Key Points
Cystic abdominal lesions are relatively common.
Diagnosis of the underlying etiology of a cystic abdominal mass may be difficult but intimate association with adjacent structures may provide clues to diagnosis.
Fetal MRI may be helpful in determining the cyst’s origin.
Sonographic evidence of associated anomalies should be sought.
Obstruction of bowel and compression of adjacent organs is common and may result in polyhydramnios.
Cyst aspiration in utero is rarely indicated.
The prenatal diagnosis of abdominal cystic lesions is relatively common (McEwing et al., 2003). Cystic abdominal masses may either represent a normal structural variant or pathologic entity that may require surgical intervention postnatally (Sherwood et al., 2008). Abdominal cystic lesions may be exceedingly difficult to accurately diagnose prenatally (Khong et al., 2003). In other chapters, we have already addressed many of the lesions in the differential diagnosis including choledochal cysts (Chapter 67), ovarian cysts (Chapter 68), meconium pseudocysts (Chapter 70), and extralobar bronchopulmonary sequestration (Chapter 34). This chapter will focus on some less common, but important, causes of cystic abdominal lesions including hepatic cysts, splenic cysts, pancreatic cysts, duplication cysts, and mesenteric cysts.
Hepatic cysts are most often isolated, simple cysts. Hepatic cysts are thought to arise from aberrant bile ducts (Cowles and Mulholland, 2000; Otani et al., 2005) or intrahepatic, peribiliary glands (Kida et al., 1992). These simple cysts are more common in girls (Otani et al., 2005) and do not communicate with the biliary system (Rogers et al., 2007). At least one case of prenatal hepatic cyst has been found to be a mesothelial cyst (Komori et al., 2008).
The majority of simple unilocular hepatic cysts detected prenatally tend to shrink or resolve postnatally (Rogers et al., 2007). There are cases of hepatic cysts reaching very large sizes with progressive enlargement resulting in symptoms (Byrne and Fonkalsrud, 1982).
Splenic cysts are usually simple serous epithelial-lined cysts in the upper pole of the spleen (Saada et al., 2006). These cysts are often diagnosed prenatally in the third trimester and may be difficult to distinguish from adrenal or pancreatic cysts.
Pancreatic cysts arise from a developmental anomaly of the pancreatic ductal system usually in the body or tail of the pancreas (Choi et al., 2007). These cysts are epithelial lined and are not pseudocysts. Pancreatic cysts can occur as part of Beckwith–Wiedemann syndrome, polycystic disease of the pancreas and kidney, or Hippel–Lindau disease but are usually multiple in these cases (Vane et al., 1993).
Duplication cysts can occur at any point along the gastrointestinal tract (Bhargava et al., 1976). Enteric duplications most commonly occur in the jejunum (53%) with 18% occurring in the colon, 6% in the duodenum, and 4% gastric (Khanna et al., 2004). There are several theories that have been proposed to account for enteric duplications ranging from errors in recanalization, partial twinning, embryonic diverticula, and split notochord theory (Goyert et al., 1991; Heis, 1997; Jimenez et al., 1999; Behrman et al., 2000). Colonic duplications frequently present with obstruction of the adjacent bowel (Jimenez et al., 1999). Colonic duplications may be associated with duplications of the genitourinary system (Heis, 1997; Jimenez et al., 1999). Duplication of the intestine may also occur in association with vertebral and spinal cord anomalies such as hemivertebrae, anterior myelomeningocele, duplication of an otherwise normal cord, or a bond between the cyst and the cervical or thoracic spine (Heis, 1997; Behrman et al., 2000).
Hepatic cysts tend to be simple unilocular cysts but may vary considerably in size. Simple hepatic cysts are thought to develop from aberrant bile ducts or intrahepatic peribiliary glands (Kida et al., 1992; Cowles and Mulholland, 2000; Otani et al., 2005; Rogers et al., 2007). These cysts may enlarge to significant proportions causing bowel obstruction.
It may be difficult at times to recognize it as a cyst as it can entirely fill the peritoneal cavity (Figure 66-1A and 66-1B). This can be distinguished from ascites by its compression of the bowel into the retroperitoneum behind the cyst. While there are case reports of cyst aspiration, they do not often require treatment (Rogers et al., 2007; Ito et al., 1997; Arzt et al., 1998).
Figure 66-1
Saggittal ultrasound image demonstrating an anechoic unilocular cyst in the lower fetal abdomen that proved to be a mesenteric cyst on postnatal imaging. Note the absence of internal echogenic lining, absence of septations, and proximity to bowel and mesentery. B. Transverse ultrasound image of the same fetus as in (A).
Determining the origin of a cyst as hepatic, splenic, mesenteric, or pancreatic may be exceedingly difficult unless the cyst is clearly surrounded by parenchyma of a specific organ. Pancreatic cysts usually develop from the ductal system in the body and tail of the pancreas and are usually epithelial lined. Usually these are solitary unilocular nonenzymatic cysts (Choi et al., 2007). Fetal MRI may be a useful adjunct to ultrasound in defining the etiology of a cystic lesion of the abdomen (Veyrac et al., 2004; Wong et al., 2006).
