Abnormal Umbilical Cord

Anne Kennedy, MD

DIFFERENTIAL DIAGNOSIS

Common

Umbilical Cord Cyst
- Allantoic Cyst with Patent Urachus
- Omphalomesenteric Duct Cyst
- Pseudocyst
Cystic Wharton Jelly
Omphalocele (Mimic)
Physiologic Gut Herniation (Mimic)

Less Common

Cord Knot
Short Cord
Abnormal Cord Coiling
Cord Hematoma
Cord Thrombosis

ESSENTIAL INFORMATION

Key Differential Diagnosis Issues

Cord assessment is an important part of all OB scans
- Look at abdominal cord insertion site
- Look at placental cord insertion site
- Evaluate cord structure
  - Are the vessels normal?
  - Is the cord length normal?
  - Is there an appropriate degree of “twist” to the vessels?

Helpful Clues for Common Diagnoses

Umbilical Cord Cyst
- Equally common at fetal & placental ends and in free loops of cord
- May be paraxial (eccentric, do not displace vessels) or axial (centrally located and splay vessels)
- Generally thin-walled, anechoic, often multiple
  - If echogenic content, consider intracystic hemorrhage, which may lead to cord compromise
- May be true cysts (allantoic, omphalomesenteric duct cysts) or pseudocysts
- Isolated cord cysts may spontaneously resolve with etiology never determined
- Allantoic Cyst with Patent Urachus
  - Always near fetal insertion
  - May grow and compress cord
  - Allantoic cysts may be isolated or communicate with the urachus
  - Patent urachus: Cystic mass superior to, and communicating with, bladder
  - Obstructed bladder decompresses into urachus and base of cord
- Omphalomesenteric Duct Cyst
  - 2° to omphalomesenteric duct remnant
  - + Abdominal wall anomalies
  - + Intraabdominal mesenteric cysts
  - + Other severe anomalies
- Pseudocyst
  - Often associated with cystic Wharton jelly
  - May also be sequela of cord hematoma
Cystic Wharton Jelly
- Mucoid degeneration of abnormal Wharton jelly
- Innumerable small pseudocysts develop surrounding cord vessels
- Likely to be associated with aneuploidy and syndromes
Omphalocele (Mimic)
- Smooth mass protruding from central anterior abdominal wall with covering membrane
- Umbilical cord inserts onto membrane, usually central but may be eccentric
- Liver and small bowel most common contents (those with small bowel most likely to be confused with abnormal cord)
Physiologic Gut Herniation (Mimic)
- Normal embryological developmental phenomenon
- Bowel elongates, herniates into base of cord, rotates 270°, then returns to peritoneal cavity
- Bowel returns to abdomen by 11.2 weeks
- Should not extend more than 1 cm into base of cord
- Never contains liver

Helpful Clues for Less Common Diagnoses

Cord Knot
- True knot
  - Most common in monoamniotic twins
  - Rarely also seen in singletons
  - Risk factors include advanced maternal age, multiparity, long umbilical cords
  - May restrict flow → hypoxia, growth restriction
  - May occlude cord → fetal demise
  - Reported to lead to a 4-fold increase in fetal loss
- False knot
  - Due to kinks in vessels, not a true knot
  - No known clinical significance
Short Cord
- Average cord is 55 cm (range 35-80 cm)
- Not possible to measure length prenatally, but short cord subjectively associated with fetus being “tethered”
- Watch fetal movement in real time to assess for akinesia/arthrogryposis sequence
- Associated with abruption/cord rupture
Abnormal Cord Coiling
- Normal cord is helical, with up to 380 helices
- Coiling is well established by 9 weeks and is thought to strengthen cord
- Lack of normal coiling and length associated with fetal akinesia
  - Look at movements in real time
  - Assess joints for abnormal posture
Cord Hematoma
- True cord hematoma is due to extravasation of blood into Wharton jelly surrounding cord vessels
- Use Doppler to look for increased vascular resistance if large hematoma
- May occur following invasive prenatal procedures
- May also be seen adherent to cord secondary to intra-amniotic bleeding from any cause
Cord Thrombosis
- Look for hypoechoic material distending vessels on grayscale images
- Lack of flow on color or power Doppler
- Venous thrombosis is a cause of sudden fetal demise
- Most cases with surviving fetuses are reported as pathological finding after emergency delivery for distress in labor
- Umbilical vein varix is a risk factor
- May occur following invasive prenatal procedures, especially if large hematoma compresses vessels
- May occur in association with large cord cysts, particularly at placental end of cord

Other Essential Information

Cord embryology
- Early connecting stalk connects the embryo to the chorion
- Allantois forms from caudal end of yolk sac
- Cord formed from fusion of allantois and connecting stalk
- Allantois functions as primitive bladder and early blood forming organ
  - Persistent segments of allantois are termed urachal remnants
  - Urachus serves as “pop-off valve” to decompress bladder if outlet obstruction
  - Allantois involutes to become median umbilical ligament
Multiple umbilical cord cysts associated with 7.6x increased risk of poor outcome
Straight cords with few or absent helices are associated with adverse fetal outcomes