Hypertrophic pyloric stenosis is the most common surgical
disorder producing emesis in infancy, with an incidence of
approximately 1 in every 400 live births in the United States.
This incidence varies with ethnic origin, and the disorder is
most common in white infants and less frequent in African-
American and Asian infants. Male infants are four times more
likely to have pyloric stenosis than females; firstborn males
are more likely to be affected than their siblings.
Approximately 5% of the sons and 2 % of the daughters of
fathers who have had pyloric stenosis develop the disorder;
the frequency increases threefold if the infant's mother had
the disorder.
The cause of infantile hypertrophic pyloric stenosis has not
been defined clearly. Many investigators have evaluated the
morphologic changes in the intrinsic nerves and ganglion
cells, including the degree of maturity, distribution, and
degeneration of these cells, with no unanimous agreement. No
clear relationship has been identified with respect to onset of
allergies, variations of infant feedings, or other specific
clinical disorders. Increased production of gastriri in either
mother or infant does not seem to be a causative factor. An
association with blood groups 0 and B and with maternal
stress in the last trimester of pregnancy has been suggested.
The etiology is considered multifactorial, with a proven
genetic X-linked factor and an uncertain environmental one.
Although the designation as congenital is questioned by
some, the presence of a partial obstruction at the pylorus in
some ways is analogous to congenital duodenal webs, which
may not produce symptoms for several days or a few weeks
after birth. It is doubtful that pyloric stenosis would produce
such severe symptoms predictably within the first 3 to 5
weeks unless a major component of the disorder were
congenital.
The pathogenesis of pyloric stenosis is believed by some to be
postnatal work hypertrophy, possibly following a congenital
delay in the opening of the pyloric sphincter. Others have
suggested a congenital redundancy of the pyloric mucosa.
Another theory suggests that milk curds passing through the
narrow channel cause additional edema and swelling with
eventual complete occlusion,
which subsides if nothing is taken by mouth for a few days or if
only clear fluids are given. This theory is consistent with the
course of the lesion because it disappears after the obstruction is
relieved. Vasoactive intestinal peptide decreases the intensity
and duration of pyloric contraction in a dose-dependent manner,
suggesting vasoactive intestinal peptide could playa role in
etiology. Studies implicate unbalanced function of the
peptidergic nervous system, but the precise relationship is not
yet proven.
The musculature of the pylorus in patients with pyloric
stenosis is markedly thickened and edematous. There is
hypertrophy of the circular muscle fibers but no increase in their
number. The spindle-shaped swelling of the hypertrophied
muscles of the pylorus usually measures approximately 2.0 to
2.5 cm long and protrudes into the duodenum, analogous to the
cervix into the vagina. The pyloric muscle is usually firm and
discrete and likened to a tumor, although it becomes softer in
older infants. The proximal portion is less abrupt and fuses with
the normal antral musculature. The gastric muscle is usually
thickened, and the mucosa is frequently edematous and
congested, occasionally leading to bleeding. After
pyloromyotomy, the pyloric muscle gradually becomes
completely normal, and when visualized at subsequent
operations, only a fine scar in the area of the myotomy can be
identified. Approximately 7% of infants with pyloric stenosis
have associated anomalies, with esophageal hiatal and inguinal
hernias being the most frequent.
Classically, projectile nonbilious emesis, the presence of a
palpable pyloric tumor, and visible gastric waves on the
abdomen in a 3- to 5-week-old infant are the clinical features of
hypertrophic pyloric stenosis. Most infants experience emesis of
small amounts by 2 weeks of life, then develop nearly complete
obstruction with vomiting of almost all feeds by 2 to 4 weeks.
