AUTHOR AND EDITOR INFORMATION

Section 1 of 10  

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• Introduction
• Relevant Anatomy
• Contraindications
• Workup
• Treatment
• Complications
• Outcome and Prognosis
• Multimedia
• References

INTRODUCTION

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• Introduction
• Relevant Anatomy
• Contraindications
• Workup
• Treatment
• Complications
• Outcome and Prognosis
• Multimedia
• References

Pyloric stenosis (PS) is the most common pediatric surgical disorder of infancy that requires surgery for associated emesis. Autopsy findings of pyloric stenosis were first reported by Blair in 1717, but it was not until 1887, when Hirschsprung presented unequivocal clinical and autopsy findings of pyloric stenosis in 2 infants, that this entity became accepted. Adequate fluid resuscitation followed by pyloromyotomy is the standard curative treatment for pyloric stenosis.

History of the Procedure

Before 1912, early successful operative treatments of pyloric stenosis included gastroenterostomy, pyloroplasty, and forcible dilatation via gastrostomy (Loreta operation). In 1912, Rammstedt observed an uneventful recovery in a patient following pyloroplasty, in which sutures that were used in reapproximating the seromuscular layer had been disrupted. Following this observation, Rammstedt left the split muscle layer unsutured in all subsequent repairs. The Rammstedt pyloromyotomy, whether performed through a right-upper-quadrant incision, an umbilical incision, or laparoscopically, remains the standard operation for pyloric stenosis today.

Problem

Pyloric stenosis involves hypertrophy of the circular muscle of the pylorus resulting in narrowing and obstruction of the pyloric channel by compression of longitudinal folds of mucosa (see Image 1). Gastric outlet obstruction results in emesis, which is characteristically nonbilious and projectile. Protracted emesis, as well as failure of the stomach to empty into the duodenum, results in progressive dehydration, electrolyte abnormalities, acid-base disorders, loss of weight, and, potentially, shock.

Frequency

Pyloric stenosis reports in the United States have shown as few as 1 case per 3,000-4,000 live births to as many as 8.2-12 cases per 1,000 live births. It is most commonly observed in whites of northern European descent, is less frequently observed in blacks, and is rarely found in patients of Asian or East Indian ancestry. Location also contributes to frequency, with areas in which the population is more than two thirds rural showing an increased risk of 1.79 (95% CI, 1.23-2.61; P <.005).

Males are affected more often than females (male-to-female ratio is 4:1). The highest incidence is in first-born males. A genetic predisposition is suggested in families with occurrences of pyloric stenosis reported in at least 3 generations. Involvement in twins has been reported, with an 85.7% concordance rate in monozygotic twins and an 8.4% concordance rate in dizygotic twins. In 1969, Carter and Evans suggested a sex-modified polygenic inheritance of pyloric stenosis. Data from more than 1200 families demonstrated a 20% risk in sons and a 7% risk in daughters of females having had pyloric stenosis, whereas data showed only a 5% risk in sons and a 2.5% risk in daughters of males with pyloric stenosis.

Etiology

No conclusive evidence for the etiology of pyloric stenosis exists; however, both hereditary and environmental influences are believed to be contributing factors. Multiple factors, including both neural and hormonal, have been implicated but not substantiated in the development of pyloric stenosis. An association with B and O blood groups and maternal stress during the third trimester has also been suggested. Although pyloric stenosis is now believed to be acquired, cases of pyloric stenosis diagnosed prenatally and in neonates have been reported.

Since 1976, several reports and cohort retrospective studies have appeared in the literature suggesting an association between pyloric stenosis and exposure to macrolide antibiotics (erythromycin). In 2002, Cooper et al suggested that early exposure to erythromycin (at 3-13 days of life) is associated with a nearly 8-fold increased risk of pyloric stenosis (adjusted incident-rate ratio, 7.88; 95% CI, 1.97-31.57). No increased risk of pyloric stenosis was observed in infants exposed to erythromycin after 13 days of life.

