GASTROINTESTINAGASTROINTESTINAL TRACT L TRACT

ANOMALIESANOMALIES

ObjectivesObjectives Describe the development of the digestive system Detail the malformations of the midgut Describe the sonographic findings of the

gastrointestinal system Describe the normal development of the stomach

and the importance of it’s sonographic visualization

Detail the fetal hepatobiliary system Describe situs inversus List the abnormalities of the gastrointestinal tract

and their sonographic findings

EmbryologyEmbryology

Foregut– Esophagus– Stomach & duodenum– Liver & Biliary system– Pancreas– Spleen

Midgut– Small intestines – Colon supplied by

the SMA Hindgut

– Structures supplied by the IMA

EmbryologyEmbryology Stomach forms at about 4 weeks Descends into abdomen from initial

position at about 7 weeks Abdominal wall muscles develop at

about 11 weeks Stomach can be seen on ultrasound

at about 9 weeks

EsophagusEsophagus Embryology

– Esophagus & trachea develop from common structure

– Partitioned by tracheo-esophageal septum Separate tracts form - 3-5 weeks

Fluid can be seen in esophagus– Fetal swallowing is normal

Esophageal AtresiaEsophageal Atresia Incomplete formation of the esophagus > 90% have a fistula between trachea &

esophagus (TEF) No sex preference

Esophageal AtresiaEsophageal Atresia Associated

anomalies– Heart– Chromosomes– GI– GU– VACTERL

Vertebral defect Anorectal

malformation Cardiac defect TracheoEsophageal

fistula Renal anomaly Limb defects

Prognosis– 22-75% mortality

if detected in utero

– Long term sequelae common Strictures Aspiration Recurrent TEF Feeding difficulties Esophageal

dysmotility nearly 100%)

Esophageal AtresiaEsophageal Atresia Ultrasound findings

– Most types have connection from mouth to stomach

Small amount of fluid may be seen in stomach

Follow-up on all fetuses with small stomach

Look for esophageal pouch (expands with swallowing)

– Polyhydramnios– IUGR late 2nd and 3rd

trimester

Polyhydraminos

Small stomach

bubble

Imaging Fetal BowelImaging Fetal Bowel

Duodenal AtresiaDuodenal Atresia

Lack of normal canalization leading to partial or complete obstruction

Most common small bowel obstruction: 1:5000 to 1:10,000 (Callen2008)

– Jejunal atresia nearly as common Unknown etiology Can result from

– Membrane across lumen– Annular pancreas– Occlusion of SMA

Duodenal AtresiaDuodenal Atresia

Associated anomalies– 30% of DA fetuses have trisomy 21– 50-70% of DA have other anomalies

Vertebral GI Heart Occasionally renal

– Overall mortality 15-40%– 95% survival if isolated with immediate

surgical treatment

Duodenal AtresiaDuodenal Atresia Ultrasound findings

– “double bubble” sign Stomach &

duodenum Seen in all

types of small bowel obstruction

– Polyhydramnios

Atresia & stenosis of small bowel and colon are less common

Obstruction usually results from vascular insult

Duodenal AtresiaDuodenal Atresia Differential diagnosis includes

Choledochal cyst Liver cyst

Jejunal, Ileal AtresiaJejunal, Ileal Atresia Best diagnostic clue:

– Hyperperistalsis within small bowel loops highly suggestive of obstruction

– Dilated, fluid-filled loops of bowel– Rarely presents as a cyst-like mass– Polyhydramnios

Associated with other GI anomalies Sensitivity for US detection near 100%

Bowel ObstructionBowel Obstruction

Exact location of dilatation may be hard to determine

Prognosis– Depends on

Site of obstruction Length of normal bowel Associated anomalies Presence/absence of perforation

– Lower obstructions have better outcome

Echogenic BowelEchogenic Bowel Controversy over what is considered echogenic

– Appears more echogenic with higher frequency transducer

Has been associated with– Cytomegalovirus (CMV) & Parvovirus– Severe IUGR & unexplained intrauterine demise– Trisomy 21– Bowel obstruction– Cystic fibrosis

Echogenic bowel suggests bowel compromise. In approximately one third of fetuses with echogenic bowel on prenatal ultrasonography, a malformation of the GI tract is later confirmed.

