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Acute Pancreatitis

Indications for surgery in acute pancreatitis

Pancreatic Necrosis

In 90% of cases, acute pancreatitis is a mild self limiting disease in which the patient recovers within a week.  In those cases where the cause of the pancreatitis was gallstone disease, the patients usually benefit from having their gallbladder removed  (cholecystectomy) when the pancreatitis is resolved.  In 10% of cases, severe pancreatitis, often associated with death of pancreatic tissue occurs.  Patients should undergo an abdominal computerized tomographic (CAT) scan to confirm the diagnosis, to determine the presence of local complications, and to estimate the adequacy of the blood supply of the pancreatic tissue. The latter is important because the likelihood of pancreatic infection is greater with greater degrees of pancreatic necrosis, and infection is often an indication for surgery.

Patients with infection of necrotic pancreas or peripancreatic tissue often benefit from debridement and drainage of the infected and devitalized tissue. This may require an operation. Viable pancreas is not removed. The systemic organ failure that ultimately is responsible for the demise of such patients, in part, is caused by this infected tissue. Removal of this material provides the best chance for recovery.

There remains a group of critically ill patients with severe acute pancreatitis, usually with significant pancreatic and/or peripancreatic necrosis, in whom infection is not present. The role of surgery in these patients with so-called sterile necrosis continues to be controversial. In general, evidence is accumulating that this group is managed effectively by non-surgical means in the majority of cases. If surgery is performed, it is done in an attempt to drain and debride the necrotic tissue that is that is thought to be the source of various noxious substances believed to be responsible for the ongoing illness. Or it may even be that infection was present, but that its diagnosis was overlooked.

Diagnosis of infected pancreatic necrosis

The diagnosis of pancreatic infection is made most reliably by CT or ultrasound-guided fine needle aspiration (FNA) with Gram staining and culture of the aspirate. The material should be sent for bacterial and fungal culture. The technique is safe, accurate, and can be performed rapidly. Although it is tempting to only perform FNA in patients who exhibit a septic clinical picture (e.g., high fever, WBC), some patients with infection have a low grade fever and a WBC <15,000. Thus, in most patients FNA should be performed in those who have evidence of necrosis and fluid collection on the CT scan.

In a minority of patients, gas bubbles are evident on the CT study in the area of the pancreas. If this is found, FNA is unnecessary. Short of some other explanation for the gas, gas should be assumed to be the product of bacterial fermentation from infection. In either case, the presence of infected pancreatic necrosis is an undisputed indication for surgical intervention.

Some patients with necrotizing pancreatitis are treated prophylactically with a broad-spectrum antibiotic until therapy can be further refined by sensitivity testing of material obtained by FNA or at operation. However, in patients with proved infection, antibiotic therapy is adjunctive treatment only. Proof of infection is an indication for drainage and debridement of the infected and necrotic material, and this may require surgery.

Except in the unusual situation of fulminating acute pancreatitis with organ failure and a rapidly progressive downhill course soon after admission to the hospital, most patients should not undergo operation during the first week of their illness. Moreover most patients do not harbor infected pancreatic necrosis during this time. When clinical deterioration is rapid and surgery is undertaken during the first week, these patients have a high mortality rate. The outcome is better when surgery is postponed at least until the second week or later, when the margins of the pancreatic necrosis have become better defined, and the acute inflammation has subsided somewhat. Fortunately, in most cases the disease has been ongoing for a week or more by the time the diagnosis of infected pancreatic necrosis has been established and the need for drainage is evident.

When surgery is required, the goals are to remove infected and devitalized pancreatic and peripancreatic tissue, to drain pus and other fluid collections, and to leave drains behind which can be used for continuous postoperative lavage of the affected areas. The CT scan provides a map to those areas which require drainage, so that uninvolved tissue planes do not need to be opened and unnecessarily contaminated. During operation viable pancreatic parenchyma should be preserved. Hemostasis may require suture ligation of bleeding vessels, but significant bleeding usually suggests that the surgeon should limit further dissection in that area. Once most of the necrotic material has been removed and the fluid collections drained, several large sump drains are placed in the most involved areas for postoperative lavage. Patients with extended areas of infected necrotic tissue, or large multiloculated or multiple abscesses may be treated better by open drainage and packing. The operative procedure is the same, but the debrided areas are packed and the incision is left open.  Multiple operations may be needed. An abdominal CT scan obtained at intervals will help guide further therapy and document improvement during the postoperative course.

The most common local postoperative complications are hemorrhage and intestinal fistulas. Enterocutaneous fistulas (pancreatic, duodenal, small bowel, or colon) occur in up to 30% of patients. They can be caused directly by the necrotizing infection, by unavoidable trauma at the time of the debridement, or by erosion into the bowel of an adjacent surgical drain. Most of the bowel fistulas eventually close spontaneously without operative intervention.

The mortality rate for all patients with acute pancreatitis is about 10%. Necrotizing pancreatitis associated with infection has a mortality rate of about 20-25%, although there is some evidence that earlier diagnosis of infection and aggressive surgical intervention may lower this figure. 

