The cause of pancreatic pseudocyst can occur due to a variety of reasons, among them pancreatitis (chronic), pancreatic neoplasm and/or pancreatic trauma.

Pancreatic pseudocysts are sometimes called false cysts because they do not have an epithelial lining.The wall of the pseudocyst is vascular and fibrotic, encapsulated in the area around the pancreas. Pancreatitis or abdominal trauma can cause its formation. Treatment usually depends on the mechanism that brought about the pseudocyst. Pseudocysts take up to 6 weeks to completely form.

First described by Smith (1953), and elaborated upon by Cameron et al. (1976), internal pancreatic fistulas can result in pancreatic ascites, mediastinital pseudocysts, enzymatic mediastinitis, or pancreatic pleural effusions, depending on the flow of pancreatic secretions from a disrupted pancreatic duct or leakage from a pseudocyst.

An external pancreatic fistula is an abnormal communication between the pancreas (actually pancreatic duct) and the exterior of the body via the abdominal wall.

Loss of bicarbonate-rich pancreatic fluid via a pancreatic fistula can result in a hyperchloraemic or normal anion gap metabolic acidosis. Loss of a small volume of fluid will not cause a problem but an acidosis is common if the volume of pancreatic fluid lost from the body is large.

Hemosuccus pancreaticus, also known as pseudohematobilia or Wirsungorrhage, is a rare cause of hemorrhage in the gastrointestinal tract. It is caused by a bleeding source in the pancreas, pancreatic duct, or structures adjacent to the pancreas, such as the splenic artery, that bleed into the pancreatic duct. Patients with hemosuccus may develop symptoms of gastrointestinal hemorrhage, such as blood in the stools, maroon stools, or melena. They may also develop abdominal pain. Hemosuccus pancreaticus is associated with pancreatitis, pancreatic cancer and aneurysms of the splenic artery. Angiography may be used to diagnose hemosuccus pancreaticus, where the celiac axis is injected to determine the blood vessel that is bleeding. Concomitant embolization of the end vessel may terminate the hemorrhage. Alternatively, a distal pancreatectomy may be required to stop the hemorrhage.

Cystic fibrosis, is a hereditary disease that affects the entire body, causing progressive disability and early death. It is caused by a mutation in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. The product of this gene helps create sweat, digestive juices, and mucus. The name "cystic fibrosis" refers to the characteristic 'fibrosis' (tissue scarring) and cyst formation within the pancreas, causing irreversible damage, and often resulting in painful inflammation (pancreatitis).

Hemosuccus pancreaticus, also known as pseudohematobilia or Wirsungorrhage is a rare cause of hemorrhage in the gastrointestinal tract. It is caused by a bleeding source in the pancreas, pancreatic duct, or structures adjacent to the pancreas, such as the splenic artery, that bleed into the pancreatic duct, which is connected with the bowel at the duodenum, the first part of the small intestine. Patients with hemosuccus may develop symptoms of gastrointestinal hemorrhage, such as blood in the stools, maroon stools, or melena, which is a dark, tarry stool caused by digestion of red blood cells. They may also develop abdominal pain. It is associated with pancreatitis, pancreatic cancer and aneurysms of the splenic artery. Hemosuccus may be identified with endoscopy (esophagogastroduodenoscopy), where fresh blood may be seen from the pancreatic duct. Alternatively, angiography may be used to inject the celiac axis to determine the blood vessel that is bleeding. This may also be used to treat hemosuccus, as embolization of the end vessel may terminate the hemorrhage. However, a distal pancreatectomy—surgery to removal of the tail of the pancreas—may be required to stop the hemorrhage.

Locoregional complications include pancreatic pseudocyst (Most common, occurring in up to 25% of all cases) and phlegmon / abscess formation, splenic artery pseudoaneurysms, hemorrhage from erosions into splenic artery and vein, thrombosis of the splenic vein, superior mesenteric vein and portal veins (in descending order of frequency), duodenal obstruction, common bile duct obstruction, progression to chronic pancreatitis, pancreatic ascites, pleural effusion, sterile/infected pancreatic necrosis.

