Dr. Moayed – Lecture 2
Pediatric Surgery
Fifth Stage
C. Gastro-duodenal Anomalies
1. Gastric Anomalies
Congenital gastric outlet obstruction is extremely rare. It occurs either in the pyloric
or antral region. Antral membranes (web or diaphragm) are thin, soft and pliable,
composed of mucosa/submucosa, and located eccentric 1-3 cm proximal to pyloro-
duodenal junction. They probably represent the developmental product of excess local
endodermal proliferation and redundancy. The diagnosis should rely on history, contrast
roentgenology studies and endoscopic findings. Symptoms are those of recurrent non-
bilious vomiting and vary according to the diameter of aperture of the membrane. There
is a slight male predominance with fair distribution between age groups in children.
Associated conditions: pyloric stenosis, peptic ulcer and cardiac. History of
polyhydramnios in the mother. Demonstration of a radiolucent line perpendicular to the
long axis of the antrum is diagnostic of a web. Endoscopy corroborates the diagnosis.
Management can be either surgical or non-surgical. Surgical Tx is successful in
symptomatic pt. and consist of pyloroplasty with incision or excision of the membrane.
Other alternative is endoscopic balloon dilatation or transection of the web. Non-
obstructive webs found incidentally can be managed medically with small curd formula
and antispasmodics. The presence of an abnormally dilated gastric bubble in prenatal
sonography should alert the physician toward the diagnosis of congenital antro-pyloric
obstruction.
2. Pyloric Stenosis
Is an abnormality of the pyloric musculature (hypertrophy) causing gastric outlet
obstruction in early infancy. The incidence is 3 per 1000 live births. The etiology is
unknown, but pylorospasm to formula protein cause a work hypertrophy of the muscle.
Diagnostic characteristics are: non-bilious projectile vomiting classically 3-6 weeks of age,
palpable pyloric muscle "olive", contrast studies are not necessary when the pyloric
muscle is palpated, enlarged width and length in ultrasonography.
The treatment consists in correction of hypochloremic alkalosis and state of
dehydration and performing a Fredet-Ramstedt modified pyloromyotomy. Post-operative
management consist of: 50% will have one to several episodes of vomiting, usually can
feed and go home in 24-36 hours, initial feeds start 812 hours after surgery.
3. Duodenal Malformations
Can be intrinsic (Atresia, Stenosis, Webs) or extrinsic (Annular pancreas, Ladd's
bands). Occur distal or proximal to the ampulla of Vater. Most commonly distal to ampulla
and therefore bilious vomiting is present. (Note: Bilious vomiting is surgical until proven
otherwise in a baby).
"Windsock" webs have clinical importance because of their tendency to be confused
with distal duodenal obstruction and because of the frequent occurrence of an anomalous
biliary duct entering along their medial margin.
Embryology: The first major event in the differentiation of the duodenum,
hepatobiliary tree, and pancreas occurs at about the third week in gestation, when the
biliary and pancreatic buds form at the junction of the foregut and the midgut. The
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duodenum at this time is a solid cord of epithelium, which undergoes vacuolization
followed by recanalization and restitution of the intestinal lumen over 3-4 weeks of normal
development. Failure of recanalization of the second part of the duodenum results in
congenital obstruction of the lumen, often in conjunction with developmental
malformation of the pancreatic anlagen and the terminal part of the biliary tree. In support
of this concept is the high incidence of annular pancreas observed, believed to represent
a persistence of the ventral pancreatic anlage in association with intrinsic duodenal
obstruction.
The diagnostic characteristics are: bilious vomiting, history of polyhydramnios in
mother, KUB with classic "Double-bubble" appearance, a microcolon in barium enema
study or malrotation.
Treatment consists in: (1) duodeno-duodenostomy bypass for atresias, annular
pancreas, and some stenosis. (2) duodenoplasty for webs, and stenosis, and (3) lysis of
Ladd’s bands and Ladd’s procedure for malrotation.
Associated anomalies are: Down's syndrome (20-30%), VACTERL syndrome, CNS
anomalies and cardiac anomalies.
