We describe a systematic approach to the ultrasound (US) examination of the antropyloric region in children. US is the modality of choice for the diagnosis of hypertrophic pyloric stenosis (HPS). The imaging features of the normal pylorus and the diagnostic findings in HPS are reviewed and illustrated in this pictorial essay. Common difficulties in performing the examination and tips to help overcome them will also be discussed

A Nasr

AA Reed

C Panteli

FN O’Keeffe

J Yoshizawa

JD Blumhagen

JO Haller

K Ohshiro

L Chandran

M Hernanz-Schulman

MI Argyropoulou

MP Hiorns

WK Rohrschneider

Insights into Imaging

English

PubMed

Sílvia Costa Dias

Sophie Swinson

Helena Torrão

Lígia Gonçalves

Svitlana Kurochka

Carlos Pina Vaz

Vasco Mendes

Springer - Publisher Connector

PICTORIAL REVIEW
Hypertrophic pyloric stenosis: tips and tricks
for ultrasound diagnosis
Sílvia Costa Dias & Sophie Swinson & Helena Torrão &
Lígia Gonçalves & Svitlana Kurochka & Carlos Pina Vaz &
Vasco Mendes
Received: 5 October 2011 /Revised: 11 February 2012 /Accepted: 19 March 2012 /Published online: 1 May 2012
# European Society of Radiology 2012
Abstract We describe a systematic approach to the ultra-
sound (US) examination of the antropyloric region in chil-
dren. US is the modality of choice for the diagnosis of
hypertrophic pyloric stenosis (HPS). The imaging features
of the normal pylorus and the diagnostic findings in HPS are
reviewed and illustrated in this pictorial essay. Common
difficulties in performing the examination and tips to help
overcome them will also be discussed.
Main Messages
• Hypertrophic Pyloric Stenosis is defined by thickening of the
muscular layer and failure in relaxation of the pyloric canal.
• The main diagnostic criterion is a measurement of more
than 3mm in thickness of the muscular layer.
• Abnormal elongation of the canal is characterised as
greater than 12 mm in length.
Keywords Hypertrophic pyloric stenosis . Ultrasound
Introduction
Hypertrophic pyloric stenosis (HPS) is the most frequent sur-
gical condition in infants in the first few months of life [1]. The
condition is characterised by thickening of the muscular layer
and failure of the pyloric canal to relax resulting in gastric outlet
obstruction. Elongation of the canal and thickened mucosa are
also seen. Ultrasound (US) is the preferred diagnostic modality
[2] as it is a non-invasive technique, allowing direct observation
of the pyloric canal morphology and behaviour. It is important
to carry out a systematic and dynamic study and to be aware of
the common technical difficulties and how to overcome them.
Clinical features
HPS is the most common surgical cause of vomiting in
infants. It has an incidence of 3 per 1,000 live births per
year, although wide variations have been documented with
geographic location, season and ethnic origin [3]. This dis-
ease usually presents between the second and sixth weeks of
life, more commonly in the white population, in males
(male:female ratio 4:1) and typically in first-born children
[4]. A history of an affected first-degree relative increases
the risk more than five-fold [5].
The US examination allows the radiologist to perform a brief
clinical history, which can reveal essential clues to the diagnosis.
A recent history of projectile and nonbilious vomiting, which
may be intermittent or with every feeding is the classical com-
plaint. Typically the infant has a voracious appetite.
When the vomiting persists, other clinical and biochemical
findings may occur such as dehydration, hypochloraemic
S. Costa Dias :H. Torrão : L. Gonçalves : S. Kurochka :
C. P. Vaz :V. Mendes
Radiology Department, Hospital de Braga,
Braga, Portugal
S. Costa Dias (*)
Rua Pedro Hispano, n 190, 2 Dto,
4100-393 Porto, Portugal
e-mail: silviacostadias@hotmail.com
S. Swinson
Radiology Department, Great Ormond Street
Hospital for Children NHS Trust,
Great Ormond Street,
London WC1N 3JH, UK
Insights Imaging (2012) 3:247–250
DOI 10.1007/s13244-012-0168-x
alkalosis and unconjugated jaundice. Late clinical manifesta-
tions include weight loss and visible gastric peristaltic activity
with a palpable pyloric ‘olive’. Prompt US diagnosis is im-
portant as these late findings make the infants sub-optimal
candidates for surgery.
Imaging technique
US is the first modality of choice when there is clinical
suspicion of HPS, as it is non-invasive and does not use
radiation, which is a crucial advantage in children. It is also
a commonly available with relatively low cost. US also
allows a dynamic study with direct observation of the pylo-
ric canal morphology and behaviour. The US should be
performed by an experienced radiologist. Having a system-