The range of presentations is 1 to 12 weeks of age. Shortly after
emesis, infants usually crave further feedings. Although withholding
fee dings for a short period may provide slight resolution
of mucosal edema, allowing the infant to retain clear liquid
feedings, this apparent improvement is almost invariably shortlived,
and emesis recurs whensmall milk feedings are resumed. The emesis is characteristically
projectile or forceful because of the high pressure generated by
the hypertrophied gastric muscles. Infants who are allowed to
continue with symptoms for more than a few days often lose
weight and may become dehydrated with metabolic alkalosis or
even malnourished. Repeated emesis that is allowed to persist for
several days may produce gastritis with mild bleeding.
DIAGNOSIS
Observation of the abdomen after a feeding in infants with wellestablished
pyloric stenosis often reveals contractions of the
stomach that proceed from left to right across the epigastrium.
These gastric waves eventually terminate in an episode of
emesis. Similar but less prominent waves can be seen in other
conditions, such as severe pylorospasm or gastric duplication.
Careful palpation of the epigastrium slightly to the right of the
midline often discloses a firm, olive-sized mass that can be
manipulated slightly upward or downward. The hypertrophied
pyloric muscle is identified most easily when the stomach is
empty, either after emesis or after tube decompression of the
stomach. Elevating and gently moving the lower extremities
while allowing the infant to suck on a pacifier or a bottle of
sugar water during the examination may relax the abdominal
musculature, permitting a more accurate examination. Repeated
examinations over a few hours occasionally may be necessary in
an active, crying infant, but sedation is rarely necessary. The
pyloric mass is pathognomonic, and depending on the experience
and patience of the examiner, it can be identified in 70% to 90%
of infants with hypertrophic pyloric stenosis.
Hypertrophic pyloric stenosis may be simulated by many
other causes of vomiting in infants. Overfeeding is the most
common and is a frequent practice in many families. There is a
frequent history of formula changes because of a suspected milk
allergy or intolerance to the current formula. Improved feeding
technique, frequent burping, and time are all that is needed for
most of these disorders to resolve. Pylorospasm,
gastroesophageal reflux, delayed gastric emptying of
undetermined etiology without mechanical obstruction, and
several anomalies including malrotation with duodenal bands,
duodenal or antral webs, and pyloric duplications rarely may
simulate pyloric stenosis. Emesis also may be associated with
metabolic disorders, inborn errors of metabolism, central
nervous system lesions, and sepsis. A good clinical rule of
thumb that aids in the differential diagnosis is that a child with
pyloric stenosis will continue to be hungry and active unless
severely dehydrated. Infants with metabolic disorders or
increased intracranial pressure are likely to be lethargic and feed
poorly, and the vomitus is often bilious.
Abdominal ultrasonography is performed on infants in whom a
tumor cannot be palpated. This study is highly reliable and is
currently the preferred approach when the pyloric mass cannot
be felt. The most commonly used criteria are a pyloric muscle
thickness of 4 mm or more and a pyloric channel length of 16
mm or more (Fig. 45-1). The barium upper gastrointestinal
(UGI) series is used for the occasional infant in whom physical
examination and ultrasound are not diagnostic.Occasionally the diagnosis may be made as early as the fourth
or fifth day of life and, in rare instances, as late as 4 months. In
our experience, the average onset of symptoms occurs at 3
weeks. Vomiting is the initial sign, and the emesis is always free
of bile. Initially the infant may vomit once or twice a day;
however, as the obstruction progresses, the emesis becomes
more constant and forceful or projectile, extending several
inches from the face. The infants characteristically have a
ravenous appetite shortly after an episode of emesis.
Occasionally the emesis in infants with more protracted
vomiting may become brownish or blood-streaked as a result of
bleeding from ruptured capillaries in the gastric mucosa induced
by the frequent vomiting.
Vomiting with an open pylorus generally results in a loss of
an isotonic mixture of duodenal, biliary, and pancreatic
secretions. In contrast, vomiting caused by pyloric stenosisOPERATIVE TREATMENT
Preoperative care is aimed at restoring fluid and electrolyte losses.
