Daily Archives: 21/12/2021

Duodenal Atresia

Duodenal atresia is the most common type of congenital small bowel obstruction resulting from failure to recanalize the duodenal lumen during the 11th week of gestation.

     Fig 1

Incidence: 1 in 5000-10,000 births. One-third have Down’s syndrome.

Sonographic findings:

• Double bubble sign and a narrow channel connecting the stomach and duodenum (the second bubble will be in the location of the duodenal bulb, which is typically in the center of the abdomen, just to the right of the midline). Fig 2, Fig 3, Fig 4
• The continuity between the two fluid-filled structures must be demonstrated, and if the connection cannot be shown, a number of other possibilities should be considered, such as choledocal cyst (most common) and the less common renal cyst, hepatic cyst, omental cyst, bowel duplication or ovarian cyst.
• A more prominent appearance with a C loop of dilated bowel may occur when duodenal atresia is associated with esophageal atresia. Fig4, Fig5
• Pitfalls:
  • A prominent normal stomach with a visible incisura angularis may be confused with a double bubble sign.
  • Bisection of the normal stomach in an oblique scan plane, giving the spurious appearance of a double bubble. This misinterpretation can be corrected by scanning the abdomen in a true transverse plane, so as to demonstrate the typical tapering configuration of the gastric antrum.
  • Any right upper quadrant mass such as a choledocal cyst, bile-filled gallbladder, or hepatic cyst may be misinterpreted as a distended duodenum.
• Polyhydramnios occurs in nearly all cases diagnosed in the third trimester.
• Perforation secondary to obstruction can occur, and ascites or meconium peritonitis may be found.
• Usually first diagnosable in the second trimester, although it can occasionally be diagnosed before 20 weeks or even in the first trimester.

Fig 1:  Schematic drawing of duodenal atresia, The fluid-filled stomach (St) and duodenum (D) cause double bubble sign on ultrasound examination

Fig 2:  Duodenal atresia  Cross-sectional scan of the abdomen: Double bubble sign: two cystic masses (* = proximal duodenum, solid circle = stomach) with connection together in the upper abdomen

Fig 3:  Duodenal atresia   Cross-sectional scan of the abdomen: Double bubble sign: two cystic masses (* = stomach, solid circle = proximal duodenum ) in the upper abdomen

Fig 4:  Duodenal atresia   Cross-sectional scan of the abdomen: Double bubble sign: two cystic masses (* = proximal duodenum, solid circle = stomach) in the upper abdomen

Associations: Gastrointestinal, genitourinary and cardiovascular anomalies occur in more than 50% of cases and trisomy 21 is found in 30% of cases (but only 5% of fetuses with trisomy 21 show duodenal atresia). Furthermore, duodenal obstruction also increases the risk of prenatal asphyxia and death, probably caused by bradycardia/asystole following vagal overactivity due to distension of the upper gastrointestinal tract.

Management: A careful search for associated anomalies and karyotyping are indicated. The delivery should occur where appropriate personnel are available for surgical correction.

Prognosis: A high mortality rate of about 20-40% due to associated abnormalities or preterm delivery. Uncomplicated cases have a good prognosis.

Recurrence risk: Sporadic (with rare familial reports).

Esophageal Atresia

This sporadic malformation results in an abrupt termination of the esophagus as a blind pouch. In approximately 90% of cases, esophageal atresia is associated with a tracheoesophageal fistula, which most often connects the trachea to the distal esophagus. Additional abnormalities occur in a high percentage of fetuses with esophageal atresia, and these include cardiac, chromosomal, gastrointestinal, genitourinary, and central nervous system lesions.

Incidence: About 1 in 3500 births, and nearly two-thirds are male.

Sonographic findings:

            Fig 1, Fig 2, Fig 3

• Polyhydramnios: massive polyhydramnios (amniotic fluid index (AFI)>40) is commonly seen in the third trimester.
• Absent fluid-filled stomach in its normal location in the left upper quadrant.
• The absent visible stomach can be identified in about 42% of fetuses. Conversely, the combination of polyhydramnios and gastric non-visualization is only seen in less than half of fetuses with a tracheoesophageal fistula.
• Proximal esophageal pouch (pouch sign): a fluid-filled pouch corresponding to the atretic segment of the esophagus may be seen in the neck or distal esophageal segment.
• Fetal growth restriction: about 40% of infants with esophageal atresia are associated with growth restriction.
• Usually first diagnosable in the second trimester, mostly after 24 weeks.
• Among fetuses with ultrasonographic features suggestive of esophageal atresia, 50% have the disorder confirmed postnatally.
• In case of suspicion, MRI may be helpful.
• Pitfalls:
  • Non-visualization of the stomach may be a transient normal finding.
  • Several cases of tracheoesophageal fistula with a connection to the stomach through the lungs have a visible stomach.
  • When combined with duodenal atresia, it may be very difficult to detect due to masking from polyhydramnios and double bubble sign.

