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					Pathology Lab VI - Congenital Anomalies of the GI System
                        PATHOLOGY LAB – Congenital Anomalies of the Gastrointestinal Tract
                                                  Igor Danelisen



CASE PRESENTATION: Helene Q

Objectives:

Describe esophageal atresia and trancheoesophageal fistula, list the most frequent anatomic forms, and identify the most typical clinical
manifestations.Describe circumstances in which normal gastric mucosa is found outside of the stomach.Describe congenital hypertrophic pyloric
stenosis: pathogenesis, gross and histopathological findings and clinical manifestations. Describe heterotopic pancreas and annular pancreas:
morphology, and clinical manifestations. Describe intestinal atresia, stenosis, and duplications: morphology and clinical manifestations. Describe
congenital diverticula in general and meckel diverticulum in particular: pathogenesis, morphology and complications. Describe congenital
diaphragmatic hernia, types, physiopathological consequences, and clinical manifestations.



Reference: Robbins and Cotran: Pathologic Basis of Disease (8h Edition) pp. pages 764-766;

Helene was born by uneventful vaginal delivery at 37 week gestation with a birth weight of 3,315 g (7 lb, 5 oz). Polyhydramnios was not noted
during gestation. She was transferred to your department because of inability to pass a nasogastric catheter. X-ray examination showed gasless
abdomen and, incidentally, a high suspicion of a tracheoesophageal fistula. Esophagoscopy and bronchoscopy revealed no sign of
tracheoesophageal fistula. You decided to perform a right thoracotomy. Mediastinal exploration was performed through a right posterolateral
extrapleural thoracotomy but did not show tracheoesophageal fistula. Exposure of the esophagus disclosed no discontinuity of the muscle layer.
At the level of the midportion of the esophagus, there was an approximately 1-cm-long difference of the caliber of the esophagus. A 10 French
firm catheter was inserted by the anesthetist but was stopped at the beginning of this segment. It seemed macroscopically like an atretic segment.
Two transfixion sutures were done at the cranial and caudal ends of this segment, and it was resected. Both transected ends showed open lumen,
and they were anastomosed primarily. The postoperative course was uneventful, and the patient was discharged on the 21st day.
ESOPHAGEAL ATRESIA AND TRACHEOESOPHAGEAL FISTULA

Definition: Esophageal atresia (EA) is a condition in which the proximal and distal portions of the esophagus do not communicate.

     The upper segment of the esophagus is a dilated blind-ending pouch with a hypertrophied muscular wall.
     The pouch typically extends to the level of the second to fourth thoracic vertebra. In contrast, the distal esophageal portion is an atretic
     pouch (i.e. without an opening) with a small diameter and a thin muscular wall; it usually extends 1-2 cm above the diaphragm.
     Tracheoesophageal fistula (TEF) is an abnormal communication between the trachea and esophagus.
     When associated with EA, the fistula commonly enters the trachea posteriorly just above the carina.
     Esophageal atresia with or without tracheoesophageal fistula, is a fairly common congenital disorder and occurs in 1 per 3,000 to 5,000
     births.




Classification: Esophageal atresia and/or tracheoesophageal (TE) fistula have been classified anatomically into 5 different types as follows:

A) Isolated esophageal atresia without tracheoesophageal fistula (8%)

B) Esophageal atresia with distal tracheoesophageal fistula (84%)

C) H-type tracheoesophageal fistula with no atresia (4%)

D) Esophageal atresia with proximal and distal tracheoesophageal fistula (3%)

E) Esophageal atresia with proximal tracheoesophageal fistula (1%)

Pathophysiology: Because the esophagus is discontinuous, an infant with EA cannot swallow and appropriately handle secretions.

           Infants exhibit persistent drooling and aspiration or regurgitation of food after attempted feedings.
           Patients who have EA with distal TEF are at risk for additional complications related to the tracheoesophageal communication.

(1) When infants with this anomaly strain, cough, or cry, air enters the stomach through the fistula. As a result, the stomach and small intestine
become dilated, elevating the diaphragm and making respiration more difficult.

(2) Gastric secretions may also reflux retrograde through the fistula into the tracheobronchial tree, contributing to pneumonia and atelectasis.

Clinical presentation: The first sign of esophageal atresia in the fetus may be polyhydramnios in the mother.

           Polyhydramnios, however, has a broad differential diagnosis, including intestinal atresia, neural tube defects, diaphragmatic hernia
           and intrathoracic lesions.
           The inability to identify the fetal stomach bubble on a prenatal ultrasonogram in a mother with polyhydramnios makes the diagnosis
           of esophageal atresia more likely
           Postnatally, infants with pure EA become symptomatic within the first few hours of life. Classically, the neonate with esophageal
           atresia presents with copious, fine, white, frothy bubbles of mucus in the mouth (i.e. excess salivation) and, sometimes, the nose.
           These secretions may clear with aggressive suctioning but eventually return because of an inability to swallow. Any attempts at
           feeding can result in choking, coughing, cyanotic episodes, and food regurgitation.
           The presence of a fistula increases respiratory complications, which result from aspiration of food and secretions into the trachea and
           lungs.
           Pneumonia and atelectasis develop quickly in these neonates, and rattles heard during respirations are common.
           Fistulas also allow air to enter into the stomach and intestines, which can lead to abdominal distension.
           With atresia alone, the abdomen appears scaphoid.
           If esophageal atresia is suspected, a radiopaque nasogastric or feeding tube should be passed through the nose to the stomach.
           In patients with atresia, the tube typically stops at 10 to 12 cm.

