Pancreatic agenesis

Pancreatic agenesis is a very rare developmental disorder of the pancreas in which patients present with neonatal diabetes and pancreatic exocrine (pancreatic enzymes) insufficiency ¹, ², ³, ⁴. Total agenesis of the pancreas is extremely rare and is incompatible with life. On the other hand, partial pancreatic agenesis also known as pancreatic hypoplasia results from the absence of the ventral or dorsal pancreatic anlage (rudimentary pancreas), with partial agenesis of the dorsal pancreas is thought to be more common than ventral pancreatic agenesis ⁵. In complete dorsal agenesis of pancreas, the anterior head, neck, body and tail of the pancreas, the duct of Santorini and the minor papilla are absent ⁶. In partial dorsal agenesis of pancreas, a variable amount of pancreatic tissue is absent but a remnant of the duct of Santorini and the minor papilla are present.

Agenesis of the dorsal pancreas is characterized by the absence of the pancreatic body and tail; if only the pancreatic tail is missing, it is called partial agenesis of the dorsal pancreas. If the pancreatic body is also lacking and only the pancreatic head is present, it is known as complete agenesis of the dorsal pancreas ⁷.

Many patients with dorsal pancreatic agenesis are asymptomatic, but some patients may present with abdominal pain or bloating and have an increased risk of diabetes mellitus because most of the islet cells are located in the distal pancreas ⁸, ⁹, ¹⁰, ¹¹.

A diagnosis of a pancreatic agenesis is made based upon identification of characteristic symptoms (if present), a detailed patient history, a thorough clinical evaluation and a variety of specialized tests including advanced imaging techniques (CT, MRI, ERCP and MRCP), blood tests and biochemical tests.

Pancreatic agenesis diagnosis is made by imaging studies revealing the partial absence of the pancreas.

There is no special treatment for agenesis of the dorsal pancreas itself, but sometimes it is necessary to treat the accompanying disease. Pancreatic agenesis management usually involves treatment of the diabetes and exocrine pancreatic insufficiency (EPI), when present.

Figure 1. Normal embryologic development of the pancreas and biliary tree

Footnotes: Drawings showing the normal embryologic development of the pancreas and biliary tree. The ventral pancreatic bud (arrow in A and B) and biliary system arise from the hepatic diverticulum, and the dorsal pancreatic bud (arrowhead in A and B) arises from the dorsal mesogastrium. (C) After clockwise rotation of the ventral bud around the caudal part of the foregut, there is fusion of the dorsal pancreas (located anterior) and ventral pancreas (located posterior). (D) Finally, the ventral and dorsal pancreatic ducts fuse, and the pancreas is predominantly drained through the ventral duct, which joins the common bile duct (CBD) at the level of the major papilla. The dorsal duct empties at the level of the minor papilla.

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Figure 2. Normal pancreas anatomy

Figure 3. Dorsal agenesis of the pancreas

Footnotes: Axial CT (A) and thick-slice coronal oblique Maximum Intensity Projection (MIP) CT (B) images show the pancreatic head (arrow) and the absence of the body and tail of the pancreas. Upper abdominal Magnetic resonance imaging (MRI) and magnetic resonance cholangiopancreatography (MRCP) were carried out with the suspicion of dorsal pancreatic agenesis. At MRCP, the major pancreatic duct was short and the dorsal pancreatic duct was not visualized.

[Source ¹⁰ ]

Figure 4. Agenesis of the dorsal pancreas

Footnotes: (A) and (B) Axial arterial phase CT image showing the absence of the pancreatic body and tail, without pancreatitis and pancreatic duct dilatation. The arrow show the pancreatic head.

[Source ¹ ]

Pancreatic agenesis causes

The exact cause of pancreatic agenesis is unknown. Most pancreatic agenesis occur randomly for no apparent reason (sporadically). Rare mutations in the GATA6, HNF1B, PDX1 (IPF1) or PTF1A gene can cause pancreatic agenesis; however, in most cases of pancreatic agenesis the cause is unknown ¹², ¹³, ¹⁴, ¹⁵, ¹⁶, ¹⁷, ¹⁸, ¹⁹. The genetic basis for most instances of pancreatic agenesis is unknown ¹⁹, ²⁰, ²¹, ²², ²³. Some individuals may have a genetic predisposition to developing agenesis of pancreas. A person who is genetically predisposed to a disorder carries a gene (or genes) for the disease, but the disorder may not be expressed unless it is triggered or activated under certain circumstances, such as due to certain environmental factors. The genetic or environmental factors associated with pancreatic agenesis are unknown. More research is necessary to determine what specific factors may play a role in the development of pancreatic agenesis.