Fig 1:  Esophageal atresia  Cross-sectional scan of the abdomen: absent stomach at the level of umbilical vein complex (arrow) with marked polyhydramnios

Fig 2:  Esophageal atresia  Cross-sectional scan of the abdomen: absent stomach at the level of umbilical vein complex (arrow) with polyhydramnios (arrowhead = spine)

Fig 3:  Esophageal atresia   Cross-sectional scan of the abdomen: absent stomach with marked polyhydramnios

Associations: Associated malformations are seen in at least 50% of cases of tracheoesophageal fistula, including gastrointestinal, genitourinary, and cardiovascular anomalies, trisomy 21 and 18.

Management: A careful search for associated anomalies is indicated. The pregnancy with fetal isolated esophageal atresia should be closely followed-up and monitored for preterm delivery. The delivery should occur where appropriate personnel are available for surgical correction.

Prognosis: Poor overall (due to associated anomalies and prematurity), but the prognosis is much improved with isolated esophageal atresia.

Recurrence risk: Sporadic.

Masses at the Anterior Body Wall

Differential diagnoses of the masses at the anterior body wall include

Fig 1, Fig 2, Fig 3, Fig 4, Fig 5, Fig 6

• Physiologic omphalocele (8-12 weeks); size of <7 mm, no liver content
• Omphalocele
• Gastroschisis
• Ectopia cordis
• Limb-body wall defect
• Bladder exstrophy
• Cloacal exstrophy
• Stack of umbilical cord (positive Doppler signal or color flow)
• Cord edema or localized Wharton’s jelly near the umbilicus
• Cord cysts (omphalomesenteric cyst or allantoic cyst)
• Placental mass (chorioangioma) close to the anterior wall
• Artifacts: pseudo-omphalocele secondary to oblique plane

Fig 1:  Omphalocele  Clubfoot and free floating sac containing liver with covering membrane (arrow)

Fig 2:  Gastroschisis  Free floating echogenic bowel (*) in the amniotic fluid (arrowhead = spine, solid circle = intra-abdominal stomach)

Fig 3:  Bladder extrosphy  Sagittal view of the fetal abdomen: complex extra-abdominal mass (*) below the umbilicus, finally proven to be bladder extrosphy

Fig 4:  Physiologic omphalocele  Sagittal scan of the fetus (10 weeks): bowel contents protruding into the proximal umbilical cord (arrow)

Fig 5:  Pseudo-omphalocele  Oblique cross-sectional scan of the fetus: the liver (*) covered by normal abdominal wall (arrow) protrudes anteriorly, may be mistaken for omphalocele (arrowhead = spine)

Fig 6:  Physiologic omphalocele  Cross-sectional scan of the embryo (8 weeks): bowel contents protruding into the proximal umbilical cord (arrowhead)

True anterior wall defect

• Omphalocele
• Gastroschisis
• Limb-body wall complex
• Amniotic band syndrome
• Bladder exstrophy
• Cloacal exstrophy
• Pentralogy of Cantrel

Cystic mass close to the umbilicus

• Allantoic cyst (urachal cyst)
• Omphalomesenteric cyst
• Pseudocyst (liquefaction of Wharton’s jelly)
• Umbilical vein varix
• Omphalocele

The approach of the anterior wall defects

•  Relationship of the cord insertion to the defect: various sites of the defect suggest the nature of pathology as follows:
  • above the umbilicus: pentalogy of Cantrell
  • at the umbilicus: omphalocele
  • paraumbilical area: gastroschisis
  • below the umbilicus: bladder/cloacal exstrophy
  • defects throughout the abdomen: limb-body wall complex
  • severe and asymmetric defect: amniotic band syndrome
• Characteristics of herniated organs: a herniated organ can suggest the nature of pathology as follows:
  • bowel: either a gastroschisis, omphalocele, or LBWC
  • liver only: highly suggestive of omphalocele (but most omphaloceles also include portions of bowel), very unlikely to be gastroschisis
  • bowel only (in omphalocele): more often related to chromosomal abnormalities
  • solid mass at the lower abdomen: bladder or cloacal exstrophy
• Presence of covering membranes:
  • presence: omphaloceles (be careful, the covering membrane may not always be seen or may be ruptured), limb-body wall complex (not always)
  • absence: gastroschisis
  • the presence of a herniated liver in a ventral wall defect without a covering membrane is more suggestive of a ruptured omphalocele
• Associated anomalies:
  • multiple anomalies: omphalocele, LBWC
  • extra-, intra-abdominal bowel obstruction: gastroschisis
  • scoliosis: LBWC
  • non-visualization of bladder: bladder or cloacal exstrophy
  • amputation defects: amniotic band syndrome

Renal Cysts

Sonographic differential diagnosis of common renal cystic conditions

Fig 1, Fig 2, Fig 3, Fig 4

Fig 1:  Hydronephrosis  Cross-sectional scan of the abdomen: markedly dilated renal pelvis (*) with calyces (arrow)

Fig 2:  Multicystic kidney  Sagittal scan of the abdomen: multiple cysts varying in size in the kidney

Fig 3:  Hydronephrosis  Coronal scan of the abdomen: bilateral dilated renal pelvis (*) (solid circle = bladder)

