 channels) (see Image 5)


Lateral view from an upper gastrointestinal study...

Lateral view from an upper gastrointestinal study demonstrates the double-track sign.

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Lateral view from an upper gastrointestinal study...

Lateral view from an upper gastrointestinal study demonstrates the double-track sign.

  • String sign (ie, barium passing through the narrowed channel, creating a single, markedly attenuated, and elongated track) (see Image 6)


Upper gastrointestinal study from a child shows t...

Upper gastrointestinal study from a child shows the string sign (see inset).

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Upper gastrointestinal study from a child shows t...

Upper gastrointestinal study from a child shows the string sign (see inset).


  • Pyloric tit (ie, outpouching created by distortion of the lesser curve by the hypertrophied muscle)
  • Retained secretions and retrograde peristalsis

Degree of Confidence

Plain film radiography provides a low degree of confidence in making the diagnosis of or in ruling out HPS. A UGI study has high sensitivity (>90%) and low specificity.

False Positives/Negatives

High intestinal obstruction can be seen with midgut volvulus, duodenal obstruction (from stenosis, duodenal web, annular pancreas), gastric outlet obstruction caused by focal foveolar hyperplasia, and eosinophilic gastroenteritis, among others. False-negative radiographs can be seen in a child who has recently vomited.

Ultrasonography

Findings

Although a false-negative clinical diagnosis causes diagnostic delay, a false-positive diagnosis results in a negative laparotomy. Therefore, imaging has become more important in the diagnosis of HPS. US is the method of choice for both the diagnosis and exclusion of HPS because this modality has a sensitivity and specificity of approximately 100%.14,15 US is recommended in patients whose disease is clinically suspected but in whom the pyloric olive cannot be felt.9,14,16,17,18,19

US is performed with a 7.5- to 13.5-MHz linear transducer in the supine child. Transverse images at the epigastrium identify the pylorus to the left of the gallbladder and anteromedial to the right kidney. A distended stomach, however, displaces and distorts the pylorus and may require the placement of a nasogastric tube to withdraw the stomach's contents. A gastric aspirate of more than 5 mL in a baby who has been without oral intake (NPO) for several hours indicates gastric outlet obstruction. Right posterior oblique positioning and scanning from a posterior approach may help to improve visualization of the pylorus.20

US signs of HPS, originally described in 197721 and further defined, are as follows:

  • MT (serosa to mucosa) greater than 3 mm (a correlation between MT and the patient's age exists; the most reliable US sign is an MT greater than 3 mm. Because this measurement can be increased falsely with off-axis imaging, attention to technique is important.)
  • Target sign on transverse images of the pylorus (see Image 3)


Transverse sonographic image in a patient with pr...

Transverse sonographic image in a patient with proven hypertrophic pyloric stenosis demonstrates the target sign and heterogeneous echo texture of the muscular layer (pylorus is deep to the anechoic gallbladder).

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Transverse sonographic image in a patient with pr...

Transverse sonographic image in a patient with proven hypertrophic pyloric stenosis demonstrates the target sign and heterogeneous echo texture of the muscular layer (pylorus is deep to the anechoic gallbladder).


  • Pyloric channel length greater than 17 mm
  • Pyloric thickness (serosa to serosa) of 15 mm or greater
  • Failure of the channel to open during a minimum of 15 minutes of scanning
  • Retrograde or hyperperistaltic contractions
  • Antral nipple sign22 (ie, a prolapse of redundant mucosa into the antrum, which creates a pseudomass) (see Image 4)


Longitudinal sonogram in a patient with hypertrop...

Longitudinal sonogram in a patient with hypertrophic pyloric stenosis demonstrates a redundant mucosa that creates the antral nipple sign.

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Longitudinal sonogram in a patient with hypertrop...

Longitudinal sonogram in a patient with hypertrophic pyloric stenosis demonstrates a redundant mucosa that creates the antral nipple sign.


  • US double-track sign23,24 (ie, redundant mucosa in the narrowed lumen, which creates 2 mucosal outlines) (see Image 5)


Lateral view from an upper gastrointestinal study...

Lateral view from an upper gastrointestinal study demonstrates the double-track sign.