     Important: The normal distance to an infant's gastric cardia is approximately 17 cm.

           In cases of suspected esophageal atresia, chest radiographs (posteroanterior and lateral views) should be obtained to confirm the
           position of the tube.
           The radiograph should include the entire abdomen.
           In patients with esophageal atresia, air in the stomach confirms the presence of a distal fistula, and the presence of bowel gas rules
           out duodenal atresia.
           Contrast studies are seldom necessary to confirm the diagnosis. Such studies increase the risk of aspiration pneumonitis and reactive
           pulmonary edema, and usually add little to plain film radiographs.

Associated anomalies: Many anomalies are associated with EA, and 50-70% of children with EA have some other defect.

           Cardiac abnormalities are the most common (occur in 28% of patients), especially ventricular septal defects, atrial septal defects and
           tetralogy of Fallot.
           Imperforate anus, duodenal atresia, meckel diverticulum, and annular pancreas may also be found on examination.
           Musculoskeletal anomalies include hemivertebrae, radial dysplasia or amelia, polydactyly, syndactyly, rib malformation, scoliosis,
           and lower limb defects.
           Genitourinary anomalies include renal agenesis or dysplasia, horseshoe kidney, polycystic kidney, ureteral and urethral
           malformations, and hypospadias.
           In the absence of such associated anomalies, the physical examination findings of infants with EA are fairly unremarkable.

Treatment: Once a diagnosis of esophageal atresia is established, preparations should be made for surgical correction. The goal of treatment is
to surgically restore esophageal continuity as soon as the baby can tolerate the procedure (within the first days postpartum).
CONGENITAL HETEROTOPIC GASTRIC MUCOSA.

Definition: Isolated cases of heterotopic gastric mucosa have been reported at all levels of the alimentary tract from the esophagus to the rectum.

           These cases are regarded as congenital in origin due to abnormal embryological development.
           Congenital heterotopic gastric mucosa exists alone or it complicates other congenital anomalies such as Meckel diverticulum,
           duplications, and heterotopic pancreas.
           Epithelium resembling gastric mucosa is also seen in a variety of conditions (for example, in Barrett esophagus, duodenitis, duodenal
           peptic ulcer and inflammatory bowel disease).

     Important: This change, associated with these conditions, occurs secondary to chronic inflammation and hence is strictly an acquired
     metaplastic change and not true heterotopia.

Clinical presentation: Congenital heterotopic gastric mucosa often remains asymptomatic only to be discovered incidentally.

Morphology-Gross: Most cases of isolated heterotopic gastric mucosa present as esophageal inlet patch or duodenal small polyps.

           Esophageal inlet patch is described as heterotopic gastric mucosa usually located in the proximal esophagus, just below the upper
           esophageal sphincter.
           Endoscopically it appears as a velvety orange-red or salmon colored patch that is well demarcated from the pearly gray squamous
           esophageal mucosa.
           Autopsy studies indicate 4.5% prevalence in the population. The majority of inlet patches are incidental findings and patients are
           asymptomatic.
           The heterotopic gastric mucosa in duodenum appears endoscopically as multiple small mucosal nodules, less than 1 cm diameter,
           situated in the first part of the duodenum.
           Histologically these nodules consist of well organized groups of gastric glands, consisting of a mixture of chief and parietal cells.
           These are covered by a surface epithelium of gastric type, which at the edges merges with the adjacent normal duodenal mucosa.
           Heterotopic gastric mucosa in duodenum is probably of little or no clinical significance.
INFANTILE HYPERTROPHIC PYLORIC STENOSIS

Definition and Clinical Presentation: Infantile hypertrophic pyloric stenosis (IHPS) is a condition affecting young infants, in which the
antropyloric portion of the stomach becomes abnormally thickened and manifests as obstruction to gastric emptying.

           Typically, infants with IHPS are clinically normal at birth; during the first few weeks of postnatal life, they develop nonbilious
           forceful vomiting described as “projectile.”
           Gastric outlet obstruction leads to emaciation and, if left untreated, may result in death.
           Surgical treatment is curative.

Epidemiology and inheritance: The incidence of IHPS is approximately 2-5 per 1,000 births per year in most white populations.

           IHPS is less common in African American and Asian populations, with a frequency that is one-third to one-fifth that in the white
           population.
           The male-to-female ratio is approximately 4:1. At present, no genetic lesion underlying IHPS has been found.
           In some cases inheritance of a polygenic mode was observed.
           The familial aggregation pattern demonstrated in IHPS has led to the proposal that it is inherited by a multifactorial threshold mode.
           This model assumes that the ``liability'' to develop IHPS is determined by the additive effects of numerous genetic and environmental
           factors. The generalized occurrence risk for siblings is 5-9%.
Gross anatomy note: The incisura angularis divides the stomach into a body to the left and a pyloric portion to the right. The sulcus intermedius
further divides the pyloric portion of the stomach: the pyloric vestibule to the left, denoted by an outward convexity of the greater curvature, and
the pyloric antrum or pyloric canal to the right. The pyloric antrum is approximately 2.5 cm in length and terminates at the pyloric orifice (pyloric
ring or sphincter). The pyloric orifice marks the opening of the stomach into the duodenum.