Hemosuccus pancreaticus is a rare entity, and estimates of its rate are based on small case series. It is the least frequent cause of upper gastrointestinal bleeding (1/1500) and is most often caused by chronic pancreatitis, pancreatic pseudocysts, or pancreatic tumors. As a result, the diagnosis may easily be overlooked. The usual presentation of hemosuccus is the development of symptoms of upper or lower gastrointestinal bleeding, such as melena (or dark, black tarry stools), maroon stools, or hematochezia, which is frank rectal bleeding. The source of hemorrhage is usually not determined by standard endoscopic techniques, and the symptoms of the condition are usually grouped as a cause of obscure overt gastrointestinal hemorrhage. Over one-half of patients with hemosuccus also develop abdominal pain, usually located in the epigastrium, or uppermost part of the abdomen. The pain is described as being "crescendo-decrescendo" in nature, meaning that it increases and decreases in intensity slowly with time. This is thought to be due to transient blockage of the pancreatic duct from the source of bleeding, or from clots. If the source of the bleeding also involves obstruction of the common bile duct (such as with some tumours of the head of the pancreas), the patient may develop jaundice, or "silver stools", an uncommon finding of acholic stools mixed with blood.

In the United States, the annual incidence is 18 cases of acute pancreatitis per 100,000 population, and it accounts for 220,000 hospitalizations in the US. In a European cross-sectional study, incidence of acute pancreatitis increased from 12.4 to 15.9 per 100,000 annually from 1985 to 1995; however, mortality remained stable as a result of better outcomes. Another study showed a lower incidence of 9.8 per 100,000 but a similar worsening trend (increasing from 4.9 in 1963-74) over time.

In Western countries, the most common cause is alcohol, accounting for 65 percent of acute pancreatitis cases in the US, 20 percent of cases in Sweden, and 5 percent of those in the United Kingdom. In Eastern countries, gallstones are the most common cause of acute pancreatitis. The causes of acute pancreatitis also varies across age groups, with trauma and systemic disease (such as infection) being more common in children. Mumps is a more common cause in adolescents and young adults than in other age groups.

Although there can be various causes of dog pancreatitis, such as drugs, fatty diet, trauma, etc., the pathophysiology is very complex. Pancreatitis can be idiopathic; no real causation factor can be found. Obese animals as well as animals fed a diet high in fat may be more prone to developing acute and chronic pancreatitis. Certain breeds of dogs are considered predisposed to developing pancreatitis including miniature schnauzers, Cocker Spaniels, and some terrier breeds. Miniature Schnauzers as a breed tend toward developing hyperlipidemia, an excess of circulating fats in the blood. The breed which appears to be at risk for the acute form of pancreatitis is the Yorkshire Terrier, while Labrador Retrievers and miniature Poodles seem to have a decreased risk for the acute form of the disease. It is suggested that genetics may play a part in the risk factor. Dogs suffering from diabetes mellitus, Cushing's disease (hyperadrenocorticism), hypothyroidism and epilepsy are at increased risk for pancreatitis. Diabetes and hypothyroidism are also associated with hyperlipidemia. Those with other types of gastrointestinal conditions and dogs who have had previous pancreatitis attacks are also at increased risk for the disorder.

There are seven classes of medications associated with acute pancreatitis: statins, ACE inhibitors, oral contraceptives/hormone replacement therapy (HRT), diuretics, antiretroviral therapy, valproic acid, and oral hypoglycemic agents. Mechanisms of these drugs causing panreatitis are not known exactly; but it is possible that statins has direct toxic effect on the pancreas or through the long term accumulation of toxic metabolites. Meanwhile, ACE inhibitors causes angioedema of the pancreas through the accumulation of bradykinin. Oral contraceptives/HRT causes arterial thrombosis of the pancreas through the accumulation of fat (hypertriglyceridemia). Diuretics such as furosemide has direct toxic effect on the pancreas. Meanwhile, thiazide diuretics causes hypertriglyceridemia and hypercalcemia, where the latter is the risk factor for pancreatic stones. HIV infection itself can cause a person to more likely to get pancreatitis. Meanwhile, antiretroviral drugs may cause metabolic disturbances such as hyperglycemia and hypercholesterolemia, which predisposes to pancreatitis. Valproic acid may have direct toxic effect on the pancreas. There are various oral hypoglycemic agents that contributes to pancreatitis including metformin. But, glucagon-like peptide-1 (GLP-1) is more strongly associated with pancreatits by promoting inflammation.

Atypical antipsychotics such as clozapine, risperidone, and olanzapine can also cause pancreatitis.

In adults in the United Kingdom, the estimated average total direct and indirect costs of chronic pancreatitis is roughly £79,000 per person on an annual basis. Acute recurrent pancreatitis and chronic pancreatitis occur infrequently in children, but are associated with high healthcare costs due to substantial disease burden. Globally, the estimated average total cost of treatment for children with these conditions is approximately $40,500 annually.

