AUTHOR AND EDITOR INFORMATION

Section 1 of 8  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Follow-up
• References

INTRODUCTION

Section 2 of 8  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Follow-up
• References

Background

Hirschsprung wrote the first complete description of hypertrophic pyloric stenosis (HPS) in 1888. He believed the disease was congenital and represented fetal pyloric development failure. Ramstedt, in 1907, described an operation to alleviate this condition. He suggested splitting the pyloric muscle and leaving it open to heal secondarily. This procedure has been used to treat infantile hypertrophic pyloric stenosis (IHPS) since that time. Although this curious disease is treated easily with surgery, its etiology remains undetermined. HPS is inherited by a multifactorial threshold model, and the generalized occurrence risk for siblings is 5-9%. Associated congenital anomalies are reported in 6-20% of patients with pyloric stenosis. The rare association with developmental delay has also been reported.

Pathophysiology

Diffuse hypertrophy and hyperplasia of the smooth muscle of the antrum of the stomach and pylorus proper narrow the channel, which then can become easily obstructed. The antral region is elongated and thickened to as much as twice its normal size. In response to outflow obstruction and vigorous peristalsis, stomach musculature becomes uniformly hypertrophied and dilated. Gastritis may occur after prolonged stasis. Hematemesis is occasionally noted. The patient may become dehydrated as a result of vomiting and develop marked hypochloremic alkalosis.

Researchers have investigated the cause of this muscle hypertrophy for several decades. Many believe the problem is induced by the pyloric musculature failing to relax. Results of studies of pyloric muscle innervation are inconclusive, possibly showing a tendency toward fewer or more immature ganglion cells in affected individuals. Deregulation of vasoactive intestinal peptide (VIP) and nitric oxide both have been demonstrated in patients with pyloric stenosis, although whether these factors are associative or causative is unclear.

No definitive cause for HPS has been found. However, various environmental and hereditary factors have been implicated. Suspected environmental factors include infantile hypergastrinemia, abnormalities in the myenteric plexus innervation, cow's milk protein allergy, and exposure to macrolide antibiotics. Hereditary factors may also play a role; HPS occurs in up to 7% of infants of affected parents. The etiology is probably multifactorial, with both genetic and environmental factors contributing. Recognition that HPS is an acquired, and not a congenital, disorder is increasing.

Frequency

United States

Pyloric stenosis is a common cause of gastric outlet obstruction in infants. The prevalence of HPS ranges from 1.5-4/1000 live births among whites, although it is less prevalent among African and Asian Americans.

Mortality/Morbidity

Operative therapy for HPS has remained unchanged for nearly 100 years. Outcomes have improved through advances in early diagnosis, preoperative resuscitation, operative anesthetics, and nutritional management. Mortality may rarely result from late diagnosis, resulting in dehydration and shock. Mortality is also rare after pyloromyotomy. Wound infection occurs in fewer than 1% of patients. Perforation of the pyloric mucosa also is unusual, occurring in fewer than 3% of reported cases. Long-term sequelae from the disease or treatment also are minimal.

Race

Reported prevalence of HPS among whites ranges from 1.5-4/1000 live births; HPS is less prevalent among African Americans, Asians, and Hispanics.

Sex

Pyloric stenosis has a well-known predilection for occurring more often in males than in females, with reported ratios ranging from 2:1 to 5:1. First-born male children are believed to have the highest risk of developing HPS.

Age

Newborns typically develop signs of gastric outlet obstruction at 4 weeks. Cases of HPS have been documented from the first week of life to 3 months. Premature infants generally develop symptoms later than full-term infants.

