Annular pancreas is a rare condition in which the second part of the
duodenum is surrounded by a ring of
pancreatic
The pancreas is an organ of the digestive system and endocrine system of vertebrates. In humans, it is located in the abdomen behind the stomach and functions as a gland. The pancreas is a mixed or heterocrine gland, i.e. it has both an endocr ...
tissue continuous with the
head of the pancreas
The pancreas is an organ of the digestive system and endocrine system of vertebrates. In humans, it is located in the abdomen behind the stomach and functions as a gland. The pancreas is a mixed or heterocrine gland, i.e. it has both an end ...
. This portion of the pancreas can constrict the duodenum and block or impair the flow of food to the rest of the
intestines. It is estimated to occur in 1 out of 12,000 to 15,000 newborns.
The ambiguity arises from the fact that not all cases are symptomatic.
Signs and symptoms
Early signs of abnormality include
polyhydramnios (an excess of
amniotic fluid),
low birth weight
Low birth weight (LBW) is defined by the World Health Organization as a birth weight of an
infant of or less, regardless of gestational age. Infants born with LBW have added health risks which require close management, often in a neonatal inten ...
, and feeding intolerance immediately after birth, in particular a tendency to develop epigastric distention associated with non-biliary vomiting (the obstruction is generally above the
papilla of Vater, therefore superior to the junction with the
bile duct
A bile duct is any of a number of long tube-like structures that carry bile, and is present in most vertebrates.
Bile is required for the digestion of food and is secreted by the liver into passages that carry bile toward the hepatic duct. It ...
s).
Different chromosomal diseases (for example
trisomy 21
A trisomy is a type of polysomy in which there are three instances of a particular chromosome, instead of the normal two. A trisomy is a type of aneuploidy (an abnormal number of chromosomes).
Description and causes
Most organisms that reprodu ...
and, with a minor frequency,
trisomy 18
A trisomy is a type of polysomy in which there are three instances of a particular chromosome, instead of the normal two. A trisomy is a type of aneuploidy (an abnormal number of chromosomes).
Description and causes
Most organisms that reprodu ...
and
trisomy 13
A trisomy is a type of polysomy in which there are three instances of a particular chromosome, instead of the normal two. A trisomy is a type of aneuploidy (an abnormal number of chromosomes).
Description and causes
Most organisms that reprodu ...
) are present in about 33% of subjects affected by annular pancreas.
In adults, the clinical picture is often dominated by the sensation of postprandial distension, abdominal pain in the epigastric region, nausea and vomiting that may be present for a long time (sometimes for years) before reaching a precise diagnosis.
Causes
It is typically associated with abnormal embryological development, however adult cases can develop. It can result from growth of a bifid ventral pancreatic bud around the duodenum, where the parts of the bifid ventral bud fuse with the dorsal bud, forming a pancreatic ring. It can also result if the ventral pancreatic bud fails to fully rotate, so it remains on the right or if the dorsal bud rotates in the wrong direction, such that the duodenum is surrounded by pancreatic tissue. Blockage of the duodenum develops if inflammation (pancreatitis) develops in the annular pancreas.
Diagnosis
Postnatal diagnostic procedures include abdominal x-ray and ultrasound, CT scan, and upper GI and small bowel series.
Abdominal radiography can show the classic sign of the "double bubble": the presence of air in the stomach and duodenum.
Unfortunately, this double-bubble sign is not
pathognomonic Pathognomonic (rare synonym ''pathognomic'') is a term, often used in medicine, that means "characteristic for a particular disease". A pathognomonic sign is a particular sign whose presence means that a particular disease is present beyond any doub ...
for annular pancreas, as it can also be observed in other conditions, such as
duodenal atresia
Duodenal atresia is the congenital absence or complete closure of a portion of the lumen of the duodenum. It causes increased levels of amniotic fluid during pregnancy ( polyhydramnios) and intestinal obstruction in newborn babies. Newborns pre ...
and
intestinal malrotation
Intestinal malrotation is a congenital anomaly of rotation of the midgut. It occurs during the first trimester as the fetal gut undergoes a complex series of growth and development. Malrotation can lead to a dangerous complication called volvulus ...
.
Upper GI series may be suggestive of annular pancreas, especially if they show a duodenal narrowing of the second portion of the duodenum and the concomitant dilatation of the proximal duodenum. In some cases it is possible to have signs of inverse peristalsis of the duodenal tract which is proximal to the narrowing caused by the annular pancreas, and the dilatation of the duodenal portion distal to the anomaly.
An abdominal CT scan or an MRI allows to highlight the narrowing of the descending duodenal tract and the ring of pancreatic tissue surrounding the duodenum: this ring can be complete or, in patients with an incomplete annular pancreas, extended in a postero-lateral or anterolateral direction with respect to the second part of the duodenum.
ERCP or MRCP with secretin allow precise delineation of the anatomical structure and in particular a good visualization of pancreatic ducts, as well as a careful analysis of pancreatic secretion into the duodenum lumen.
Treatment
In neonates, treatment for relief of obstruction usually is bypassing the obstructed segment of duodenum by duodeno-jejunostomy.
In adults, due to the minor duodenal mobility, the approach is laparoscopic gastrojejunostomy or duodenojejunostomy.
References
External links
{{Congenital malformations and deformations of digestive system
Congenital disorders of digestive system