Declining incidence of pyloric stenosis in New Zealand.

BACKGROUND: Pyloric stenosis is a relatively common paediatric surgical condition, but a worldwide decline in its incidence has been observed in recent decades. The objective of this study was to identify if the incidence of pyloric stenosis in New Zealand has been declining. METHODS: A retrospective review of the four New Zealand paediatric surgical centres' theatre databases from 2007 to 2017. Demographic data were recorded for all infants who had a pyloromyotomy and annual incidences of pyloric stenosis calculated. RESULTS: A total of 393 infants underwent a pyloromyotomy for pyloric stenosis during the study period. Most infants (81%) were of European ethnicity. There was a significant decline (P = 0.0001) in the national incidence of pyloric stenosis from 0.73/1000 live births (LB) in 2007 to 0.39/1000 LB in 2017. From 2007 to 2017, the incidence of male infants with pyloric stenosis declined from 1.27/1000 LB to 0.62/1000 LB. The current annual incidence of pyloric stenosis in New Zealand is 0.39/1000 LB. CONCLUSIONS: The incidence of pyloric stenosis in New Zealand has significantly declined in the last decade and is currently the lowest reported incidence in the world involving a predominantly European cohort. A decline in male infants developing pyloric stenosis was also observed. Further study is required to investigate causes for this low incidence and declining trend.

Prediction of three year outcomes using the Bayley-III for surgical, cardiac and healthy Australian infants at one year of age.

BACKGROUND: Previous predictive research has predominantly focussed on infants who are preterm, low birth weight, who have a specific condition or who have undergone a specific procedure. AIM: This study investigated the ability of outcomes at one year of age to predict outcomes at three years using the Bayley-III for infants who have undergone early major cardiac surgery (CS) or non-cardiac (NC) surgery and their healthy peers. STUDY DESIGN: Participants who were part of the Development After Infant Surgery (DAISy) study who had complete Bayley-III assessments at one and three years of age were included in the analyses. This included 103 infants who had undergone CS, 158 who had NC surgery and 160 controls. RESULTS: Bayley-III outcomes at one, although statistically significantly associated with three year outcomes in all domains were weak predictors of those outcomes for CS, NC surgical and healthy infants. Specificity for three year outcomes was good for cognitive, receptive language and fine motor domains for infants who had undergone CS and NC surgery. Sensitivity for <-1 SD at three years was poor for cognitive, expressive and receptive language, and fine motor outcomes for CS and NC surgical participants. CONCLUSION: It remains difficult to predict how performance at one year on the Bayley-IIII predicts performance at three on the Bayley-III for infants who have undergone early major CS or NC surgery and for healthy Australian infants.

Intraoperative Endoscopic Botox Injection During Total Esophagectomy Prevents the Need for Pyloromyotomy or Dilatation.

BACKGROUND: Esophagectomy may lead to impairment in gastric emptying unless pyloric drainage is performed. Pyloric drainage may be technically challenging during minimally invasive esophagectomy and can add morbidity. We sought to determine the effectiveness of intraoperative endoscopic injection of botulinum toxin into the pylorus during robotic-assisted esophagectomy as an alternative to surgical pyloric drainage. MATERIALS AND METHODS: We performed a retrospective analysis of patients with adenocarcinoma and squamous cell carcinoma of the distal esophagus or gastroesophageal junction who underwent robotic-assisted transhiatal esophagectomy (RATE) without any surgical pyloric drainage. Patients with and without intraoperative endoscopic injection of 200 units of botulinum toxin in 10 cc of saline (BOTOX group) were compared to those that did not receive any pyloric drainage (noBOTOX group). Main outcome measure was the incidence of postoperative pyloric stenosis; secondary outcomes included operative and oncologic parameters, length of stay (LOS), morbidity, and mortality. RESULTS: From November 2006 to August 2014, 41 patients (6 females) with a mean age of 65 years underwent RATE without surgical drainage of the pylorus. There were 14 patients in the BOTOX group and 27 patients in the noBOTOX group. Mean operative time was not different between the comparison groups. There was one conversion to open surgery in the BOTOX group. No pyloric dysfunction occurred in the BOTOX group postoperatively, and eight stenoses in the noBOTOX group (30%) required endoscopic therapy (P < .05). There were no differences in incidence of anastomotic strictures or anastomotic leaks. One patient in group noBOTOX required pyloroplasty 3 months after esophagectomy. There was one death in the noBOTOX group postoperatively (30-day mortality 2.4%). Mean LOS was 9.6 days, and BOTOX patients were discharged earlier (7.4 versus 10.7, P < .05). CONCLUSION: Intraoperative endoscopic injection of botulinum toxin into the pylorus during RATE is feasible, safe, and effective and can prevent the need for pyloromyotomy.