In 1993, Huang et al, by homologous recombination, generated mutant mice (knockout mice) lacking the neuronal nitric oxide synthase (NOS) gene. Nitric oxide (NO) mediates nonadrenergic noncholinergic smooth muscle relaxation throughout the gut. The stomachs of homozygous mutant mice were larger than normal in this group, and the circular muscle layer of the stomach and pylorus was hypertrophied. Wild-type mouse stomachs contained NOS in the myenteric plexus and nerve fibers of the circular muscle layer, whereas mutant homozygous mice lacked NOS in both locations. Applying these observations to the human condition, Huang et al hypothesized that the stomach and pylorus may be particularly dependent on NO and prone to dysfunction in its absence. Although human pyloric stenosis does not appear to be due to a complete absence of neuronal NOS gene product, the absence of NOS in this area may result in pyloric smooth muscle hypertrophy.

Associated anomalies, though rare, have been reported with pyloric stenosis. Approximately 4-7% of infants with pyloric stenosis have associated anomalies, with hiatal and inguinal hernias being the most common ones. Other anomalies include congenital heart disease, esophageal atresia, tracheoesophageal fistulas, renal abnormalities, rubella, and chromosomal abnormalities such as Turner syndrome and trisomy 18. Jackson et al (1993) found that 3.8% of infants (12 of 308) with de Lange syndrome had pyloric stenosis. Infants with Smith-Lemli-Opitz (SLO), a cholesterol deficiency syndrome, are reported to have an increased tendency for pyloric stenosis. Additionally, Liede et al (2000) proposed a convincing argument of a common genetic association between endometriosis, breast cancer, and pyloric stenosis in several families.

Pathophysiology

Pyloric stenosis involves hypertrophy of the circular muscle of the pylorus, resulting in narrowing and obstruction of the pyloric channel by compression of longitudinal folds of mucosa. Grossly, the pylorus is enlarged, resembling a tumor approximating the size and shape of an olive (ie, 2 cm long, 1 cm diameter). Microscopically, the circular muscle hypertrophies, with increased connective tissue in the septa between the muscle bundles. An increase of chondroitin sulfate within the extracellular matrix may account for the cartilaginous quality of the pyloric tumor.

Gastric fluid loss is associated with the loss of H⁺ and Cl^-. This fluid loss is unlike that in conditions caused by vomiting with an open pylorus, which involves losses of gastric, pancreatic, biliary, and intestinal fluid. Hypochloremic, hypokalemic metabolic alkalosis is the characteristic biochemical disturbance observed in pyloric stenosis. Urinary Na⁺ and HCO₃^- losses, which compensate for Cl^- losses, perpetuate this alkalosis.

With protracted vomiting, an extracellular volume deficit ensues, and urinary excretion of K⁺ and H⁺ increases in an attempt to preserve Na⁺ and volume. The initially alkalotic urine then becomes acidotic (paradoxic aciduria). This sign of protracted dehydration should alert the clinician to the severity of the volume and total body K⁺ deficit. The severity of electrolyte abnormalities depends on the duration of vomiting before resuscitation. Greater awareness of the presenting signs of pyloric stenosis by pediatricians and primary care physicians, along with ultrasonographic examination, has resulted in earlier diagnosis and less severe electrolyte and acid-base abnormalities.

Clinical

History

Pyloric stenosis most often occurs in neonates and infants aged 1-10 weeks (mean, 5 wk), with a range of 5 days to 5 months. Although uncommon in premature infants younger than corrected age for a full-term infant, pyloric stenosis has been detected on prenatal ultrasound and could be considered in the differential diagnoses for nonbilious vomiting in the newborn. Pyloric stenosis is observed in premature infants older than corrected age for a full-term baby. Regardless of age, projectile vomiting typically occurs and is always nonbilious but may have brown discoloration or a coffee-ground appearance from associated gastritis, particularly if emesis has persisted for several days. The vomiting occurs within 30-60 minutes after feeding. The infant remains hungry and usually attempts to feed immediately after vomiting. Weight loss and evidence of dehydration (eg, decreased tearing and urinary output, with poor skin turgor) are present if vomiting is allowed to continue for more than a few days.

