ROLE OF ULTRASOUND IN ASSESSING FETAL GIT- final (1).pptx

GI tract abnormalities

1. ROLE OF ULTRASOUND IN ASSESSING FETAL GIT. Moderator: Dr.Nagarajmurthy . Presenter:Dr.Vinaya

2. Embryology of GIT: Initial Development (3rd-4th Weeks) Primitive Gut Tube Formation Formed by incorporating the dorsal part of the yolk sac into the embryo. Result of longitudinal and lateral folding of the embryonic disc. Lining and Closure Lined by embryonic endoderm. Closed at cranial end by oropharyngeal membrane. Closed at caudal end by cloacal membrane. Regionalization of the Gut Tube Foregut (Cranial Portion) Gives rise to: Esophagus Stomach Duodenum Liver and bile ducts Pancreas

3. Midgut (Intermediate Portion) Gives rise to the largest part of the intestine. Supplied by the superior mesenteric artery. Includes: Second half of the duodenum (distal to the ampulla of Vater ) Jejunum Ileum Ascending colon Proximal two-thirds of the transverse colon Remains connected to the yolk sac via the yolk stalk ( omphalomesenteric duct or vitelline duct). Hindgut (Caudal Portion) Differentiates into the distal part of the colon (beyond the splenic flexure). Partially supplied by the inferior mesenteric artery.

4. Development of the Trachea and Esophagus Differentiation Process The trachea and esophagus differentiate inferiorly from the posterior pharynx. Incomplete Differentiation Consequences Can lead to esophageal atresia . May be associated with tracheoesophageal fistulas. The main sonographic signs of esophageal atresia include : absent or small stomach polyhydramnios , esophageal pouch sign (fluid collection in the blind end of the esophagus ) At times a distended oropharynx will be seen.

5. There are five types of esophageal atresia - with the most common having a fistula to the distal esophagus . Because most types of esophageal atresia (90%)are associated with tracheoesophageal fistulas - in many cases the stomach will be visualized on ultrasound, and polyhydramnios may be absent or mild or present only later in gestation.

6. The types of esophageal atresia / tracheo -esophageal fistula can be divided into : type A: isolated esophageal atresia (8%) type B: proximal fistula with distal atresia (1%) type C: proximal atresia with distal fistula (85% - most common) type D: double fistula with intervening atresia (1%) type E: isolated fistula (H-type) (4%)

7. The most frequent problems are- respiratory distress syndrome , postoperative esophageal stricture pneumothorax , often from tracheal leak rather than esophageal leak , congenital heart disease and heart failure congenital malformation of the abdominal alimentary tract , recurrent tracheoesophageal fistula, empyema and mediastinitis

8. Stomach The fetal stomach can be seen as early as 7 weeks and should be noted routinely by 13 to 14 weeks’ gestation. The stomach should be seen as a cystic structure in the left upper abdomen. It is important to confirm the location of the stomach because a midline or right-sided stomach is associated with heterotaxy syndrome.

9. Differential Diagnosis for Dilated Fetal Stomach: Normal variation in stomach size. Gastrointestinal atresia (e.g., duodenal atresia , pyloric atresia ). Pyloric stenosis. Pyloric Atresia A rare form of intestinal atresia . Underlying cause different from other GI tract atresias . Familial form with autosomal recessive transmission documented. Association with Epidermolysis Bullosa Often fatal skin disorder. Characterized by blisters in skin and mucosal membranes. Inherited in an autosomal recessive pattern.

10. Sonographic Findings in Pyloric Atresia Gastric dilatation (can be massive). Esophageal dilatation caused by gastroesophageal reflux. Severe polyhydramnios . Additional Diagnostic Indicators Elevated maternal serum alpha-fetoprotein. Snowflake appearance of amniotic fluid. Confirmed by molecular analysis of fetal skin biopsy.