Echogenic BowelEchogenic Bowel Highly operator dependant High frequency transducers falsely

increase bowel echogenicity Differential Diagnosis

– Meconium peritonitis– Anal atresia– Swallowed debris (10% from swallowed

blood)

Fetal GallstonesFetal Gallstones

Gallbladder lies more anterior in the abdomen than the stomach

Echogenic foci with shadowing can be seen

Usually resolve in first year of life

Infectious ProcessesInfectious Processes

Bowel PerforationBowel Perforation

Incidence of bowel perforation 3.3:100,000

Many possible causes Meconium peritonitis

– Distension from obstruction (any kind) can cause perforation of small intestine

– Leakage of meconium into abdomen– Chemical peritonitis– Inflammatory response may seal over perforation

forming a pseudocyst (meconium pseudocyst)

Bowel PerforationBowel Perforation

Meconium Cyst/Pseudocyst– Result of bowel perforation– Hyperechogenic cyst, resolving through

pregnancy Primary/Idiopathic perforation (95%)

– No obstruction– Appear early (first and early 2nd trimester)– Spontaneous sealing – Favorable outcome

Secondary perforation– Intestinal obstruction– Occurs late in pregnancy– Intra-abdominal calcifications

Meconium PeritonitisMeconium Peritonitis Sonographic findings

– Hyperechogenic bowel – main marker– Intraperitoneal echogenic material– Ascites– Dilated bowel loops– Meconium pseudocysts – Intraperitoneal calcifications– Polyhydramnios

Meconium PeritonitisMeconium Peritonitis

Prognosis– Perforation may seal over

May form pseudocyst

– Serious condition – Management depends on cause &

evolution of pathology

Meconium IleusMeconium Ileus Obstruction and dilatation of the ileum

– Caused by impaction of thick meconium – Nearly always found in fetuses with cystic

fibrosis– Can progress to meconium

peritonitis/pseudocyst if perforation occurs

Meconium PeritonitisMeconium Peritonitis

Pseudocyst

**

VolvulusVolvulus Bowel loop twisted on it’s

mesentery, resulting in vascular compromise– Dilated, non-peristalsing bowel loop– Single “kinked” loop very suggestive

Differential diagnosis– Jejunal/ ileal atresia– Intussusception

Cystic Lesions of the Cystic Lesions of the AbdomenAbdomen

Choledochal CystCholedochal Cyst Congenital cystic dilatation of biliary

system (choledochal cyst) Ducts may be dilated Cystic structures seen in fetal

abdomen anterior to right kidney

Choledochal CystCholedochal Cyst

**

Liver CystLiver Cyst

*

Stomach

Enteric Duplication CystEnteric Duplication Cyst May be cystic (80%) or tubular (20%) Best diagnostic clue: Thick-walled cyst Generally anechoic but can be echogenic Rarely bowel dilatation Excellent prognosis Differential diagnosis

– Ovarian cyst– Mesenteric cyst– Choledochal cyst– Meconium pseudocyst

Mesenteric CystsMesenteric Cysts Represent obstructed lymphatic

drainage Lymphangioma Sonographic findings

– Mid-line cystic lesion– May be multisepated or unilocular– Solid appearance if hemorrhage present

Malignancy rare

Hepatic CalcificationsHepatic Calcifications Liver-associated calcifications Determination of intraparenchymal vs

capsular Acoustic shadowing may or may not be

present Isolated, single hepatic calcifications

generally of no consequence Multiple calcifications more likely to be

associated with abnormal karyotype (T21,T18,T13)

Hepatic CalcificationsHepatic Calcifications

Ovarian CystsOvarian Cysts

*Bladder

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