Physical examination of the infant is conducted in a warm environment with the baby quiet or sleeping. A general sense of hydration is assessed first (see Table below), with particular attention paid to the baby's level of consciousness (arousability if sleeping), eyes, fontanelles, skin turgor, mucous membranes, and tearing. Infants with depressed fontanelles and decreased skin turgor have at least a 5% deficit of total body water. The lungs should be examined carefully, looking for signs of aspiration pneumonia in any infant who presents with a history of vomiting.

Clinical Findings in Dehydrated Infants With Pyloric Stenosis

Upon identifying a suspected olive (pyloric tumor), the examiner must attempt to outline or palpate discrete borders of the mass to avoid mistaking the liver edge, contracted rectus muscle, or the upper pole of the right kidney for the mass. With persistence and experience, the pyloric tumor should be palpated in 85-100% of cases. Difficulty in locating the mass is encountered if the mass is obscured by the liver, a distended stomach, or tense rectus muscles in crying infants.

Feeding the patient a small volume of warm sugar water may be useful in the examination, for 2 reasons: (1) a feeding infant cannot cry and, thus, does not tense the abdominal muscles, thereby making the examination of the pylorus easier and (2) observation of the abdomen of the infant with pyloric stenosis after feeding often reveals visible gastric contractions occurring in a wavelike manner from left to right across the abdomen. These waves generally terminate in emesis and are often associated with, but are not pathognomonic for, PS. Further examination of the abdomen is facilitated by nasogastric decompression and by lifting the lower extremities to help relax the abdominal musculature.

RELEVANT ANATOMY

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Pyloric stenosis involves hypertrophy of the circular muscle of the pylorus, resulting in narrowing and obstruction of the pyloric channel by compression of longitudinal folds of mucosa. Gastric distention results (see Image 1). Intraoperatively, the surgeon must pay strict attention to the serosal demarcation between the duodenum and the pylorus. The prepyloric vein, or Mayo vein, is located at this junction. The risk of duodenal perforation is prevented by stopping the distal extent of the myotomy 1-2 mm short of this point.

CONTRAINDICATIONS

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Adequate resuscitation preoperatively is essential. Fluid resuscitation is guided by adequate urine output (1 mL/kg/h) and by normalization of acid-base disturbances and electrolyte and bicarbonate levels.

WORKUP

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Lab Studies

• Electrolyte panel
• • An electrolyte panel is essential for estimating the state of dehydration and acidosis/alkalosis in patients with PS.
  • Hypochloremic, hypokalemic metabolic alkalosis is the characteristic biochemical disturbance observed in PS.
• Liver function studies (not routinely obtained or necessary for diagnosis): Jaundice occurs in approximately 2% of infants with PS. Although the cause is uncertain, this finding (similar to findings in Gilbert syndrome) is thought to reflect a decrease in hepatic glucuronosyltransferase activity associated with starvation, as occurs in high gastrointestinal obstruction. The jaundice resolves spontaneously and rapidly after pyloromyotomy.
• Urinalysis: Urinalysis with normalization of urinary pH (correction of paradoxic aciduria) also helps determine adequacy of resuscitation.

