11/14/24, 10\:48 AM Pyloric Stenosis

Pyloric Stenosis

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Pyloric stenosis\: thickening of the pyloric muscle, narrowing the opening between the stomach and small intestine,
causing gastric outlet obstruction; incidence 1-3 per 1000 live births.
Aetiology\: hypertrophy of the circular and longitudinal muscle layers in the pylorus, narrowing the lumen and causing
postprandial projectile vomiting; possible neurogenic cause linked to nitric oxide synthase gene.
Risk factors\: more common in males,
Symptoms\: non-bilious projectile vomiting between 2-6 weeks of age, weight loss or failure to thrive, constipation, lethargy,
haematemesis from oesophagitis.
Clinical
epigastrium (often di
Di
malrotation causes bilious vomiting).
Investigations\:
Bedside\: test feed with dextrose water to palpate pyloric mass.
Laboratory\: blood gas (hypochloraemic hypokalaemic metabolic alkalosis), U&Es (monitor electrolytes).
Imaging\: abdominal ultrasound (pyloric muscle >4mm thick, length >18mm, obstruction preventing
Other\: contrast studies showing 'string sign'
.
Diagnosis\: presence of a pyloric mass on examination or con
Management\:
Medical\: nasogastric tube insertion, preoperative rehydration, and correction of electrolyte abnormalities.
Surgical\: Ramstedt’s pyloromyotomy, longitudinal incision of the hypertrophic pyloric muscle, leaving the defect open for a
wider passage to the duodenum.
Complications\:
Pre-operative\: electrolyte abnormalities, dehydration.
Surgical\: perforation, haemorrhage, post-operative infection.
Prognosis\: good, most patients experience no long-term complications post-surgery.
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Introduction

Pyloric stenosis describes a thickening of the pyloric muscle. This results in the narrowing of the opening between the
stomach and the small intestine, which can cause complete obstruction of the gastric outlet.
The incidence of pyloric stenosis varies between countries and is between 1-3 per 1000 live births.
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Aetiology

In pyloric stenosis, there is hypertrophy of the circular and longitudinal muscle layers in the pylorus. This hypertrophy
narrows the lumen of the gastric outlet. The length of the pylorus also increases. Over time, the lumen will become
obstructed, resulting in the postprandial projectile vomiting classically associated with the condition.
The cause of pyloric stenosis is unclear. However, there is evidence to support a neurogenic cause and a link with the
neuronal nitric oxide synthase gene.

Risk factors

There are no strongly associated risk factors of pyloric stenosis. However, it is more common in males,
with a family history of the condition.

Clinical features

History

The most typical presentation of pyloric stenosis is non-bilious vomiting, which occurs between 2-6 weeks of age. Parents
often describe this as projectile vomiting.
This prolonged vomiting can result in weight loss or failure to thrive, constipation, lethargy and haematemesis caused by
oesophagitis.
For more information, see the Geeky Medics guide to paediatric history taking.

Clinical examination

Typical clinical
Dehydration
Thin but hungry
Visible gastric peristalsis
Palpable pyloric mass in the epigastrium (often di

Di

The main di
Gastroesophageal re
Malrotation
These two di
causes bilious vomiting.

Investigations

Bedside investigations

Relevant bedside investigations include\:
Test feed with dextrose water\: this causes the pylorus to contract, making an epigastric mass more obvious on
examination. This may also result in projectile vomiting. If the pylorus was palpable from this test feed, no further
imaging is required, and the diagnosis can be con

Laboratory investigations

Relevant laboratory investigations include\:
Blood gas\: this will show hypochloraemic hypokalaemic metabolic alkalosis caused by the loss of
chloride through excessive vomiting
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U&Es\: this is vital to monitor electrolytes, which will likely be deranged from dehydration

Imaging

Relevant imaging investigations include\:
Abdominal ultrasound\: to meet the requirements for diagnosing pyloric stenosis on ultrasound, the pyloric muscle must
be over 4mm in thickness, the pyloric muscle length must be over 18mm, and there must be an obstruction preventing
the passage of
Figure 1. Abdominal ultrasound
demonstrating pyloric stenosis in a 6-
week-old.

Other investigations

If the previous investigations have been inconclusive, contrast studies can be undertaken, demonstrating a 'string
sign' due to the thin long pylorus. This study can also be useful in identifying malrotation.

Diagnosis

There are no set criteria for diagnosing pyloric stenosis. The diagnosis is made by the presence of a pyloric mass on
examination or abdominal ultrasound (see ultrasound criteria above).

Management

Patients with pyloric stenosis require both medical and surgical management.

Medical management

Medical management includes\:
Nasogastric tube insertion\: this decompresses the stomach and allows accurate recording & replacement of gastric
losses
Preoperative rehydration and correction of electrolyte abnormalities\: this should consist of initial
sodium chloride, IV maintenance
replacement

Surgical management

The de
muscle
the incision and providing a wider passage between the pylorus and the duodenum.
Figure 2. Surgical scar following pyloric
stenosis surgery
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Complications

Complications of pyloric stenosis (pre-operatively) include\:
Electrolyte abnormalities
Dehydration
Surgical complications include perforation, haemorrhage and post-operative infection. The prognosis of pyloric stenosis is
good, with most patients experiencing no long-term complications following surgical repair.

References

Harper, Sciences.
S.J. and Saeb-Parsy, K., 2013. E s s e n t i a l S u r g e r y E-B o o k \: P r o b l e m s , D i a gn o s i s a n d M a n a g e m e n t . Elsevier Health
John M. Hutson, et al. J o n e s' C l i n i c a l P a e d i a t r i c S u r g e r y \: D i a gn o s i s a n d M a n a g e m e n t . 2008. J o h n W i l e y & S o n s
Gar
Publishing; 2022. Available from\: [LINK]

Image references

Figure 1. Dr Laughlin Dawes. Pyloric stenosis as seen on ultrasound in a 6 week old. License\: [CC BY-SA]
Figure 2. Kiu77. PyloricStenosisHorizontal. License\: [CC BY-SA]

Reviewer

Paediatric registrar

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Contents

Introduction
Aetiology
Risk factors
Clinical features
Di
Investigations
Diagnosis
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