The scars of time: the disappearance of peptic ulcer-related pyloric stenosis through the 20th century.

BACKGROUND: The changing pattern of haemorrhage and perforation from peptic ulcer disease is well documented but little is known about pyloric stenosis, the third complication of the disease. METHODS: We reviewed records relating to definitive operations (with intent to cure) for peptic ulcer disease carried out in York, UK from 1929-1997. We categorised the patients as pyloric stenosis and no pyloric stenosis based on findings at operation and examined the change in total number of cases with pyloric stenosis and proportion of cases with pyloric stenosis, by year of operation and by decade of birth. To place our results in perspective, we reviewed world literature to examine rates of pyloric stenosis as a percentage of operative cases reported in other case series in the 20th century. RESULTS: 4178 patients were included in the analysis; 3697 without pyloric stenosis and 481 with pyloric stenosis (11.5%). Analysis by birth cohort showed that the proportion found to have pyloric stenosis at surgery fell from 17% in the first cohort (birth 1880-89) to only 2.9% in the last cohort (birth 1950-59; p<0.001). Mean age at operation fell more steeply for those with pyloric stenosis: 74 to 30 years vs. 65 to 28 years (p <0.001). The trend of final decline started before the introduction of modern medical treatment. Review of similar case series from across the world shows a similar decline in the proportion of peptic ulcer cases showing pyloric stenosis at operation. CONCLUSION: The reduction in pyloric stenosis over the last several decades is disproportionately greater than the change seen in peptic ulcer disease requiring surgery. Our findings suggest that this reduction in pyloric stenosis is largely the result of the changing natural history of the disease rather than due to the introduction of acid-suppressing medication.

Hospitalization of rural and urban infants during the first year of life.

OBJECTIVES: To examine hospitalizations and length of stay (LOS) for infants aged <1 year in rural and urban counties, hypothesizing that infants living in rural counties experience significantly different hospital use compared with urban infants. METHODS: Birth certificates for infants born in California hospitals between 1993 and 2005 and surviving to discharge were linked to hospital discharge records and death certificates during the first year of life, resulting in a study population of >6.4 million. Hospitalizations, cumulative LOS, readmission rates, and mortality were compared by using univariate and multivariable analysis for infants living in small rural, large rural, small urban, and large urban counties. Odds of hospitalization and cumulative LOS were also examined for common infant diagnoses. RESULTS: Infants living in increasingly rural counties experienced decreasing rates of hospitalization and decreasing number of hospitalized days during the first year of life. Infants living in small rural counties experienced 370 hospital days per 1000 infants compared with 474 hospital days per 1000 infants living in large urban counties. In multivariable analysis, infants in large urban counties experienced increased odds of hospitalization (odds ratio: 1.20 [95% confidence interval: 1.06-1.36]) and increased hospitalized days (incidence risk ratio: 1.17 [95% confidence interval: 1.06-1.29]) compared with infants in small rural counties. For most common diagnoses, urban residence was associated with either increased odds of hospitalization or increased cumulative LOS. CONCLUSIONS: Infants living in rural California counties experienced decreased hospital utilization, including decreased hospitalization and decreased LOS, compared with infants living in urban counties.