CLINICAL

Section 3 of 8  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Follow-up
• References

History

• Typical presentation of an infant with HPS is onset of initially nonbloody, always nonbilious vomiting at 4-8 weeks. Although vomiting may initially be infrequent, over several days it becomes more predictable, occurring at nearly every feeding. Vomiting intensity also increases until pathognomonic projectile vomiting ensues. Slight hematemesis of either bright red flecks or a coffee-ground appearance is sometimes observed.
• Patients are usually not ill-looking or febrile. The baby in the early stage of the disease remains hungry and sucks vigorously after episodes of vomiting.
• Prolonged delay in diagnosis can lead to dehydration, poor weight gain, malnutrition, metabolic alterations, and lethargy.
• Parents often report trying several different baby formulas because they (or their physicians) assume vomiting is due to intolerance.

Physical

• Careful physical examination provides a definitive diagnosis for most infants with HPS. However, some of the classic signs that would lead to diagnosis may be absent due, in part, to the early diagnosis of HPS.
• An enlarged pylorus, classically described as an "olive," can be palpated in the right upper quadrant or epigastrium of the abdomen. In order to assess the pylorus, the patient must be calm and cooperative. A pacifier or small amount of dextrose water may help. If the stomach is distended, aspiration using a nasogastric tube is necessary. With the infant supine and the examiner on the child's left side, gently palpate the liver edge near the xiphoid process. Then displace the liver superiorly; downward palpation should reveal the pyloric olive just on or to the right of the midline. To be assured of the diagnosis, the physician should be able to roll the pylorus beneath the examining finger. The tumor (mass) is best felt after vomiting or during, or at the end of, feeding. The diagnosis is easily made if the presenting clinical features are typical, with projectile vomiting, visible peristalsis, and a palpable pyloric tumor.
• When diagnosis is delayed, the infant may develop severe constipation associated with signs of dehydration, malnutrition, lethargy, and shock.

DIFFERENTIALS

Section 4 of 8  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Follow-up
• References

Other Problems to be Considered

Adrenal crisis
Cow's milk protein allergy
Eosinophilic gastroenteritis
Gastric outlet obstruction
Inborn errors of metabolism
Pyloric antral web

WORKUP

Section 5 of 8  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Follow-up
• References

Lab Studies

• Serum electrolytes: Document adequacy of fluid resuscitation and correction of electrolyte imbalances before surgical repair of HPS (see Medical Care). Infants with severe vomiting can develop profound hypochloremia and hypokalemia. The classic biochemical abnormality in HPS is hypochloremic, hypokalemic metabolic alkalosis.

Imaging Studies

• Ultrasonography has become the criterion standard imaging technique for diagnosing HPS. It is reliable, highly sensitive, highly specific, and easily performed. An experienced ultrasonographer increases the test's predictive value. Necessary measurements include pyloric muscle thickness and pyloric channel length. Muscle wall thickness 3 mm or greater and pyloric channel length 14 mm or greater are considered abnormal in infants younger than 30 days.
• Barium upper gastrointestinal (UGI) study is an effective means of diagnosing HPS when ultrasonography is not diagnostic. It should demonstrate an elongated pylorus with antral indentation from the hypertrophied muscle. The UGI may demonstrate the "double track" sign when thin tracks of barium are compressed between thickened pyloric mucosa or the "shoulder" sign when barium collects in the dilated prepyloric antrum. After UGI barium study, irrigating and removing any residual barium from the stomach is advisable to avoid aspiration.
• Although UGI endoscopy would demonstrate pyloric obstruction, physicians would find it difficult to differentiate accurately between HPS and pylorospasm. Endoscopy is reserved for patients with atypical clinical signs when ultrasonography and UGI studies are nondiagnostic. Endoscopic dilatation has rarely been employed as a method of treatment. This treatment is not standard for HPS; endoscopy should be used rarely, if ever.