D. Malrotation and Volvulus Embryology:
Embryology: The rotation and normal fixation of the intestinal tract takes place
within the first three months of fetal life. In the earliest stages when the intestinal tract is
recognizable as a continuous tube, the stomach, small intestine, and colon constitute a
single tube with its blood supply arising posteriorly. The midgut portion of this tube, from
the second portion of the duodenum to the mid-transverse colon, lengthens and migrates
out into an extension of the abdomen, which lies at the base of the umbilical cord. Here
this loop of bowel undergoes a 270-degree counterclockwise twist at its neck. In the center
of the twisted loop lie the blood vessels that will become the superior mesenteric artery
and vein. After rotation, the small intestine quite rapidly withdraws into the abdominal
cavity, with the duodenum and the proximal jejunum going first. During this process the
duodenojejunal junction goes beneath and to the left of the base of the superior
mesenteric vessels. This leaves the upper intestine, including the stomach and the
duodenum, encircling the superior mesenteric vessels like a horseshoe with its opening
on the left side of the embryo. The small intestine then follows into the abdomen, and
withdrawal of the right half of the colon takes place so that it lies to the left. At the next
step, the cecum and the right colon begin to travel across the top of the superior
mesenteric vessels and then down to the right lower quadrant. The colon now lies draped
across the top of the superior mesenteric vessels, again like a horseshoe, with its opening
placed inferiorly. The duodenojejunal loop is said to attach to the posterior abdominal wall
soon after its turn, whereas the mesenteric attachments of the entire colon and of the
remaining small bowel gradually adhere after they arrive in their normal positions. In
malrotation the right colon can create peritoneal attachments that include and obstruct
the third portion of the duodenum (Ladd’s bands).
The diagnostic hallmarks are: bilious vomiting (the deadly vomit), abdominal
distension and metabolic acidosis. A UGIS is more reliable than barium enema, most
patients present in first month of life (neonatal), but may present at any time.
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The treatment is immediate operation; volvulus often means strangulation. Needs
fluid and electrolyte replacement. Ladd’s procedure consist of: reduce volvulus with a
counterclockwise rotation, place small bowel in right abdomen, lysed Ladd’s bands, place
large bowel in left abdomen, do an appendectomy. In cases of questionable non-viable
bowel a second look procedure is required.
Failure to make early diagnosis and operate may lead to dead midgut with resultant
short bowel syndrome.
E. Intestinal Atresias
Intestinal atresias are the product of a late intrauterine mesenteric vascular
accident (blood supply was not received by a portion of bowel) as attested by Louw and
Barnard in 1955. They are equally distributed from the ligament of treitz to the ileocecal
junction. Colonic atresias are very rare. There is proximal bowel dilatation, with distal
(unused) micro-bowel. The diagnosis is suspected with maternal history of
polyhydramnios (the higher the atresia), bilious vomiting, abdominal distension and
obstipation. KUB shows ?thumb-size? dilated bowel loops, and barium enema a microcolon
of disuse. Louw classified them into: Type I: an intraluminal diaphragm with seromuscular
continuity. Type II: cord-like segment between the bowel blinds ends. Type IIIA: atresia
with complete separation of blind ends and V-shaped mesenteric defect (see figure), the
most commonly found. Type IIIB: jejunal atresia with extensive mesenteric defect and
distal ileum acquiring its blood supply entirely from a single ileocolic artery. The distal
bowel coils itself around the vessel, giving the appearance of an "apple peel"deformity.
Type IV: multiple atresias of the small intestine. After preoperative stabilization (GI
decompression,
electrolytes
disturbances?
correction,
antibiotherapy,
and
normothermia), treatment consists of exploratory laparotomy, resection of proximal
dilated intestine, and end to oblique anastomosis in distal jejuno-ileal atresias. Tapering
jejunoplasty with anastomosis is preferred in proximal defects.
F. Meconium Ileus
Meconium ileus is a neonatal intraluminal intestinal obstruction caused by
inspissated meconium blocking the distal ileum. Occurs in 10-15% of all patients with
cystic fibrosis, and 85-95% of patients with meconium ileus have cystic fibrosis. The
meconium has a reduced water, abnormal high protein and mucoprotein content, the
result of decreased pancreatic enzyme activity and prolonged small bowel intestinal
transit time.