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Pancreatic Abscess

A pancreatic abscess is a collection of pus within a defined cavity, and with little if any associated necrosis. It is different from infected pancreatic necrosis and an infected pancreatic pseudocyst. Pancreatic abscesses usually require 3 to 4 weeks to become apparent. Diagnosis should be suspected when the patient begins to run a septic course, and it can be confirmed with CT and percutaneous fine needle aspiration of the pus. An external drain should be left in place. Unlike infected pancreatic necrosis, non-surgical tube drainage is often effective treatment. However, unless the patient improves rapidly within 24-48 hours of external drainage, surgical drainage of the abscess is required. Antibiotics are adjunctive management only.

Pseudocyst

Pseudocysts are usually complications of acute or chronic pancreatitis or pancreatic trauma.  A pancreatic pseudocyst is a collection of fluid usually in the vicinity of the pancreas, which develops in association with a leak of pancreatic juices from the inflamed parenchyma or from a disrupted duct. The wall of the pseudocyst is comprised of fibrous non-epithelialized tissue. Occasionally a pseudocyst may present at great distance from the pancreas (e.g., thorax, groin), when the fluid dissects through tissue planes. As many as 30% of patients with acute pancreatitis form acute fluid collections around the time of the acute attack, but these must be distinguished from chronic pseudocysts. The majority of these acute "pseudocysts" resolve without intervention. Only about 5% of these patients develop chronic pseudocysts, which are characterized by their ovoid or spherical shape and well formed wall. Because of this natural history, acute "pseudocysts" (fluid collections) should be managed expectantly. If they develop into chronic pseudocysts, they may require treatment.

The management of pseudocysts varies according to their size and the presence of associated symptoms. Asymptomatic pseudocysts up to 5-6 cm in diameter may be safely observed, and are usually followed with either serial ultrasound or CT examinations. Larger cysts or pseudocysts of any size that are symptomatic require treatment.

Symptoms are most often from gastrointestinal obstruction when the cyst distorts the stomach or duodenum, or abdominal pain. Serious complications also can occur, although they are uncommon (<5% of cases). These include hemorrhage into the cyst, perforation of the cyst, and infection of the cyst.

Hemorrhage is usually caused by erosion of the splenic or gastroduodenal artery or other major vessel within the wall of the cyst, and the bleeding is usually confined to the cyst lumen. The diagnosis should be suspected if there are clinical signs of hypovolemia, and a falling hematocrit. There may be abdominal pain, and a mass may be palpable. An abdominal CT scan shows the cyst with the contained blood clot. Angiography confirms the diagnosis, and the radiologist should attempt to embolize the bleeding vessel. If not, emergency surgery with ligation of the vessel or excision of the cyst is required.

In the absence of a life-threatening complication, elective surgery of pseudocysts is usually delayed until the cyst has developed a mature wall that will hold sutures at the time of repair. For those cysts that develop following an episode of acute pancreatitis, this requires 4-6 weeks. In most cases the patient can eat and be discharged from the hospital during the interval. Pseudocysts that resolve spontaneously usually will do so during this time.

Pseudocysts may be treated surgically, or by endoscopic or radiologic drainage. Endoscopic methods require the placement of a plastic stent through the stomach or duodenal wall into the adjacent cyst. The stent is eventually removed, and in about 80% of cases, the cyst is permanently eradicated. These endoscopic techniques require expertise which is available at UCLA. Radiologic approaches usually consist of percutaneous external drainage of the cyst with eventual removal of the drainage catheter many weeks later. Many of these pseudocysts recur.

Surgical treatment usually consists of drainage of the cyst internally to either the stomach (cystgastrostomy) or to a Roux-en-Y limb of jejunum (cystjejunostomy). Both are safe and effective, with recurrence rates <10%. If the pseudocyst is in the tail of the pancreas, a distal pancreatectomy with excision of the cyst may be best. The recurrence rate is <1% in this case.

Some pseudocysts are also amenable to laparoscopic surgical drainage, and the patient may avoid the additional discomfort associated with an open operation.

Pancreatic fistula

Pancreatic fistula develops during pancreatitis as a result of a ductal disruption associated with pancreatic necrosis, or as a complication of operative debridement. Most fistulas will close spontaneously as long as ductal continuity can be re-established as healing occurs, infection is eradicated, and nutrition is adequate. Parenteral nutrition is usually not required. Somatostatin does not speed fistula closure, although if fistula output is higher than 200 -500 ml/day, the use of somatostatin may simplify the fluid and electrolyte management of the patient. Fistulas that persist for as long as 1 year, or those with pancreatic ductal obstruction or discontinuity will require operative repair by creating an anastomosis between the pancreatic duct at the point of the leak and a Roux-en-Y limb of jejunum. The success rate of operative repair is >90%.

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*Disclaimer
The condition information provided is not for self-diagnosis or self-treatment. Diagnostic testing and physician expertise are required for diagnosing your symptoms. Please check with your physician to determine what may be causing your symptoms and the treatment that is right for you.

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