Clinical scenario 4: Lucian

Next to be seen is Lucian, a six week old male infant presenting with projectile non-bilious vomiting after feeds for the past two weeks, now increasing in frequency. Lucian’s mother has noted a macular rash on his chest and a wrinkly appearance of his skin.

The following six questions refer to Lucian's clinical scenario.

Question 18

Which one of the following is the most likely diagnosis?
Acute gastroenteritis
Cow’s milk protein intolerance
Hypertrophic pyloric stenosis
Gastro-esophageal reflux
Biliary atresia
Check answer

Explanation

The history is highly suggestive of hypertrophic pyloric stenosis.

Question 19

Which of the following features is LEAST typical for pyloric stenosis?
Male gender
Lucian's age
Macular rash
Projectile non-bilious vomiting
Wrinkly skin
Check answer

Explanation

Macular rash is a non-specific rash not typically associated with pyloric stenosis. Pyloric stenosis typically presents between two and seven weeks of age, irrespective of gestational age. It is more common in boys (4:1), particularly first-borns.

Signs include projectile non-bilious vomiting after feeds, increasing in frequency and severity, thus potentially leading to marked dehydration (reduced skin turgor=wrinkly skin).

Question 20

On examination, you find Lucian is crying and generally unsettled, with reduced skin turgor. Which one of the following is the LEAST likely clinical feature you might encounter?

Weight loss or poor weight gain
Hypochloraemic acidosis
Hypochloraemic alkalosis and low plasma potassium
Gastric peristalsis “wave moving from left to right across the abdomen”
Palpable “olive” in right upper quadrant
Check answer

Explanation

Answer: Hypochloraemic acidosis is the least likely. Typically a patient with pyloric stenosis presents with hypochloraemic alkalosis from vomiting acid stomach contents. While the potassium is sometimes low, if there is a prolonged history, it is often normal in spite of vomiting.

Weight loss or poor weight gain may be present if presentation is delayed. Gastric peristalsis may be seen as a “wave moving from left to right across the abdomen” after the infant has been given a test feed. The palpable “olive” in right upper quadrant is the pyloric mass.

Question 21

This is the venous blood gas.

What is the most important next step in managing Lucian’s condition?
Test feed, which will calm the hungry infant, allowing examination
Insert oro-gastric tube to deflate stomach
Ultrasound examination to confirm the diagnosis
Correct the biochemical abnormalities
Barium meal
Check answer

Explanation

Once you have addressed the biochemical abnormalities, the other options outlined would be reasonable.

Lucian presents in a delayed manner (signs of dehydration). Delay in diagnosis can lead to continuous vomiting, dehydration, electrolyte imbalance and death. Initial management of Lucian’s condition is intravenous fluid resuscitation to correct any fluid and electrolyte disturbances. The chloride and potassium deficits should be replaced.

Question 22

You have successfully inserted an intravenous cannula and given IV fluids. You have been lucky to obtain an urgent abdominal ultrasound, which has confirmed hypertrophic pyloric stenosis. Which of the following is an estimate measurements to diagnose hypertrophic pyloric stenosis?
Pyloric muscle wall thickness > 3 mm
Pyloric canal length 14–20 mm
Pylorus diameter > 12 mm
All of the above
Check answer

Explanation

All are correct. Current imaging techniques, particularly sonography, is safe, accurate and gives quick diagnosis of hypertrophic pyloric stenosis. The sonographic criteria for positive hypertrophic pyloric stenosis are pyloric muscle wall thickness > 3 mm, pyloric canal length 14–20 mm, pylorus diameter > 12 mm.

Question 23

Which one of the following is the next best step in Lucian’s management?

Call the surgical registrar because you think Lucian needs a pyloromyotomy
Continue maintenance IV fluids and reassess after four hours
Complete septic work up
Continue half maintenance IV fluids and test feed
Test feed via orogastric tube
Check answer

Explanation

The definite treatment is a pyloromyotomy, when the muscle, not the mucosa, is cut. The operation can be performed through a variety of incisions, including through the umbilicus or laparoscopically. Postoperatively, Lucian can be fed the next day and discharged within two-to-three days of surgery.

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