Morphology- Gross: The characteristic gross pathological feature in IHPS consists of thickening of the pyloric sphincter and crowding of
redundant and edematous mucosa within the lumen.
          Abnormally circumferentially thickened pyloric sphincter (thickness; 0.3–0.6 cm, length; 1.5–2.0 cm) separates the normally
          distendable portion of the antrum from the duodenal cap. It stops abruptly at both the ends. The normal thickness in the distensible
          portion of the antrum is 1 mm.
          The rigid pyloric canal is unable to accommodate the redundant mucosa, which protrudes into the gastric antrum.
          These anatomical abnormalities cause obstruction to the passage of gastric contents.
          When viewed endoscopically, the mucosa protrudes as a nipplelike projection.




Morphology- Microscopy: Histologically, IHPS is characterized by hypertrophied circular muscle coat and thickened, hypertrophied, and
edematous mucosa. The outer longitudinal muscle coat often appears thinner than normal.
Clinical manifestations: The condition is seldom present at birth, but rather the functional obstruction typically develops in the first 2–12 weeks
of life.

           Sonographic evaluation indicates that the anatomy is also normal at birth. Typical presentation of an infant with IHPS is onset of
           initially nonbloody, always nonbilious vomiting at 4-8 weeks.
           Although vomiting may initially be infrequent, over several days it becomes more predictable, occurring at nearly every feeding.
           Vomiting intensity also increases until pathognomonic projectile vomiting ensues.
           The baby in the early stage of the disease remains hungry and sucks vigorously after episodes of vomiting.
           Prolonged delay in diagnosis can lead to dehydration, metabolic alterations, and lethargy. Vomiting of gastric contents leads to
           depletion of sodium, potassium, and hydrochloric acid, which results in hypochloremic alkalosis and sodium and potassium deficits.
           Renal mechanisms designed to maintain intravascular volume conserve sodium at the expense of hydrogen ions, leading to
           paradoxical aciduria.
           Weight loss may be extensive, and the infant may be below birth weight at the time of presentation to the radiologist.

Diagnosis: Careful physical examination provides a definitive diagnosis for most infants with hypertrophic pyloric stenosis.

           The classic sign is a hard muscle mass (pylorus), classically described as an "olive," that can be palpated in the right upper quadrant
           or epigastrium. In experienced hands, abdominal palpation can be successful in 85%–100% of infants.
           Ultrasonography has become the criterion standard imaging technique for diagnosing IHPS.
           Necessary measurements include pyloric muscle thickness and pyloric channel length.
           Muscle wall thickness 3 mm or greater and pyloric channel length 14 mm or greater are considered abnormal in infants younger than
           30 days.

Therapy: Surgical pyloromyotomy remains the standard of treatment, and outcome is excellent.



Pathogenesis: The etiology of IHPS remains elusive.

           During the past decade, advanced techniques have been applied to examination of the hypertrophied muscle, with some interesting
           results.
           It has been found that, when compared with control specimens, the basic pathological defect in IHPS is an intramuscular neuropathy
           involving peptidergic, nitrergic, cholinergic and adrenergic nerve fibers in hypertrophic pyloric muscle.
                  o In normal individuals, the ongoing contractile tone in the smooth muscle sphincters is independent of the nervous system and
                       is generated by myogenic mechanisms.
                  o This implies that the contractile state is an intrinsic property.
           On the other hand, transient relaxation of the sphincter to permit the forward passage of material is accomplished by activation of
           inhibitory non-adrenergic non-cholinergic (NANC) motor neurons. NANC inhibitory innervation is mediated by neuropeptides (such
           as VIP and neuropeptide Y) and nitric oxide (NO).
           An absence of immunoreactivity for VIP and neuropeptide Y in the intramuscular nerve fibers supplying the circular pyloric muscle
           in IHPS has been demonstrated with immunohistochemical techniques.
           No such reduction was observed in the cell bodies and nerves within the myoenteric plexus in IHPS.
           On the other hand, it has been demonstrated recently that enzyme NADPH diaphorase, which is identical to NO synthase, is absent or
           markedly reduced in hypertrophic pyloric muscle while it is preserved in myenteric plexus in IHPS.
           Furthermore, low levels of neuronal NO synthase mRNA have been demonstrated using PCR technique in pyloric muscle of IHPS
           patients compared to normal controls.
           There is also a marked reduction in cholinergic as well as adrenergic nerve fibers in the hypertrophied muscle, which contrasted with
           the myenteric plexus, where many nerve fibers and ganglion cells are positive for acetylcholinesterase.
           Pharmacologically, acetylcholine has a role in increasing pyloric muscular tone.
           It is postulated that the absence of NANC, nitrergic, cholinergic and adrenergic inhibitory nerves in the circular muscular coat leads
           to failure of relaxation of the pyloric muscle, increased synthesis of growth factors, subsequent hypertrophy, hyperplasia of smooth
           muscle cells, and luminal obstruction.

CASE PRESENTATION: URSULA M.