In some cases, abscesses may be prevented by draining an existing pseudocyst which is likely to become inflamed. However, in most cases the developing of abscesses cannot be prevented.

The outlook is generally based on the severity of the infection. It is however a severe complication which may result in the death of the patient if the appropriate treatment is not administered. Patients are at risk of sepsis and multiple organ failure and in cases in which the infected abscess is not removed through surgery, the mortality rate can reach 100%.

A pancreatic cyst is a fluid filled sac within the pancreas.

Causes range from benign to malignant. Pancreatic pseudocysts can occur in the setting of pancreatitis, though they are only reliably diagnosed 6 weeks after the episode of acute pancreatitis.

Benign tumors such as serous cystadenomas can occur. Main branch intraductal papillary mucinous neoplasms (IPMNs) are associated with dilatation of the main pancreatic duct, while side branch IPMNs are typically benign, and not associated with dilatation. MRCP can help distinguish the position of the cysts relative to the pancreatic duct, and direct appropriate treatment and follow-up. The most common malignancy that can present as a pancreatic cyst is a mucinous cystic neoplasm.

Annular pancreas is a rare condition in which the second part of the duodenum is surrounded by a ring of pancreatic tissue continuous with the head of the pancreas. 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.

Pancreas or Pancreatic divisum is a congenital anomaly in the anatomy of the ducts of the pancreas in which a single pancreatic duct is not formed, but rather remains as two distinct dorsal and ventral ducts.

Pancreaticobiliary maljunction is a congenital malformation, in which the pancreatic and bile ducts join anatomically outside the duodenal wall, forming a markedly long common channel. This anomaly prevents normal control by the sphincter of Oddi located in the duodenal wall, allowing regurgitation of pancreatic juices into the biliary tract and possibly leading to a higher probability of pancreaticobiliary cancers.

Meckel's diverticulum occurs in about 2% of the population. Prevalence in males is 3–5 times higher than in females. Only 2% of cases are symptomatic, which usually presents among children at the age of 2.

Most cases of Meckel's diverticulum are diagnosed when complications manifest or incidentally in unrelated conditions such as laparotomy, laparoscopy or contrast study of the small intestine. Classic presentation in adults includes intestinal obstruction and inflammation of the diverticulum (diverticulitis). Painless rectal bleeding most commonly occurs in toddlers.

Inflammation in the ileal diverticulum has symptoms that mimic appendicitis, therefore its diagnosis is of clinical importance. Detailed knowledge of the pathophysiological properties is essential in dealing with the life-threatening complications of Meckel's diverticulum.

Early signs of abnormality include polyhydramnios (an excess of amniotic fluid), low birth weight, and feeding intolerance immediately after birth.

The lifetime risk for a person with Meckel's diverticulum to develop certain complications is about 4–6%. Gastrointestinal bleeding, peritonitis or intestinal obstruction may occur in 15–30% of symptomatic patients (Table 1). Only 6.4% of all complications requires surgical treatment; and untreated Meckel's diverticulum has a mortality rate of 2.5–15%.

Table 1 – Complications of Meckel's Diverticulum:

Papillary stenosis is a disturbance of the sphincter of Oddi, a muscular valve, that prevents the opening and release of bile or pancreatic fluids into the duodenum in response to food entering the duodenum.

Obstruction of the valve can cause:

- pancreatic pain

- jaundice - bile leaking back into the blood stream.

- attacks of pancreatitis

There are no approved treatments for canine pancreatitis. Treatment for this disease is supportive, and may require hospitialization to attend to the dog's nutritional and fluid needs, pain management, and addressing any other disease processes (infection, diabetes, etc.) while letting the pancreas heal on its own. Treatment often involves "resting" the pancreas for a short period of time by nil per os/nothing per os (NPO)/nil by mouth (NBM), in which the patient receives no food or fluids by mouth, but is fed and hydrated by intravenous fluids and a feeding tube. Dehydration is also managed by the use of fluid therapy. However, a specialist from Texas A&M University has stated "There is no evidence whatsoever that withholding food has any beneficial effect." Other specialists have agreed with his opinion.

Canine pancreatitis is complex, often limiting the ability to approach the disease.

Treatment of accessory pancreas depends on the location and extent of the injured tissue. Surgery may be an option, or some physicians order prophylactic antibiotics.