11. Abnormal Position of the Stomach Importance of Abnormal Position Indicates the presence of a severe abnormality. Requires detailed anatomic assessment. Right-Sided Stomach Raises the possibility of heterotaxy syndrome. Characteristics of Heterotaxy Syndrome: Abnormal symmetry of the viscera and veins. Associated with complex cardiac anomalies. Associated with intestinal malrotation . Associated with splenic abnormalities ( asplenia or polysplenia ). Associated with hepatic abnormalities. Midline Stomach - Can represent intestinal malrotation .

12. Small Bowel and Colon Development: Appearance in Early Pregnancy: First Trimester and Early Second Trimester: Small and large bowel appear heterogeneous. Echogenicity similar to that of the liver. Appearance in Later Pregnancy: Later in Pregnancy: Fluid can be seen in small bowel loops. Meconium can be seen in the colon. Gastrointestinal Atresia : Most cases are thought to represent a failure of recanalization of the bowel lumen. Early in fetal life, the bowel is a solid tube.

13. Bowel Obstruction Duodenal Obstruction: Dilatation of the duodenum resulting from duodenal stenosis or duodenal atresia - most common type of bowel obstruction in the fetus . Duodenal atresia may result from: failure of recanalization of the duodenal lumen, periampullary obstruction, complete absence of a duodenal segment, or vascular ischemia. Less commonly- may be secondary to mechanical factors such as: annular pancreas, superior mesenteric artery syndrome, or volvulus . Duodenal atresia is also associated with anomalies of the VACTERL spectrum.

14. Sonographic Hallmarks of Duodenal Atresia Severe Polyhydramnios May not be present until the late second or third trimester. Frequently present by the late second trimester. Often absent in the early second trimester. Double-Bubble Sign Presence of a second echolucent mass medial to the stomach bubble in a transverse view of the fetal abdomen. Caused by a dilated segment of the duodenum proximal to the atretic area. Highly suggestive of duodenal obstruction. Important to demonstrate continuity between fluid-filled structures to confirm duodenal stenosis/ atresia . Differential Diagnosis for Double-Bubble Sign Prominent incisura angularis of the stomach. Choledochal cyst. Duodenal duplication cyst.

15. Transient Double-Bubble Sign Reported cases during the second trimester with normal outcomes. Polyhydramnios and Timing Related to the difference in the amount of amniotic fluid swallowed at different gestation times. Fetus swallows 2-7 mL /day in early second trimester vs. 450 mL /day at term. Diagnosis Timing and Accuracy Commonly diagnosed during the third trimester. Early second trimester diagnoses can have false negatives and false positives. Prenatal Diagnosis and Management Potential to decrease neonatal morbidity. Finding the double-bubble sign should prompt: Detailed anatomic survey. Fetal echocardiography. Genetic counseling . Consideration of amniocentesis due to high association with trisomy 21.

16. Differences Between Jejunal and Ileal Atresia Jejunal atresia : More likely to involve multiple sites. Less often associated with in utero perforation. Higher association with extra-GI anomalies and chromosomal disorders (up to 42% of cases). Ileal atresia : Lower compliance of the ileum. Rate of associated anomalies is about 2%. Both conditions associated with GI abnormalities (e.g., malrotation , meconium peritonitis, duplication cysts).

17. Apple Peel Jejunal Atresia Involves agenesis of the mesentery. Often familial and likely has a different etiology . Cystic Fibrosis and Ileal Obstruction Common underlying cause of ileal obstruction. Thick meconium can lead to meconium ileus , with or without echogenic bowel. Prenatal Diagnosis Based on dilated loops of bowel, often without a dilated stomach. Sometimes with hyperperistalsis . Cutoff for dilated small bowel: Loop diameter > 7 mm. Loop length > 13 mm. Diagnosis typically made late in the second trimester. Polyhydramnios is less common than in duodenal or esophageal atresia .

18. Polyhydramnios : Reported in about one-third of cases of jejunal atresia . Less common in cases of ileal atresia . Associated Sonographic Signs Echogenic bowel (reflecting thickened meconium due to intestinal stasis). Ascites and abdominal calcifications (more common in cases complicated by perforation).