Imaging Studies

• Radiography: Although a careful history and physical examination lead to diagnosis in the vast majority of patients with pyloric stenosis, those in whom a palpable mass is not identified require further diagnostic studies. Plain abdominal radiography may show a dilated stomach bubble, which suggests the diagnosis but should not be considered a diagnostic finding.
• Upper gastrointestinal series
• • Ultrasonographic examination has largely replaced upper gastrointestinal (UGI) contrast studies as the study of choice for confirming pyloric stenosis. Although UGI studies have been reported as having an accuracy of 96%, obvious disadvantages of such studies include radiation exposure and the risk of aspiration of contrast material.
  • A UGI study may be helpful in ruling out gastroesophageal reflux, duodenal atresia, and malrotation in cases in which uncertainty exists as to the nature of the emesis (ie, bilious versus nonbilious) and in which a pyloric mass is indiscernible.
  • Failure of gastric emptying demonstrated on UGI studies is not diagnostic of pyloric stenosis, because pyloric spasm and CNS lesions may be associated with delayed gastric emptying (see Image 3).
• Ultrasonography
• • In 1977, Teele first described the use of ultrasonography in the diagnosis of PS. Objective criteria in measuring the pylorus have increased the diagnostic accuracy of ultrasonography.
  • On ultrasonography, a diagnosis of pyloric stenosis can be made by identification of an elongated sausage-shaped mass with a pyloric diameter greater than 14 mm, a muscular thickness greater than 4 mm, and a length greater than 16 mm (see Image 4). A sensitivity of 91-100% and a specificity of 100% have been reported with these criteria. Ultrasonography is best performed with the stomach evacuated, because food or milk curds may interfere with the study. If a hypertrophied pylorus is not demonstrated on ultrasonographic examination, a UGI examination should follow to assess for other causes of vomiting.

Histologic Findings

Microscopically, circular muscle hypertrophies, with increased connective tissue in the septa between the muscle bundles. An increase in chondroitin sulphate within the extracellular matrix may account for the cartilaginous quality of the pyloric tumor. Note that histologic specimen is not obtained nor is it necessary for the diagnosis of PS.

TREATMENT

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Medical therapy

Although medical treatment has been employed for pyloric stenosis, pyloromyotomy has been firmly established as the treatment of choice for this condition. Medical management of pyloric stenosis, however, remains important. Early assessment and treatment of fluid, electrolyte, and acid-base disturbances are paramount. Urgent resuscitation, rather than emergent surgical intervention, is the rule. Once the diagnosis is made, fluid resuscitation is begun. Clinical and biochemical assessments are made and repeated to guide appropriate fluid repletion.

Nonsurgical management was described originally in Europe using a low-curd feeding of dextrose or breast milk; however, this treatment reportedly took months to complete and was associated with significant morbidity. Reports from Sweden showed that using intravenous nutrition alone also usually failed. Additionally, a biochemical approach of giving atropine or scopolamine was employed to compensate for the lack of nitric oxide synthase in the pylorus, which is thought to cause the hypertrophy. These anticholinergics were thought to decrease pyloric contractions; however, early success was lacking and, until recently, was thought to be only of historical interest.

In 1996, Nagita et al, in a Japanese study, reported successfully treating 21 of 23 infants (91%) with pyloric stenosis using intravenous atropine, administered at a dosage of 0.04-0.11 mg/kg/d until vomiting ceased, followed by oral atropine for 2 weeks. Another Japanese study, by Kawahara et al (2005), reported a success rate of 87% in 52 patients treated with intravenous and oral atropine. Manometric studies were used to find the level of atropine that caused a decrease in tonic and phasic contractions in the pylorus. The dosing regimen of atropine was 0.01 mg/kg IV 6 times a day before feedings (median time, 1 wk) followed by 0.02 mg/kg orally after vomiting stopped and infants could tolerate formula in the amount of 150 mL/kg (median time, 44 d). Hospital stays ranged from 6-36 days (median, 13 d); however, despite the longer hospital stay, the costs for the medical group were similar to those for the surgical group, without the inherent risks of general anesthesia and surgery. Regarding

generaloutcomes, the 2 groups showed no difference in weight at age 1 year. Applying medical treatment for pyloric stenosis could prove useful to patients without sufficient access to surgical care or when surgery on an infant would be too risky. The authors of the study concluded that this medical treatment of pyloric stenosis is an effective alternative to pyloromyotomy if the length of hospitalization and the necessity of continuing oral atropine are accepted. Long-term studies have yet to be conducted to address recurrence rates, hospital costs in other countries, and caregiver compliance for atropine-treated patients with pyloric stenosis. In the United States, the Ramstedt pyloromyotomy remains the optimal treatment for pyloric stenosis.

