What is hypertrophic pyloric stenosis?
Hypertrophic pyloric stenosis (HPS) is an abnormal thickening of the pylorus
muscle, through which food and other stomach contents pass into the small
intestine. The thickened pyloric muscle causes a narrowing of the pyloric
channel. As a result, breastmilk or infant formula feedings cannot pass out of
the stomach into the small intestine.
What are the symptoms of HPS?
Because infants with pyloric stenosis are unable to tolerate their feedings,
they may have the following symptoms:
- Frequent episodes of projectile vomiting (forceful vomiting)
within 30 to 60 minutes after feedings
- Small stools
- Dehydration
- Weight loss
- Irritability
- Hunger after feedings
How common is HPS?
HPS affects three out of every 1,000 babies born. It is more likely to
affect full-term, first-born male infants and is less likely to affect female
infants. HPS is more common in Caucasian infants, especially those of European
descent.
About 15 percent of infants born with HPS have a family history of the
condition. An infant is three times more likely to develop HPS if the mother had
the disease as an infant, as compared to the father.
When does HPS occur?
The symptoms of HPS usually occur between the third and sixth week of life.
How is HPS diagnosed?
Your health care provider will ask you several questions about your child's
feeding habits and will then examine your child. During the physical exam, the
health care provider may be able to feel an olive-sized lump (the thickened
pyloric muscle) in your child's abdomen. If the thickened pylorus is felt, no
further studies are needed.
If the thickened pylorus cannot be felt, an abdominal ultrasound may be done.
During this examination, a probe is gently applied against the abdomen. The
probe transmits sound waves through the body tissues, receives the echoes, and
transforms them into diagnostic images. Often, the enlarged pyloric muscle can
be seen on the ultrasound images.
In some cases, an upper gastrointestinal series must be done if the physical
exam and abdominal ultrasound do not reveal any abnormalities. This test
requires that your child drink a special liquid. This liquid can be seen on an
X-ray as it travels through the stomach and small intestine. The pediatric
radiologist will be viewing the X-ray while your child drinks the liquid to
determine whether or not the liquid is able to move out of the stomach through
the pylorus.