ABSTRACT
Hypertrophic pyloric stenosis (HPS) is the most common
condition requiring surgery in the first few months of life. It
is characterized by hypertrophy of the circular muscle of the
pylorus, causing pyloric channel narrowing and elongation.
The incidence of pyloric stenosis varies widely with geo-
graphic location, season, and ethnic origin.1 The incidence
has been reported to be approximately three per 1000 live
births.2 There is some evidence that in recent years the
incidence of pyloric stenosis has increased significantly in
some parts of the UK.35 Boys are affected four times more
often than girls.6 Recently, a dramatic rise in incidence among
male infants but not for females was reported, so that rates
for the two sexes were 6.2 and 0.9 per 1000 infants per year.7,8
Although earlier diagnosis, advances in fluid and electrolyte
therapy, and pediatric anesthesia have reduced the mortality to
practically zero, the exact etiology of pyloric stenosis is
unknown.9 This condition is usually classified as a congenital
disorder. It is almost unknown in stillbirths, associated
anomalies are very uncommon, and the patient usually
presents with vomiting after the second week of life. For these
reasons, it has been suggested that it may be an acquired
condition. Rollins et al.10 measured pyloric muscle dimensions
on ultrasonography in 1400 consecutive newborn infants. Nine
of these infants subsequently developed pyloric stenosis and
were operated upon. Their pyloric muscle measurements at
birth were all within the normal range. This study clearly
showed that congenital pyloric muscular hypertrophy is not
present in babies who later develop pyloric stenosis.
