What is the significance of a small hepatic parenchymal calcification measuring 5.5 x 4.4 x 3.4 mm, adjacent to the umbilical vein, in a 20-week fetus?

Hepatic Parenchymal Calcification in a 20-Week Fetus

This small isolated hepatic calcification (5.5 x 4.4 x 3.4 mm) adjacent to the umbilical vein requires immediate comprehensive evaluation to exclude chromosomal abnormalities and congenital infections, but if these are ruled out, the prognosis is excellent with likely spontaneous resolution. 1, 2

Immediate Diagnostic Workup Required

The detection of fetal hepatic calcification mandates a systematic evaluation to identify potentially serious underlying conditions:

• Detailed anatomic ultrasound survey to identify any additional fetal abnormalities, as 40 of 61 cases (66%) with hepatic calcifications had associated structural anomalies 1
• Amniocentesis for karyotype analysis should be offered, as chromosomal abnormalities occur in approximately 18% of cases, with trisomy 13 being the most common (4/11 abnormal karyotypes), followed by trisomy 21 and trisomy 18 1
• Maternal TORCH serologies (Toxoplasma, rubella, cytomegalovirus, herpes simplex virus, syphilis) plus parvovirus B19 serology to exclude transplacental infections 3, 1, 2
• Amniotic fluid culture for cytomegalovirus if amniocentesis is performed 2

Differential Diagnosis and Pathophysiology

The calcification's location adjacent to the umbilical vein suggests several possible etiologies:

• Calcified vascular thrombi (hepatic vein or portal vein) are the most common pathologic finding in spontaneously aborted fetuses with hepatic calcifications, accounting for 30 of 33 cases (91%) in one autopsy series 4
• Transplacental TORCH infections remain a critical consideration, though cytomegalovirus and parvovirus B19 are the most commonly identified infectious causes in live-born infants 3, 1
• Ischemic necrosis from various severe fetal illnesses can predispose to hepatic calcifications 4
• Vascular tumors (hemangioma, hemangioendothelioma) are less likely given the small size and single focus 3

Prognosis Based on Findings

The outcome depends critically on whether the calcification is isolated or associated with other abnormalities:

Isolated Hepatic Calcification (Best Prognosis)

• If isolated with normal karyotype and negative infection workup, the prognosis is excellent with 20 of 21 such cases (95%) having good outcomes in the largest series 1
• A separate series of 10 fetuses with isolated calcifications and negative workup all had normal outcomes, with 9 followed for 4 months to 4.5 years showing healthy development 2
• Spontaneous resolution is common, with documented cases showing decrease in number and size of calcifications on postnatal follow-up 3, 5

Associated Abnormalities (Poor Prognosis)

• When additional major abnormalities are present, there is high risk for chromosomal abnormalities, particularly trisomy 13 1
• In cases with associated anomalies, 18 of 40 underwent pregnancy termination, one fetus died in utero, one newborn died, and two infants had neurologic sequelae 1

Critical Management Algorithm

Step 1: Perform detailed anatomic survey immediately to classify as isolated versus associated with other abnormalities 1, 2

Step 2: If isolated, offer amniocentesis for karyotype and obtain complete maternal infectious workup 1, 2

Step 3: If karyotype normal and infections excluded, provide reassurance that prognosis is excellent 5, 1, 2

Step 4: Plan postnatal ultrasound evaluation to document resolution, typically showing decrease in size and number of calcifications 3

Common Pitfalls to Avoid

• Do not assume benign etiology without complete workup, as 18% of cases have chromosomal abnormalities even when calcifications appear isolated on initial ultrasound 1
• Do not miss associated abnormalities by performing only limited ultrasound, as 10 of 11 fetuses with abnormal karyotypes had other ultrasound findings that could have prompted earlier investigation 1
• Do not overlook parvovirus B19 testing, as this was identified in cases initially thought to be isolated 1