Pancreas

Structure and Function

Structure

It's a 15cm long exocrine and endocrine gland. It's an elongated structure that lies in the epigastrium and left upper quadrant. It is soft and lobulated and is retroperitoneal. It crosses the transpyloric plane.

The pancreas is divided into a head, neck, body and tail. Part of the head extends to the left behind the superior mesenteric vessels and is called the uncinate process, whilst the tail passes into the splenicorenal ligament and comes in contant with the hilum of the spleen.

Functions

Exocrine

Produces enzymes capable of digesting fats, lipids and proteins:

• Trypsinogen – type of zymogen granule
• Pancreatic amylase
• Pancreatic lipase.

It also has ductal cells which secrete bicarbonate ions. Secretions are controlled by Cholescystokinin (CCK), secretin and gastrin. The more of those hormones there are about the more the pancreatic secretions are.

Endocrine

Produces hormones in the islets of langerhans, in three different cells:

• Alpha – secret glucagons; which performs glycogen -> glucose
• Beta – secrete insulin; glucose -> glycogen
• Delta - secrete somatostatins; it's the "party pooper" of all hormones, cos it reduces glucagons, insulin and growth hormone.
• PP Cells – secrete pancreatic polypeptide.
• Enterochromaffin – produce serotin.

Arterial and Venous supply

The splenic artery supplies the tail of the pancreas through a few random branches.

The superior and inferior pancreaticoduodenal arteries supply the head and body and it all drains back into the portal, via the pancreaticoduodenal veins. This is cool, when you realise that that means hormones, like insulin, get sent straight to the liver.

Nervous Supply

Sympathetic and parasympathetic (vagal) nerves supply the gland, and eventually drain into the celiac and superior mesenteric nodes.

Lymph

Nodes are situated along the arteries that supply the gland. The efferent vessels ultimately drain into the celiac and superior mesenteric lymph nodes.

Histology

Exocrine

It is divided roughly into lobules, each of which is a roughly spherical cluster (acini) of secretory cells. Each acinus has an individual intra-acinar duct which drains into progressively larger ducts, which eventually join into the pancreatic duct and drain into the duodenum.

Endocrine

Round, separate clusters of cells scattered through the pancreatic tissue, called Islets of Langerhans. They are imbedded in the exocrine bit, and are most common in the tail. Each islet has a capillary network which is in contact with each cell. There are 5 main types of cell, alpha (20%), beta (70%), delta (8%) PP cells (1-2%) and enterochromaffin (1%)

Clinical Conditions

Diagnosis is difficult with the pancreas because it is very deep and hidden behind the stomach/colon – so disease of the pancreas can be confused with these again. Pain from the pancreas is also often referred to the back which can make diagnosis easier to miss.

Pancreatitis

Acute Pancreatitis

About: 75% of cases are mild, but 25% can lead to haemodynamic instability and multiple organ failure – not a good thing, with its lovely 80% mortality. There is no great test to predict which it will be, but age>55 and various serum levels can sometimes predict it. Nnumonic for causes:

Gallstones Ethanol Trauma

Steroids Mumps Autoimmune Scorpion venom Hyperlipidaemias ERCP Drugs

Symptoms: Pain, nausea, diarrhoea and vomiting. Can vary from abdominal tenderness but no other abnormalities, to tachycardia and hypotension. The best sign to look for is Cullun's sign (grey discoloration round the umbilicus) and Grey Turner's sign (flank bruising).

Investigations:

• Serum Amylase level. If done 24hours after pain presents, there will be an elevation to three time the normal upper limit. However, after 3-5 days the level goes back to normal, so late presentation may lead to a false negative in this test. Others tests like urinary amylase, serum lipase will be done too. You get the idea.
• Chest Xray is mandatory to rule out gastroduodenal perforation. Spiral CT scanning is vital in nearly all cases, to find out level of pancreatic necrosis, and future prognosis.

Treatment: Basically not much. Replace fluids, help them if vomiting occurs, grin and bear it until they recover or die.

Chronic Pancreatitis

Cystic Fibrosis is a common cause in children. In adults well over 70% of cases are caused by alcohol. Cancer obstructing the bile ducts can also cause it. Chronic pancreatitis is basically just repeated attacks of acute. Always be aware that the symptoms could be pancreatic carcinoma, and that chronic pancreatitis is a recognised potential precancerous condition.

Pancreatic Carcinoma

Important sign here – if someone comes in with sudden asymptomatic jaundice, with no discernable cause, and a palpable gall bladder – then you assume pancreatic carcinoma until proven otherwise.

Fifth most common type of cancer. 2% 5 year survival. Smoking brings a two fold increase. Two types: lesions of the head and lesions of the body and tail

Carcinoma at the head of the pancreas: Presents earlier, with obstruction to the bile duct, giving jaundice.

Carcinoma at the tail of the pancreas: Presents with abdominal pain that radiates to the back, and non specific symptoms such as weight loss and anorexia.

Treatment: Surgery is the only hope for survival. Whipple's procedure removing the lower part of the duodenum is often performed.