Maria Moes, M.D.
Punctate and linear calcifications are seen throughout the abdomen in this second trimester pregnancy.
Meconium peritonitis (MP) should be considered as a diagnostic possibility when hyperechogenic areas are seen within the fetal abdomen during the second and third trimesters of pregnancy. Neonatal studies suggest a prevalence of 1 in 35,000 live births. The etiology of MP is thought to be the result of a sterile chemical reaction resulting from bowel perforation in utero. A secondary inflammatory response results in the production of fluid (ascites), fibrosis, calcification and sometimes cyst formation. The end result of the process varies leading to four descriptive categories of meconium peritonitis: fibroadhesive, cystic, generalized and healed. Eighty-six percent of fetuses with meconium peritonitis have intra-abdominal calcifications. Experimental research in animals indicates that it takes at least 8 days after meconium has escaped into the peritoneal cavity before calcifications are detected. The most common causes of meconium peritonitis are ischemic lesions of the small bowel associated with mechanical obstruction (atresia, volvulus, intussusception, congenital bands, Meckel diverticulum and internal hernia). These likely account for 50% of the cases of meconium peritonitis. Meconium peritonitis may also be caused by viral infections (cytomegalovirus, or parvovirus B19). Meconium ileus accounts for less than 25% of cases of meconium peritonitis.
Hill LM Ultrasound of the fetal gastrointestinal tract. In: Ultrasonography in Obstetrics and Gynecology. Ed. Peter W. Callen, 4th Ed. W. B Saunders and Co., Philadelphia, 2000
Scioscia AL, Pretorius DH, Budorick NE et al. Second-trimester echogenic bowel and chromosomal abnormalities. Am J Obstet Gynecol 167:889-894, 1992
Park RW, Grand RJ. Gastrointestinal manifestation of cystic fibrosis: A review. Gastroenterology 1981;81:1143-1161.
Payne RM, Nielsen AM. Meconium peritonitis. Am Surg 1983;28:224-231.
Finkel LI, Slovis SL. Meconium peritonitis, intraperitoneal calcifications and cystic fibrosis. Pediatr Radiol 1982;12:92-93.
Rypens FE, Avni EF, Ababsena MM, Donner C et al. Areas of increased echogenicity in the fetal abdomen: Diagnosis and significance Radiographics 15:1329-1344, 1995
Ohmichi M, Kanai H, Kanzaki T et al. Meconium peritonitis: Changes in Fetal C-reactive protein and CA 125 levels in relation to stage of disease. J Ultrasound Med 16:289-292, 1997
Williams J, Nathan RO, Worthen JNJ. Sonographic demonstration of the progression of meconium peritonitis. Obstet Gynecol 64:822, 1984
Foster MA, Nyberg DA, Mahony BS, Mack LA et al. Meconium peritonitis: Prenatal sonographic findings and their clinical significance. Radiology 165:661-665, 1987
Dirkes K, Crombleholme TM, Craigo SD, Latchaw LA, Jacir NN, Harris BH, DAlton ME. The natural history of meconium peritonitis diagnosed in-utero. J Pediat Surg 1995;30:979-982.
Pan EY, Chen LY, Zang JZ, Wang ZZ. Radiographic diagnosis of meconium peritonitis. A report of 200 cases including six fetal cases. Pediatr Radiol 1983; 13:199-205.
Patole S, Whitehall J, Almonte R, Stalewski H, Lee-Tannock A, Murphy A. Meconium thorax: A case report and review of the literature. Am J Perinatol 1998;15:53-56.
Professor of Radiology, Obstetrics, Gynecology and Reproductive Science
University of California Medical Center, San Francisco, California