The pancreas develops by ventral and dorsal endodermal buds. The dorsal bud forms the upper part of the head, body and tail of the pancreas which drains through the Santorini duct. The ventral bud gives rise to the major part of the head and uncinate process which drains through Wirsung duct ²⁴. Pancreatic agenesis results from an embryological failure of the dorsal pancreatic bud to form the body and tail of the pancreas. Partial dorsal pancreatic agenesis may be appreciated as a short, rounded pancreatic head adjacent to the duodenum with absence of the pancreatic neck, body, and tail. With complete agenesis of the dorsal pancreas, the neck, body, and tail of the pancreas, the duct of Santorini, and the minor duodenal papilla are all absent. With partial agenesis of the dorsal pancreas, the size of the body of the pancreas varies, there is a remnant of the duct of Santorini, and the minor duodenal papilla is present. Agenesis of the ventral pancreas and complete agenesis of the pancreas are lethal conditions ²⁵. Dorsal pancreatic agenesis is an extremely rare congenital anomaly.

Failure of the ventral and dorsal pancreatic ducts to fuse is called pancreas divisum. In pancreas divisum, the ventral duct drains into major papilla, while the dorsal duct drains into separate minor papilla ²⁴. Atrophy of the body and the tail of the pancreas secondary to chronic pancreatitis and sparing of the pancreatic head is called pseudo-agenesis ²⁶. Pseudo-agenesis of the pancreas may mimic dorsal pancreatic agenesis. In the differential diagnosis of pseudo-agenesis of the pancreas, histories of previous abdominal pain, pancreatitis, CT scanning and the serum amylase level may be helpful ¹⁰. The complete absence of the dorsal duct and demonstration of short ventral duct is important in the diagnosis of the dorsal agenesis of pancreas ¹⁰.

Pancreatic agenesis symptoms

Total agenesis of the pancreas is extremely rare and is incompatible with life. Many patients with dorsal pancreatic agenesis are asymptomatic, but some patients may present with abdominal pain and have an increased risk of diabetes mellitus because most of the islet cells are located in the distal pancreas ⁸, ⁹, ¹⁰, ¹¹.

Dorsal pancreatic agenesis may be associated with other conditions ²⁷, ⁸, ²⁸, ²⁹, ⁹:

• Hyperglycemia (high blood sugar level) may be present in a significant proportion of cases (up to 50%)
• Solid pseudopapillary tumor of the pancreas: possible association
• Polysplenia syndrome (the presence of two or more spleens associated to various chest or abdominal congenital abnormalities)
• Pancreatitis
• Intestinal malrotation

In addition, agenesis of the dorsal pancreas associated with other organ malformations has also been reported, including polycystic kidney disease, Kartagener syndrome, multiple splenic deformities, congenital choledochal cysts and biliary atresia ³⁰, ³¹.

Pancreatic agenesis is commonly associated with other malformations, in particular pancreaticobiliary duct anomalies, leading to acute or chronic pancreatitis, hyperglycemia (50% of cases), or, more rarely, polysplenia. In the majority of cases, patients are diagnosed after reporting abdominal pain. Agenesis of the dorsal pancreas usually manifests as diabetes.

Pancreatic agenesis diagnosis

A diagnosis of a pancreatic agenesis is made based upon identification of characteristic symptoms (if present), a detailed patient history, a thorough clinical evaluation and a variety of specialized tests including advanced imaging techniques (CT, MRI, ERCP and MRCP), blood tests and biochemical tests.

The diagnosis of agenesis of the dorsal pancreas mainly relies on imaging examinations. The complete absence of the dorsal duct and demonstration of short ventral duct is important in the diagnosis of the dorsal bud agenesis. Schnedl supported that the loss of the accessory pancreatic duct and the absence of the tail of the pancreas are conditions for the diagnosis of complete dorsal pancreatic hypoplasia ⁷. As most agenesis of the dorsal pancreas patients are accidentally discovered because of abdominal pain, they mainly first undergo ultrasound and CT. Ultrasound is affected by the gas in the intestine so it is difficult for this modality to identify the part of pancreas near the splenic vessels; therefore, it is easy for ultrasound to miss the disease. CT and MRI can show the complete or partial disappearance of the pancreatic body and tail ³². The splenic vessels are only visible in that area, and the pancreatic head could be compensated and slightly full. Abdominal CT may not evaluate the pancreatic duct in a detailed fashion. Therefore ERCP or MRCP is necessary for revealing the major and the accessory duct systems and has high value for identifying the complete or incomplete types of agenesis of the dorsal pancreas ³³, ³². ERCP is an invasive technique. There is also radiation risk to the patient. MRCP can help the diagnosis of the dorsal pancreatic agenesis noninvasively with no radiation risk ²⁶, ³⁴, ³⁵, ³⁶.

