Ultrasound diagnosis of infantile hypertrophic pyloric stenosis: determinants of pyloric length and the effect of prematurity

Diagnostic accuracy of palpation and ultrasonography for diagnosing infantile hypertrophic pyloric stenosis: a systematic review and meta-analysis

Objective:

Although infantile hypertrophic pyloric stenosis (IHPS) is a well-known disease, there is no systematic review regarding the optimal diagnostic strategy. We conducted a systematic review and meta-analysis to obtain diagnostic accuracy of all methods to diagnose IHPS.

Methods:

According to the Preferred Reported Items for Systematic Reviews and Meta-Analysis guidelines, we searched MEDLINE and Embase to identify studies reporting sensitivity and specificity of all methods used to diagnose IHPS. Inclusion criteria were infants with suspicion of/or diagnosed with IHPS who underwent pyloromyotomy or had clinical follow-up. A random-effects model was used to obtain pooled estimates of sensitivity, specificity and area under the receiver operating characteristic curve.

Results:

After screening 5364 studies, we included 43 studies with in total 6085 infants (n = 4241 IHPS; n = 1844 controls). The diagnostic sensitivity of palpation ranged from 10.0 to 93.4% and decreased over time. Different parameters for ultrasonography were found. Most used parameters were pyloric muscle thickness (PMT) ≥ 3 mm (pooled sensitivity 97.6% and specificity 98.8%), PMT ≥ 4 mm (pooled sensitivity 94.0% and specificity 98.0%) or a combination of PMT ≥ 4 mm and/or pyloric canal length ≥16 mm (pooled sensitivity 94.0% and specificity 91.7%). The AUC showed high diagnostic accuracy (0.997, 0.966 and 0.981 respectively), but large heterogeneity exists. Due to the large differences in cut-off values no meta-analysis could be conducted for pyloric canal length and pyloric diameter.

Conclusion:

Palpation has limited sensitivity in diagnosing IHPS. We showed that ultrasonography has highest diagnostic accuracy to diagnose IHPS and we advise to use PMT ≥ 3 mm as cut-off.

Advances in knowledge:

This is the first systematic review and meta-analysis on diagnosing IHPS, which summarizes the available literature and may be used as a guideline.

Stratifying features for diagnosing hypertrophic stenosis on ultrasound: a diagnostic accuracy study

Background

Our aims were to determine if the diagnostic threshold for diagnosing hypertrophic pyloric stenosis (HPS) on ultrasound scan (USS) should be adjusted based on birth weight (BW), current weight (CW), gestational age (GA), chronological age (CA) or corrected gestational age (CGA).

Methods

All patients who underwent either an USS and pyloromyotomy (Group 1) or an USS for possible HPS (Group 2) at our tertiary centre between July 2013 and June 2019 were identified. Ideal threshold values are identified by measuring Youden's Index (J = sensitivity + specificity – 1; higher is better). Mean maximum Youden's Index for stratified results was compared to that for combined results.

Results

Two hundred and eighty‐four patients were included (142 patients in both Group 1 and Group 2). Combined maximum Youden's Index for all patients was 0.92 for pyloric canal thickness (PMT) and 0.87 for pyloric canal length (PCL). Mean maximum Youden's Index was higher when patients were stratified by GA, CGA, BW or CW, and equivalent for CA. For pyloric canal length (PCL), mean maximum Youden's Index was lower for all variables when stratified compared to combined. There was no visual trend observed in the diagnostic thresholds between groups.

Conclusion

Stratifying USS PMT diagnostic thresholds values based on age and weight is statistically more accurate than a single threshold in diagnosing HPS. However, the lack of visual correlation indicates a larger dataset is required to validate these results.

Evaluating the validity of ultrasound in diagnosing hypertrophic pyloric stenosis: a cross-sectional diagnostic accuracy study

BACKGROUND

Our aims were to evaluate the ultrasound scan (USS) criteria in diagnosing hypertrophic pyloric stenosis (HPS), determine the best diagnostic threshold values for pyloric muscle thickness (PMT) and pyloric canal length (PCL), and assess the accuracy of flow through the pylorus.

