Acute Pancreatitis

Pathogenesis

Traditionally, AP was thought to be the result of organ autodigestion as a final common pathway of a variety of insults. More recently, other hypotheses, such as increased endoplasmic reticulum stress and the unfolded protein response, have been proposed. Inflammation can be localized to the pancreas or, in severe cases, can result in systemic inflammatory response leading to acute respiratory distress syndrome (ARDS), vascular leakage, renal dysfunction, hypovolemia, and shock. ^{, ,}

Clinical Manifestations

Abdominal pain is the predominant symptom occurring in about 80%–90% of cases. ^, Continuous, dull pain typically occurs in the epigastric area. Pain begins abruptly, increases in severity, and peaks within a few hours. Nausea and vomiting occur in about 70% of pediatric patients. Referred pain and radiation to the back are thought to be less common in children compared with adults. The child’s position of comfort usually is with the knees flexed on the abdomen.

Compared with older children with pancreatitis, infants and toddlers can have significantly fewer signs and symptoms of abdominal pain, epigastric tenderness, or nausea, and irritability can be predominant. Epigastric or midabdominal tenderness with guarding often is found on physical examination. Bowel sounds disappear as ileus develops. An abdominal mass can develop as a manifestation of a pancreatic pseudocyst. Rigid abdomen and periumbilical discoloration suggesting intra-abdominal hemorrhage are rare and represent signs of severe pancreatitis. ^,

Diagnosis

Evidence-based consensus guidelines have been published for the diagnosis and management of acute pancreatitis in children. A diagnosis of AP requires findings in 2 of 3 areas: clinical presentation, biochemical analysis, and radiographic evaluation ( Box 62.1 ). There is no single, definitive test that reliably captures or excludes AP.

Serum lipase is likely the most consistent and reliable serum biomarker with a sensitivity of 87%–95%. Serum lipase levels peak at 24–30 hours and can remain elevated for more than 1 week, making them helpful for late diagnoses. False-positive results can occur in a number of conditions, including decompensated liver failure, renal failure, intestinal inflammation, abdominal trauma, diabetic ketoacidosis, and head trauma. ^, Serum amylase is less reliable unless measured within 24 hours of onset, and sp e cificity and positive predictive value of an elevated serum amylase level are low. Some studies cite the combination of elevated serum amylase and lipase having a specificity of 90%–95%. Persistence of elevated amylase levels beyond 48 hours after the onset of symptoms raises the possibility of a pancreatic pseudocyst.

Abdominal ultrasonography is the most commonly used modality of evaluation in children, likely due to its ability to identify obstructive disease and a desire to avoid radiation exposure. Although not recommended in all cases, ultrasonography can be especially helpful to exclude surgically treatable causes of pancreatitis such as gallstones and extrapancreatic masses. A plain film of the abdomen is useful to exclude other causes of abdominal pain. Pancreatic calcification can occur in patients with acute recurrent or chronic pancreatitis.

Intravenous contrast-enhanced abdominal CT is useful for the diagnosis of significant abdominal trauma, necrotizing pancreatitis, and pseudocyst. Endoscopic retrograde cholangiopancreatography (ERCP) or magnetic resonance cholangiopancreatography (MRCP) are not routinely needed and typically are reserved for selected cases when therapeutic intervention is needed.

Differential Diagnosis

The differential diagnosis of acute pancreatitis is broad and varies with age and severity of disease. The most commonly identified causes of AP are trauma and systemic disease; a comprehensive history highlighting potential causes should be elicited in all cases ( Boxes 62.2 and 62.3 ). In its mild forms, pancreatitis can mimic acute gastroenteritis, and mild acute pancreatitis can occur during acute viral gastroenteritis. Biliary tract disease (e.g., cholelithiasis, choledocholithiasis, choledochal cyst), peptic ulcer disease (i.e., penetrating or perforated peptic ulcer), intestinal obstruction, and factitious pancreatitis should be excluded. Renal failure and diabetic ketoacidosis can be responsible for falsely elevated serum amylase levels and should be excluded.