Managing severe acute pancreatitis
ABSTRACTSevere acute pancreatitis causes high rates of illness and death. Simple scoring predictors can help identify patients at risk so that treatment, primarily supportive, can begin promptly after presentation. Medical therapy is the mainstay, with supportive therapy consisting of controlled volume resuscitation and enteral feeding. Minimally invasive drainage and debridement play a role in managing infective pancreatic necrosis but in general should not be used until at least 4 weeks after the acute illness.
KEY POINTS
- Routine early computed tomography to evaluate patients with severe acute pancreatitis wastes time and is necessary only if the diagnosis at presentation is not clearly consistent with acute pancreatitis.
- Optimum fluid resuscitation is now recommended, using lactated Ringer’s solution at a rate of 5 to 10 mL/kg per hour, with 2,500 to 4,000 mL given in the first 24 hours.
- Enteral feeding with either an elemental diet or a polymeric enteral formulation is first-line nutritional therapy.
- Antibiotics are no longer routinely used to prevent infection.
- Relief of abdominal compartment syndrome should be attempted by multiple means before resorting to open abdominal decompression.
IDENTIFYING INFECTION
Fine-needle aspiration if clinical and imaging signs are not clear
Untreated infected pancreatitis is associated with a much higher risk of death than sterile pancreatic necrosis. Unfortunately, it can be difficult to determine if a patient with necrotizing pancreatitis has an infection because fever, tachycardia, and leukocytosis are usually present regardless. It is important to determine because mechanically intervening for sterile necrosis does not improve outcome.
Fine-needle aspiration, either guided by CT or done at the bedside with ultrasonography, with evaluation with Gram stain and culture, was widely used in the 1990s in cases of necrotizing pancreatitis to determine if infection was present. There has been a shift away from this because, although it can confirm the presence of infection, the false-negative rate is 15%. Clinical and imaging signs can be relied on in most cases to determine the presence of infection, and it is now recognized that fineneedle aspiration should be used only for select cases. Clinical studies have not shown that fine-needle aspiration improves outcomes.
Clinical scenarios typical of infected pancreatic necrosis include patients who have obvious signs of infection with no identifiable source, such as those who stabilize after acute severe acute pancreatitis, and then 10 to 14 days later become worse, with a dramatically higher white blood cell count and tachycardia. Such a patient likely needs an intervention regardless of the results of fine-needle aspiration.
On the other hand, a patient with a continually up-and-down course that never stabilizes over 3 weeks, with no identifiable source of infection, and with no peripancreatic gas apparent on imaging would be a good candidate for fine-needle aspiration.
If peripancreatic gas is seen on imaging, fine-needle aspiration is unnecessary. Peripancreatic gas is traditionally attributed to gasforming bacteria within the pancreas, but in my experience, it is usually from a fistula from the necrosis to the duodenum or the colon, the fistula being caused as the necrosis erodes at the hepatic flexure, the transverse colon, or the splenic flexure.
MECHANICAL INTERVENTIONS FOR INFECTIVE NECROSIS
Late, minimally invasive procedures preferred
Conventional management has shifted away from removing the necrosis with early surgical debridement of the pancreas. Experience with myocardial infarction shows that it is not necessary to remove a sterile necrotic organ, and studies with sterile pancreatic necrosis have found that surgical intervention is associated with a higher risk of death than medical management.
Documented infection has traditionally been considered a definite indication for debridement, but even that is being called into question as more studies are emerging of infected necrosis treated successfully with antibiotics alone.
Sterile necrosis with a fulminant course is a controversial indication for surgery. It was traditionally felt that surgery was worth trying for such patients, but this is no longer common practice.
For cases in which debridement was deemed advisable, surgery was done more frequently in the past. Now, a minimally invasive approach such as with endoscopy or percutaneous catheter is also used. Waiting until at least 4 weeks after the onset of acute pancreatitis is associated with a better outcome than intervening early.
WALLED-OFF NECROSIS
Watchful waiting or minimally invasive intervention
Patients who survive multiorgan failure but are still ill more than 4 weeks after the onset of pancreatitis should be suspected of having walled-off necrosis, formerly referred to as a pancreatic phlegmon. This term was abandoned after the 1992 Atlanta symposium.13 In the mid to late 1990s, the process was referred to as organized pancreatic necrosis. It is characterized by a mature, encapsulated collection of pancreatic or peripancreatic necrosis that contains variable amounts of amylase-rich fluid from pancreatic duct disruption.
Walled-off pancreatic necrosis (WOPN) is often confused with pancreatic pseudocyst; these may appear similar on CT, and higherdensity solid debris may be visible in walled-off necrosis within an otherwise homogenous-appearing collection. Magnetic resonance imaging defines liquid and solid much better than CT.
The best way to distinguish WOPN from pseudocyst is by clinical history: a patient with a preceding history of clinically severe acute pancreatitis almost always has necrotizing pancreatitis that evolves to walled-off necrosis, usually over 3 to 4 weeks.
Endoscopic removal and other minimally invasive approaches, such as aggressive percutaneous interventions, have replaced open necrosectomy for treatment, which was associated with high morbidity and mortality rates.14–16
Intervening for sterile walled-off necrosis is still a controversial topic: although systemically ill, the patient is no longer having life-threatening consequences, and watchful waiting might be just as expedient as intervention. Evidence to support either view is lacking. Most experts believe that intervention should be done if the patient has gastric outlet obstruction and intractable pain and is unable to eat 4 to 6 weeks after the onset of pancreatitis with WOPN. Infected WOPN is considered an indication for drainage.