Pre- and perinatal risk factors for pyloric stenosis and their influence on the male predominance.

Pyloric stenosis occurs with a nearly 5-fold male predominance. To what extent this is due to environmental factors is unknown. In a cohort of all children born in Denmark, 1977-2008, the authors examined the association between pre- and perinatal exposures and pyloric stenosis and investigated whether these factors modified the male predominance. Information on pre- and perinatal factors and pyloric stenosis was obtained from national registers. Poisson regression models were used to estimate rate ratios. Among 1,925,313 children, 3,174 had surgery for pyloric stenosis. The authors found pyloric stenosis to be significantly associated with male sex, age between 2 and 7 weeks, early study period, being first born, maternal smoking during pregnancy, preterm delivery, small weight for gestational age, cesarean section, and congenital malformations. Among cases, 2,595 were males and 579 were females. Lower male predominance was associated with age at diagnosis outside the peak ages, early study period, no maternal smoking during pregnancy, preterm delivery, and congenital malformations. The authors have previously found a strong familial aggregation of pyloric stenosis indicating a genetic influence. This study shows that environmental factors during and shortly after pregnancy also play a role and that several of these modify the strong male predominance.

Early life events: infants with pyloric stenosis have a higher risk of developing chronic abdominal pain in childhood.

OBJECTIVE: We hypothesize that children who had pyloric stenosis are at greater risk for developing chronic abdominal pain because this cohort combines various risk factors: an early stressful event, gastric surgery, and perioperative nasogastric tube placement in most cases. STUDY DESIGN: This was a case control study of all children diagnosed with pyloric stenosis during infancy (cases) between January 1, 2000, and June 31, 2005, at Children's Memorial Hospital, Chicago. Because of their similar genetic and socioeconomic backgrounds, siblings aged 4 to 20 years without a history of pyloric stenosis were selected as controls. Parents of children with symptoms completed the parental form of the Pediatric GI Symptoms Rome III version questionnaire for both cases and controls. The primary outcome was the prevalence of chronic abdominal pain, and the secondary outcome was the presence of pain-associated functional gastrointestinal disorder (FGID), in accordance with Rome III criteria. RESULTS: Cases (n = 100; mean age, 7.49 ± 1.43 years; 29 girls) and controls (n = 91; mean age, 9.20 ± 4.19 years; 29 girls) participated in the study. Mean time to follow-up was 7.2 ± 1.6 years. Chronic abdominal pain was significantly more common in cases than in controls (20/80 [25%] vs 5/91 [5.8%]; OR, 4.3; 95% CI, 1.5-12; P = .0045). Seven out of 20 subjects (35%) met the Rome III criteria for diagnosis of a pain-associated FGID (3 with irritable bowel syndrome, 2 with functional dyspepsia, and 2 with functional abdominal pain), and 1 patient in the control group (with irritable bowel syndrome) met these criteria (OR, 6.8; 95% CI, 0.82-56; P = .043). CONCLUSION: We have described a new model to study early life events in infants. Our findings suggest that the presence of pyloric stenosis in infancy and factors involved in its perioperative care represent risk factors in the development of chronic abdominal pain in children at long-term follow-up. This study provides important data to sustain the multifactorial theoretical construct of pain-associated FGID and underscores the importance of early life events in the development of chronic abdominal pain in children.

Testosterone levels in umbilical-cord blood and risk of pyloric stenosis.

