Hypertrophic pyloric stenosis

Case contributed by Rad_doc

Presentation

4-week-old male with projectile vomiting and poor weight gain.

Patient Data

Age: 1 month
Gender: Male

Focused Ultrasound of the Upper Abdomen

Modality: Ultrasound

Hypertrophied hypoechoic pylorus.

Normal comparison demonstrates a normal sized pylorus.

Cine views (not provided) demonstrate that no fluid passes through the pylorus.

Diagram

Modality: Diagram

After taking a look at this diagram, switch back to the ultrasound images and make sure you understand the anatomy here. 

Occasionally, young patients with vomiting may undergo abdominal radiography as part of their evaluation, especially if they are being evaluated at an institution without experienced pediatric sonographers to perform a pylorus ultrasound (which can be a challenging study to perform).

Plain Radiograph of the Abdomen

Modality: X-ray

Marked gaseous distention of stomach with the so-called "caterpillar sign." This occurs from gastric contractions against a hypertrophied, obstructing pylorus. Stool and gas identified in non-dilated small bowel and colon.

When obtaining patient history from the patient's mother, she thought that some of the vomit was "green tinged." 

As previously discussed, bilious vomiting changes your differential diagnosis and an upper GI would be the next study to further evaluate this patient. Typically, emesis in the setting of hypertrophic pyloric stenosis looks like stomach contents (eg formula or breast milk), rather than bilious, since the obstruction is proximal to the ampulla of Vater.

Also, at hospitals without readily available experienced ultrasonographers, the patient may undergo upper GI evaluation to confirm HPS prior to surgery or transfer to a dedicated pediatric specific.

Upper GI Study

Modality: Fluoroscopy

Contrast administered through the NG tube pools in the distal stomach.

Small streak of contrast passes through a narrowed pyloric channel. This is the so-called "string sign." 

Clinical followup:

Patient was admitted to the inpatient unit, rehydrated, and laboratory abnormalities corrected. Laparoscopic evaluation confirmed the diagnosis of Hypertrophic Pyloric Stenosis and patient underwent pyloromyotomy.

Case Discussion

Hypertrophic pyloric stenosis: 

The patient's clinical presentation is a common one in paediatrics with a wide differential diagnosis. In this case, the ultrasonographic findings of a hypertrophied pylorus with no passage of gastric contents cinches the diagnosis of hypertrophic pyloric stenosis (HPS). There is an additional bonus of having an upper GI series which demonstrates suggestive findings including an elongated narrow pyloric channel ("string sign") and pooling of contrast in the distal stomach. Most patients with abdominal complaints (pain, vomiting, etc) will get a plain radiograph of the abdomen. Unfortunately, plain film is usually non specific in HPS but may be suggestive of hypertrophic pyloric stenosis when a distended stomach and a paucity of distal bowel gas are identified.

In pediatric patients presenting with vomiting, the first question that you should ask is "billious or not". Unfortunately, differentiating non-billious from billious vomit is hard! So, it is not uncommon for patients with HPS to undergo an Upper GI Study based on history from mother of yellow'ish appearing vomit in order to evaluate for possible midgut malrotation and volvulus.

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Case Information

rID: 46342
Case created: 1st Jul 2016
Last edited: 1st May 2017
Inclusion in quiz mode: Included

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