Because the diagnosis of pyloric stenosis usually is made earlier
than in previous years, few infants are seen in an advanced state of
severe dehydration, malnutrition, and alkalosis. Most infants with
pyloric stenosis can be operated on within 12 hours after
admission to the hospital. Although a clear liquid feed may be
tolerated preoperatively, most pediatric anesthesiologists prefer
that these infants not be fed for 8 to 12 hours preoperatively
because of delayed gastric emptying. In some cases, it is necessary
to lavage the stomach with normal saline solution to remove
obstructing milk curds or barium.
For most infants, intravenous fluids are initiated as the infant is
being admitted to the hospital for treatment. A solution containing
5% dextrose in 0.45% saline is administered intravenously at a
rate of approximately 150 to 175 mL/kg/2 4 hours, depending on
the amount of hydration necessary. After the infant has voided, 10
to 15 mEq of potassium chloride is added to each 500-mL intravenous
bottle. The total amount of potassium chloride in the fluids
administered should not exceed 40 mEq/L in 24 hours.
Dehydration with more severe electrolyte deficits requires the
administration of normal saline solution at a rate of 175 to 185
mLIkg/24 hours until the infant voids. Dehydrated patients
occasionally require resuscitation for 24 to 36 hours. When the
stomach has been emptied, most infants with pyloric stenosis stop
vomiting.
The Ramstedt-Fredet pyloromyotomy, performed with the
infant under general anesthesia, is universally accepted as the
preferred operation. The stomach should be emptied again just
before induction of anesthesia to minimize the risk of aspiration.
The procedure can be performed through a variety of approaches,
although the one used most frequently is a transverse skin incision
followed by a vertical splitting of the right rectus muscle and
fascia. The right upper abdominal transverse muscle-splitting
gridiron incision (Robertson) is used by many. Because it provides
a better cosmetic appearance, a supraumbilical, curvilinear
incision has been used by some surgeons; however, there is a
higher incidence of wound-related complications. After entering
the abdomen, the omentum can be readily retrieved into the
wound, which when elevated lifts the transverse colon and leads
directly to the gastric antrum. The lower stomach may be elevated
with gentle traction using moistened gauze to minimize slipping as
the pyloric mass is delivered into the wound. A vertical incision is
made on the mid anterior surface through the serosa and
superficial muscularis extending from approximately 2 mm
proximal to the pyloric vein (an avascular area) to a point 0.5 cm
onto the lower antrum . Although most surgeons use a
straight, longitudinal incision, a superficial V-shaped extension at
the duodenal end of the myotomy incision has been helpful in
reducing the risk of duodenal mucosal injury. The circular muscle
is opened bluntly using the Benson pyloromyotomy spreader or
the back of the knife handle.COMPLICATIONS
Gastritis and gastroesophageal reflux are the most common causes
of persistent postoperative vomiting. Incomplete pyloromyotomy as
a cause of persistent vomiting is rare but should be considered if
vomiting continues for more than 7 to 10 days postoperatively, if it
is forceful, and if it follows every feeding. It is usually due to an
incomplete separation of the muscles on the antral side of the
pylorus. Contrast radiography in this instance may diagnose
gastroesophageal reflux or show whether the stomach readily
empties, but it is of little help in diagnosing an incomplete
myotomy because the radiographic appearance of pyloric stenosis
has been relieved. If a second myotomy is deemed necessary, which
is rare, the procedure consists of a fresh pyloromyotomy in an area
that is well away from the original incision. This is done by turning
the pylorus 45 to 90 degrees to either side and performing the
standard pyloric incision.
The rare unrecognized duodenal perforation is identified by the
postoperative presence of emesis, distention, fever, and peritonitis.
In this instance, prompt reoperation is mandatory, consisting of
simple duodenal repair and placement of a tongue of omentum over
the closure. Wound infections with Staphylococcus occasionally
occur and may be related to the proximity of the umbilical stump.
Postoperative incisional dehiscence and delayed incisional hernias
are uncommon. The mortality associated with pyloromyotomy is
less than 0.4% in the experience of almost all major children's
centers. The rare deaths encountered in most instances have
occurred in patients with multiple congenital anomalies.
disorder producing emesis in infancy, with an incidence of
approximately 1 in every 400 live births in the United States.