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Lateral view from an upper gastrointestinal study...

Lateral view from an upper gastrointestinal study demonstrates the double-track sign.


  • Other findings - Reversible portal venous gas; nonuniform echogenicity of the pyloric muscle (see Image 3)

Degree of Confidence

A positive HPS finding by US almost always indicates HPS. A negative examination can be false in a patient who is seen early in the disease or in a younger patient whose MT is less than 3 mm.

False Positives/Negatives

The diagnostic accuracy of US for HPS is high. Sensitivity and specificity approach 100%.14,15 Possible sources of false negatives (see Limitations of Techniques) are an overdistended stomach (the pylorus is hidden behind the antrum), failure to identify the pylorus (eg, operator inexperience in performing US for evaluation of HPS), and a small infant or early presentation. Another possible source for a false-positive finding is pylorospasm (typically transient).

Nuclear Imaging

Findings

Nuclear medicine scanning is not routinely used for HPS; however, possible findings include delayed gastric emptying.

Degree of Confidence

The degree of confidence is poor.

False Positives/Negatives

Nuclear medicine scanning has a high sensitivity but low specificity for HPS.

More on Hypertrophic Pyloric Stenosis

Overview: Hypertrophic Pyloric Stenosis
Imaging: Hypertrophic Pyloric Stenosis
Follow-up: Hypertrophic Pyloric Stenosis
Multimedia: Hypertrophic Pyloric Stenosis
References
Further Reading
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References

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  2. Sommerfield T, Chalmers J, Youngson G, Heeley C, Fleming M, Thomson G. The changing epidemiology of infantile hypertrophic pyloric stenosis in Scotland. Arch Dis Child. Dec 2008;93(12):1007-11. [Medline].

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  11. Mandell GA, Wolfson PJ, Adkins ES, et al. Cost-effective imaging approach to the nonbilious vomiting infant. Pediatrics. Jun 1999;103(6 Pt 1):1198-202. [Medline]. [Full Text].

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  14. Hernanz-Schulman M, Sells LL, Ambrosino MM, et al. Hypertrophic pyloric stenosis in the infant without a palpable olive: accuracy of sonographic diagnosis. Radiology. Dec 1994;193(3):771-6. [Medline]. [Full Text].

  15. Stunden RJ, LeQuesne GW, Little KE. The improved ultrasound diagnosis of hypertrophic pyloric stenosis. Pediatr Radiol. 1986;16(3):200-5. [Medline].

  16. Blumer SL, Zucconi WB, Cohen HL, Scriven RJ, Lee TK. The vomiting neonate: a review of the ACR appropriateness criteria and ultrasound's role in the workup of such patients. Ultrasound Q. Sep 2004;20(3):79-89. [Medline].

  17. Rohrschneider WK, Mittnacht H, Darge K, Tröger J. Pyloric muscle in asymptomatic infants: sonographic evaluation and discrimination from idiopathic hypertrophic pyloric stenosis. Pediatr Radiol. Jun 1998;28(6):429-34. [Medline].

  18. Sorantin E, Fotter R, Schimpl G. Reversible portal venous gas in hypertrophic pyloric stenosis: detection by ultrasound. J Ultrasound Med. Sep 1995;14(9):699-701. [Medline].

  19. Spevak MR, Ahmadjian JM, Kleinman PK, et al. Sonography of hypertrophic pyloric stenosis: frequency and cause of nonuniform echogenicity of the thickened pyloric muscle. AJR Am J Roentgenol. Jan 1992;158(1):129-32. [Medline]. [Full Text].

  20. Sargent SK, Foote SL, Mooney DP, Shorter NA. The posterior approach to pyloric sonography. Pediatr Radiol. Apr 2000;30(4):256-7. [Medline].

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  22. Hernanz-Schulman M, Dinauer P, Ambrosino MM, Polk DB, Neblett WW 3rd. The antral nipple sign of pyloric mucosal prolapse: endoscopic correlation of a new sonographic observation in patients with pyloric stenosis. J Ultrasound Med. Apr 1995;14(4):283-7. [Medline].