METHODS

All patients who underwent pyloromyotomy at our tertiary paediatric surgery centre between July 2013 and June 2019 were identified (Group 1). All patients undergoing an USS to investigate for a possible HPS and did not undergo pyloromyotomy were also identified (Group 2). Accuracy was determined by Youden's Index (J) with the highest J determining the ideal cut-off value.

RESULTS

Two hundred and eighty-four patients (142 patients in each group) were included in the analysis. Using only the last USS before surgery, PMT provided an area under the curve (AUC) of 0.987 (n = 275), and PCL an AUC of 0.977 (n = 267). Ideal threshold values were 3.0 mm for PMT (J = 0.92), and 14.5 mm for PCL (J = 0.87). Combining PMT ≥3.0 mm with a PCL ≥14.5 mm resulted in a sensitivity of 95% and specificity of 99% (J = 0.94). The absence of flow through the pylorus on dynamic USS provided a sensitivity of 99% and specificity of 91% (J = 0.91; n = 277).

CONCLUSION

Combining threshold values of 3.0 mm for PMT and 14.5 mm PCL provides the highest accuracy for diagnosing pyloric stenosis on an ultrasound scan. These combined values were more accurate than observing for the absence of flow through the pylorus.

Current Applications of Pediatric Abdominal Point-of-Care Ultrasound

Point-of-care ultrasound (POCUS) for pediatric abdominal symptoms has expanded in both the inpatient and outpatient settings. POCUS may be used to aid in the diagnosis of appendicitis, hypertrophic pyloric stenosis, and intussusception in the pediatric population. This article reviews the benefits of POCUS for the diagnosis of these pediatric pathologies. This article also provides instruction on how to perform these important examinations. [Pediatr Ann. 2021;50(10):e419-e423.].

Pediatric emergency gastrointestinal ultrasonography: pearls & pitfalls

Ultrasonography is an essential tool in pediatric imaging, particularly in the emergency setting. Although ultrasound is often the favored initial modality for abdominal imaging in children, it is highly operator-dependent and therefore prone to misinterpretation which can lead to false positive or negative exams, or even incorrect diagnoses. Conditions discussed in this series include ileocolic intussusception, hypertrophic pyloric stenosis, appendicitis, and ingested foreign bodies. We will review diagnostic criteria, highlight crucial findings, and illustrate commonly-encountered difficulties and mimics.

The ins and outs of pyloromyotomy: what we have learned in 35 years

PURPOSE/BACKGROUND

The aim of the study is to evaluate a large series of infantile hypertrophic pyloric stenosis (IHPS) patients treated by one pediatric surgeon focusing on their diagnostic difficulties and complications.

METHODS

From July 1969 to December 2003 (inclusive), the charts of 791 infants with IHPS were retrospectively reviewed.

RESULTS

There were 647 (82%) males and 144 (18%) females; mean age was 38 days, median 51 (range 7 days-10 months). When ultrasonography (US) was routinely used (1990), the age at diagnosis decreased to <40 days. The mean weight before and after routine US was 3.2 kg, median 3 (range 1.5-6). Twenty-five (3.1%) were premature at diagnosis, mean age 49 days, median 56, (range 1-3 months) and mean weight 2.5 kg, median 2.3 (range 1.5-3.2). Eighty-one (10%) had a positive family history. Forty-four (5%) were non-Caucasians. Seventy-five (9 %) had other medical conditions, anomalies and/or associated findings. Sixty (7%) patients had abnormal preoperative electrolytes. Ten (1.2%) pylorics occurred after newborn operations. Of the entire total (791) who were treated, there were 13 (1.7%) not operated on. All operations were done open initially through one of two right upper quadrant incisions, and then through an upper midline incision under general endotracheal anesthesia; 14 (1.7 %) had concomitant procedures. Prophylactic antibiotics (from 1982) decreased the wound infection rate to 3.9%. There were a total of 87 (10%) complications which included 9 (1.1%) intraoperative, (including mistaken diagnoses) 78 (9%) postoperative: 59 (2%) early (<1 month) and 19 (2.4%) late (>1 month). The 13 (1.6%) postoperative transfers (12 from non-pediatric surgeons) had 16 (18%) complications (including 1 death); five (33%) requiring reoperation (4 incomplete, 1 perforation). There were two deaths.

