meconium peritonitis

Röntgenbild

eines Neugeborenen mit großer, raumfordernder Mekoniumzyste (besser - pseudozyste), die Magen und Darmstrukturen nach außen verdrängt. Man erkennt gut die zarte, randständige Verkalkung. Ursächlich war in diesem Fall ein Atresie des terminalen Ileums. Die schräg verlaufende Verschattung unten in der Mitte ist die Nabelklemme.

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Meconium peritonitis refers to a sterile chemical peritonitis due to intra-uterine bowel perforation and spillage of fetal meconium into the fetal peritoneal cavity. It is a common cause of peritoneal calcification.

Epidemiology

The estimated prevalence is at ~1 in 35,000.

Pathology

The etiology is thought to be the result of a sterile chemical reaction resulting from bowel perforation in utero. The bowel perforates as a result of bowel obstruction, such as an atresia or meconium ileus. Secondary inflammatory response results in the production of fluid (ascites), fibrosis, calcification and sometimes cyst formation. Usually, the perforation seals off and the bowel is intact at birth. Intra-peritoneal meconium usually calcifies, sometimes within 24 hours.

Classification

At least four types are recognized:

fibro-adhesive (dense mass: the intense chemical reaction causes the formation of a dense mass with calcium deposits that eventually seal off the perforation)
cystic
generalized
healed

Associations

cystic fibrosis: does not usually calcify in these cases due to lack of enzymes
intestinal atresia
polyhydramnios

Radiographic features

Plain radiograph

Abdominal radiographs may show

intra-abdominal (peritoneal) calcification (can be curvilinear, linear or flocculant)
a mass containing calcification in the context of a meconium pseudocyst
if the processus vaginalis is patent at the time of perforation, calcification may also be seen in the scrotum

Ultrasound

may show highly echogenic linear or clumped foci which represent calcification
can also give a snowstorm appearance
differentiated from other causes of intra-uterine calcification by its peritoneal distribution
may show fetal ascites (most common antenatal sonographic finding ) and/or polyhydramnios
the abdominal circumference may be increased
may also show associated anomalies such as dilated fetal bowel and/or meconium pseudocysts
may show dilated stomach due to ileus

Treatment and prognosis

When the calcifications are isolated, there generally is a favorable neonatal outcome and intervention is not necessary . These cases are thought to represent perforation of bowel that spontaneously heals in utero. Therefore, in the absence of other findings, isolated calcifications can be followed sonographically during pregnancy.

Complications

ascites: tends to be more echogenic than simple ascites
bowel obstruction from the formation of fibro-adhesive bands
meconium pseudocyst formation (a walled-off mass of meconium surrounded by a calcific rim)