19. Meconium Ileus : Definition : Obstruction of the ileum by thickened meconium . Association with Cystic Fibrosis : Some cases are linked to cystic fibrosis. Only up to 20% of cystic fibrosis cases present with meconium ileus during pregnancy. Sonographic Signs : General signs of bowel obstruction. Presence of echogenic bowel increases the likelihood of meconium ileus .

20. Congenital diaphragmatic hernia : Most congenital diaphragmatic hernias (CDHs) are detected either soon after birth or on antenatal ultrasound. Mortality Cause : Mortality is predominantly due to the development of pulmonary hypoplasia . Pathophysiology : Pulmonary hypoplasia is thought to be caused by the mass effect of the hernia on the developing lung. Clinical Presentation in Neonates : Neonates with CDH are often hypoxic. They have persistent fetal circulation due to pulmonary hypoplasia and pulmonary hypertension.

21. Types: Bochdalek hernia most common fetal congenital diaphragmatic hernia more common on the left: 75-90% posterolateral large and associated with poorer outcome presents earlier Morgagni hernia less common anterior presents later 

22. Findings: Absent bowel loops in the abdomen Intrathoracic herniation of the liver, noted in up to 85% of cases, which is associated with a worse prognosis. Peristaltic bowel movements in the chest .Herniation into the chest may occur intermittently. Abdominal circumference is reduced due to herniation of organs. Left-sided CDH: Stomach and small bowel (echo-free) at the same transverse level as the heart on four-chamber view, making left-sided hernias comparatively easier to detect on ultrasound. Stomach and small bowel superior to the inferior margin of the scapula. Leftward displacement of the gallbladder. Right-sided CDH: Stomach and small bowel are typically present above the diaphragm. Color Doppler study may reveal: Leftward bowing of the umbilical segment of the portal vein. Portal branches to the lateral segment of the left hepatic lobe coursing towards or above the diaphragm. Gallbladder present above the diaphragm. Echogenic space between the left heart border and stomach, representing the left hepatic lobe.

23. Indirect sonographic findings that should prompt a search for CDH include  7 : polyhydramnios cardiomediastinal shift +/- abnormal cardiac axis inability to demonstrate the normal stomach bubble

24. Anorectal malformations Anorectal malformations are classified as: Low : Bowel ends below the level of the levator ani muscle. Intermediate : Bowel ends at the same level as the levator ani muscle. High : Bowel ends above the level of the levator ani muscle. Low Malformations : Majority (>90%) of cases. High Malformations- Less common, often associated with vesicocolic fistulas. Main sonographic sign- dilated loops of small or large bowel. Polyhydramnios is absent in the majority of cases.

25. Inability to visualize the anal mucosa on transverse transperineal view-known as the anal dimple , which is the result of the echogenic mucosa surrounded by the hypoechoic muscle of the anal sphincter, has been suggested as an important sonographic marker in cases of imperforated anus

26. Definition : Congenital disorder of the colon characterized by absence of ganglia in the distal colon, leading to functional colonic obstruction. Segment Involvement : Distal colon, including the internal anal sphincter, and may extend proximally to involve variable portions of the colon. Severe forms can involve the entire colon. Associated Abnormalities : Chromosomal and structural abnormalities are present in about 10% to 20% of cases. Up to 10% of cases are associated with trisomy 21 (Down syndrome). Hirschsprung Disease

27. Prenatal Diagnosis : Uncommon; usually diagnosed in severe cases involving the entire length of the colon. Sonographic signs include: Bowel dilatation Polyhydramnios Echogenic bowel Clinical Presentation : Most cases diagnosed in the early neonatal period. Common sign is failure to pass meconium shortly after birth.

28. Enteric Duplication Cysts: Result from abnormal recanalization of the GI tract. Can occur anywhere along the GI tract, but most common in the terminal ileum. May present: In utero or postnatally . Incidentally or with symptoms of bowel obstruction. Sonographic Appearance : Present as cystic or echogenic tubular structures with well-defined borders. Classically anechoic and cystic but can contain echogenic material. Borders may show a double layer ("gut signature"), which may require high-resolution linear transducers to visualize. Peristalsis within the cysts can aid in distinguishing them from non-GI masses. Differential Diagnosis : Includes hepatic cysts, choledochal cysts, bowel atresias , and ovarian cysts depending on the site of presentation.