CONCLUSIONS

IHPS should be considered in any vomiting infant. US allows earlier diagnosis. Serious complications are uncommon and avoidable, but recognizable and easily corrected. Higher surgeon volume of pyloromyotomies (>14 per year) is associated with fewer complications.

Single-site umbilical laparoscopic pyloromyotomy in neonates less than 21-day old

PURPOSE

Single-site umbilical laparoscopic pyloromyotomy for hypertrophic pyloric stenosis in neonates <3-week old has rarely been reported in the literature. This article reports our initial experience with this procedure.

METHODS

Overall, 13 cases of hypertrophic pyloric stenosis occurred in neonates <3-week old from January 2010 to April 2013 in our hospital. All neonates were treated by a single-site laparoscopic procedure. A 5-mm trocar and endoscope were introduced through an incision in the center of the umbilicus, and two 3-mm working instruments were inserted directly into the abdomen via separate lateral fascial stab incisions in the umbilical fold, and a single-site umbilical laparoscopic pyloromyotomy was then performed.

RESULTS

The procedure was performed in 13 infants (12 male) with mean age of 17.3 days. The average length of the operation was 26 min. The mean postoperative hospital stay was 4.5 days. All patients were discharged home on full feeds. Follow-up examinations were scheduled 2 to 6 weeks after discharge, and no postoperative complications were noted in any of the patients.

CONCLUSION

These cases had shorter and thinner pylori than their older counterparts. However, the laparoscopic procedure was safe and feasible, with good postoperative results and excellent cosmesis. Surgeons should have a firm foundation of advanced minimal access surgical skills prior to attempting the procedure.

Postoperative emesis after laparoscopic pyloromyotomy in infantile hypertrophic pyloric stenosis

AIM

This study aimed to determine the causes of postoperative emesis (PE) in neonates with infantile hypertrophic pyloric stenosis (IHPS) after laparoscopic pyloromyotomy (LP).

METHODS

Retrospective review of the hospital database for infants with IHPS managed between 2000 and 2010 was performed. Relevant data were collected from the clinical records in the Medocs(®) system and used for statistical analysis.

RESULTS

During the 10-year period, 95 patients with IHPS were identified and 43 (36 boys and seven girls) fulfilled the inclusion criteria. PE occurred in 21 infants (48.8%), of which nine presented with manifestations of enteric infections, with confirmed diagnosis in four. PE was significantly higher in the fast track feeding protocol (FTFP) group 12/15 compared with the conventional slow feeding protocol (CSFP) group 8/21 (p = 0.019). Gastro-oesophageal reflux (GER) confirmed by 24-h impedance monitoring was responsible for PE in three. Operative revision for suspected incomplete pyloromyotomy was performed in five infants. However, incomplete myotomy could only be confirmed in two infants during surgery.

CONCLUSION

Postoperative emesis in IHPS after LP requires careful evaluation as it can be a result of enteric viral infections, aggressive feeding protocols or GER. Decisions to perform reoperations for incomplete myotomy after LP due to PE are challenging.

Evaluation of hypertrophic pyloric stenosis by pediatric emergency physician sonography

OBJECTIVES

The objective was to evaluate the accuracy of pediatric emergency physician (EP) sonography for infants with suspected hypertrophic pyloric stenosis (HPS).