A 25-year-old woman presents in your clinic with complaints of progressive dyspeptic symptoms over a few weeks without concomitant weight
loss. On physical examination, the patient was in good health; bowel sounds were normal and there was no tenderness in the epigastric area; the
liver and the spleen were not palpable. Blood count and liver function tests were normal. An upper gastrointestinal endoscopy was performed and
revealed an intraluminal protrusion with normal overlying mucosa in the antrum. A surface biopsy revealed normal mucosa. Abdominal CT scan
showed a polycystic gastric mass of 3.2 cm in diameter, without any enlarged lymph nodes. Endoscopic ultrasonography identified a hypoechoic
lesion with well-defined margins, located in the gastric wall and originating from within the submucosa and the muscular propria layer. You
postulated that the patient had a malignant gastrointestinal stromal tumor. An exploratory laparoscopy revealed a 3.0 cm cystic tumor located in
the posterior wall of the gastric antrum. A laparoscopic resection was performed, with only a 1 cm resection margin. Frozen section analysis
identified a heterotopic pancreas. The postoperative course was uneventful and she was discharged four days after surgery. The final histological
diagnosis was gastric heterotopic pancreas without any evidence of malignancy. The lesion was composed of exocrine acinar tissue, ducts and
endocrine islets. The cysts corresponded to a dilated duct with erosions and inflammation located essentially in the submucosa and in the muscle
layer.
HETEROTOPIC PANCREAS

Definition: Heterotopic pancreas is a congenital disorder defined as pancreatic tissue found outside the pancreatic frame without any anatomic or
vascular connections between them.

           Heterotopic pancreas can be isolated or can be associated with intestinal duplications and Meckel diverticulum.
           Gastric antrum and prepyloric region of the stomach form common sites for isolated heterotopic pancreas.
           The gastric heterotopic pancreas is often asymptomatic.
           Rarely, it may cause recurrent epigastric pain, gastric ulceration, or manifest with upper gastrointestinal bleeding.

Morphology- Gross: Grossly and endoscopically, the lesion usually appears well demarcated.

           Herotopic pancreas presents as a mass lesion that, on cut surface, has a solid, tan or cystic, lobular appearance, depending on whether
           or not the pancreatic ducts are dilated.
           The presence of a central mucosal dimple usually corresponds to the entrance of pancreatic ducts into the intestinal lumen.

Morphology- Microsocopy: The lesion lies in the mucosa, in the submucosa (70% of cases), transmurally, or on the serosa. Pancreatic acini,
ducts, or endocrine islets occur alone or in combination with one another.

ANNULAR PANCREAS.

Definition: Annular pancreas is a rare condition in which the second part of the duodenum is surrounded by a ring of pancreatic tissue continuous
with the head of the pancreas.

           This portion of the pancreas can constrict the duodenum and block or impair the flow of food to the rest of the intestines.
           It is estimated to occur in 1 out of 20,000 newborns.

Pathogenesis: Annular pancreas results from abnormal rotation of the ventral pancreatic bud, and usually functions normally.

           The pathogenesis of pancreatitis associated with annular pancreas remains obscure.
           It may result from partial obstruction of the pancreatic duct by a swollen annular pancreas and mainly occurs within the head portion.

Clinical presentation: An annular pancreas can be asymptomatic (the lesion is found incidentally) or can cause external compression on the
second portion of the duodenum, which creates a partial or complete obstruction.

           In neonates this disease is detected by the presence of nausea due to duodenal obstruction.
           In adults symptoms vary from chronic upper abdominal pain and discomfort, to nausea or vomiting.
           Adults with annular pancreas are at risk of developing peptic ulcers and chronic pancreatitis. Peptic ulcer results from gastric stasis
           due to partial duodenal obstruction and secondary hypergastrinemia, hyperchlorhydria.
INTESTINAL ATRESIA AND STENOSIS.

Definition: Intestinal atresias and stenoses are major causes of neonatal intestinal obstruction.

          Atresia refers to a congenital obstruction with complete occlusion of the intestinal lumen and accounts for 95% of obstructions.
          Stenosis, on the other hand, refers to a partial occlusion with incomplete obstruction and accounts for the remaining 5% of
          obstructions.
          Intestinal atresia or stenosis can occur anywhere along the GI tract, and the anatomic location of the obstruction determines the
          clinical presentation.
          Duodenal atresia is the most common small intestinal atresia, followed by jejunal and ileal lesions.
          Colonic atresias account for the fewest number of cases. Their incidence varies from 1 per 2,000 to 6,000 live births. Boys and girls
          are equally affected.

Clinical presentation:

          Duodenal atresia is typically characterized by onset of vomiting within hours of birth.
          While vomitus is most often bilious, it may be non-bilious because 15% of defects occur proximal to the ampulla of Vater.
          Dehydration, weight loss, and electrolyte imbalance soon follow unless fluid and electrolyte losses are adequately replaced.
          Signs of dehydration consist in decreased urine output, sunken fontanel, dry membranes, tachycardia and neurological involvement
          (manifested by irritability, lethargy, or coma).
          If intravenous hydration is not begun, a hypokalemic and hypochloremic metabolic alkalosis with paradoxical aciduria develops, as
          with other high GI obstruction.
          An orogastric tube typically yields a significant amount of bile-stained fluid.
          Polyhydramnios is present in 50% of cases of duodenal atresia.
                o Polyhydramnios (amniotic fluid exceeds 2500 mL) occurs in about 2 out of 100 of pregnancies and is diagnosed with
                      ultrasound.
                o In 2 out 3 cases, the cause of polyhydramnios is not known.
                o When the cause is known, it usually is secondary to serious congenital malformations. It is well established that a major
                      mechanism for amniotic fluid reabsorption is through the fetal gastrointestinal tract.
          The relatively high frequency of CNS and GI abnormalities amongst fetuses with polyhydramnios has led to the well-accepted notion
          that decreased swallowing and/or decreased gastrointestinal reabsorption lead to the development of polyhydramnios.
          While this is an attractive and largely accurate theory, it hardly explains all cases of polyhydramnios.
          The fetus swallows about 30% of the amniotic fluid in the 5th month, and the fluid is reabsorbed in the first 30 cm of the jejunum.
          Therefore, duodenal and proximal intestinal atresias are more likely to be associated with polyhydramnios than distal intestinal and
          colonic atresias.
           Jejunoileal atresias can be identified on the basis of polyhydramnios present during prenatal evaluation (in 30% of cases), bilious
           vomiting, abdominal distension, and jaundice in 30% of cases (indirect hyperbilirubinemia).