TREATMENT

Section 6 of 8  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Follow-up
• References

Medical Care

• Preoperative resuscitation: Surgical repair of HPS is fairly straightforward and without many complications, yet properly preparing the infant for this procedure is vitally important. Most infants with HPS do not have complete gastric outlet obstruction and can tolerate their inherent gastric secretions. Repeated episodes of vomiting following attempts to feed the infant cause progressive dehydration and loss of hydrogen chloride from the gastric juices. Preoperative management is directed at correcting the fluid deficiency and electrolyte imbalance.
• • Base fluid resuscitation on the infant's degree of dehydration. Most infants can have their fluid status corrected within 24 hours; however, severely dehydrated children sometimes require several days for correction.
  • If necessary, administer an initial fluid bolus of 10 mL/kg with lactated Ringer solution or 0.45 isotonic sodium chloride solution. Continue intravenous (IV) therapy at an initial rate of 1.25-2 times the normal maintenance rate until adequate fluid status is achieved.
  • Adequate amounts of both chloride and potassium are necessary to correct metabolic acidosis. Unless renal insufficiency is a concern, initially add 2-4 mEq of KCL per 100 mL of IV fluid. Adequate chloride for resuscitation can usually be provided by 5% dextrose in 0.4% sodium chloride solution. Avoid adding hypertonic chloride or ammonium chloride.
  • Urine output and serial electrolyte determinations are performed during resuscitation. Correction of serum chloride level to 90 mEq/L or greater usually is adequate to proceed with surgical intervention.
  • Before induction of anesthesia, aspirate the infant's stomach with a large-caliber suction tube to remove any residual gastric fluid or barium. Saline irrigation is occasionally necessary to remove a large quantity of barium.

Surgical Care

Surgery remains the definitive mode of treatment. The best surgical outcome and lowest complications are more likely when the surgeon has specialist pediatric surgical training.

• Ramstedt pyloromyotomy remains the standard procedure of choice for HPS because it is easily performed and is associated with minimal complications. The usual approach is via a right upper quadrant transverse incision that splits the rectus muscle and fascia.
• Laparoscopic pyloromyotomy has a significantly shorter recovery time compared with open pyloromyotomy. However, open pyloromyotomy has a higher efficacy and fewer complications.
• Endoscopic pyloromyotomy is a simple procedure and can be performed as an outpatient procedure.
• Recently, endoscopic balloon dilatation of HPS after failed pyloromyotomy has been used with greater frequency.
• Several other approaches have been described. A supraumbilical curvilinear approach has gained popularity with good cosmetic results.
• Postoperative management
  • Continue IV maintenance fluid until the infant is able to tolerate enteral feedings. In most instances, feedings can begin within 8 hours following surgery. Graded feedings can usually be initiated every 3 hours, starting with Pedialyte and progressing to full-strength formula.
  • Although schedules that advance the volume of feeds more quickly or those that begin with ad lib feeds are associated with more frequent episodes of vomiting, they do not increase morbidity and actually may decrease the time to hospital discharge.
  • Addition of a histamine 2 (H2) receptor blocker sometimes can be beneficial.
  • Treat persistent vomiting expectantly because it usually resolves within 1-2 days.
  • Avoid the temptation to repeat ultrasonography or UGI barium study; these invariably demonstrate a deformed pylorus and results are difficult to interpret.

Consultations

Early consultation with a surgeon familiar with neonatal care is warranted because treatment is essentially surgical. Early consults facilitate decisions for diagnostic studies, fluid resuscitation, and scheduling the operative procedure. This is especially important if the child requires transfer to another facility for surgical care. The American Pediatric Surgical Association offers guidelines for appropriate consultation and transfer of small infants. Good outcome has been shown to be dependent on the quality of preoperative correction of fluid and electrolyte abnormalities, availability of a pediatric anesthetist, and training level of the surgeon.

Diet

Feedings are usually resumed 6-8 hours after operation. In most instances, gradually increasing the volume and strength of feedings is recommended (see Postoperative management).

FOLLOW-UP

Section 7 of 8  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Follow-up
• References

Further Inpatient Care

• Feeding can be resumed and advanced over a 24-hour period for most patients. Premature infants sometimes require apnea monitoring if they have a history of apnea spells. Narcotic pain medications should be avoided in the postoperative period because opioids may precipitate apnea in the alkalotic newborn.
• Infants can be discharged from hospital care once they can remain hydrated and have adequate enteral intake.