OBJECTIVE: The risk of infantile hypertrophk pylonc stenosis is ∼5 times more common in male than female infants. It has been hypothesized that the higher risk among male infants is associated with high levels of testosterone causing hypertrophy of the pylorus muscle. To test this hypothesis, we examined the association between the testosterone levels in the umbilical-cord blood and the risk of infantile hypertrophic pyloric stenosis. PATIENTS AND METHODS: We conducted a matched case-control study nested in the Danish National Birth Cohort using risk-set sampling. From a cohort of 101 042 pregnancies, we identified umbilical-cord blood samples from 46 case subjects (43 male and 3 female infants) who developed infantile hypertrophic pyloric stenosis in the first year of life and 150 gender- and gestational age-matched control subjects. The testosterone levels were measured by liquid chromatography-tandem mass spectrometry. Rate ratios were estimated by using conditional logistic regression. RESULTS: In male infants, the mean testosterone level at birth was 0.78 nmol/L in case subjects and 0.91 nmol/L in control subjects. The rate of infantile hypertrophic pyloric stenosis was inversely, albeit insignificantly, associated with the testosterone levels in male infants; there was a 29% (95% confidence interval: -46% to 65%; P = 35) lower rate per nmol/L. The association was not modified according to age, gestational age, or birth order. CONCLUSIONS: We found no support for the hypothesis that high testosterone levels in the umbilical-cord blood are strongly associated with a subsequently higher risk for infantile hypertrophic pyloric stenosis in male infants.

Familial aggregation and heritability of pyloric stenosis.

CONTEXT: Pyloric stenosis is the most common condition requiring surgery in the first months of life. Case reports have suggested familial aggregation, but to what extent this is caused by common environment or inheritance is unknown. OBJECTIVES: To investigate familial aggregation of pyloric stenosis from monozygotic twins to fourth-generation relatives according to sex and maternal and paternal contributions and to estimate disease heritability. DESIGN, SETTING, AND PATIENTS: Population-based cohort study of 1,999,738 children born in Denmark between 1977 and 2008 and followed up for the first year of life, during which 3362 children had surgery for pyloric stenosis. MAIN OUTCOME MEASURE: Familial aggregation of pyloric stenosis, evaluated by rate ratios. RESULTS: The incidence rate (per 1000 person-years) of pyloric stenosis in the first year of life was 1.8 for singletons and 3.1 for twins. The rate ratios of pyloric stenosis were 182 (95% confidence interval [CI], 70.7-467) for monozygotic twins, 29.4 (95% CI, 9.45-91.5) for dizygotic twins, 18.5 (95% CI, 13.7-25.1) for siblings, 4.99 (95% CI, 2.59-9.65) for half-siblings, 3.06 (95% CI, 2.10-4.44) for cousins, and 1.60 (95% CI, 0.51-4.99) for half-cousins. We found no difference in rate ratios for maternal and paternal relatives of children with pyloric stenosis and no difference according to sex of cohort member or sex of relative. The heritability of pyloric stenosis was 87%. CONCLUSION: Pyloric stenosis in Danish children shows strong familial aggregation and heritability.

The safety of macrolides during lactation.

BACKGROUND: Infantile exposure to macrolides has been associated with hypertrophic pyloric stenosis causing projectile vomiting, dehydration, electrolyte abnormalities, and in rare cases death possibly via macrolide interaction with gastric motilin receptors. Large population-based cohorts have suggested that exposure to macrolides via breastmilk may be associated with pyloric stenosis. METHODS: In this prospective, controlled observational study designed to assess the safety of macrolides during lactation, we followed infants whose mothers contacted our Drug Consultation Center at the Assaf Harofeh Medical Center (Zerrifin, Israel) inquiring about safety of macrolides during lactation and compared them to a cohort of infants exposed to amoxicillin during breastfeeding. RESULTS: Fifty-five infants exposed to macrolide antibiotics were compared to a control cohort of 36 infants exposed to amoxicillin via lactation. The infants in the macrolide group were all exposed to erythromycin and the newer macrolides: azithromycin, clarithromycin, and roxithromycin. The rate of adverse reactions the infant experienced while being exposed to both antibiotics was comparable. Seven (12.7%) infants in the macrolide group experienced adverse reactions versus three infants (8.3%) in the amoxicillin group (odds ratio = 1.6, 95% confidence interval, 0.38-6.65, p = 0.73). The adverse reactions in the infants exposed to macrolides were rash, diarrhea, loss of appetite, and somnolence, whereas the infants exposed to amoxicillin experienced rashes and somnolence. Factors such as gestational age, age and weight at exposure, maternal age, or type of macrolide were not associated with the infant's adverse reaction in multivariate regression analysis. CONCLUSIONS: Rates and types of minor adverse reactions in breastfed infants exposed to a macrolide or amoxicillin in breastmilk were comparable. Macrolide exposure during breastfeeding was not associated with pyloric stenosis, although larger prospective studies are required to confirm our observation.

