Fishtail pancreas (also known as pancreas bifidum or bifid tail of the pancreas) is a rare anatomical variant of the pancreas produced by a branching anomaly during its development. It is named as such due to the fishtail-like appearance of the pancreas.

Epidemiology

It is a rare anatomical anomaly with only a small number of cases reported, its exact prevalence is unknown in the general population ¹. In one study of patients with duplication variants of the pancreatic ductal system on ERCP, patients with fishtail pancreas represented less than 1% of these anomalies ². 

Clinical presentation

Fishtail pancreas is usually an asymptomatic anomaly detected incidentally on imaging performed for other indications ¹.

Pathology

Fishtail pancreas is thought to be caused by the failure of part of the ventral pancreatic anlage to regress. The ventral pancreatic anlage develops into the majority of the pancreatic gland ². During pancreatic development, the ventral anlage initially has two lobes with two primitive ducts ³. One lobe tends to dominate and persists to become the head of the pancreas, while the other regresses and becomes the uncinate process of the pancreas. Fishtail pancreas is caused by failure of one of these lobes to regress producing duplication of the main pancreatic duct creating a dorsal and ventral tail ¹.

Radiographic features

MRCP

Fishtail pancreas may be visible as a duplication of the major duct in the body of the pancreas and the presence of two pancreatic tails ⁴.

ERCP

Like MRCP, on ERCP it also shows duplication of the major pancreatic duct ⁴.

Treatment and prognosis

No treatment is necessary for fishtail pancreas ⁵. In patients with fishtail pancreas pancreatitis has been reported to occur in a single tail as opposed to both ⁶. Due to the rarity of this variant it is unclear if patients with fishtail pancreas are at higher risk of acute pancreatitis or other pancreatic disease ¹.