atic approach will improve the sensitivity of the technique.
US examination of the antropyloric region
Before performing the US, some general conditions for
examining infants should be addressed, as these can affect
the quality of the examination. The key is to keep the baby
comfortable, for example with US gel warmed to a suitable
ambient temperature. If possible the examination should be
performed after a feeding and accompanied by a parent.
A high-frequency transducer adjusted to the size of the
patient and the depth of the pylorus should be used. In the
majority of the cases a 6–10 MHz linear probe will provide
the depth required to visualise the pylorus [5].
Identification of the pylorus
First step: In the supine position with the transducer in a
transverse position and sometimes with slight anti-clockwise
rotation, identify the gallbladder. The pylorus is usually located
slightly medial and posterior in relation to the gallbladder
(Fig. 1).
Observe the pyloric morphology
Second step: Assess the appearance and measurements of
the pylorus (Fig. 1). The muscular layer is usually a hypo-
echogenic thin layer less than 2 mm in thickness. It is
important to be aware that tangential views and contractions
can produce pseudo-thickening.
Observe the pyloric behaviour
Third step: Visualize the passage of the gastric content
through the pylorus, distending the antropyloric region. This
dynamic evaluation is vital, as a wide open pylorus with
normal passage of the gastric contents excludes HPS (Fig. 2).
Fig. 1 The pylorus (arrow) between the gastric antrum (A) and the
duodenum (D) lying posterior to the gallbladder (*)
Fig. 2 Passage of the gastric content through the pylorus, distending
the antropyloric region (arrow)
Fig. 3 The stomach distended with gas (arrow)
248 Insights Imaging (2012) 3:247–250
Tips and tricks
One common difficulty is a stomach filled with gas (Fig. 3).
The easiest way to avoid this is by placing the infant in an
oblique position with the right side down, as this will allow
fluid to fill the antrum, acting as an acoustic window. A
stomach completely filled with milk can also cause artefacts,
other possibilities are to give the infant water or even to place a
nasogastric tube, empty the stomach and then fill it with water.
Another frequent problem is that a markedly distended
stomach can displace the pylorus dorsally making it very
difficult to access (Fig. 4). In this situation, moving the
infant into an oblique position with the left side down will
help to move the pylorus to a more anterior position.
The identification of the pylorus can be difficult, but a
systematic approach will improve chances of success.
Remember that a normal pylorus is much harder to visualise
than a hypertrophied one.
US diagnostic criteria of HPS
The main diagnostic criterion is measurement of the thick-
ness of the muscular layer. An abnormal cut off value of
3 mm in thickness has been described in the literature
(Figs. 5 and 6) [6–9].
The other principal sonographic size criterion is the
length of the pyloric canal. Abnormal elongation of the
canal is defined as greater than 12 mm in length (Fig. 6)
[9], however this measure is more difficult to perform and
for this reason is considered a less reliable criterion [10].
In HPS the thickened muscle and elongated pylorus are
fixed over time, which helps the operator to identify this
condition. The appearance of the hypertrophied pylorus has
previously been described as the cervix sign [11], as it
resembles the appearance of the uterine cervix (Fig. 4).
Fig. 4 The distended stomach (*), posteriorly displacing the pylorus
(arrow), which resembles the appearance of the uterine cervix
Fig. 5 The hypertrophied muscular layer
Fig. 6 Abnormal elongation of the pyloric canal (measure 1)
Fig. 7 a The double layer of thickened mucosa (*), b protruding
through the antrum
Insights Imaging (2012) 3:247–250 249
Additional US findings in HPS are hypertrophy of the
mucosa and a markedly distended and actively peristalsing
stomach. A double internal layer of crowded and redundant
mucosa may be identified (Fig. 7a), protruding through the
antrum (Fig. 7b). This was classically described as the nipple
sign in conventional contrast studies. The double layer of
thickened mucosa is hyperechogenic and can be confused
with echogenic contents passing through the pylorus.
Borderline measures
Thickening of the pyloric canal may be transient due to peri-
stalsis or pylorospasm. In the majority of cases of pylorospasm,
the muscle is not hypertrophied. Sometimes the muscle can be
slightly thick, but it usually measures less than 3 mm. With
prolonged observation, pyloric opening may be visualised.
If the muscle layer is 2–3 mm thick, and it does not relax