METHODS

This was a prospective observational pilot study in an urban academic pediatric emergency department (PED). Patients were selected if the treating physician ordered an ultrasound (US) in the department of radiology for the evaluation of suspected HPS.

RESULTS

Sixty-seven patients were enrolled from August 2009 through April 2012. When identifying the pylorus, pediatric EPs correctly identified all 10 positive cases, with a sensitivity of 100% (95% confidence interval [CI] = 62% to 100%) and specificity of 100% (95% CI = 92% to 100%). There was no statistical difference between the measurements obtained by pediatric EPs and radiology staff for pyloric muscle width or length (p = 0.5 and p = 0.79, respectively).

CONCLUSIONS

Trained pediatric EPs can accurately assess the pylorus with US in the evaluation of HPS with good specificity.

Hypertrophic pyloric stenosis in premature infants: evaluation of sonographic criteria and short-term outcomes

PURPOSE

To examine the sonographic measurements of pyloric muscle and pyloric thickness in premature infants with hypertrophic pyloric stenosis (HPS) and to correlate these measurements with patients variables. We aimed also to evaluate the clinical features and short-term outcome of HPS in premature compared to term infants.

METHODS

The medical notes and the pyloric ultrasounds of all premature infants (<37 weeks) admitted to the Neonatal Surgical Unit with HPS over a 20-year period (1990-2010) were retrospectively reviewed. Sonographic measurements of the pyloric length, muscle thickness and the pyloric ratio (muscle thickness divided by pyloric diameter) were correlated to weight at presentation, duration of symptoms and corrected gestational age. Multiple regression and correlation analysis was carried out.

RESULTS

Seventy-five preterm infants were identified (51M:24F). Median gestational age was 34 weeks. Median weight at presentation was 2.74 kg. Forty-two had an ultrasound (US) before surgery, 37 measurements were analysed. Pyloric length, muscle thickness and pyloric ratio were not affected by weight at presentation (p = 0.67, p = 0.122, p = 0.849), corrected gestational age (CGA) (p = 0.921, p = 0.678, p = 0.076), or duration of symptoms (p = 0.827, p = 0.268, p = 0.281). Mean length of stay was 6 days and overall complication rate was 27 %, both higher than reported in term infants (p < 0.001).

CONCLUSIONS

Premature infants with HPS have a higher female preponderance than expected. Ultrasound measurements in premature infants with HPS are not affected by weight, corrected gestational age or duration of symptoms. In addition, they have a longer hospital stay and increased complication rate compared to term infants.

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.

Bilious vomiting does not rule out infantile hypertrophic pyloric stenosis

OBJECTIVE

To describe the incidence of bilious vomiting in infants with infantile hypertrophic pyloric stenosis that presented to a pediatric emergency department.

METHODS

A retrospective medical record review included all infants who presented to our level 1 pediatric emergency department from January 1, 2005, through December 31, 2009, who were diagnosed intraoperatively with infantile hypertrophic pyloric stenosis. Emesis was determined to be bilious if the vomit was described as "green," "containing bile," or "bilious."

RESULTS

The authors identified 354 infants with infantile hypertrophic pyloric stenosis. The median age was 4 weeks 6 days (range = 11 days to 13 weeks). Bilious emesis was encountered in 1.4% (5/354; 95% confidence interval = 0.5% to 3.2%). The pyloric thickness measurements on ultrasound were significantly smaller in those with bilious emesis compared with those without bilious emesis (z score = 2.64; P = .014).

CONCLUSION

Bilious emesis was the presenting symptom in a small proportion of infants with infantile hypertrophic pyloric stenosis.

Accuracy of sonographic criteria in the decision for surgical treatment in infantile hypertrophic pyloric stenosis

INTRODUCTION

Abdominal ultrasonography has replaced barium studies in establishing the diagnosis in difficult cases of infantile hypertrophic pyloric stenosis (IHPS). The aim of this retrospective study was to establish sonographic criteria of qualification for surgical treatment in children with IHPS.