Preoperative details

Pyloric stenosis is not a surgical emergency. Urgent resuscitation, rather than emergent surgical intervention, is the rule. The preoperative medical management of patients with pyloric stenosis is paramount for safe general anesthesia. Once the diagnosis is made, fluid resuscitation is begun to treat dehydration and electrolyte and acid-base disturbances. Clinical and biochemical assessments are made and repeated to guide appropriate fluid repletion.

Intravenous therapy consists of 5% dextrose in one-half isotonic sodium chloride solution (0.45% NaCl/D5W) at 1.5 times the maintenance rate. Although children with severe dehydration should receive deficit fluid therapy with isotonic sodium chloride solution (20 mL/kg) initially, ongoing resuscitation should be performed with 0.45% NaCl/D5W to prevent rapid changes in volume and electrolyte levels, which can result in seizures. When urine output has been demonstrated, potassium chloride (10-20 mEq/L) can be added to the fluids.

In some patients with severe volume abnormalities (>20%) and electrolyte abnormalities (Cl^- <80 mEq/dL; HCO₃^- >35; Na⁺ <120 mEq/L), resuscitation may take 48-72 hours. With serum bicarbonate levels above 30 mEq/dL, the potential exists for myocardial dysfunction and respiratory depression. The patients should therefore be monitored for signs of apnea; if such signs are present, the patient may need to be intubated and mechanically ventilated until surgery is performed.

Intraoperative details

Once the diagnosis of pyloric stenosis has been confirmed, adequate ongoing preoperative fluid resuscitation must be maintained by establishing adequate urine output (1 mL/kg/h) and correcting acid-base disorders and electrolyte abnormalities. Regarding anesthetic induction for infants with pyloric stenosis, tracheal intubation with muscle paralysis seems to be superior to awake intubation, because the former reduces the risk of desaturation and bradycardia from multiple attempts at intubation.

Pyloromyotomy may be performed either as an open procedure (see Image 5), via a right-upper-quadrant horizontal incision or an umbilical incision (Tan-Bianchi operation), or a laparoscopic procedure (see Image 6). In 1986, a Tan-Bianchi approach was described in which a pyloromyotomy was performed through a supraumbilical incision that afforded superior cosmesis. Blumer et al (2004) compared the umbilical approach with the right-upper-quadrant approach in 237 patients and found that the umbilical approach took 3.1 minutes longer (28.5 min vs 31.6 min; P <.025). This difference was clinically irrelevant, however, as there were no significant differences regarding length of hospital stay, mucosal perforations, or wound infections. Blumer et al also concluded that the umbilical approach provided a superior cosmetic outcome.

In 2004, Alberti et al reported modifying the Tan-Bianchi approach with a right semicircular umbilical incision, thus keeping all the incisions in the same axis, allowing for delivery of a larger pylorus, and decreasing the amount of retractor strain on the wound. This approach resulted in a lower rate of hematoma formation and lower wound infection rates (0%) than supraumbilical incisions (16%), despite the use of prophylactic antibiotics with the semicircular umbilical approach. In this modified Tan-Bianchi operation, after the pyloric channel is delivered from the abdomen, a seromuscular incision is made along the anterior border of the hypertrophied pylorus from 1-2 mm proximal to the duodenum to the distal antrum just proximal to the pylorus. Great care must be taken not to incise or perforate the underlying mucosa. An alternative superficial V-shaped extension can be made at the duodenal end of the myotomy to reduce the risk of duodenal mucosal injury.