during examination, clinical follow-up with repeat US is
advisable [5, 6, 12]. Particular attention should be paid to
pre-term infants and those in the younger age range. In
premature infants, HPS develops at the same age as in term
infants, but their smaller size should be taken into consid-
eration. Argyropoulou et al. [13] showed that normal pyloric
dimensions increase with the gestational age and docu-
mented an even stronger correlation with body weight,
providing normal values for muscle thickness, canal length
and canal width from prematurity to full-term infants.
Haider et al. [14] performed a study with 190 infants operated
for HPS and found a strong correlation with the ultrasound
measurement of the pyloric length and the weight of the
infant, which can be helpful in small and premature patients.
However these authors also highlight the importance of the
morphological appearance of the pylorus in premature infants.
Post-treatment imaging of HPS
The treatment of HPS is surgical pyloromyotomy. A further
US examination may be requested if vomiting persists fol-
lowing surgery. However, the radiologist and the surgeon
should be aware that the pyloric muscle may remain thick-
ened after successful surgery and can take up to 5 months to
return to normal thickness.
In the first week after surgery, the muscle can be the same
thickness or even thicker than before surgery and then the
dimensions gradually return to normal. The anterior part of
the muscle tends to normalize first, usually measuring less
than 3 mm by 3 months. The posterior part is last to
normalise, usually after 5 months, when the pylorus regains
its appearance of an elongated ring. This order of changes is
related to the anterior surgical approach to the muscle [15].
An upper GI examination may also be performed if
emesis continues post-operatively, in order to exclude a
duodenal leak or to assess an incomplete pyloromyotomy
or gastro-oesophageal reflux [16].
Conclusion
Pyloric US examination is a dynamic investigation, which should
be performed in a systematic way. The radiologist should be aware
of the pitfalls of the examination and how to overcome them. It is
important to be familiar with the normal and hypertrophied pyloric
appearances, as this will provide a greater diagnostic confidence,
assisting in early diagnosis and improving the management of
infants with HPS.
References
1. Ohshiro K, Puri P (1998) Pathogenesis of infantile hypertrophic
pyloric stenosis: recent progress. Pediatr Surg Int 13:43–252
2. Hiorns MP (2011) Gastrointestinal tract imaging in children: current
techniques. Pediatr Radiol 41:42–54
3. Panteli C (2009) New insights into the pathogenesis of infantile
pyloric stenosis. Pediatr Surg Int 25:1043–1052
4. Chandran L, Chitkara M (2008) Vomiting in children: reassurance,
red flag, or referral? Pediatr Rev 29:183–192
5. Hernanz-SchulmanM (2003) Infantile hypertrophic pyloric stenosis.
Radiology 227:319–331
6. O’Keeffe FN, Stansberry SD, Swischuk LE, Hayden CK (1991)
Antropiloric muscle thickness at US in infants: what is normal.
Radiology 178:827–830
7. Hernanz-Schulman M, Sells LL, Ambrosino MM, Heller RM,
Stein SM, Neblett WW (1994) Hypertrophic pyloric stenosis in
the infant without a palpable olive: accuracy of sonographic
diagnosis. Radiology 193:771–776
8. Rohrschneider WK, Mittnacht H, Darge K, Tröger J (1998) Pyloric
muscle in asymptomatic infants: sonographic evaluation and
discrimination from idiopathic hypertrophic pyloric stenosis.
Pediatr Radiol 28:429–434
9. Reed AA, Michael K (2010) Hypertrophic pyloric stenosis. J
Diagn Med Sonography 26:157–160
10. Blumhagen JD, Maclin L, Krauter D, Rosenbaum DM, Weinberger
E (1988) Sonographic diagnosis of hypertrophic pyloric stenosis.
AJR Am J Roentgenol 150:1367–1370
11. Haller JO, Cohen HL (1986)Hypertrophic pyloric stenosis: diagnosis
using US. Radiology 161:335–339
12. Hernanz-Schulman M (2009) Pyloric stenosis: role of imaging.
Pediatr Radiol 39(Suppl 2):S134–S139
13. Argyropoulou MI, Hadjigeorgi CG, Kiortsis DN (1998) Antro-pyloric
canal values from early prematurity to full-term gestational age: an
ultrasound study. Pediatr Radiol 28:933–936
14. Haider N, Spicer R, Grie D (2002) Ultrasound diagnosis of infantile
hypertrophic pyloric stenosis: determinants of pyloric length and the
effect of prematurity. Clin Radiol 57:136–139
15. Yoshizawa J, Eto T, Higashimoto Y, Saitou T, Maie M (2001)
Ultrasonographic features of normalization of the pylorus after
pyloromyotomy for hypertrophic pyloric stenosis. J Pediatr Surg
36:582–586
16. Nasr A, Ein SH, Connolly B (2008) Recurrent pyloric stenosis: to
dilate or operate? A preliminary report. J Pediatr Surg 43:E17–E20
250 Insights Imaging (2012) 3:247–250


