Congenital Anomalies
Time
period: birth
A
relatively common congenital abnormality is cleft lip and/or cleft
palate which affects around 1 in 600–700 live births and has a collection
of defects.
Cleft
lip (cheiloschisis) can be incomplete (affects upper lip only) or
complete (continues into the nose) and unilateral (Figure 35.1) or bilateral.
It is caused by the incomplete fusion of the medial nasal prominence with the
maxillary process (Figure 35.2). When these fuse normally they form the
intermaxillary segment, which goes on to become the primary (soft) palate.
The
secondary (hard) palate forms from outgrowths of the maxillary process called
the palatine shelves. Failure of these shelves to fuse or ascend to a
horizontal position causes cleft palate (palatoschisis). In very
severe cases the cleft can continue into the upper jaw. Cleft palate is often
accompanied by cleft lip (complete), but not always (incomplete; Figure 35.3),
and can also be unilateral or bilateral.
A
cleft lip is generally diagnosed at the 20‐week anomaly scan, whereas cleft
palates are diagnosed after birth. Cleft lips require surgical intervention
before 3 months, whereas cleft palate surgery should happen before the child
reaches 12 months old. Cleft lip and palate can affect feeding and speech, but
also hearing. To aid prevention of cleft lip and palate maternal dietary folic
acid is recommended (see also spina bifida, Chapter 17).
Abnormalities
in development of the foregut can include stenosis and atresia at various
points along its length, and hypertrophy of the pylorus of the stomach.
Depending upon the point of restriction projectile vomiting can be a symptom,
and the presence or absence of bile in the vomit can help diagnose the
location.
The
respiratory tract forms as a bud from the foregut, so a tracheoesophageal
fistula can form (Figure 35.4). The most common variant sees the proximal
oesophagus end blindly and the trachea connected to the distal oesophagus.
There are many other variations and frothy oral secretions are often a symptom.
Surgery is required.
A congenital
hiatal hernia is caused by the oesophagus not
lengthening
fully, preventing the diaphragm from forming normally and pulling the top of
the stomach up into the thorax. This can affect the development of respiratory
structures, and occurs in varying severity.
A
remnant of the vitelline duct that connected the yolk sac to the midgut may
persist as an ileal diverticulum (also known as Meckel’s diverticulum; Figure
35.5) or as a vitelline cyst (also known as an omphalomesenteric duct
cyst) in the distal ileum. An ileal diverticulum is present in around 2% of the
population, but the majority are asymptomatic. Ulceration may form here with
bleeding. If the vitelline duct persists as fibrous cords between the abdominal
wall and the ileum loops of intestine may become twisted around it. The duct
may survive as a true duct between the ileum and the external umbilicus.
The
midgut may fail to complete its rotation or to fail to rotate in the normal
direction during development, giving abnormal rotation or reverse
rotation of intestine. Abnormal rotation is caused by only a 90° rotation
and gives a left‐sided colon, whereas reverse rotation causes the transverse
colon to lie posterior to the superior mesenteric artery after a 90° clockwise
rotation of the midgut instead of the normal 270° counterclockwise rotation.
Omphalocoele (or exomphalos)
is the herniation of abdominal contents into the umbilicus, and the contents
remain covered by peritoneum and amnion (Figure 35.6). This can normally be
diagnosed by antenatal ultrasound scanning. Omphalocoele is thought to occur as
a failure of the midgut to reenter the abdominal cavity after the normal
herniation of weeks 6–10. Omphalocoele is often associated with cardiac and
neural tube defects, trisomy 13 and 18 and Beckwith–Wiedemann syndrome.
The
urorectal septum normally separates the cloaca into urogenital and hindgut
spaces. If this fails to occur normally links between the two spaces can occur,
such as a rectourethral (urorectal) fistula (Figure 35.7) or a rectovaginal
fistula (Figure 35.8).
Anal atresia can occur,
possibly as a result of interrupted blood supply during development. Imperforate
anus may also occur if the cloacal membrane does not break down. There are
different degrees of severity, and some require a colostomy whereas others are
repairable with surgical intervention, often within 24 hours of birth.
Liver
Jaundice affects 60% of
healthy newborn infants and has multi- ple causes, often categorised by age of
onset. It is normally identified through the infant’s skin colour and bilirubin
levels. Most cases of jaundice do not need treatment, but phototherapy helps
reduce bilirubin levels. In extreme cases an exchange transfusion is necessary.
Pancreas
Due
to abnormalities in the rotation of the ventral bud pancreatic tissue can end
up surrounding the duodenum. This is called an annular pancreas. It is
possible that this tissue can constrict the duodenum and cause a complete
blockage. Early signs can include polyhydramnios. It is normally treated
with surgery.
Spleen
Splenic
lobulation and an accessory spleen are relatively common. Rarer conditions
include a wandering spleen and polysplenia (multiple accessory spleens).
Splenogonadal fusion, a very rare
developmental anomaly, results from the abnormal fusion of the splenic and
gonadal primordia during prenatal development.
Hyposplenism (reduced splenic
function) may occur because of a congenital failure of the spleen to ted
individuals are at increased risk of bacterial sepsis.