MATERIAL AND METHODS

Hundred and fifteen infants (98 boys and 17 girls) with suspected IHPS were treated between 2000 and 2009. Pyloric muscle thickness, pyloric diameter and pyloric length were measured in US scans in all patients. Results were compared with US results of 19 infants with negative diagnosis and 29 children of the reference group.

RESULTS

Diagnosis of IHPS was confirmed by US examination in 96 children (83.5%). There were 86 boys in the group with male prevalence 8.6 : 1. The remaining 19 infants (16.5%) had a negative ultrasound. The mean PL (20.89 vs. 12.73), PMT (5.41 vs. 2.24), and PD (14.1 vs. 7.42) differed significantly between patients with and without pyloric stenosis (p < 0.0001). The mean PL (12.34), PMT (2.2), and PD (7.48) in the reference group did not differ statistically from values obtained in patients with negative IHPS diagnosis and were significantly lower than in children from the IHPS group (p < 0.0001). US imaging had a sensitivity of 98%, specificity of 100%, with a positive and negative predictive value of 100% and 90% respectively.

CONCLUSIONS

This study confirmed that ultrasonography is the first choice of diagnostic method in an infant with suspected hypertrophic pyloric stenosis. In cases with an uncertain clinical diagnosis of IHPS the examination can be easily repeated.

Infantile hypertrophic pyloric stenosis before 3 weeks of age in infants and preterm babies

BACKGROUND

Most infantile hypertrophic pyloric stenosis (IHPS) cases are diagnosed between 3 and 12 weeks after birth. Few data exist regarding Asian infants with IHPS who are younger than 3 weeks or are preterm. The goal of this study is to identify unusual clinical manifestations, clinical course, duration of hospital stay, and complications of Asian infants with IHPS who are preterm or younger than 3 weeks of age.

METHODS

From 1991 to 2004, all IHPS patients admitted to three tertiary centers in southern Taiwan were enrolled. The clinical manifestations, duration of hospital stay and complications were further compared between the IHPS patients diagnosed before and after 3 weeks; preterm and term infants.

RESULTS

A total of 214 patients were enrolled into the study; the mean age of diagnosis was 40 days of age; the average duration of hospital stay was 6.27 days. Eighteen (8.41%) patients were diagnosed before 3 weeks of age. A significantly shorter timeframe of diagnosis, a higher rate of jaundice, a lower daily body weight gain and longer duration of hospital stay were noted in the IHPS group prior to 3 weeks compared with those in IHPS group after 3 weeks. Eighteen were preterm infants. A significantly older age of symptom onset, a lower body weight at admission, more cases diagnosed by barium meal study and higher postoperative complication rates were noted in the preterm group versus full-term infants with IHPS.

CONCLUSIONS

The IHPS cases diagnosed before 3 weeks of age had longer duration of hospital stay. Preterm infants with IHPS had more postoperative complications.

Early pyloric stenosis: a case control study

OBJECTIVE

Pyloric stenosis (PS) is rare in the first 2 weeks of life, often leading to delays in diagnosis and treatment. We conducted a case control study to delineate the characteristics of patients with early PS (EPS). In addition, we tested the hypothesis that patients with EPS present with a smaller pylorus than older patients.

METHODS

A database of all patients presenting with PS to a children's hospital over a 5-year period (2002-2006) was obtained. Each patient admitted during the first 2 weeks of life (subject) was matched to a patient admitted after 4 weeks of age (control), with the same gender, electrolyte status, and treating surgeon. A single pediatric radiologist, blinded to patient age, reviewed all available ultrasounds retrospectively. Demographic, clinical, diagnostic, therapeutic, and outcome data were compared.