Hypertrophic pyloric stenosis: tips and tricks for ultrasound diagnosis

We describe a systematic approach to the ultrasound (US) examination of the antropyloric region in children. US is the modality of choice for the diagnosis of hypertrophic pyloric stenosis (HPS). The imaging features of the normal pylorus and the diagnostic findings in HPS are reviewed and illustrated in this pictorial essay. Common difficulties in performing the examination and tips to help overcome them will also be discussed. Main Messages • Hypertrophic Pyloric Stenosis is defined by thickening of the muscular layer and failure in relaxation of the pyloric canal. • The main diagnostic criterion is a measurement of more than 3mm in thickness of the muscular layer. • Abnormal elongation of the canal is characterised as greater than 12 mm in length

Costa-Dias, S

Swinson, S

Torrão, H

Gonçalves, L

Kurochka, S

Vaz, CP

Mendes, V

Repositório Comum

PICTORIAL REVIEWHypertrophic pyloric stenosis: tips and tricksfor ultrasound diagnosisSílvia Costa Dias & Sophie Swinson & Helena Torrão &Lígia Gonçalves & Svitlana Kurochka & Carlos Pina Vaz &Vasco MendesReceived: 5 October 2011 /Revised: 11 February 2012 /Accepted: 19 March 2012 /Published online: 1 May 2012# European Society of Radiology 2012Abstract We describe a systematic approach to the ultra-sound (US) examination of the antropyloric region in chil-dren. US is the modality of choice for the diagnosis ofhypertrophic pyloric stenosis (HPS). The imaging featuresof the normal pylorus and the diagnostic findings in HPS arereviewed and illustrated in this pictorial essay. Commondifficulties in performing the examination and tips to helpovercome them will also be discussed.Main Messages• Hypertrophic Pyloric Stenosis is defined by thickening of themuscular layer and failure in relaxation of the pyloric canal.• The main diagnostic criterion is a measurement of morethan 3mm in thickness of the muscular layer.• Abnormal elongation of the canal is characterised asgreater than 12 mm in length.Keywords Hypertrophic pyloric stenosis . UltrasoundIntroductionHypertrophic pyloric stenosis (HPS) is the most frequent sur-gical condition in infants in the first few months of life [1]. Thecondition is characterised by thickening of the muscular layerand failure of the pyloric canal to relax resulting in gastric outletobstruction. Elongation of the canal and thickened mucosa arealso seen. Ultrasound (US) is the preferred diagnostic modality[2] as it is a non-invasive technique, allowing direct observationof the pyloric canal morphology and behaviour. It is importantto carry out a systematic and dynamic study and to be aware ofthe common technical difficulties and how to overcome them.Clinical featuresHPS is the most common surgical cause of vomiting ininfants. It has an incidence of 3 per 1,000 live births peryear, although wide variations have been documented withgeographic location, season and ethnic origin [3]. This dis-ease usually presents between the second and sixth weeks oflife, more commonly in the white population, in males(male:female ratio 4:1) and typically in first-born children[4]. A history of an affected first-degree relative increasesthe risk more than five-fold [5].The US examination allows the radiologist to perform a briefclinical history, which can reveal essential clues to the diagnosis.A recent history of projectile and nonbilious vomiting, whichmay be intermittent or with every feeding is the classical com-plaint. Typically the infant has a voracious appetite.When the vomiting persists, other clinical and biochemicalfindings may occur such as dehydration, hypochloraemicS. Costa Dias :H. Torrão : L. Gonçalves : S. Kurochka :C. P. Vaz :V. MendesRadiology Department, Hospital de Braga,Braga, PortugalS. Costa