Diagnostic ultrasound ( PDFDrive )

CHAPTER 53 The Pediatric Gastrointestinal Tract 1835
A
B
FIG. 53.3 Normal Stomach. (A) Normal antrum of stomach (S), pyloric canal (P), and proximal duodenum (D). Four gastric wall layers
are visible (from inside out): echogenic mucosa, hypoechoic muscularis mucosae, echogenic submucosa, and hypoechoic outer circular muscle.
(B) Fluid passes freely through the normal pylorus (arrow). D, Duodenum; S, stomach.
thickening of the pyloric muscle can be suggested erroneously.
Similarly, if tangential images are obtained on the longitudinal
plane, the muscle may erroneously appear thickened (Fig. 53.4).
his same phenomenon is also seen with the echogenic mucosal
layer.
Hypertrophic Pyloric Stenosis
Muscle width ≥3 mm
Pyloric canal length ≥1.5 cm
No peristalsis through pylorus
Hypertrophic Pyloric Stenosis
During the past decade, sonography has replaced the radiographic
upper GI series for the diagnosis of infantile hypertrophic pyloric
stenosis (HPS). Unlike the upper GI series, which demonstrates
only the indirect efects of pyloric muscle hypertrophy on the
gastric lumen, ultrasound allows direct visualization of the gastric
muscle thickening that is the hallmark of the disease. Although
a few pitfalls in the sonographic diagnosis of HPS exist, the
technique is relatively easily mastered and results in greatly
improved accuracy of diagnosis and patient outcome. Indeed,
the accuracy approaches 100%, and ultrasound is now the
procedure of choice for the detection of pyloric stenosis. 9-12
Ater the initial documentation of the sonographic detection
of the hypertrophied pyloric muscle in pyloric stenosis by Teele
and Smith, 13 many studies described the characteristic indings
of HPS. 14-18 Increased pyloric muscle thickness and canal length;
increased transverse diameter of the pylorus; thickened, redundant
mucosa; estimation of the degree of gastric outlet obstruction;
and calculation of pyloric muscle volume have all been used to
diagnose pyloric stenosis. However, of all the criteria, thickening
of the pyloric muscle and elongation of the pyloric canal have
emerged as the most consistently useful. he thickness at which
the muscle is considered hypertrophied is 3 mm or greater
when measuring the hypoechoic single muscle layer transversely.
7 Pyloric canal length of 1.5 cm is considered diagnostic
of pyloric stenosis when seen in conjunction with thickened
pyloric muscle.
In the classic case of HPS, the thickened muscle mass is seen
as a hypoechoic layer just supericial to the more echogenic
mucosal layer of the pyloric canal (Fig. 53.5). In cross section,
this “olive,” on clinical palpation, resembles a sonolucent
“doughnut” medial to the gallbladder and anterior to the right
kidney. Oten, small amounts of luid are visible trapped between
the thickened echogenic mucosal folds, corresponding to the
“string” (elongated canal) and “double tract” (folded mucosa)
signs previously described on radiographic upper GI series. 19
In longitudinal section, sonography also permits evaluation of
functional alterations at the pylorus. Active gastric peristalsis
that ends abruptly at the margin of the hypertrophied muscle,
absence of a normal opening of the pylorus, and diminished
passage of luid from the stomach into the duodenum are useful
adjunctive indings in pyloric stenosis. hickened mucosa
within the pylorus oten accompanies the muscle hypertrophy. 20
Although most oten an isolated abnormality, HPS occasionally
accompanies other obstructive antropyloric lesions, such as
duodenal feeding tubes (Fig. 53.6), eosinophilic gastroenteritis,
antral polyps, 21 and idiopathic or prostaglandin-induced foveolar
hyperplasia. 22
he length of the pyloric channel is typically shorter in
premature infants with pyloric stenosis, but normal pyloric
measurements for premature infants are not well established.
At surgery of premature infants with HPS, the mass is reportedly