Large Abdominal Circumference

Janice L. B. Byrne, MD

DIFFERENTIAL DIAGNOSIS

Common

Fetal Overgrowth
- Macrosomia
- Diabetes
- Beckwith-Wiedemann Syndrome
Bowel Obstruction
- Small Bowel Atresia
- Volvulus
- Meconium Pseudocyst
- Meconium Ileus
Urinary Tract Anomalies
- Multicystic Dysplastic Kidneys
- Autosomal Recessive Polycystic Kidney Disease (ARPKD)
- Posterior Urethral Valves
- Urethral Atresia
- Prune Belly Syndrome
Hydrops

Less Common

Ascites, Massive
Mesoblastic Nephroma
Hepatomegaly, Splenomegaly

Rare but Important

Liver Tumors
Lymphangioma

ESSENTIAL INFORMATION

Key Differential Diagnosis Issues

Is there generalized overgrowth, or is increased size limited to the abdomen?
Is there increased fat deposition?
Is there a history of maternal diabetes?
Are there dilated loops of bowel or other masses in the abdomen?
Are the kidneys enlarged or dilated?
Is the bladder of normal size and shape?
Is the amniotic fluid normal?
Are there other structural anomalies?
Is there associated hydrops or ascites?

Helpful Clues for Common Diagnoses

Fetal Overgrowth
- Macrosomia
  - Generalized increase in size of all parameters
  - Commonly seen in poorly controlled diabetes, but may be isolated
  - Associated polyhydramnios
  - 3rd trimester phenomenon
- Diabetes
  - Overall increased size in fetus
  - Abdominal circumference increase often disproportionate
  - Greatest increase in growth velocity in 3rd trimester
  - Associated polyhydramnios
  - Growth acceleration associated with poor glycemic control, especially in gestational diabetes, but may also occur in pre-gestational diabetes
- Beckwith-Wiedemann Syndrome
  - Generalized overgrowth
  - Visceromegaly with enlarged kidneys, liver, and spleen
  - Omphalocele common
  - Macroglossia can be seen prenatally
Bowel Obstruction
- Small Bowel Atresia
  - One or several loops of dilated bowel, depending on level of obstruction
  - May be seen as early as the late 2nd trimester
  - Hyperperistalsis seen in obstructed loops
- Volvulus
  - Multiple loops of dilated bowel may fill abdomen
  - No peristalsis if bowel is infarcted
  - Evaluate presence/absence of anal dimple: Absence suggests associated anorectal malformation
- Meconium Pseudocyst
  - Large, irregular fluid collection in the abdomen
  - Echogenic “rind”
  - Association with in-utero bowel perforation
  - May or may not be associated with fetal cystic fibrosis
- Meconium Ileus
  - Focal area of echogenic bowel may precede appearance of dilated loops
  - Dilation may be severe
  - Associated ascites
  - Check for family history of cystic fibrosis
Urinary Tract Anomalies
- Multicystic Dysplastic Kidneys
  - Enlarged echogenic kidneys with multiple macrocysts of variable sizes
  - Bilateral or unilateral
  - Bilateral with anhydramnios is lethal
- Autosomal Recessive Polycystic Kidney Disease (ARPKD)
  - Severe end of spectrum usually lethal, with markedly enlarged, echogenic kidneys
  - Small chest and anhydramnios with worst outcome
  - Gross cysts not seen on prenatal ultrasound
- Posterior Urethral Valves
  - Found only in male fetus
  - Dilated renal pelves may be severe
  - Bladder enlarged with “keyhole” shape due to dilated prostatic urethra
  - If severe, may be associated with complete bladder outlet obstruction early in gestation
- Urethral Atresia
  - Bladder distension massive with anhydramnios an early finding
  - Male and female fetuses
- Prune Belly Syndrome
  - Triad of abnormal abdominal muscle development, undescended testes, and marked bladder distension
  - Entire urinary tract dilated, with dramatic ureterectasis and hydronephrosis
Hydrops
- Ascites, pleural &/or pericardial effusions, and skin edema
- Associated polyhydramnios or oligohydramnios
- Cystic hygroma common association

Helpful Clues for Less Common Diagnoses

Ascites, Massive
- Isolated without other signs of hydrops
- Poor prognosis for normal outcome
- Associated bowel or renal abnormalities common
Mesoblastic Nephroma
- Large, homogeneous-appearing renal tumor
- Association with polyhydramnios
- Mass effect on surrounding vessels such as aorta
Hepatomegaly, Splenomegaly
- Association with edema from hydrops, heart failure, intrauterine infection
- “Speckled” appearance concerning for infection

Helpful Clues for Rare Diagnoses

Liver Tumors
- Associated hepatomegaly
- Cystic/vascular component more commonly associated with hemangioma or hemangioendothelioma
- Solid tumor more likely to be hepatoblastoma
Lymphangioma
- Complex lesion with multiple cysts
- Lesions may be superficial or within the chest or abdomen
- Involvement of neck common

Image Gallery

Clinical photograph of a 12 lb 12 oz newborn. Note the protuberant abdomen and increased subcutaneous fat. The mother was not diabetic but did a have history of delivering large babies.

Coronal ultrasound shows a 33 week fetus with macrosomia related to poorly controlled maternal type II diabetes. The obviously enlarged abdomen

is comparable in size to that of a 38 week fetus.

(Left) Axial ultrasound shows the enlarged kidneys

seen in a 3rd trimester fetus with Beckwith-Wiedemann syndrome. The abdomen was large when compared to the other biometric parameters. (Right) Coronal ultrasound shows multiple loops of dilated bowel