Dias (*)Rua Pedro Hispano, n 190, 2 Dto,4100-393 Porto, Portugale-mail: silviacostadias@hotmail.comS. SwinsonRadiology Department, Great Ormond StreetHospital for Children NHS Trust,Great Ormond Street,London WC1N 3JH, UKInsights Imaging (2012) 3:247–250DOI 10.1007/s13244-012-0168-xalkalosis and unconjugated jaundice. Late clinical manifesta-tions include weight loss and visible gastric peristaltic activitywith a palpable pyloric ‘olive’. Prompt US diagnosis is im-portant as these late findings make the infants sub-optimalcandidates for surgery.Imaging techniqueUS is the first modality of choice when there is clinicalsuspicion of HPS, as it is non-invasive and does not useradiation, which is a crucial advantage in children. It is alsoa commonly available with relatively low cost. US alsoallows a dynamic study with direct observation of the pylo-ric canal morphology and behaviour. The US should beperformed by an experienced radiologist. Having a system-atic approach will improve the sensitivity of the technique.US examination of the antropyloric regionBefore performing the US, some general conditions forexamining infants should be addressed, as these can affectthe quality of the examination. The key is to keep the babycomfortable, for example with US gel warmed to a suitableambient temperature. If possible the examination should beperformed after a feeding and accompanied by a parent.A high-frequency transducer adjusted to the size of thepatient and the depth of the pylorus should be used. In themajority of the cases a 6–10 MHz linear probe will providethe depth required to visualise the pylorus [5].Identification of the pylorusFirst step: In the supine position with the transducer in atransverse position and sometimes with slight anti-clockwiserotation, identify the gallbladder. The pylorus is usually locatedslightly medial and posterior in relation to the gallbladder(Fig. 1).Observe the pyloric morphologySecond step: Assess the appearance and measurements ofthe pylorus (Fig. 1). The muscular layer is usually a hypo-echogenic thin layer less than 2 mm in thickness. It isimportant to be aware that tangential views and contractionscan produce pseudo-thickening.Observe the pyloric behaviourThird step: Visualize the passage of the gastric contentthrough the pylorus, distending the antropyloric region. Thisdynamic evaluation is vital, as a wide open pylorus withnormal passage of the gastric contents excludes HPS (Fig. 2).Fig. 1 The pylorus (arrow) between the gastric antrum (A) and theduodenum (D) lying posterior to the gallbladder (*)Fig. 2 Passage of the gastric content through the pylorus, distendingthe antropyloric region (arrow)Fig. 3 The stomach distended with gas (arrow)248 Insights Imaging (2012) 3:247–250Tips and tricksOne common difficulty is a stomach filled with gas (Fig. 3).The easiest way to avoid this is by placing the infant in anoblique position with the right side down, as this will allowfluid to fill the antrum, acting as an acoustic window. Astomach completely filled with milk can also cause artefacts,other possibilities are to give the infant water or even to place anasogastric tube, empty the stomach and then fill it with water.Another frequent problem is that a markedly distendedstomach can displace the pylorus dorsally making it verydifficult to access (Fig. 4). In this situation, moving theinfant into an oblique position with the left side down willhelp to move the pylorus to a more anterior position.The identification of the pylorus can be difficult, but asystematic approach will improve chances of success.Remember that a normal pylorus is much harder to visualisethan a hypertrophied one.US diagnostic criteria of HPSThe main diagnostic criterion is measurement of the thick-ness of the muscular layer. An