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The fetal presacral pseudo-mass: a normal sonographic variant
T J Karcnik1, J B Rubenstein, L C Swayne
1Department of Radiology, Morristown Memorial Hospital, New Jersey 07960.
Summary
A common fetal presacral mass found in the third trimester is often a normal variant: a meconium-filled rectum. This finding, seen in 6.3% of gestations, resolves postnatally without issue.
Area of Science:
- Medical Imaging
- Fetal Medicine
- Pediatric Surgery
Background:
- Fetal presacral masses identified during the third trimester can cause clinical concern.
- Distinguishing normal anatomic variants from pathological conditions is crucial for appropriate management.
Purpose of the Study:
- To determine the incidence and nature of hypoechoic masses in the fetal presacral space during the third trimester.
- To evaluate the long-term outcomes of neonates with these findings.
Main Methods:
- Retrospective review of 416 third-trimester intrauterine gestations.
- Sonographic examination to identify and measure presacral masses.
- Clinical follow-up of neonates.
Main Results:
- Twenty-six hypoechoic presacral masses were identified (6.3% incidence).
- Masses ranged from 15 to 30 mm (mean 21.5 mm).
- All neonates had normal follow-up examinations with no masses or neurologic deficits.
Conclusions:
- A meconium-filled fetal rectosigmoid colon is a common cause of third-trimester presacral masses.
- The high incidence of this normal variant (6.3%) contrasts with rare presacral teratomas (0.0025%).
- This finding should be recognized as a normal anatomic variant, avoiding unnecessary interventions.