Meconium Ileus is classified into two types: (1) Simple meconium ileus: The distal
small bowel (10-30 cm of distal ileum) is relatively small, measuring less than 2 cm in
diameter and contains concretions of gray, inspissated meconium with the consistency of
thick glue or putty. It is often beaklike in appearance, conforming to the shape of the
contained pellets. Proximally, the mid-ileum is large, measuring up to 7 cm in diameter.
It is greatly distended by a mass of extremely thick, tenacious, dark green or tarry
meconium. The unused small colon (microcolon) contains a small amount of inspissated
mucus or grayish meconium. (2) Complicated meconium ileus: usually occurs during the
prenatal period associated to volvulus, atresias, gangrene, perforation or peritonitis. A
cystic mass or atresia of the bowel may occur.
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The degree of obstruction varies, may be cured in mild cases by rectal irrigations.
Failure to pass meconium, abdominal distension and vomiting are seen in more severe
cases. The diagnosis is suspected with findings of: multiple loops of dilated small bowel
and coarse granular "soap-bubble" appearance on plain abdominal films. Some cases may
show calcifications in the peritoneum (Meconium peritonitis). The Sweat Test is diagnostic
of cystic fibrosis (value over 60 meq/L of sweat sodium or chloride are diagnostic). This
test is not useful in infant during first weeks of life.
Therapy is either: (1) Nonoperative- should be tried first. It consists of a careful
gastrografin enema after the baby is well-hydrated. Gastrografin is a hyperosmolar
aqueous solution of meglumine diatrizoate containing 0.1% polysorbate-80 (tween-80, a
wetting agent) and 37% iodine. Its success is due to the high osmolarity (1700 mOsm/liter)
which draws fluid into the bowel and softens and loosens the meconium. (2) Surgical
therapy that has included: ileostomy with irrigation, resection with anastomosis, and
resection with ileostomy (Mikulicz, Bishop-Kopp, and Santulli). Post-operative
management includes: 10% acetylcysteine p.o., oral feedings (Pregestimil), pancreatic
enzyme replacement, and prophylactic pulmonary therapy. Longterm prognosis depends
on the degree of severity and progression of cystic fibrosis pulmonary disease.
G. Hirschsprung's Disease
Hirschsprung's is the congenital absence of parasympathetic innervation of the
distal intestine. The colon proximal to the aganglionic segment, in an effort to overcome
the partial obstruction, becomes distended and its wall markedly thickened because of
muscle hypertrophy. Occurs 1 in 1000-1500 live births with a 4:1 male predominance.
96% are TAGA. 4% prematures.
The parasympathetic ganglion cell network located between the circular and
longitudinal muscle layers is referred to as Auerbach's plexus, whereas Meissner's plexus
is the submucosal layer of ganglion cells just beneath the muscularis mucosa. In
Hirschsprung's disease, ganglion cells are absent from all layers. That aganglionic
segment usually involves the terminal intestine, i.e. the rectum or rectosigmoid. The
aganglionic segment may, however, include the entire large bowel and even small bowel.
Hirschsprung's disease (HD) is characterized by lack of enteric ganglion cells,
hyperplasia of abnormal nerve fibers and a non-propulsive, non-relaxing segment of
bowel. Classically the etiology is attributed to a failure of cranio-caudal migration of
parasympathetic neural crest cells to the distal bowel. A plausible explanation for the
failure of relaxation of the bowel involved is a deficiency of enteric inhibitory nerves that
mediates the relaxation phase of peristalsis. These nerves are intrinsic to the gut and are
classify as non-adrenergic and non-cholinergic. Nitric oxide (NO) has recently been
implicated as the neurotransmitter which mediates the relaxation of smooth muscle of
the GI tract in HD. It's absence in aganglionic bowel might account for the failure of
relaxation during peristalsis. Besides, adhesions molecules (absent in aganglionic bowel)
during early embryogenesis might restrict the neuro-ectodermal origin involved in the
initial contact between nerves and muscle cell (synaptogenesis) suggesting that
developmental anomaly of innervated muscle and absent NO causes the spasticity
characteristic of HD.
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Symptoms usually begin at birth, frequently with delayed passage of meconium.
Any newborn who fails to pass meconium in the first 24-48 hours of life should be
evaluated for possible Hirschsprung's disease. In some infants, the presentation is that of
complete intestinal obstruction. Others have relatively few symptoms until several weeks
of age, when the classic symptom of constipation has its onset. Diarrhea is not uncommon
but differs from the usual infantile diarrhea in that it is associated with abdominal
distension. Occasionally the patient will go many years with mild constipation and
diagnosis will be delayed.