abnormal cut off value of3 mm in thickness has been described in the literature(Figs. 5 and 6) [6–9].The other principal sonographic size criterion is thelength of the pyloric canal. Abnormal elongation of thecanal is defined as greater than 12 mm in length (Fig. 6)[9], however this measure is more difficult to perform andfor this reason is considered a less reliable criterion [10].In HPS the thickened muscle and elongated pylorus arefixed over time, which helps the operator to identify thiscondition. The appearance of the hypertrophied pylorus haspreviously been described as the cervix sign [11], as itresembles the appearance of the uterine cervix (Fig. 4).Fig. 4 The distended stomach (*), posteriorly displacing the pylorus(arrow), which resembles the appearance of the uterine cervixFig. 5 The hypertrophied muscular layerFig. 6 Abnormal elongation of the pyloric canal (measure 1)Fig. 7 a The double layer of thickened mucosa (*), b protrudingthrough the antrumInsights Imaging (2012) 3:247–250 249Additional US findings in HPS are hypertrophy of themucosa and a markedly distended and actively peristalsingstomach. A double internal layer of crowded and redundantmucosa may be identified (Fig. 7a), protruding through theantrum (Fig. 7b). This was classically described as the nipplesign in conventional contrast studies. The double layer ofthickened mucosa is hyperechogenic and can be confusedwith echogenic contents passing through the pylorus.Borderline measuresThickening of the pyloric canal may be transient due to peri-stalsis or pylorospasm. In the majority of cases of pylorospasm,the muscle is not hypertrophied. Sometimes the muscle can beslightly thick, but it usually measures less than 3 mm. Withprolonged observation, pyloric opening may be visualised.If the muscle layer is 2–3 mm thick, and it does not relaxduring examination, clinical follow-up with repeat US isadvisable [5, 6, 12]. Particular attention should be paid topre-term infants and those in the younger age range. Inpremature infants, HPS develops at the same age as in terminfants, but their smaller size should be taken into consid-eration. Argyropoulou et al. [13] showed that normal pyloricdimensions increase with the gestational age and docu-mented an even stronger correlation with body weight,providing normal values for muscle thickness, canal lengthand canal width from prematurity to full-term infants.Haider et al. [14] performed a study with 190 infants operatedfor HPS and found a strong correlation with the ultrasoundmeasurement of the pyloric length and the weight of theinfant, which can be helpful in small and premature patients.However these authors also highlight the importance of themorphological appearance of the pylorus in premature infants.Post-treatment imaging of HPSThe treatment of HPS is surgical pyloromyotomy. A furtherUS examination may be requested if vomiting persists fol-lowing surgery. However, the radiologist and the surgeonshould be aware that the pyloric muscle may remain thick-ened after successful surgery and can take up to 5 months toreturn to normal thickness.In the first week after surgery, the muscle can be the samethickness or even thicker than before surgery and then thedimensions gradually return to normal. The anterior part ofthe muscle tends to normalize first, usually measuring lessthan 3 mm by 3 months. The posterior part is last tonormalise, usually after 5 months, when the pylorus regainsits appearance of an elongated ring. This order of changes isrelated to the anterior surgical approach to the muscle [15].An upper GI examination may also be performed ifemesis continues post-operatively, in order to exclude aduodenal leak or to assess an incomplete pyloromyotomyor gastro-oesophageal reflux [16].ConclusionPyloric US examination is