Pyloric stenosis
Updates to Article Attributes
Hypertrophic pyloric stenosis (HPS) refers to the idiopathic thickening of gastric pyloric musculature which then results in progressive gastric outlet obstruction.
Epidemiology
Pyloric stenosis is relatively common and has a male predilection (M:F ~4:1), and is more commonly seen in Caucasians 4. ItWhile symptoms may start as early as 3 weeks, it typically occurs between the first week6 to 3 months12 weeks of age. ThereFirst born children are at higher risk and there may be a positive family history in some cases.
Incidence of hypertrophic pyloric stenosis is approximately 2-5 per 1,000 births per year in most white populations. HPS is less common in India and among black and other Asian populations.
Clinical presentation
Clinical presentation is typical with non-bilious projectile vomiting. The hypertrophied pylorus can be palpated as an olive-sized mass in the right upper quadrant. A succussion splash may be audible, and although common, is only relevant if heard hours after the last meal 6.
Risk factors
- maternal history of pyloric stenosis 10
Pathology
HPS is the result of both hyperplasia and hypertrophy of the pyloric circular muscles fibres. The pathogenesis of this is not understood. There are four main theories 9:
- immunohistochemical abnormalities
- genetic abnormalities
- infectious cause
- hyperacidity theory
Associations
Radiographic features
Plain radiograph
Abdominal x-ray findings are non-specific but may show a distended stomach with minimal distal intestinal bowel gas.
Fluoroscopy
An upper gastrointestinal series (barium meal) excludes other, more serious causes of pathology, but the findings of a UGI series infer rather than directly visualise the hypertrophied muscle. On upper gastrointestinal fluoroscopy:
- delayed gastric emptying
- peristaltic waves (caterpillar sign)
- elongated pylorus with a narrow lumen (string sign) which may appear duplicated due to puckering of the mucosa (double-track sign)
- the pylorus indents the contrast-filled antrum (shoulder sign) or base of the duodenal bulb (mushroom sign)
- the entrance to the pylorus may be beak-shaped (beak sign)
Ultrasound
Ultrasound is the modality of choice in the right clinical setting because of its advantages over a barium meal are that it directly visualises the pyloric muscle and does not use ionising radiation. Unfortunately, it is incapable of excluding other diagnoses such as midgut volvulus. Easy ultrasound technique is to find gallbladder then turn the probe obliquely sagittal to the body in an attempt to find pylorus longitudinally 7.
The hypertrophied muscle is hypoechoic, and the central mucosa is hyperechoic. Diagnostic measurements include (mnemonic "number pi"):
- pyloric muscle thickness, i.e. diameter of a single muscular wall on a transverse image: >3 mm (most accurate 3)
- length, i.e. longitudinal measurement: >15-17 mm
- pyloric volume: >1.5 cc
- pyloric transverse diameter: >13 mm
With the patient right side down the pylorus should be watched and should not be seen to open.
Described sonographic signs include:
Treatment and prognosis
Initial medical management is essential with rehydration and correction of electrolyte imbalances. This should be completed prior to 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 and has very low morbidity 4-5.
Differential diagnosis
There is usually little differential when imaging findings are appropriate. Of course, clinically it is important to consider other causes of vomiting in infancy.
A degree of pylorospasm is common in infancy and is responsible for some delay in gastric emptying. The pylorus, however, appears sonographically normal. In cases where the doubts persist, fluid gastric distention can be performed to "open" a tapered pylorus.
Gastro-oesophageal reflux which represents the cause of vomiting in two-thirds of infants referred to radiology 8.
Other causes of proximal gastrointestinal obstruction can be considered 8:
-<p><strong>Hypertrophic pyloric stenosis (HPS)</strong> refers to the idiopathic thickening of gastric pyloric musculature which then results in progressive <a href="/articles/gastric-outlet-obstruction">gastric outlet obstruction</a>.</p><h4>Epidemiology</h4><p>Pyloric stenosis is relatively common and has a male predilection (M:F ~4:1), and is more commonly seen in Caucasians <sup>4</sup>. It typically occurs between the first week to 3 months of age. There may be a positive family history. </p><p>Incidence of hypertrophic pyloric stenosis is approximately 2-5 per 1,000 births per year in most white populations. HPS is less common in India and among black and other Asian populations.</p><h4>Clinical presentation</h4><p>Clinical presentation is typical with non-bilious projectile vomiting. The hypertrophied pylorus can be palpated as an olive-sized mass in the right upper quadrant. A succussion splash may be audible, and although common, is only relevant if heard hours after the last meal <sup>6</sup>. </p><h5>Risk factors</h5><ul><li>maternal history of pyloric stenosis <sup>10</sup>- +<p><strong>Hypertrophic pyloric stenosis (HPS)</strong> refers to the idiopathic thickening of gastric pyloric musculature which then results in progressive <a href="/articles/gastric-outlet-obstruction">gastric outlet obstruction</a>.</p><h4>Epidemiology</h4><p>Pyloric stenosis is relatively common and has a male predilection (M:F ~4:1), and is more commonly seen in Caucasians <sup>4</sup>. While symptoms may start as early as 3 weeks, it typically occurs between the 6 to 12 weeks of age. First born children are at higher risk and there may be a positive family history in some cases. </p><p>Incidence of hypertrophic pyloric stenosis is approximately 2-5 per 1,000 births per year in most white populations. HPS is less common in India and among black and other Asian populations.</p><h4>Clinical presentation</h4><p>Clinical presentation is typical with non-bilious projectile vomiting. The hypertrophied pylorus can be palpated as an olive-sized mass in the right upper quadrant. A succussion splash may be audible, and although common, is only relevant if heard hours after the last meal <sup>6</sup>. </p><h5>Risk factors</h5><ul><li>maternal history of pyloric stenosis <sup>10</sup>
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