This incidence varies with ethnic origin, and the disorder is
most common in white infants and less frequent in African-
American and Asian infants. Male infants are four times more
likely to have pyloric stenosis than females; firstborn males
are more likely to be affected than their siblings.
Approximately 5% of the sons and 2 % of the daughters of
fathers who have had pyloric stenosis develop the disorder;
the frequency increases threefold if the infant's mother had
the disorder.
The cause of infantile hypertrophic pyloric stenosis has not
been defined clearly. Many investigators have evaluated the
morphologic changes in the intrinsic nerves and ganglion
cells, including the degree of maturity, distribution, and
degeneration of these cells, with no unanimous agreement. No
clear relationship has been identified with respect to onset of
allergies, variations of infant feedings, or other specific
clinical disorders. Increased production of gastriri in either
mother or infant does not seem to be a causative factor. An
association with blood groups 0 and B and with maternal
stress in the last trimester of pregnancy has been suggested.
The etiology is considered multifactorial, with a proven
genetic X-linked factor and an uncertain environmental one.
Although the designation as congenital is questioned by
some, the presence of a partial obstruction at the pylorus in
some ways is analogous to congenital duodenal webs, which
may not produce symptoms for several days or a few weeks
after birth. It is doubtful that pyloric stenosis would produce
such severe symptoms predictably within the first 3 to 5
weeks unless a major component of the disorder were
congenital.
The pathogenesis of pyloric stenosis is believed by some to be
postnatal work hypertrophy, possibly following a congenital
delay in the opening of the pyloric sphincter. Others have
suggested a congenital redundancy of the pyloric mucosa.
Another theory suggests that milk curds passing through the
narrow channel cause additional edema and swelling with
eventual complete occlusion,
which subsides if nothing is taken by mouth for a few days or if
only clear fluids are given. This theory is consistent with the
course of the lesion because it disappears after the obstruction is
relieved. Vasoactive intestinal peptide decreases the intensity
and duration of pyloric contraction in a dose-dependent manner,
suggesting vasoactive intestinal peptide could playa role in
etiology. Studies implicate unbalanced function of the
peptidergic nervous system, but the precise relationship is not
yet proven.
The musculature of the pylorus in patients with pyloric
stenosis is markedly thickened and edematous. There is
hypertrophy of the circular muscle fibers but no increase in their
number. The spindle-shaped swelling of the hypertrophied
muscles of the pylorus usually measures approximately 2.0 to
2.5 cm long and protrudes into the duodenum, analogous to the
cervix into the vagina. The pyloric muscle is usually firm and
discrete and likened to a tumor, although it becomes softer in
older infants. The proximal portion is less abrupt and fuses with
the normal antral musculature. The gastric muscle is usually
thickened, and the mucosa is frequently edematous and
congested, occasionally leading to bleeding. After
pyloromyotomy, the pyloric muscle gradually becomes
completely normal, and when visualized at subsequent
operations, only a fine scar in the area of the myotomy can be
identified. Approximately 7% of infants with pyloric stenosis
have associated anomalies, with esophageal hiatal and inguinal
hernias being the most frequent.
Classically, projectile nonbilious emesis, the presence of a
palpable pyloric tumor, and visible gastric waves on the
abdomen in a 3- to 5-week-old infant are the clinical features of
hypertrophic pyloric stenosis. Most infants experience emesis of
small amounts by 2 weeks of life, then develop nearly complete
obstruction with vomiting of almost all feeds by 2 to 4 weeks.
The range of presentations is 1 to 12 weeks of age. Shortly after
emesis, infants usually crave further feedings. Although withholding
fee dings for a short period may provide slight resolution
of mucosal edema, allowing the infant to retain clear liquid
feedings, this apparent improvement is almost invariably shortlived,
and emesis recurs whensmall milk feedings are resumed. The emesis is characteristically
projectile or forceful because of the high pressure generated by
the hypertrophied gastric muscles. Infants who are allowed to
continue with symptoms for more than a few days often lose
weight and may become dehydrated with metabolic alkalosis or
even malnourished. Repeated emesis that is allowed to persist for
several days may produce gastritis with mild bleeding.