Diagnosis: Intestinal atresias can be prenatally diagnosed using ultrasonography.

           Duodenal obstruction is characterized by a double-bubble sign on ultrasonography.
           The first bubble corresponds to the stomach and the second to the postpyloric and prestenotic dilated duodenal loop.
            Intestinal atresia is characterized by echogenic distended bowel loops.
           Upper-GI contrast study demonstrates a dilated stomach and duodenum, with an enlarged upper jejunum, a lack of passage of
           contrast agent to the distal small bowel.
           Most neonates with intestinal atresia have a small caliber unused microcolon (i.e. a colon of abnormally small caliber in barium
           enema investigation).




DUPLICATIONS.

Definition: Duplications are rare congenital malformations of the GI tract that consist of complete or partial doubling of a variable length of
bowel.

           Duplications contain all three bowel layers. The small intestine is the most frequent site involved, whereas gastric, duodenal, and
           colonic involvement is relatively rare.
           Duplications are included in the mesentery and share a common blood supply with the normal bowel.

Morphology-Gross: Grossly, duplications appear as hollow, cylindric, or spherical cysts ranging in size from a few millimeters to up to 15 cm.

           Duplications of small intestine appear as non-communicating spherical cysts of varying sizes or as cylindric duplications that
           comprise a large amount of the length and communicate with the normal intestine at one or several points along the common wall.

Clinical presentation: Clinical presentation depends on the size and location of the duplication.

           Gastric duplications present with vomiting, and a palpable mass upon physical examination.
           Small intestinal duplications can be anchor points for intussusception or can result in volvulus.
           Long intestinal duplications with proximal communication drain poorly, and retention of intestinal contents can obstruct adjacent
           intestine.
           Duplications that contain ectopic gastric mucosa are predisposed to peptic ulceration, which is associated with painless
           gastrointestinal hemorrhage or progresses to perforation.
           Rectal duplications present with constipation or rectal bleeding.
CONGENITAL DIVERTICULA

Definition: Duplication cysts that widely communicate with the lumen are termed congenital diverticula.

           Congenital diverticula are less frequent than duplications.
           Congenital diverticula present as localized outpouchings that consist of all three bowel layers.
           Diverticula containing ectopic gastric mucosa may develop peptic ulceration and bleeding within them.
           If the diverticular orifice becomes blocked, diverticulitis develops followed by ulceration.
           Other symptoms include abdominal pain, and distension.
           Congenital diverticula may also remain asymptomatic, only to be discovered incidentally in adults.
CASE PRESENTATIO: MARIA C.

Maria is a 45-year-old woman brought to the ER with abdominal pain of three to four hours’ duration. The pain is epigastric, nonradiating,
waxing and waning and is with accompanied by nausea. Patient denies any history of fever, diarrhea, constipation, melena, hematochezia or
urinary symptoms. Maria has a history of cholecystectomy 10 years ago, total abdominal hysterectomy 5 years ago, and appendectomy 1 year
earlier. During appendectomy the surgeon noted the presence of Meckel diverticulum but determined that it was asymptomatic and elected to
leave the diverticulum in place. Since the patient has persistently looked for medical attention due to the occurrence of nonspecific pain,
abdominal ultrasounds, multiple upper gastrointestinal studies and an air contrast barium enema had an all been performed by multiple medical
care providers and they were all unremarkable. On physical examination she was afebrile, normotensive, with a normal pulse and respiration rate.
Abdominal examination demonstrated infraumbilical tenderness with no guarding or rebound. There were positive bowel sounds and no organ
enlargement or masses were noted.Laboratory examination demonstrated leukocytosis to 18,100/mm3, 97% neutrophils, and hemoglobin of 12.5
g/dL. Stool guaiac test (for occult blood in the stool) was negative. Electrolytes, liver function, urinalysis and amylase levels were all normal. The
chest radiograph was clear, and the flat and upright abdominal films were normal, without air-fluid level, dilation or free air. The patient was
placed on maintenance intravenous fluids. The next day, her temperature had climbed to 37.5°C (99.6°F) and abdominal examination revealed
right lower quadrant tenderness with slight guarding and rebound.

In light of the patient's current condition, surgery was recommended for suspected Meckel diverticulum. At laparotomy, an axially torsed,
gangrenous Meckel diverticulum was found without ileal volvulus. The lead point for the torsion was a fibrous adhesion attached between the
distal tip of the diverticulum and the peritoneal surface. A diverticulectomy and segmental ileal resection were performed, and the patient had an
uneventful postoperative course and recovery.



MECKEL DIVERTICULUM.

Definition: Meckel diverticulum is a congenital outpouching of the distal ileum occurring in 2-3% of the population.

           It is located on the antimesenteric border usually 30-100 cm proximal to the ileocecal valve.

Morphology-Gross: Meckel diverticulum varies in length from 2 to 15 cm but on average it is 3 cm long and 2 cm wide and has a narrow lumen.