A laparoscopic pyloromyotomy follows the same principles as an open procedure. First described by Alain et al in 1991, the laparoscopic approach has been demonstrated as being a safe alternative to exteriorizing the pylorus and improving cosmetic results. The authors' approach entails creating a 5-mm camera port at the umbilicus. A 3-mm atraumatic, locking, grasping instrument is inserted in the right upper quadrant, over the duodenum. The grasping instrument is used to stabilize the pyloric channel. A 3-mm incision is made in the midepigastrium, over the pyloric olive, through which a sheathed arthrotome is passed (without a trocar). The pylorus is then incised in the same fashion as with the open procedure. A laparoscopic pyloric spreader is then used to bluntly split the hypertrophied muscle.

The laparoscopic pyloromyotomy procedure has a significant learning curve. Hendrickson et al (2005) reported an initial operative time of 70 minutes at a teaching hospital, with operative time decreasing to 15 minutes after 25 procedures. A conversion rate of 8% from the laparoscopic to the open procedure was reported. Similar learning curves have been reported at other centers. Yagmurlu et al (2004) compared open pyloromyotomy (n = 225) with laparoscopic pyloromyotomy (n = 232) and found the overall complication rates to be 4.4% for the open procedure and 5.6% for the laparoscopic procedure. The open approach resulted in a higher rate of mucosal perforation (3.6% versus 0.4%; P = .016), and laparoscopy had a higher rate of postoperative complications, such as incomplete pyloromyotomy (0% for open vs 2.2% for laparoscopic; P = 0.027).

Campbell et al (2002), in a retrospective study, reported on 117 patients showing a trend toward significantly higher complications with laparoscopic pyloromyotomy than with the open procedure (18% vs 12%; P=.31). Additionally, significantly higher hospital costs were associated with the laparoscopic approach. The International Pediatric Endosurgery Group (2002) has reported that laparoscopic pyloromyotomy provides cost savings, decreases operating room time, reduces tissue trauma, and improves cosmetic outcome.

Postoperative details

Crystalloid resuscitation is continued postoperatively until the patient returns to full feeding. Recent data suggest that infants with pyloric stenosis have an increased incidence of postoperative apnea and bradycardia. These infants should be placed on an apnea and cardiac monitor for 24 hours following the operation.

A decrease in the number of hospital days after operation depends to a certain degree on how rapidly feeding is started and advanced. In one study, Michalsky et al (2002) reported that having a clinical pathway decreased surgeon variability by advancing the diet to oral feedings within 5 hours after operation. Additionally, the length of hospital stay was significantly reduced (41.8 ± 9.7 h vs 57.8 ± 11.7 h; P <.001), as well as hospital costs ($4555 ± $464 vs $5400 ± $1017; P< .001).

By contrast, Puapong et al (2002) showed that feeding ad libitum after the patient is awake resulted in a significantly faster return to full-strength feeding than a controlled feeding regimen (29.1 h vs 5.1 h; P <.05), along with a shorter hospital stay (38.8 d ± 16.6 d vs 25.1 d ± 10.9 d; P <.05) and a significant decrease in cost per patient ($3560 vs $2290; P <.05). Both studies found that early initiation of feeding leads to better recovery and to cost savings.

The author has found the following feeding regimen to be safe and adequate:

• Give the patient nothing by mouth (NPO) for 6 hours in the recovery room.
• Then, on demand, give 15 mL of Pedialyte every 2-3 hours for 2 feedings.
• If 15 mL is tolerated, advance to 30 mL of Pedialyte every 2-3 hours for 2 feedings.
• If 30 mL is tolerated, advance to 30 mL of full-strength formula every 2-3 hours for 2 feedings.
• If full-strength formula is tolerated, advance to spontaneous feedings.
• If vomiting occurs, repeat the step at which vomiting occurs and advance when tolerated.
• If the patient is being breastfed and the mother has bottled milk, follow the above schedule.
• If the patient is being breastfed and no bottled milk is available, follow the schedule below:
• • Follow steps 1, 2, and 3 above.
  • Have the patient breastfeed on each side for 5 minutes every 2 hours for 2 feedings.
  • Have the patient breastfeed on each side for 10 minutes every 2 hours for 2 feedings.
  • Have the patient breastfeed spontaneously.