29. Meconium Peritonitis: Result of in utero bowel perforation followed by leakage of meconium into the peritoneal cavity. Leads to chemical irritation and inflammatory response. Sonographic Hallmark : Abdominal Calcifications : Representing calcification of the peritoneum outlining bowel or liver. Additional Sonographic Findings : Ascites : Accumulation of fluid in the abdominal cavity (Video 38.7). Echogenic Bowel : Reflecting thickened meconium . Dilated Bowel : Due to obstruction or inflammation. Polyhydramnios : Excess amniotic fluid.

30. Embryonic Development of Abdominal Wall : Develops from lateral plate mesoderm and ectoderm between day 16 and day 26 of embryonic life. Each lateral plate of mesoderm splits into parietal and visceral layers. The space between these layers becomes the body cavity ( coelom ), which later differentiates into peritoneal, pericardial, and pleural cavities.

31. Types of Defects Based on Location : Depending on the location of the defect in the ventral abdominal wall: Gastroschisis (abdominal region). Ectopia cordis (thoracic region). Bladder exstrophy (pelvic region). Physiologic Midgut Herniation : Occurs concurrently with ventral body wall development. Rapid growth and elongation of the bowel cause temporary overcrowding in the abdominal cavity. Intestines protrude into the extraembryonic coelom at the base of the umbilical cord. Visible on ultrasound from 9 to 11 weeks gestation and resolves by 12 weeks.

32. Ectopia cordis : is a midline defect of the upper fetal ventral body wall. It involves the protrusion of all or part of the heart outside the chest cavity, with or without a covering membrane. Location and Presentation : Most commonly, the heart protrudes at the level of the chest through a defect involving the sternum. The heart can also be found in the cervical (neck) or abdominal regions. Association with Other Anomalies : Ectopia cordis is often associated with structural cardiac anomalies. It can also be associated with other abdominal wall defects. Prognosis is generally poor due to the severity of the defect. Associated with Trisomy 18, particularly when additional abnormalities are present. Trisomy 18 is a chromosomal disorder that can affect multiple organs and systems, leading to severe developmental and health challenges.

33. Bladder exstrophy : is an infraumbilical abdominal wall defect caused by incomplete closure of the lower abdominal wall and anterior wall of the bladder. It is rare. Prenatal Diagnosis : Diagnosis is mainly based on the inability to visualize the bladder during prenatal ultrasound. The exposed bladder mucosa may appear inflamed and thickened, causing an irregular contour of the lower anterior abdominal wall. Caudal displacement of the umbilical cord insertion site can also suggest the diagnosis. Associated Anomalies : Frequently associated with genital abnormalities such as epispadias . The combination of bladder exstrophy and epispadias is known as the bladder exstrophy-epispadias complex.

34. Cloacal exstrophy : is a complex multisystem abdominal wall defect. Includes the bladder and urethra, genitalia, and rectum. It may also involve abnormalities of the lower spine. Also known as OEIS complex , which stands for omphalocele - exstrophy -imperforate anus-spinal dysraphism . Genital abnormalities are common. Pathogenesis : The exact cause is unclear but may involve: Premature rupture of the cloacal membrane. Early defect in the closure of the ventral body wall. There is a higher incidence in monozygous twins compared to dizygous twins, suggesting a possible vascular component in its pathogenesis.

35. Prenatal diagnosis is based on several findings: Omphalocele (protrusion of abdominal organs through a defect in the abdominal wall). Inability to visualize the bladder. Presence of an anal dimple. Spine anomalies such as meningomyelocele . Additional findings may include genital abnormalities (e.g., epispadias ), single umbilical artery, renal abnormalities, and ascites. Unique Sonographic Sign : A distinctive sign is the " elephant trunk " which results from a prolapsed loop of bowel between the two halves of the open bladder. Diagnosis of OEIS complex has been reported as early as 13 weeks gestation.

36. Thank you.