           A fibrous band may connect meckel diverticulum to the umbilicus if the fibrous portion of omphalomesenteric duct fails to be
           completely absorbed.
           Meckel diverticulum is a true diverticulum composed of all layers of the intestinal wall and is lined by small intestinal mucosa.
           Heterotopic gastric mucosa is present in 60% of cases and heterotopic pancreatic tissue is found in 5-15% of cases.
Embryology: During early fetal development, fetal midgut communicates with the yolk sac via the omphalomesenteric duct (vitelline duct).
This structure involutes during the 6-7 week of embryogenesis and the omphalomesenteric duct becomes a thin fibrous band which eventually
disintegrates and is absorbed.

Other omphalomesenteric duct anomalies: Incomplete atrophy of the omphalomesenteric duct may result in a variety of anomalies:
     A.   Umbilicoileal fistula results from a completely patent omphalomesenteric duct and is the least common of these anomalies. The duct
          remains open through its entire course. Patients usually come to clinical attention in the newborn period because of fecal drainage
          from the umbilicus.
     B.   Omphalomesenteric duct sinus occurs when the distal (umbilical) end fails to close and forms a sinus tract that may vary in length.
          The ileum remains connected by a fibrous band. Clinically, mucus discharge from the umbilicus is noted during infancy.
     C.   Omphalomesenteric cyst develops when the midportion of the duct remains patent while each end obliterates. The cyst may be located
          at any location along the duct. Mucus accumulates within the cyst because it is lined by intestinal mucosa.
     D.   A fibrous cord connecting the umbilicus to the ileum results from an atrophic omphalomesenteric duct that is not completely
          obliterated and absorbed. Congenital fibrous bands are clinically significant because they may lead to intestinal obstruction or
          volvulus.
     E.   Meckel diverticulum is the most common (98% of cases) of the omphalomesenteric duct anomalies. The diverticulum results from
          fibrous obliteration of the umbilical end of the omphalomesenteric duct and complete patency of the ileal end of the duct.




Complications: In the majority of patients, Meckel diverticulum has no clinical consequences unless complications develop. Overall only 5% of
Meckel diverticula develop complications.

          About 80% of patients who develop symptoms related to diverticulum complications do so during the first 5 years of life.
          The most frequent complication is painless hemorrhage, which is due to peptic ulceration from heterotopic gastric mucosa located
          within the diverticulum.

     A.   Hemorrhage usually presents as hematochezia but can manifest less often as black/tarry or bright red bleeding.
                o Hematochesia is the passage of maroon (dark red) colored stool and needs to be distinguished from melena, which is stool
                      with blood that has been altered by the gut flora and appears black/tarry.
                o Hematochesia is also different from bright-red blood per rectum.
     B.   The second most common complication is intestinal obstruction, which if secondary to numerous mechanisms including volvulus
          around a persistent Meckel fibrous band attached to the umbilicus, intussusceptions or luminal obstruction from inverted diverticulum.
          Clinical manifestations include bilious vomiting, abdominal distension, periumbilical pain and constipation.
     C.   Acute Meckel diverticulitis develops secondary to obstruction of the diverticular orifice by an enterolith, fecolith, foreign body or
          fibrosis from peptic ulceration. The clinical presentation is similar to that of acute appendicitis, but with a point of maximal abdominal
          tenderness located in the left lower quadrant or mid-abdomen.
     D.    Meckel diverticulum may invaginate or invert into the lumen of the small intestine causing intestinal obstruction. In pediatric ages the
           most common presentation is painless hemorrhage. In adults, obstruction and diverticulitis are more common presentations than lower
           GI bleeding.




Diagnosis: Meckel diverticulum has been described as the “great mimic”. The clinical diagnosis of symptomatic Meckel diverticulum is rare
with less than 10% of cases diagnosed preoperatively.

           Delayed diagnosis of Meckel diverticulum may result in perforation, just as in complicated appendicitis.



CONGENITAL DIAPHRAGMATIC HERNIA.

Definition: Congenital diaphragmatic hernia (CDH) is a defect in the formation of the diaphragm of the fetus combined with pulmonary
hypoplasia.

           The diaphragm is normally fully formed by the end of the third month of pregnancy. In infants with CDH, one of the components of
           diaphragm does not form properly, creating a defect that allows some of the intestines to enter into the chest cavity.
           The intestines take up space in the chest, which in turn prevents adequate lung development and growth.
           The lungs are often small because of the lack of space during maturation.

Epidemiology: CDH occurs in 1/2,500 to 1/5,000 live births.

Etiology: No specific causal gene defects have been identified in humans and most cases are sporadic.

           A few drugs such as pyridoxine, thalidomide, quinine, and antiepileptic drugs have been implicated in the occurrence of CDH.

Anatomic types of CHD: The two basic types of congenital diaphragmatic hernia include the Bochdalek hernia, and the Morgagni hernia.

     A.   The Bochdalek hernias typically arise on the left side and occur in approximately 85% of cases. Left-sided hernias allow herniation of
          both the small and large bowel and intraabdominal solid organs into the thoracic cavity.
     B.   The Morgagni hernia concerns the antero-medial retrosternal portion of the diaphragm (13% of cases), and only the liver and a portion
          of the large bowel tend to herniate. Bilateral hernias (2% of cases) are uncommon and are usually fatal.

Embryonal development of diaphragm: The diaphragm normally forms between the 3rd and 8th week of gestation.