The diagnosis is first suspected based on history and physical examinations
(characteristically there is no stool in rectum and abdominal distension is painless). Initial
evaluation includes an unprepped barium enema (the first enema should be a barium
enema!). The aganglionic rectum appears of normal caliber or spastic, there is a transition
zone and then dilated colon proximal to the aganglionic segment. 24-hrs delayed films
shows poor emptying with barium throughout the colon, as opposed to the child with
psychogenic stool holding in whom the barium generally collects in the distal
rectosigmoid. Rectal suction biopsy is then performed. This can be done without
anesthesia and the submucosal plexus is examined for ganglion cells. With experience, a
good pathologist (should be an expert!), can identify the presence or absence of ganglion
cells in this specimen without a full thickness biopsy. Difficulty in interpreting the
specimen or not enough to include several slides of submucosa would require a full-
thickness biopsy for definitive diagnosis generally done under general anesthesia. Some
centers employ manometry, histochemical studies or special stains for diagnosis. These
special studies are only as good as the person performing them and interpreting the
results.
The initial treatment requires performing a "leveling" colostomy in the most distal
colon with ganglion cells present. This requires exploration with multiple seromuscular
biopsies of the colon wall to determine the exact extend of the aganglionosis. The
colostomy is placed above the transition zone. Placement of the colostomy in an area of
aganglionosis will lead to persistent obstruction. Once the child has reached an adequate
size and age (6-12 months; 20 pounds or more), a formal pull-through procedure is done.
Some of this are: Swenson, Duhamel and Soave procedures. Current preference is for
Soave procedure (modified endorectal pull-through) and consists of resection of the
majority of aganglionic bowel except for the most distal rectum, the mucosa and
submucosa of this rectum is excised and the normally innervated proximal bowel is pulled
through the seromuscular coat of retained rectum and suture immediately above the
dentate line. Recently a laparoscopic pull-through procedure avoiding the colostomy is
being used in early life with promising results.
Intestinal Neuronal Dysplasia (IND) is a colonic motility disorder first described in
1971 by Meier-Ruge associated to characteristic histochemical changes of the bowel wall
(hyperplasia of submucous & myenteric plexus with giant ganglia formation, isolated
ganglion cells in lamina propria and muscularis mucosa, elevation of acetylcholinesterase
in parasympathetic fiber of lamina propria and circular muscle, and myenteric plexus
sympathetic hypoplastic innervation), also known as hyperganglionosis associated to
elevated acetylcholinesterase parasympathetic staining. The condition can occur in an
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isolated form (either localized to colon or disseminated throughout the bowel), or
associated to other diseases such as Hirschsprung's (HD), neurofibromatosis, MEN type
IIB, and anorectal malformations. It is estimated that 2075% of HD cases have IND
changes proximal to the aganglionic segment. Clinically two different types of isolated
IND have been described: Type A shows symptoms of abdominal distension, enterocolitis,
bloody stools, intestinal spasticity in imaging studies (Ba Enema) since birth, is less
common and associated with hypoplasia of sympathetic nerves. Type B is more frequent;
symptoms are indistinguishable from that of HD, with chronic constipation, megacolon,
and repeated episodes of bowel obstruction. Management depends on clinical situation;
conservative for minor symptoms until neuronal maturation occurs around the 4th year
of life, colostomy and resectional therapy for life threatening situations.
H. Imperforate Anus
Embryology- Between 4-6 weeks, the cloaca becomes the common depository for
the developing urinary, genital and rectal systems. The cloaca is quite promptly divided
into an anterior urogenital sinus and a posterior intestinal canal by the urorectal septum.
Two lateral folds of cloacal tissue join the urorectal septum to complete the separation of
the urinary and rectal tracts.
Diagnostic evaluation include physical exam for clues such as: meconium "pearls",
bucket handle anus, a fistula or meconium at meatus (urethra). Radiography could be of
help initially by using the Wangensteen-Rice "upside-down" film with opaque marker,
sacral films, urogram (IVP and cystourethrogram). Through the distal stoma of the initial
colostomy a contrast study (colostogram) can be done to further delineate the recto-
urethral fistula associated.