Further Outpatient Care

• Infants generally recover rapidly after operative correction of HPS. Advise parents to increase food volume in the days after discharge. A single postoperative visit 1-2 weeks after surgery is often all that is necessary to document weight gain. Long-term sequelae from pyloromyotomy are virtually unheard of. Studies have documented normal function returns in months to years after surgery.

In/Out Patient Meds

• Postoperative analgesics are employed as with any other surgical patient. Once PO intake has resumed, acetaminophen usually suffices.

Complications

• Undetected mucosal perforation: Perform a diligent search for mucosal transgressions at the time of operation and examine the infant again before initiating feedings. In those rare cases where a perforation was not detected, the infant develops fever, tenderness in the abdomen, and abdominal distention. Return to the operating theater if perforation is suspected.
• Bleeding: In most instances, venous oozing from the myotomy site is self-limited and is not a concern in the postoperative period. Reports of continued bleeding are exceedingly rare but can occur, especially in children with undetected coagulopathy.
• Persistent vomiting: Incomplete pyloromyotomy is rare in the hands of an experienced pediatric surgeon and usually presents as persistent vomiting until after the second week postsurgery. This problem is confounded when repeat studies performed after surgery provide a confusing picture. Patient observation resolves the problem in most cases.

REFERENCES

Section 8 of 8

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Follow-up
• References

• Alain JL, Grousseau D, Terrier G. Extramucosal pyloromyotomy by laparoscopy. Surg Endosc. 1991;5(4):174-5. [Medline].
• Allan C. Determinants of good outcome in pyloric stenosis. J Paediatr Child Health. Mar 2006;42(3):86-8. [Medline].
• Dahshan A, Donovan KG, Halabi IM, et al. Helicobacter pylori and infantile hypertrophic pyloric stenosis: is there a possible relationship?. J Pediatr Gastroenterol Nutr. Mar 2006;42(3):262-4. [Medline].
• Elinoff JM, Liu D, Guandalini S, Waggoner DJ. Familial pyloric stenosis associated with developmental delays. J Pediatr Gastroenterol Nutr. Jul 2005;41(1):129-32. [Medline].
• Gasseling J. Hypertrophic pyloric stenosis. Radiol Technol. Mar-Apr 2004;75(4):314-6. [Medline].
• Georgeson KE, Corbin TJ, Griffen JW, Breaux CW Jr. An analysis of feeding regimens after pyloromyotomy for hypertrophic pyloric stenosis. J Pediatr Surg. Nov 1993;28(11):1478-80. [Medline].
• Hall NJ, Van Der Zee J, Tan HL, Pierro A. Meta-analysis of laparoscopic versus open pyloromyotomy. Ann Surg. Nov 2004;240(5):774-8. [Medline]. [Full Text].
• Ibarguen-Secchia E. Endoscopic pyloromyotomy for congenital pyloric stenosis. Gastrointest Endosc. Apr 2005;61(4):598-600. [Medline].
• Kawahara H, Takama Y, Yoshida H, et al. Medical treatment of infantile hypertrophic pyloric stenosis: should we always slice the "olive"?. J Pediatr Surg. Dec 2005;40(12):1848-51. [Medline].
• Ly DP, Liao JG, Burd RS. Effect of surgeon and hospital characteristics on outcome after pyloromyotomy. Arch Surg. Dec 2005;140(12):1191-7. [Medline].
• Rogers IM. The true cause of pyloric stenosis is hyperacidity. Acta Paediatr. Feb 2006;95(2):132-6. [Medline].
• Schwartz MZ. Hypertrophic Pyloric Stenosis. Pediatric Surgery. 1998;1111-1118.

Article Last Updated: Jul 20, 2006