Prevalence of infantile hypertrophic pyloric stenosis in Texas, 1999-2002.

BACKGROUND: The cause of infantile hypertrophic pyloric stenosis (IHPS) is poorly understood. This descriptive study of IHPS focuses on the effect of maternal nativity, maternal Hispanic ethnicity, subtypes of maternal Asian ethnicity, and the timing of the infant's surgery, that is, pyloromyotomy. METHODS: All cases of IHPS born in Texas from 1999 through 2002 were retrieved from the Texas Birth Defects Registry. Crude prevalence ratios and adjusted prevalence ratios (aPRs) were calculated using logistic regression. RESULTS: IHPS occurred predominantly in boys (aPR 4.21; 95% CI: 3.81, 4.65) compared with girls. Compared with Whites, there was a lower prevalence among Blacks (aPR 0.36; 95% CI: 0.30, 0.43), foreign-born Hispanics (aPR 0.61; 95% CI: 0.54, 0.69), Chinese (aPR 0.11; 95% CI: 0.01, 0.78), Vietnamese (aPR 0.17; 95% CI: 0.06, 0.46), Asian Indians (aPR 0.33; 95% CI: 0.15, 0.75), and Filipinos (aPR 0.22; 95% CI: 0.05, 0.91). In aggregate, foreign born Asians had a decreased risk of IHPS (aPR 0.20; 95% CI: 0.11, 0.37) compared to Whites. We observed no decrease in the risk of IHPS among US-born Asians (in aggregate) or US-born Hispanics. The strength of these risk factors did not vary according to the timing of the pyloromyotomy. CONCLUSIONS: This study confirmed previous findings that female infants and Black infants have a lower rate of IHPS. Large decreases in rates of IHPS were observed among foreign-born Hispanics and foreign-born Asians, but not among their US-born counterparts. These findings may be explained by differences in the frequency of behavioral risk factors for IHPS or differences in the frequency of ascertainment of mild cases of IHPS by ethnicity or nativity.

Changes in frequencies of select congenital anomalies since the onset of folic acid fortification in a Canadian birth defect registry.

OBJECTIVES: Fortification of grain products with folic acid has been shown to significantly reduce the occurrence of neural tube defects (NTDs) in Canada and elsewhere. However, the impact on non-NTD anomalies has not been well studied. METHODS: Using the Alberta Congenital Anomalies Surveillance System (ACASS), we examined changes in occurrence of select congenital anomalies where folic acid supplementation with multivitamins had previously been suggested to have an effect. Anomalies documented in the ACASS 1992-1996 (pre-fortification) were compared to 1999-2003 (post-fortification). RESULTS: A significant decrease in spina bifida (OR 0.51, 95% CI 0.36-0.73) and ostium secundum atrial septal defects (OR 0.80, 95% CI 0.69-0.93) was evident, but there was a significant increase in obstructive defects of the renal pelvisand ureter (OR 1.45, 95% CI 1.24-1.70), abdominal wall defects (OR 1.40, 95% CI 1.04-1.88) and pyloric stenosis (OR 1.49, 95% CI 1.18-1.89). CONCLUSIONS: Consistent with other studies, a 50% reduction in spina bifida was associated with the post-fortification time period. Supporting the possibility that folic acid fortification may play a role in preventing other birth defects, a 20% reduction in atrial septal defects was also associated. The increase in abdominal wall defects, most notably gastroschisis, is likely related to pre-existing increasing trends documented in several regions around the world. The increase in pyloric stenosis and obstructive urinary tract defects was not expected and any causal relationship with folic acid fortification remains unclear. Similar studies by other birth defects surveillance systems in Canada and elsewhere are needed to confirm these trends.