Slow feeding and gentle burping help prevent wet burps postoperatively. Intermittent vomiting persisting through the first postoperative week is sometimes observed in patients with a protracted course of emesis and severe dehydration preoperatively. Vomiting lasting longer than 7 days postoperatively should alert the physician to the possibility of an incomplete pyloromyotomy.A UGI study may be obtained but is useful only for demonstrating gastroesophageal reflux, because the radiographic appearances of pyloric stenosis may persist for several months following complete pyloromyotomy.

Follow-up

follow-up care regimen involves a routine postoperative visit at 1 week to check wounds and to ensure that the patient is once again gaining weight.

COMPLICATIONS

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Although pyloromyotomy is safe, curative, and performed virtually without operative mortality (<0.5%) and morbidity (<10%), it is not without potential complications. Potential intraoperative and postoperative complications include bleeding, perforation, and wound infection. Duodenal or gastric perforation, the most serious complication, rarely occurs; however, if it goes unrecognized before wound closure, devastating or lethal consequences are possible. The infant with an enteric leak develops pain, distention, fever, and peritonitis. Ongoing fluid requirements, generalized sepsis, vascular collapse, and death follow if the enteric leak is not recognized and treated. Suspected perforation postoperatively requires immediate reexploration. Recognition of this complication at the time of surgery is important.

Mucosal perforation most commonly results from extending the myotomy beyond the pyloric-duodenal junction. If perforation occurs, the mucosal defect should be repaired and the myotomy completed. An omental patch may be sutured to the perforation site, and a paraduodenal drain may be considered. If any question exists about the success of the closure, a UGI study can be obtained before feedings are initiated. The patient should continue to receive antibiotics until feedings are resumed.

Bleeding is a rare complication of pyloromyotomy. Other complications that are more common but less serious include superficial wound infections (usually Staphylococcus aureus) and postoperative vomiting. Patients with wound erythema, drainage, or both undergo wound opening and debridement and antibiotic therapy. Incomplete myotomy results in ongoing gastric outlet obstruction and requires reoperation. However, ongoing emesis after pyloromyotomy does not mean an incomplete myotomy was performed. Patients with prolonged preoperative obstruction develop gastric distention and dysmotility, which may cause postoperative emesis for up to 1 week after an adequate pyloromyotomy.

OUTCOME AND PROGNOSIS

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Pyloromyotomy that is adequately performed is curative of pyloric stenosis. There have been reports of recurrent pyloric stenosis despite performance of an adequate pyloromyotomy, but recurrence is considered to be a rare exception after incomplete pyloromyotomy has been ruled out.

Yoshizawa et al (2001) has demonstrated in ultrasound studies that after pyloromyotomy, the pylorus changes significantly within 3 days postoperatively and returns to normal within 5 months. Specific changes are provided below:

• The dorsal pyloric aspect temporarily thickens from 5.1 mm ± 0.8 mm to 6.0 mm ± 0.3 mm within 3 days postoperatively (P<.5) and thins out to 2.8 mm ± 0.2 mm within 5 months.
• The pyloric length decreases from 20.1 mm ± 2.9 mm preoperatively to 16.9 mm ± 2.7 mm (P<.5) within 3 days postoperatively and to less than 15 mm within 4 months.
• The change in pyloric diameter is comparable to the change in pyloric length
• The transverse muscle thickness of the incision site changes from 4.3 mm ±0.4 mm to 4.6 mm ± 0.4 mm (P<.5) within 3 days postoperatively and to 2.1 mm ± 0.9 mm (P<.5) within 7 days (normal, <3 mm).