RESULTS

During the study period, 278 pyloromyotomies were performed for PS. Sixteen patients (5.8%) presented with EPS between 2 and 14 days of life. EPS patients had a higher prevalence of positive family history (31 vs. 0%, P = 0.043), and breast milk feeding (75 vs. 31%, P = 0.045). Sonographic measurements showed a pylorus that was of significantly less length (17.1 +/- 0.6 vs. 20.5 +/- 0.9 mm, P = 0.006) and muscle thickness (3.5 +/- 0.2 vs. 4.9 +/- 0.2 mm, P < 0.001) in patients with EPS. Hospital stay was significantly longer for EPS patients (4.3 +/- 0.9 vs. 2.0 +/- 0.1 days, P = 0.19).

CONCLUSIONS

Babies presenting with EPS are more likely to be breast fed and to have a positive family history. EPS is associated with a longer hospital stay. Use of sonographic diagnostic measurements specific to this age group may prevent delays in diagnosis and treatment, and improve outcomes.

Sonographic assessments of gastrointestinal and biliary functions

Ultrasound has been established as a routine work-up imaging method in abdominal diseases. It assesses the morphology of intra-abdominal organs and depicts the normal and pathological anatomy of the gastrointestinal tract as well as of the biliopancreatic system. Ultrasound is the method of choice for visualisation of motion sequences since it is, in contrast to other imaging methods, a real-time method. The non-invasiveness and the repeatability of the method are important advantages when performing investigations of functional processes. Therefore, ultrasound is most suited for functional studies. Up to now, functional ultrasound and its potential have been undervalued. Functional ultrasound provides a widely available method to increase our understanding of functional processes and motility. The authors review the options of functional ultrasound and discuss its practical relevance.

Use of ultrasound in 187 infants with suspected infantile hypertrophic pyloric stenosis

The diagnostic efficacy of ultrasound (US) in the diagnosis of infantile hypertrophic pyloric stenosis (IHPS) was evaluated, with particular attention paid to whether prematurity, age or weight correlate significantly to the sonographic measurements. The medical records of 187 infants with suspected IHPS were reviewed retrospectively. Eighty-seven had an US examination with details of the pylorus. Fifty-nine of these gave a positive diagnosis. The US criteria for a positive diagnosis were pyloric muscle thickness (PMT)>or=3 mm and pyloric muscle length (PML)>or=17 mm. The mean overall PMT was 4.14 mm and mean overall PML was 18.99 mm. Premature infants had a lower mean PML (17.8 mm) than the term infants (PML mean 19.3 mm); however, this was not significant (t-value 1.92, P=0.062). The sensitivity and specificity of PMT was 91 and 85%, respectively, and of PML 76 and 85%, respectively. The ability of US to diagnose IHPS using our criteria was significant (t-value, PMT 14.93 and PML 6.89; P<0.0001). There was no significant correlation between age, weight or prematurity and a sonographic diagnosis of IHPS (Pearson's coefficient<0.3). Therefore, the same US criteria should apply irrespective of prematurity, age or weight. Borderline PMT and PML measurements necessitate repeat US or alternative imaging.

Pyloric stenosis in in vitro fertilized triplets--is it a coincidence?

Infantile hypertrophic pyloric stenosis was previously reported in multiple births, but there were only 3 triplets in the literature and all were naturally conceived. Assisted reproductive technologies, such as in vitro fertilization, are accused for increasing the risk for some anomalies in children. Triplets of in vitro fertilization, all of whom were operated on because of pyloric stenosis, are presented.

Ultrasound evaluation of acute abdominal emergencies in infants and children

Ultrasound is extremely beneficial in the evaluation of acute pediatric abdominal disease, such as HPS, intussusception, and acute appendicitis. As techniques and equipment improve, its role in the evaluation of infants and children continues to increase.

Investigation in vomiting children

This article discusses how to investigate various surgical causes of vomiting. Particular emphasis is placed on plain radiographic, ultrasound, and contrast study findings. The article touches upon nineteen different diseases, and encompasses diseases found in neonates to adolescents.