DIAGNOSISObservation of the abdomen after a feeding in infants with wellestablished
pyloric stenosis often reveals contractions of the
stomach that proceed from left to right across the epigastrium.
These gastric waves eventually terminate in an episode of
emesis. Similar but less prominent waves can be seen in other
conditions, such as severe pylorospasm or gastric duplication.
Careful palpation of the epigastrium slightly to the right of the
midline often discloses a firm, olive-sized mass that can be
manipulated slightly upward or downward. The hypertrophied
pyloric muscle is identified most easily when the stomach is
empty, either after emesis or after tube decompression of the
stomach. Elevating and gently moving the lower extremities
while allowing the infant to suck on a pacifier or a bottle of
sugar water during the examination may relax the abdominal
musculature, permitting a more accurate examination. Repeated
examinations over a few hours occasionally may be necessary in
an active, crying infant, but sedation is rarely necessary. The
pyloric mass is pathognomonic, and depending on the experience
and patience of the examiner, it can be identified in 70% to 90%
of infants with hypertrophic pyloric stenosis.
Hypertrophic pyloric stenosis may be simulated by many
other causes of vomiting in infants. Overfeeding is the most
common and is a frequent practice in many families. There is a
frequent history of formula changes because of a suspected milk
allergy or intolerance to the current formula. Improved feeding
technique, frequent burping, and time are all that is needed for
most of these disorders to resolve. Pylorospasm,
gastroesophageal reflux, delayed gastric emptying of
undetermined etiology without mechanical obstruction, and
several anomalies including malrotation with duodenal bands,
duodenal or antral webs, and pyloric duplications rarely may
simulate pyloric stenosis. Emesis also may be associated with
metabolic disorders, inborn errors of metabolism, central
nervous system lesions, and sepsis. A good clinical rule of
thumb that aids in the differential diagnosis is that a child with
pyloric stenosis will continue to be hungry and active unless
severely dehydrated. Infants with metabolic disorders or
increased intracranial pressure are likely to be lethargic and feed
poorly, and the vomitus is often bilious.
Abdominal ultrasonography is performed on infants in whom a
tumor cannot be palpated. This study is highly reliable and is
currently the preferred approach when the pyloric mass cannot
be felt. The most commonly used criteria are a pyloric muscle
thickness of 4 mm or more and a pyloric channel length of 16
mm or more (Fig. 45-1). The barium upper gastrointestinal
(UGI) series is used for the occasional infant in whom physical
examination and ultrasound are not diagnostic.Occasionally the diagnosis may be made as early as the fourth
or fifth day of life and, in rare instances, as late as 4 months. In
our experience, the average onset of symptoms occurs at 3
weeks. Vomiting is the initial sign, and the emesis is always free
of bile. Initially the infant may vomit once or twice a day;
however, as the obstruction progresses, the emesis becomes
more constant and forceful or projectile, extending several
inches from the face. The infants characteristically have a
ravenous appetite shortly after an episode of emesis.
Occasionally the emesis in infants with more protracted
vomiting may become brownish or blood-streaked as a result of
bleeding from ruptured capillaries in the gastric mucosa induced
by the frequent vomiting.
Vomiting with an open pylorus generally results in a loss of
an isotonic mixture of duodenal, biliary, and pancreatic
secretions. In contrast, vomiting caused by pyloric stenosisOPERATIVE TREATMENT
Preoperative care is aimed at restoring fluid and electrolyte losses.