[Surgical tactics in the ulcer pyloroduodenal stenosis in decompensation stage].

In the ulcer pyloroduodenal stenosis the stages of complete and noncomplete decompensation are suggested. In 73% of observations, while performing an adequate preoperative preparation it was possible to convert pyloroduodenal stenosis from the stage of complete decompensation into the stage of noncomplete decompensation, in which the performance of organpreserving operation is possible. In the patients, suffering pyloroduodenal stenosis in the stage of noncomlete decompensation, resection of 2/3 of stomach is performed.

[Infrared spectroscopy in assessment of the morpho-functional stomach changes at ulcerous pyloroduodenal stenosis].

In the present study authors have analyzed the suitability of the infrared (IR) spectroscopy for diagnosis of morphological and functional changes of the stomach in ulcer pyloroduodenal stenosis. Data obtained from 64 patients have shown that the IR spectroscopic features of the stomach were dependent on the stage of stenosis, secretory function of the stomach and the presence of the Helicobacter Pylori (HP) infection. IR spectroscopy can be a multi-purpose mean of assessment of the morphological and functional properties of the stomach in pyloroduodenal stenosis. IR spectroscopy provides the opportunity to assess the secretory state of the stomach at different stages of the disease. Using IR spectroscopy we were able to reveal the presence of HP in the stomach and the dynamics of its eradication during of conservative treatment and at any time after surgical intervention.

The continuing enigma of pyloric stenosis of infancy: a review.

Striking features of the descriptive epidemiology of pyloric stenosis of infancy have been identified but until recently have not suggested any useful etiologic lead. The disease first received serious attention approximately 100 years ago and has since occurred throughout the Western world at a rate between 2 and 5 per thousand live births; it appears to be uncommon elsewhere. Its age distribution is essentially limited to the period between the third and eighth weeks after birth. It is 4 to 5 times more common in boys than girls. It is less common in blacks than whites in the United States and less common among Asians than whites in the United States and elsewhere. Its incidence is highest in first-born infants. Evidence on a role for maternal age is not consistent. The disease re-occurs in families with sufficient frequency to incite the interest of geneticists, although no genetic model yet proposed offers a better basis for counseling than do the empiric observations on which it is based. Monozygous twins are concordant for the disease not much more frequently than are dizygous twins, and indeed not a great deal more often than nontwin siblings, which should prompt a search for environmental explanations of the disease's familial nature. Sharp declines in the incidence of the disease in Denmark and Sweden during the 1990s led to the hypothesis that infants sleeping in the prone position-a practice discouraged with some success by Scandinavian campaigns to reduce the frequency of sudden infant death syndrome (SIDS)-may also be at increased risk of pyloric stenosis. If supported, this hypothesis may offer the first-ever possibility of reducing the frequency of this disease, as well as SIDS. If the hypothesis is not supported, the recent declines in the disease in Denmark and Sweden add another facet to its enigmatic nature.

Population demographic indicators associated with incidence of pyloric stenosis.