Associated Anomalies: (1) Gastrointestinal- 10-20% of patients with imperforate
anus have another GI lesion such as esophageal atresia, intestinal atresia or malrotation.
(2) Cardiovascular- approximately 7% have associated CV lesions. (3) Skeletal-
approximately 6% have skeletal lesions such as spina bifida or agenesis of the sacrum.
(4) Genitourinary- 25-40% of patients will have associated genitourinary anomalies. The
incidence is higher with supralevator lesions than with infralevator lesions.
The repair has been revolutionized by Pe?a approach (Posterior sagittal
anorectoplasty procedure). The most important decision in the initial management of
Imperforate Anus (IA) male patient during the neonatal period is whether the baby needs
a colostomy and/or another kind of urinary diversion procedure to prevent sepsis or
metabolic derangements. Male patients will benefit from perineal inspection to check for
the presence of a fistula (wait 16-24 hours of life before deciding). During this time start
antibiotherapy, decompress the GI tract, do a urinalysis to check for meconium cells, and
an ultrasound of abdomen to identify urological associated anomalies. Perineal signs in
low malformations that will NOT need a colostomy are: meconium in perineum, bucket-
handle defect, anal membrane and anal stenosis. These infants can be managed with a
perineal anoplasty during the neonatal period with an excellent prognosis. Meconium in
urine shows the pt has a fistula between the rectum and the urinary tract. Flat "bottom"
or perineum (lack of intergluteal fold), and absence of anal dimple indicates poor muscles
and a rather high malformation needing a colostomy. Patients with no clinical signs at 24
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hours of birth will need a invertogram or cross-table lateral film in prone position to decide
rectal pouch position. Bowel > 1 cm from skin level will need a colostomy, and bowel < 1
cm from skin can be approach perineally. Those cases with high defect are initially
managed with a totally diverting colostomy. Diverting the fecal stream reduces the
chances of genito-urinary tract contamination and future damage.
The most frequent defect in females’ patient with imperforate anus (IA) is vestibular
fistula, followed by vaginal fistulas. In more than 90% of females cases perineal inspection
will confirm the diagnosis. These infants require a colostomy before final corrective
surgery. The colostomy can be done electively before discharge from the nursery while
the GI tract is decompressed by dilatation of the fistulous tract. A single orifice is
diagnostic of a persistent cloacal defect usually accompany with a small-looking genitalia.
Cloacas are associated to distended vaginas (hydrocolpos) and urologic malformations.
This makes a sonogram of abdomen very important in the initial management of these
babies for screening of obstructive uropathy (hydronephrosis and hydroureter).
Hydrocolpos can cause compressive obstruction of the bladder trigone and interfere with
ureteral drainage. Failure to gain weight and frequents episodes of urinary tract infections
shows a poorly drained urologic system. A colostomy in cloacas is indicated. 10% of babies
will not pass meconium and will develop progressive abdominal distension. Radiological
evaluation will be of help along with a diverting colostomy in these cases. Perineal fistulas
can be managed with cutback without colostomy during the neonatal period.
I. Duplications
Duplications of the gastrointestinal tract are considered uncommon congenital
anomalies usually diagnosed or unexpectedly encountered intraoperatively during the
first two years of life. The duplicated bowel can occur anywhere in the GI tract, is attached
to the mesenteric border of the native bowel, shares a common wall and blood supply,
coated with smooth muscle, and the epithelial lining is GI mucosa. May contain ectopic
gastric or pancreatic tissue. Most are saccular, other tubular. Theories on their origin (split
notochord syndrome, twining, faulty solid-stage recanalization) do not explain all cases of
duplicated bowel. Three-fourth are found in the abdomen (most commonly the ileum and
jejunum), 20% in the thorax, the rest thoraco-abdominal or cervical. Symptoms vary
according to the size and location of the duplication. Clinical manifestations can range
from intestinal obstruction, abdominal pain, GI bleeding, ulceration, or mediastinal
compression. Ultrasound confirms the cystic nature of the lesion (muscular rim sign) and
CT the relationship to surrounding structures. Management consists of surgical excision
avoiding massive loss of normal bowel and removing all bowel suspect of harboring
ectopic gastric mucosa.
To be continued ,,,