Because the diagnosis of pyloric stenosis usually is made earlier
than in previous years, few infants are seen in an advanced state of
severe dehydration, malnutrition, and alkalosis. Most infants with
pyloric stenosis can be operated on within 12 hours after
admission to the hospital. Although a clear liquid feed may be
tolerated preoperatively, most pediatric anesthesiologists prefer
that these infants not be fed for 8 to 12 hours preoperatively
because of delayed gastric emptying. In some cases, it is necessary
to lavage the stomach with normal saline solution to remove
obstructing milk curds or barium.
For most infants, intravenous fluids are initiated as the infant is
being admitted to the hospital for treatment. A solution containing
5% dextrose in 0.45% saline is administered intravenously at a
rate of approximately 150 to 175 mL/kg/2 4 hours, depending on
the amount of hydration necessary. After the infant has voided, 10
to 15 mEq of potassium chloride is added to each 500-mL intravenous
bottle. The total amount of potassium chloride in the fluids
administered should not exceed 40 mEq/L in 24 hours.
Dehydration with more severe electrolyte deficits requires the
administration of normal saline solution at a rate of 175 to 185
mLIkg/24 hours until the infant voids. Dehydrated patients
occasionally require resuscitation for 24 to 36 hours. When the
stomach has been emptied, most infants with pyloric stenosis stop
vomiting.
The Ramstedt-Fredet pyloromyotomy, performed with the
infant under general anesthesia, is universally accepted as the
preferred operation. The stomach should be emptied again just
before induction of anesthesia to minimize the risk of aspiration.
The procedure can be performed through a variety of approaches,
although the one used most frequently is a transverse skin incision
followed by a vertical splitting of the right rectus muscle and
fascia. The right upper abdominal transverse muscle-splitting
gridiron incision (Robertson) is used by many. Because it provides
a better cosmetic appearance, a supraumbilical, curvilinear
incision has been used by some surgeons; however, there is a
higher incidence of wound-related complications. After entering
the abdomen, the omentum can be readily retrieved into the
wound, which when elevated lifts the transverse colon and leads
directly to the gastric antrum. The lower stomach may be elevated
with gentle traction using moistened gauze to minimize slipping as
the pyloric mass is delivered into the wound. A vertical incision is
made on the mid anterior surface through the serosa and
superficial muscularis extending from approximately 2 mm
proximal to the pyloric vein (an avascular area) to a point 0.5 cm
onto the lower antrum . Although most surgeons use a
straight, longitudinal incision, a superficial V-shaped extension at
the duodenal end of the myotomy incision has been helpful in
reducing the risk of duodenal mucosal injury. The circular muscle
is opened bluntly using the Benson pyloromyotomy spreader or
the back of the knife handle.COMPLICATIONS
Gastritis and gastroesophageal reflux are the most common causes
of persistent postoperative vomiting. Incomplete pyloromyotomy as
a cause of persistent vomiting is rare but should be considered if
vomiting continues for more than 7 to 10 days postoperatively, if it
is forceful, and if it follows every feeding. It is usually due to an
incomplete separation of the muscles on the antral side of the
pylorus. Contrast radiography in this instance may diagnose
gastroesophageal reflux or show whether the stomach readily
empties, but it is of little help in diagnosing an incomplete
myotomy because the radiographic appearance of pyloric stenosis
has been relieved. If a second myotomy is deemed necessary, which
is rare, the procedure consists of a fresh pyloromyotomy in an area
that is well away from the original incision. This is done by turning
the pylorus 45 to 90 degrees to either side and performing the
standard pyloric incision.
The rare unrecognized duodenal perforation is identified by the
postoperative presence of emesis, distention, fever, and peritonitis.
In this instance, prompt reoperation is mandatory, consisting of
simple duodenal repair and placement of a tongue of omentum over
the closure. Wound infections with Staphylococcus occasionally
occur and may be related to the proximity of the umbilical stump.
Postoperative incisional dehiscence and delayed incisional hernias
are uncommon. The mortality associated with pyloromyotomy is
less than 0.4% in the experience of almost all major children's
centers. The rare deaths encountered in most instances have
occurred in patients with multiple congenital anomalies.
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