           The diaphragm develops from 4 components including the septum transversum, the pleuroperitoneal membranes, the dorsal
           mesentery of the esophagus, and from growth of diaphragmatic muscle inward from the lateral body walls.
           By the 7th week, these components fuse with each other.
           Congenital anomalies of the diaphragm are due to either fusion defects or a defect in the formation of the diaphragmatic muscle from
           the lateral body walls.
Pathophysiology of disease in the infant: Long-term compression of fetal lungs by the herniation of the viscera into the thoracic cavity results
in pulmonary hypoplasia.

           This may also occur on the contralateral side if a large amount of abdominal contents causes the mediastinum to shift, compressing
           the lung on the non-affected side.
           Structural alterations in CDH lungs include a decreased number of airway divisions and a decreased number of pulmonary arteries
           per unit of lung volume.

     (A) Airway divisions in the lung are limited; only the 12th and 14th generations develop on the affected side and only up to the 16th to 18th
     generations develop on the contralateral side. Normally, airway development would result in 23 to 35 divisions. Alveolarization is reduced
     in infants with CDH because the alveolar development follows airway development.

     (B) Development of the pulmonary arterial system parallels development of the bronchial tree, and therefore, fewer arterial branches are
     observed in CDH. The corresponding decrease in pulmonary vascular beds, leads to increased pulmonary vascular resistance. Pulmonary
     arteries of all sizes display an increase in the medial wall thickness (including abnormal muscularization of the small intra-acinar arterioles).
     All these changes lead to decreased pulmonary blood flow, and persistent pulmonary hypertension. Pulmonary hypertension leads to right-
     to-left shunting in the atrium through the foramen ovale and through the ductus arteriosus, right-sided heart strain or failure and progressive
     hypoxemia, hypercapnia, and acidosis in the neonatal period.

     (C)In many infants with CDH, the lungs are immature even at full-term gestation, with fewer septa, thicker interstitium, fewer capillaries
     and even insufficient surfactant phospholipids and proteins. This insufficient surfactant contributes to the respiratory distress that is seen
     soon after birth.



Clinical presentation: Infants with CDH often present in the neonatal period with severe respiratory distress (nasal flaring retractions, cyanosis,
grunting respirations) in the first minutes or hours of life.

           Auscultation of the lungs in left-sided Bochdalek hernia reveals diminished breath sounds on the left, and a shift of cardiac sounds
           over the right chest. About 5% of individuals with CDH, even those with a Bochdalek hernia, do not show symptoms in the newborn
           period.
           Presenting symptoms after infancy can be acute onset of respiratory or gastrointestinal distress, or low-grade symptoms such as
           abdominal pain from chronic intestinal obstruction or pleural effusion from entrapment of the bowel in the chest.
            About 1% of individuals are completely asymptomatic and the defect is discovered incidentally on imaging studies.

Diagnostic evaluation: Over 50% of cases with CDH are detected prenatally by ultrasound examination.

           MRI is especially useful for the prenatal diagnosis of thoracic lesions that are atypical. In the newborn, the abdomen is scaphoid.
           Early chest radiography after delivery confirms the diagnosis of CHD when bowel gas visible above the diaphragm is accompanied
           by a mediastinal shift.
                                                                 1.

A 24-hour old neonate born after 36 weeks gestation was admitted with complaints of regurgitation of all the feeds. Examination
revealed a 2.4 kg baby with scafoid, soft abdomen. Ultrasound examination before delivery showed polyhydramnios and complete
lack of gas in the stomach. A number 8 French nasogastric tube passed into the esophagus and stopped at 10 cm. What is the most
likely diagnosis?


      Zenker diverticulum

      Pyloric stenosis

      Achalasia

      Esophageal atresia

      Diaphragmatic hernia

                                                                 2.

24-day-old boy was brought to the emergency department with a 4-day history of frequent projectile vomiting, which only occurred
shortly after breastfeeding. The baby had an uncomplicated, term, vaginal delivery with a birth weight of 3.7 kg. He had not
experienced any previous medical or surgical problems. The child’s parents denied any recent fever, coughing, or other complaints.
The infant had a small bowel movement, of normal consistency, the previous day. Urinary output was only mildly diminished. Vital
signs were normal. Physical examination revealed bilaterally clear breath sounds, bowel tones in all quadrants, and a soft, non-
tender abdomen. Of note, a small, moveable, oval mass was palpated in the child’s epigastric region. Neurologic findings were
unremarkable. The patient appeared hungry and very eager to feed. Three minutes after breastfeeding, the patient experienced
projectile vomiting of the recently consumed breast milk. The child’s basic metabolic panel and complete blood cell count results
were all unremarkable. Which of the following is the most likely diagnosis?


      Duodenal atresia

      Infantile hypertrophic pylosic stenosis

      Annular pancreas

      Intestinal atresia

      Esophageal atresia

                                                                 3.

A 25-year-old man presented with a 2-day history of lower abdominal pain and vomiting. Physical examination revealed diffuse
abdominal tenderness, selectively painful at the left iliac fossa, without rebound tenderness. Laboratory studies revealed a WBC
count of 18,000/mm3 (reference range: 4,000-10,000). A plain film of the abdomen was normal. A diagnostic laparotomy was
performed under general anesthesia. At laparotomy an inflammatory mass surrounding a 20 cm long ileal segment was found. A
normal appendix was also identified. The inflammatory mass turned out to be a perforated outpouching of the ileum 60 cm proximal
to the ileocecal junction. The outpouching was located on the antimesenteric border, was 4 cm long and 2 cm wide and its tip was
not connected to abdominal wall. The adjacent loop of small bowel was grossly inflamed and dilated. Wedge resection of the
perforated ileum was performed with primary anastomosis of the adjacent small bowel. The patient made an uneventful recovery
postoperatively and was discharged on day 5 with further follow-up in the surgical outpatient clinic. The most likely diagnosis is:


      Perforated duodenal ulcer

      Hemorrhoids

      Meckel diverticulitis

      Acute appendicitis

      Intussusception
                                                                  4.