OBJECTIVES: To calculate incidence rates of pyloric stenosis (estimated by the rate of pyloromyotomy) among infants in Ontario and determine their association with population sociodemographic indicators. METHODS: Pyloromyotomy rates were calculated from hospital discharge data from 1993 through 2000. Four-year data (1993-1996 and 1997-2000) were combined to ensure the stability of the rates. Small-area variations in pyloromyotomy rates and correlations between sociodemographic indicators were studied. RESULTS: Approximately 84.0% of the patients were male infants (younger than 1 year). The sex-adjusted pyloromyotomy rates were 1.57 and 1.86 per 1000 with a 3.4-fold and 3.0-fold regional variation in 1993-1996 and 1997-2000, respectively. Urban areas consistently had the lowest pyloromyotomy rate (1.04 and 1.11 per 1000 in Metropolitan Toronto), but the highest rates were from more rural areas (3.30 and 3.38 per 1000 in Quinte, Kingston, Rideau). After adjusting for socioeconomic status and availability of surgeons in the region, living in a rural area remained a significant factor associated with a higher incidence of pyloromyotomy. The risk of pyloromyotomy for an infant who lives in a region with more than two thirds of its area classified as rural was 1.79 (95% confidence interval, 1.23-2.61; P<.005). CONCLUSIONS: The observed changes in incidence and a higher rate among male infants are consistent with results from previous comparative studies conducted in North America and Sweden. The rural/urban differences suggest that environmental influences related to living in these areas may have a role in the etiology of pyloric stenosis. Further research is needed to evaluate these differences.

Is erythromycin therapy teratogenic in humans?

The possible teratogenic effect of erythromycin therapy, noted previously, was studied. Women who had taken erythromycin or penicillin V in early pregnancy and their infants were studied, using the Swedish Medical Birth Register where information on drug use during pregnancy was recorded based on interviews in early pregnancy. The risk for any congenital malformation after erythromycin therapy (but not after penicillin V therapy) was increased (odds ratio 1.24, 95% confidence interval: 1.01-1.51) and this was due to an effect on cardiovascular malformations (odds ratio 1.92, 95% CI: 1.37-2.68). There was also an indicated increased risk for pyloric stenosis (risk ratio 3.0, 95% CI: 1.1-8.5 after exposure in early pregnancy). Various explanations to the finding are discussed, one of them linked to the fact that erythromycin inhibits a specific cardiac potassium channel (IKr) which seems to play a major role in cardiac rhythm regulation in the early embryo. Potent blocking drugs cause as a class effect cardiac defects in animal experiments.

Clinical presentation of pyloric stenosis: the change is in our hands.

BACKGROUND: Hypertrophic pyloric stenosis classically presents as projectile vomiting during the third to fourth week of life, associated with good appetite. Additional classical presenting findings include palpation of the pyloric tumor, described as olive-shaped; a visible gastric peristaltic wave after feeding; and hypochloremic, hypokalemic metabolic alkalosis. It was recently claimed that this presentation has changed due to the easier access to gastrointestinal imaging. OBJECTIVE: To validate this contention and discuss possible reasons. METHODS: We conducted a retrospective chart review of all patients who underwent pyloromyotomy for HPS between 1990 and 2000. Only patients with confirmed HPS at the time of surgery were included. We also performed a comprehensive review of older studies for comparison. RESULTS: Seventy patients underwent pyloromyotomy over the 10 year period. Overall, 81% of patients were male infants and the mean age at diagnosis was 40 days. The mean duration of symptoms was 8 days. A firstborn child was noted in 43% of the cases. The classical symptom of projectile vomiting was absent in one-third of the patients, a pyloric tumor was not palpated in one-half of the cases, bicarbonate was higher than 28 mEq/L in 20%, and a pH of above 7.45 was present in 25% of patients. Hypochloremia was noted in about one-third. We found a good correlation between ultrasonographic width and length of the pylorus and the intraoperative findings. Pylorus length +/- 24 mm correlated with significantly longer duration of symptoms. When compared with previous studies, the main findings were not significantly different; namely, mean age at diagnosis, percentage of male gender, and duration to diagnosis. The decrease in the number of pyloric tumors palpated paralleled the increase in the use of upper gastrointestinal series and ultrasonography in particular. CONCLUSIONS: The clinical presentation of HPS has not actually changed despite the easier accessibility of GI imaging studies. However, the one significant change is the low percentage of pyloric tumors palpated, probably due to declining clinical skills accompanied by earlier utilization of imaging studies. The use of imaging and laboratory studies did not change the age at diagnosis but may have shortened the time for diagnosis and reduced the postoperative stay. Imaging and laboratory studies may be helpful for the subgroup with a non-classical clinical presentation.