a dynamic investigation, which shouldbe performed in a systematic way. The radiologist should be awareof the pitfalls of the examination and how to overcome them. It isimportant to be familiar with the normal and hypertrophied pyloricappearances, as this will provide a greater diagnostic confidence,assisting in early diagnosis and improving the management ofinfants with HPS.References1. Ohshiro K, Puri P (1998) Pathogenesis of infantile hypertrophicpyloric stenosis: recent progress. Pediatr Surg Int 13:43–2522. Hiorns MP (2011) Gastrointestinal tract imaging in children: currenttechniques. Pediatr Radiol 41:42–543. Panteli C (2009) New insights into the pathogenesis of infantilepyloric stenosis. Pediatr Surg Int 25:1043–10524. Chandran L, Chitkara M (2008) Vomiting in children: reassurance,red flag, or referral? Pediatr Rev 29:183–1925. Hernanz-SchulmanM (2003) Infantile hypertrophic pyloric stenosis.Radiology 227:319–3316. O’Keeffe FN, Stansberry SD, Swischuk LE, Hayden CK (1991)Antropiloric muscle thickness at US in infants: what is normal.Radiology 178:827–8307. Hernanz-Schulman M, Sells LL, Ambrosino MM, Heller RM,Stein SM, Neblett WW (1994) Hypertrophic pyloric stenosis inthe infant without a palpable olive: accuracy of sonographicdiagnosis. Radiology 193:771–7768. Rohrschneider WK, Mittnacht H, Darge K, Tröger J (1998) Pyloricmuscle in asymptomatic infants: sonographic evaluation anddiscrimination from idiopathic hypertrophic pyloric stenosis.Pediatr Radiol 28:429–4349. Reed AA, Michael K (2010) Hypertrophic pyloric stenosis. JDiagn Med Sonography 26:157–16010. Blumhagen JD, Maclin L, Krauter D, Rosenbaum DM, WeinbergerE (1988) Sonographic diagnosis of hypertrophic pyloric stenosis.AJR Am J Roentgenol 150:1367–137011. Haller JO, Cohen HL (1986)Hypertrophic pyloric stenosis: diagnosisusing US. Radiology 161:335–33912. Hernanz-Schulman M (2009) Pyloric stenosis: role of imaging.Pediatr Radiol 39(Suppl 2):S134–S13913. Argyropoulou MI, Hadjigeorgi CG, Kiortsis DN (1998) Antro-pyloriccanal values from early prematurity to full-term gestational age: anultrasound study. Pediatr Radiol 28:933–93614. Haider N, Spicer R, Grie D (2002) Ultrasound diagnosis of infantilehypertrophic pyloric stenosis: determinants of pyloric length and theeffect of prematurity. Clin Radiol 57:136–13915. Yoshizawa J, Eto T, Higashimoto Y, Saitou T, Maie M (2001)Ultrasonographic features of normalization of the pylorus afterpyloromyotomy for hypertrophic pyloric stenosis. J Pediatr Surg36:582–58616. Nasr A, Ein SH, Connolly B (2008) Recurrent pyloric stenosis: todilate or operate? A preliminary report. J Pediatr Surg 43:E17–E20250 Insights Imaging (2012) 3:247–250

Institutional repository of Hospital de Braga

Abstract
          We describe a systematic approach to the ultrasound (US) examination of the antropyloric region in children. US is the modality of choice for the diagnosis of hypertrophic pyloric stenosis (HPS). The imaging features of the normal pylorus and the diagnostic findings in HPS are reviewed and illustrated in this pictorial essay. Common difficulties in performing the examination and tips to help overcome them will also be discussed.
          
            Main Messages
          
          • Hypertrophic Pyloric Stenosis is defined by thickening of the muscular layer and failure in relaxation of the pyloric canal.
          
          • The main diagnostic criterion is a measurement of more than 3mm in thickness of the muscular layer.
          
          • Abnormal elongation of the canal is characterised as greater than 12 mm in length.
          </jats:p

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Hypertrophic pyloric stenosis: tips and tricks for ultrasound diagnosis

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