A newborn male infant with a birth weight of 1.68 kg was admitted with antenatally diagnosed absence of stomach bubble and
polyhydramnios. Amniocentesis had revealed a normal karyotype. The mother was epileptic and was on carbamezepine. There was
no respiratory distress at birth. Physical examination on admission was remarkable only for copious and clear frothy oral secretions,
which cleared with suctioning. An x-ray examination revealed a dilated esophageal pouch. Nasogastric tube was seen to stop at the
level of 7th thoracic vertebra. Gastrostomy was fashioned to feed the baby and the upper pouch was drained using a suction
catheter. A contrast study via the gastrostomy showed a gap of single vertebra in between the two esophageal pouches. The child
underwent bronchoscopy and thoracotomy. On bronchoscopy no tracheoesophageal fistula was found. The esophagus was
identified and showed narrowing on external appearance. On incising the esophagus it was evident that the mucosa was not
continuous. The margins of the two pouches were freshened and primary anastomosis was done without any tension. The post-
operative course was uneventful and oral feeding was quickly established. Which of the following anatomical types of esophageal
atresia does this infant most likely have?


      Esophageal atresia with proximal and distal tracheoesophageal fistula

      Isolated esophageal atresia without tracheoesophageal fistula

      Esophageal atresia with proximal tracheoesophageal fistula

      Esophageal atresia with distal tracheoesophageal fistula

      H-type tracheoesophageal fistula with no atresia

                                                                  5.

A 27-year-old primigravida woman presents at 25 weeks of gestation because of severe polyhydramnios; amniotic fluid index was
51. Amniocentesis was performed by an obstetrician. Interestingly it had to be repeated because of unusually rapid accumulation of
amniotic fluid after the procedure. A total of 7 amniocenteses were performed before delivery, and the total amount of amniotic fluid
removed was about 7 liters. To evaluate the cause of the severe polyhydramnios, fetal chromosomal study and antenatal high
resolution fetal sonogram were done and those results were normal. At 32 weeks of gestation, a male newborn baby was delivered
through cesarean section due to uncontrolled preterm labor. At birth the baby weighed 1870 g. This baby is most likely to show
which of the following anomalies? [Note: Amniotic fluid index (AFI) is a rough estimate of the amount of amniotic fluid and is an
index for the fetal wellbeing. Amniotic fluid index is the score given to the amount of amniotic fluid (by adding up centimeters of
depth of four pockets of fluid) seen on pregnant uterus by ultrasound. An AFI < 5-6 is considered as oligohydramnios and an AFI >
20-24 is considered as polyhydramnios].


      Ventricular septal defect

      Duodenal atresia

      Hypospadia

      Cleft lip

      Meckel diverticulum

                                                                  6.

A female infant was delivered stillborn at term to a 24-year-old primigravida Caucasian woman. Routine prenatal care for this
pregnancy began at 12 weeks of gestation. There were no reported pregnancy complications, but the woman had a 10 pack/year
history of cigarette smoking and had continued to smoke throughout this pregnancy. She presented at 41 weeks of gestation for a
routine checkup, whereupon intrauterine fetal demise was diagnosed with delivery that same day. Postmortem examination of the
stillborn infant revealed a markedly dilated small bowel containing inspissated meconium with a mucosal web in the very distal ileum
at the region of the ileocecal valve that occluded the bowel lumen. The mesentery was intact and unremarkable. The entire colon
was hypoplastic, displayed a small caliber and contained scant white mucus. The postmortem findings represent an example of
which of the following errors of morphogenesis?


      Involution failure

      Atresia

      Aplasia
      Dysraphia

      Heterotopia

                                                                      7.

A 4-month-old male infant was admitted because of rectal bleeding and anemia. The infant had been in good general health until the
day of admission when, in the morning of the same day, he had a rather marked episode of painless frank rectal bleeding without
any recognizable preceding event. The blood in the diaper was maroon-colored, and there were clots. There was no history of ano-
rectal trauma or previous rectal bleeding. No fever, diarrhea, or vomiting were reported. Growth and weight gain as well as
psychomotor development were normal. On physical examination, the infant appeared well-nourished, alert, and in no acute
distress. Vital signs were normal. Abdomen was soft and nontender. Rectal exam showed hemoccult-positive material on the
examining glove. Laboratory studies showed normal WBC count and low hemoglobin levels. Because of a suspected bleeding
Meckel diverticulum, a radionuclide scan with 99 m Tc-pertechnetate was performed which showed an increased radiotracer uptake
in the mid-lower abdomen, which was highly suggestive of a Meckel diverticulum. Subsequently, a laparoscopy-assisted
diverticulectomy was done one day after admission. Histopathological examination of the excised diverticulum will most likely show:


      Neutrophilic infiltration of diverticular wall

      Absence of non-adrenergic non-cholinergic nerve fibers in the muscular coat

      Heterotopic pancreatic tissue

      Absence of intramural ganglion cells

      Heterotopic gastric mucosa




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