Pancreatic agenesis needs to be differentiated from pancreatic fat infiltration, chronic pancreatitis and pancreatic body and tail atrophy. According to previous literature, agenesis of the dorsal pancreas mostly manifests as the absence of the pancreatic body and tail, the density and morphology of the remaining pancreatic head should be normal, except with compensatory enlargement of pancreatic head. Pancreatic fat infiltration have unique echo characteristics in ultrasound examination and fat signal fraction (FSF) is increased in MRI image, it shows more severe signal suppression than pancreatic tissue on fat suppression imaging; while chronic pancreatitis mostly has pancreatic duct dilatation, pancreas calcification and a lower apparent diffusion coefficient (ADC) values in MRI image, which means an increase in fibrosis ¹. The full pancreatic head needs to be differentiated from pancreatic head tumor and pancreatitis. By observing the peripancreatic fat gap, the presence of calcifications and enlarged lymph nodes can help to confirm the diagnosis ¹.

Pancreatic agenesis treatment

The severity of pancreatic agenesis depends on the amount of functional pancreatic tissue present. Because pancreatic agenesis may be associated with other malformations, the therapeutic management of individuals with agenesis of the pancreas may require the coordinated efforts of a team of medical professionals, such as physicians who specialize in the diagnosis and treatment of diabetes and pancreatic exocrine insufficiency (endocrinologists), specialists in diagnosis and treatment of gastrointestinal disorder (gastroenterologists), dietitians, surgeons, and other healthcare specialists. Pancreatic agenesis management involves treatment of the diabetes and exocrine deficiency, when present. Dorsal pancreatic agenesis can be started on insulin and a pancreatic enzyme replacement.

Dorsal pancreatic agenesis may be associated with other conditions ²⁷, ⁸, ²⁸, ²⁹, ⁹:

• Hyperglycemia (high blood sugar level) may be present in a significant proportion of cases (up to 50%)
• Solid pseudopapillary tumor of the pancreas: possible association
• Polysplenia syndrome (the presence of two or more spleens associated to various chest or abdominal congenital abnormalities)
• Pancreatitis
• Intestinal malrotation

In addition, agenesis of the dorsal pancreas associated with other organ malformations has also been reported, including polycystic kidney disease, Kartagener syndrome, multiple splenic deformities, congenital choledochal cysts and biliary atresia ³⁰, ³¹.

Approximately half of these patients need insulin therapy. A young woman with agenesis of the dorsal pancreas was reported to have asymptomatic insulin-dependent diabetes mellitus and already had severe retinal lesions at the time of presentation ³⁷. Other studies reported agenesis of the dorsal pancreas combined with ampullary tumors, and the pathological types included cystic adenocarcinoma, solid pseudopapillary tumors, intraductal papillary mucinous neoplasms, pancreatic neuroendocrine tumors (PNETs) and cholangiocarcinoma ³⁸, ³⁹. Some patients with pancreatic pseudocysts were also found ⁴⁰.The surgical treatment of these types of patients is no different from that for patients with normal pancreatic development, but after pancreatic head resection, due to the lack of the tail of the pancreas, postoperative pancreatic exocrine insufficiency and exogenous insulin dependence will be needed. The association between tumorigenesis and agenesis of the dorsal pancreas is unclear, but chronic pancreatitis caused by the latter is indeed one of the risk factors for cancer ¹.

Pancreatic agenesis prognosis

Pancreatic agenesis prognosis is variable and it depends on the quality of treatment received and its associated with other malformations.

Nicolino et al. ⁴¹ reported a boy and girl, first cousins born of consanguineous parents, who had permanent neonatal diabetes treated by insulin pump with excellent linear growth thereafter: both patients’ weight, length, and bone age were within normal ranges at 4 years of age. Although there were no clinical signs of exocrine pancreas deficiency, biochemical investigation revealed low or undetectable serum lipase levels, and stool examination showed slightly increased fecal fat excretion, low chymotrypsin, and low elastase levels. In addition, IGF1 levels were very low, and vitamins A, D, E, and K levels were at the lower limits of normal, consistent with some degree of malabsorption ⁴¹. Abdominal ultrasound revealed a normal-sized pancreas in the boy, whereas the girl had a well-individualized and homogeneous head of the pancreas, but the body and tail of the pancreas could not be identified ⁴¹.

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