Fig 4:  Normal kidney   The kidneys consisting of multiple normal pyramids (arrow), looking like multicystic kidney (* = renal pelvis)

Severe hydronephrosis:

• visible renal parenchyma
• peripheral oval cysts communicating with each other and the renal pelvis
• often ureteral dilatation
• underlying cause in some cases such as bladder outlet obstruction
• abnormalities in the contralateral kidney (10-40%)

Autosomal recessive polycystic kidneys

• bilateral enlarged echogenic kidneys with reniform shape
• oligohydramnios

Multicystic kidney disease

• multiple round non-communicating cysts of variable size
• multiple cysts with grape-like appearance in many cases
• unilateral (77%)
• abnormalities in the contralateral kidney (39%)

Renal cystic dysplasia

• echogenic parenchyma and subcapsular or cortical cyst
• evidence of hydronephrosis in some cases
• evidence of an underlying cause such as bladder outlet obstruction in some cases

Fig 1:  Fetal dermoid cyst  Cross-section at the upper abdomen: cystic mass (*) containing echogenic debris or sebum (arrowhead = spine, circle = liver)

Fig 2:  Fetal ovarian cyst  Cross-section of the fetal upper abdomen: simple anechoic cyst (*) (arrowhead = spine)

Fig 3:  Fetal ovarian cyst  Cross-sectional scan of the abdomen: Simple anechoic cyst (*) in the rightside of the abdomen, note normal kidney and adrenal gland (arrowhead)

Fig 4:  Large urachal cyst  Sagittal scan of the fetal trunk: large cystic mass (*) connecting with the bladder, externally protruding from the lower abdomen

Fig 5:  Large umbilical vein aneurysm  Cross-sectional scan of the abdomen: cystic mass (solid circle) connecting with umbilical vein (arrow) with Doppler signal on flow study (* = stomach, arrowhead = spine)

Fig 6:  Choledocal duct cyst  Coronal scan of the abdomen: anechoic cystic mass (*) located at the right upper abdomen with pressure effect on the liver (arrowhead = renal cystic dysplasia)

Fig 7:  Duodenal atresia  Cross-sectional scan of the abdomen: Double bubble sign: two cystic masses (* = proximal duodenum, solid circle = stomach) in the upper abdomen

Fig 8:  Proximal jejunal atresia  Cross-sectional scan of the abdomen: marked dilatation of the bowel loop with continuation of stomach (solid circle), duodenum (*) and proximal jejunal

Fig 9:  Small bowel obstruction  Cross-sectional scan of the abdomen: Multiple loop of small bowel loops with marked dilatation (*)

The main sonographic differential diagnoses include

Choledochal cyst/hepatic cyst:

• anechoic single cyst in liver, choledochal cyst located adjacent to hepatic ducts
• more common in females
• not associated with other anomalies

Multicystic kidneys:

• anechoic multicysts of variable size which are non-communicating
• located posteriorly
• unilateral or bilateral
• male or female

Hydronephrosis:

• anechoic single or often multiple communicating cysts within renal fossa
• more common in males
• probably associated with other GU anomalies

Hydroureter:

• anechoic tubular cyst in nature
• communicating with renal pelvis and bladder
• located posteriorly
• more common in males
• may be associated with megacystis

Meconium pseudocyst:

• echogenic cyst with calcified wall at mid-abdomen
• associated with bowel obstruction
• male or female

Mesenteric/omental cyst:

• isolated anechoic cyst, unilocular or less commonly septated
• often mobile
• located centrally
• male or female

Urachal cyst:

• isolated anechoic simple
• communicates with the bladder and also commonly with the umbilicus
• located anteriorly
• male or female

Ovarian cyst:

• isolated unilocular, sometimes septated, or daughter cyst
• usually unilateral
• located lower or laterally
• only in females

Duodenal atresia:

• double bubble sign in upper abdomen
• connection between the two bubbles
• polyhydramnios
• male or female
• commonly related to trisomy 21

Small bowel obstruction:

• multiple bowel loops with echogenic contents
• tubular in nature
• located centrally or throughout the abdomen
• peristalsis
• male or female

Hydrometrocolpos:

• anechoic to echogenic cyst
• located retrovesically
• only in females

Fig 1:  Splenomegaly  Cross-sectional scan of the abdomen: enlarged spleen behind the stomach (*) (arrow= the umbilical vein, arrowhead = spine)

Fig 2:  Splenomegaly  
Cross-sectional scan of the upper abdomen: The enlarged spleen (solid circle) behind the stomach, Note adrenal gland (*) close to the spine (arrowhead) (arrow = umbilical vein)

Fig 1:  Hyperechoic bowel  Coronal scan of the abdomen: hyperechogenic bowel (*)

Fig 2:  Hyperechoic bowel  Sagittal scan of the abdomen: hyperechoic bowel (*)

Fig 3:  Hyperechoic bowel   Cross-sectional scan of the abdomen: hyperechoic bowel (*) (arrowhead = spine)