Several studies have focused on patient outcomes with respect to advanced training and experience of surgeons. Pranikoff et al (2002) reported that pediatric surgeons performing pyloromyotomy had a mucosal perforation rate of 0.5%, compared with a 2.9% rate for general surgeons (P = .0015), and that this difference in rate of mucosal perforation correlated with a decrease in total hospital charges ($4806 ± $79 vs $6592 ± $492; P = .002) and a shorter hospital stay (2.7 d ± 0.1 d vs 3.1 d ± 0.1 d; P =0.01).

In a study of 11,003 patients with pyloric stenosis, Safford et al (2005) stratified patient outcomes on the basis of surgeon volume and hospital volume of pyloric stenosis cases. For surgeons, low volume was considered fewer than 1 procedure per year; intermediate, 1-5 procedures per year; and high, more than 5 procedures per year. For hospitals, low volume was considered fewer than 5 procedures per year; intermediate, 5-15 procedures per year; and high, more than 15 procedures per year. They reported that patients operated on by low- and intermediate-volume surgeons were more likely to have complications than patients operated on by high-volume surgeons (95% CI, 1.25-3.78 and 1.25-2.69, respectively). Patients operated on at low-volume hospitals were 1.6 times more likely to have complications than patients operated on at intermediate- or high-volume hospitals (95% CI, 1.19-2.20). Procedures performed at high-volume hospitals were less expensive than those done at intermediate-volume hospitals, by a

margin of $910 (95% CI, $443-$1377). High-volume surgeons were more expensive than low-volume surgeons, by a margin of $511 (95% CI, $25-$962). Low-volume surgeons at low-volume hospitals had mucosal perforation rates 4.0-6.7 times higher than high-volume surgeons at high-volume hospitals.

It is important to note that between 1994 and 2000, the frequency of laparoscopic pyloromyotomy was likely increasing; however, the rates of open pyloromyotomy and laparoscopic pyloromyotomy were not included in procedure coding. The data have shown that for pyloromyotomy procedures, complication rates are lower and cost savings greater with high-volume surgeons operating at high-volume hospitals.

MULTIMEDIA

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• Outcome and Prognosis
• Multimedia
• References

Media file 1:  Diagram of the anatomic changes associated with pyloric stenosis.
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Media file 2:  Technique used for examining an infant with pyloric stenosis. The infant is best examined from the right, with mild pressure applied using the first 3 fingers of the right hand in a cephalad direction. Careful examination reveals an oblong, smooth, hard mass that is 1-2 cm in length. This mass is the hypertrophied pylorus and is commonly referred to as an olive.
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Media type:  Photo

Media file 3:  Upper gastrointestinal study used for diagnosing pyloric stenosis.
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Media file 4:  Longitudinal ultrasonogram of pyloric stenosis. Pyloric stenosis is diagnosed by the demonstration of an elongated sausage-shaped mass with a pyloric diameter greater than 14 mm, a muscular thickness greater than 4 mm, and a length of more than 16 mm.
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Media type:  Image

Media file 5:  Open pyloromyotomy.
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Media file 6:  Laparoscopic pyloromyotomy.
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Media type:  Presentation

REFERENCES

Section 10 of 10

• Authors and Editors
• Introduction
• Relevant Anatomy
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• Outcome and Prognosis
• Multimedia
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• Abel RM. The ontogeny of the peptide innervation of the human pylorus, with special reference to understanding the aetiology and pathogenesis of infantile hypertrophic pyloric stenosis. J Pediatr Surg. Apr 1996;31(4):490-7. [Medline].
• Alain JL, Grousseau D, Longis B, et al. Extramucosal pyloromyotomy by laparoscopy. J Laparoendosc Surg. Mar 1996;6 Suppl 1:S41-4. [Medline].
• Alain JL, Grousseau D, Terrier G. Extramucosal pylorotomy by laparoscopy. J Pediatr Surg. Oct 1991;26(10):1191-2. [Medline].
• Alberti M, Cheli M, Locatelli G. A new technical variant for extramucosal pyloromyotomy, The Tan-Bianchi operation moves to the right. J Ped Surg. 2004;39:53-6. [Medline].
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Article Last Updated: Aug 15, 2006