Surgeons were in the past reluctant to embark upon pancreatic resection because of technical difficulties and frequent post-operative complications. This has changed in recent decades, and pancreatic surgery is now more frequently and successfully undertaken on an elective basis. Surgery is most commonly undertaken for pancreatic carcinoma, for relief of pain in chronic pancreatitis, and in the course of treatment for acute necrotizing pancreatitis. Procedures range from subtotal pancreatectomy for relief of pain in chronic pancreatitis, removal of the head of the pancreas for carcinoma in the course of Whipple's procedure, and distal pancreatectomy for a variety of indications. Diabetes is a frequent complication, and usually requires treatment with insulin following subtotal pancreatectomy. Insulin requirements tend to be low because of lack of pancreatic glucagon, and the prognosis tracks with that of the underlying condition.
The pancreas is dangerous territory for the surgeon because of the high risk that pancreatic juices loaded with digestive enzymes will leak into and digest the surrounding tissues, with consequences such as formation of a pancreatic fistula to the surface of the abdomen, or of a pancreatic pseudocyst in the posterior abdomen.
Pancreatic carcinoma was for many decades the only indication considered to justify the risk of surgery, and the first pancreatic resection for carcinoma was undertaken in 1898; the patient died of tumour recurrence 7 months later.
Allen Whipple, an American surgeon, refined the operation for cancer of the head of the pancreas into something closely resembling its modern form in 1935, but the results of surgery remained dire, to the point at which the procedure lost favour in the 1960s and 1970s.
Subsequent experience showed that the perioperative mortality dropped from around 25% to under 5% when the procedure was undertaken by experienced surgical teams at specialized centres .
The operation removes the distal stomach, gall bladder, first two parts of the duodenum and head of the pancreas. Diabetes develops in 20-50% of patients.
Total pancreatectomy is less frequently undertaken because the outcome of surgery is no better and the extensive surgery required (which entails removal of the spleen) results in total loss of endogenous insulin production and digestive function.
Chronic and sometimes intractable pain is a common feature of chronic pancreatitis, affecting up to 85% of its victims. Attempts to relieve this symptom by surgery began in the 1950s; distal pancreatectomy (40-80% removal of the pancreas) was attempted but brought little symptomatic relief.
Distal subtotal pancreatectomies (80-95%) were more effective in pain relief, but the proportion with post-operative diabetes increased from 32% to 72%, and the number of patients requiring insulin for its management rose sharply. Whipple's procedure has been increasingly used for pain relief as its prognosis improved.
Surgery to the exocrine pancreas may be undertaken as an emergency procedure in acute necrotizing pancreatitis, a condition in which necrotic material is sloughed and easily becomes infected; the main aim of the surgeon is to limit the damage after a pancreas has largely destroyed itself. Diabetes is common after necrotizing pancreatitis.
Diabetes as a Complication of Surgery
Paradoxically, diabetes may improve following successful resection of a pancreatic carcinoma with preservation of the tail of the pancreas, since some tumours are known to precipitate new diabetes or aggravate pre-existing diabetes, most probably by increasing insulin resistance, as described in the entry on Pancreatic carcinoma.
This apart, the likelihood of post-operative diabetes will reflect the prior predisposition of the patient (age, obesity, family history of diabetes) together with the extent of pancreatic resection.
Insulin may or may not be required, but is usually needed following >80% pancreatic resection. Insulin requirements are often low because of loss of pancreatic glucagon, but hypoglycaemia avoidance may sometimes be difficult owing to the combination of counter-regulatory failure with erratic food absorption.