When Milk Won’t Pass

Written by: Dr. Khin Oo 

Edited by: Dr. Joann Hsu

Case: 

A 5 week old female ex-full term, twin birth, presenting with vomiting and diarrhea for the past few days.

Patient’s mother described that the diarrhea continued and despite giving her formula or Pedialyte, 2 oz every 2 hours, and the baby vomited every single time, a large amount. Patient was not tolerating PO today.  Last urine was this morning. The patient was described to be hungry after each vomit.

Physical exam is unremarkable.

Vitals:

BP 96/46 |   HR 144  |  T 37.4 C  |  SpO2 100% RA 

Using a linear ultrasound probe a flat footprint to create high-resolution images of shallow or surface-level structures in children, let’s take a look at what we saw on the epigastric and RUQ region in transverse and sagittal views:

Figure 1: sagittal view

Figure 2: transverse view

What do you see? 

  • You see the fluid-filled antrum of the stomach and following it distally, you see the pylorus.

  • Long axis view of the pyloric muscle highlighted by arrows at the distal end of the stomach

  • In between the thickened hypoechoic pyloric muscles (muscularis externa) is the hyperechoic pyloric channel made up of gastric mucosa.

Figure 3: Hypertrophied pyloric muscle in long axis

Figure 4: Hypertrophied pyloric muscle in short axis 

Tip: Identify known landmarks if you have trouble locating the pylorus 

  • Find the gallbladder adjacent to the medial edge of the liver and look even more medially to locate the pylorus.

  • Alternatively, find the fluid-filled stomach and follow it distally to the pylorus.

  • Use the aorta/ superior mesenteric artery as additional landmarks if necessary (pylorus is anterior to them).

Pyloric Muscle Thickness

  • Thickness of the pyloric muscle can be measured in the long or short axis view

  • Pyloric muscle thickness, i.e. diame­ter of a single muscular wall (hypoechoic component)

  • Hypertrophied pyloric muscle in short axis measuring 3.8 mm

  • A thickness of 3 mm is considered abnormal or hypertrophied

Figure 5: Hypertrophied pyloric muscle in short axis measuring 3.8 mm

Pyloric Transverse Diameter

  • Pyloric transverse diameter measuring 13.8 mm

  • Pyloric transverse diameter >14 mm considered abnormal or hypertrophied

Figure 5: Pyloric diameter in short axis measuring 13.8 mm 

Pyloric Channel 

  • Pyloric channel measuring 19.1 mm

  • Length, i.e. longitudinal measurement of >15-17 mm considered abnormal or elongated 

Figure 6: Elongated Pyloric channel in long axis 19.1 mm 

The "Pi" Breakdown (π = 3.1415) :

  • 3 — Pyloric muscle thickness: Greater than 3 mm (measured as a single muscular wall on a transverse ultrasound image).

  • 14 — Transverse diameter: Greater than or equal to 14 mm (wall-to-wall transverse measurement).

  • 15 — Pyloric length: Greater than 15 mm (longitudinal channel measurement, sometimes noted up to 15–17 mm

Based on the patient’s ultrasound findings, the appearance is consistent with a pyloric stenosis 

Key Sonographic Signs 

  1. Target Sign - echogenic mucosa surrounding thickened pyloric hypoechoic muscle

  2. Antral nipple sign- redundant pyloric mucosa protruding into the gastric antrum

  3. Cervix sign - indentation of the elongated, narrow pylorus canal into the fluid-filled antrum. The most telling sign, however, was that no gastric contents were seen to pass through the pylorus at any time during the examination.

Figure 7: Target Sign 

Figure 8: Antral Nipple Sign 

Figure 9: Cervix Sign  

Pyloric Stenosis

  • Hypertrophic pyloric stenosis is an idiopathic, acquired condition generally presenting at 2-12 weeks of age.

  • Caused by hypertrophy of the circular muscle of the pylorus, causing gastric outlet obstruction.

  • Classic findings:  projectile non-bilious vomiting, palpable “olive” at the epigastrium, and hypochloremic metabolic alkalosis in bloodwork

  • Ultrasound is the gold standard in diagnosis, with sensitivity 97-100% and specificity 99-100%

  • Initial medical management is essential with rehydration and correction of electrolyte imbalances. This should be completed before surgical intervention.

  • Treatment is surgical with a pyloromyotomy in which the pyloric muscle is divided down to the submucosa. This can be performed both open and laparoscopically. The operation is curative.

Back to the Case

  • US shows pyloric channel is thickened, measuring up to 5 mm with an elongated channel measuring up to 1.8 cm. Gastric contents are not seen passing through the pylorus.

  • Surgery was consulted.

  • The patient was admitted PIMU under the surgical service with for operative treatment

  • Started the patient on 1 x M IV fluids


Take Home Points

  • Use π = 3.1415, 3 for Pyloric muscle thickness, 14 for Transverse diameter and 15 for Pyloric length

  • Hypertrophic pyloric stenosis is an idiopathic, acquired condition generally presenting at 2-12 weeks of age.

  • Try feeding the child and follow the stomach contents as it moves through the pylorus

Happy scanning!

References

https://www.acep.org/sonoguide/advanced/pediatric-pyloric-stenosis

https://radiopaedia.org/cases/infantile-hypertrophic-pyloric-stenosis

https://radiopaedia.org/articles/pyloric-stenosis-1?lang=us

https://radiopaedia.org/articles/cervix-sign-pyloric-stenosis?lang=us

https://radiopaedia.org/cases/pyloric-stenosis#image-207

NYPQ