  23. Cohen HL, Blumer SL, Zucconi WB. The sonographic double-track sign: not pathognomonic for hypertrophic pyloric stenosis; can be seen in pylorospasm. J Ultrasound Med. May 2004;23(5):641-6. [Medline].

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  32. Oue T, Puri P. Abnormalities of elastin and elastic fibers in infantile hypertrophic pyloric stenosis. Pediatr Surg Int. 1999;15(8):540-2. [Medline].

  33. Oue T, Puri P. Smooth muscle cell hypertrophy versus hyperplasia in infantile hypertrophic pyloric stenosis. Pediatr Res. Jun 1999;45(6):853-7. [Medline]. [Full Text].

  34. Taylor MT, Lawson KR, Ignatenko NA, et al. Sulindac sulfone inhibits K-ras-dependent cyclooxygenase-2 expression in human colon cancer cells. Cancer Res. Dec 1 2000;60(23):6607-10. [Medline]. [Full Text].

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Further Reading

Related eMedicine topics

Pediatrics, Pyloric Stenosis (Emergency Medicine)

Pyloric Stenosis, Hypertrophic (Pediatrics)

Hypertrophic Pyloric Stenosis, Surgical Treatment (Pediatrics)

Evidence based clinical practice guideline hypertrophic pyloric stenosis. Cincinnati Children's Hospital Medical Center - Hospital/Medical Center.  2001 Aug 8 (revised 2007 Nov 4).  17 pages.  NGC:006224

Clinical guidelines

ACR Appropriateness Criteria® vomiting in infants up to 3 months of age. American College of Radiology - Medical Specialty Society.  1995 (revised 2005).  7 pages. [NGC Update Pending] NGC:004792

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Keywords

idiopathic hypertrophic pyloric stenosis, infantile hypertrophic pyloric stenosis, pyloric stenosis, HPS, IHPS, projectile vomiting, nonbilious infantile projectile vomiting

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Contributor Information and Disclosures

Author

Janet R Reid, MD, FRCP(C), Associate Professor of Radiology, Section Head of Pediatric Radiology, Children's Hospital of Cleveland Clinic
Janet R Reid, MD, FRCP(C) is a member of the following medical societies: American Association for Women Radiologists, American Society of Neuroradiology, Ohio State Medical Association, Radiological Society of North America, Royal College of Physicians and Surgeons of Canada, and Society for Pediatric Radiology
Disclosure: Nothing to disclose.

Medical Editor

Robert J Starshak, MD, Medical Director, Assistant Clinical Professor, Department of Radiology, Medical College of Wisconsin, Falls Medical Group
Disclosure: Nothing to disclose.

Pharmacy Editor

Bernard D Coombs, MB, ChB, PhD, Consulting Staff, Department of Specialist Rehabilitation Services, Hutt Valley District Health Board, New Zealand
Disclosure: Nothing to disclose.

Managing Editor

David A Stringer, MBBS, FRCR, FRCPC, Professor, National University of Singapore; Head, Diagnostic Imaging, KK Women's and Children's Hospital, Singapore
David A Stringer, MBBS, FRCR, FRCPC is a member of the following medical societies: British Columbia Medical Association, Canadian Association of Radiologists, European Society of Paediatric Radiology, Ontario Medical Association, Radiological Society of North America, Royal College of Physicians and Surgeons of Canada, Royal College of Radiologists, and Society for Pediatric Radiology
Disclosure: Sirius d'innovation None Board membership

CME Editor

Robert M Krasny, MD, Resolution Imaging Medical Corporation
Robert M Krasny, MD is a member of the following medical societies: American Roentgen Ray Society and Radiological Society of North America
Disclosure: Nothing to disclose.

Chief Editor

John Karani, MBBS, FRCR, Clinical Director of Radiology and Consultant Radiologist, Department of Radiology, King's College Hospital, London
John Karani, MBBS, FRCR is a member of the following medical societies: British Institute of Radiology, British Society of Interventional Radiology, Cardiovascular and Interventional Radiological Society of Europe, European Society of Gastrointestinal and Abdominal Radiology, European Society of Radiology, Radiological Society of North America, and Royal College of Radiologists
Disclosure: Nothing to disclose.

 
 
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