Pancreatitis Complications & Pancreatic Cystic Lesions

Peripancreatic fluid collections

Revised Atlanta classification. Collections are named by pancreatitis type and age, split at 4 weeks. Interstitial edematous pancreatitis produces an acute peripancreatic fluid collection (APFC) that usually resolves; the few that persist beyond 4 weeks become encapsulated pseudocysts. Necrotizing pancreatitis produces an acute necrotic collection (ANC) that matures into walled-off necrosis (WON).

Observe, whatever the size. A pseudocyst is walled by fibrous or granulation tissue with no epithelial lining. Asymptomatic pseudocysts and WON are observed regardless of size or duration; the old "6 cm or 6 weeks" rule is obsolete. Drain a mature collection only if it causes:

• pain
• early satiety or gastric outlet obstruction
• biliary obstruction
• infection
• steady enlargement

How to drain. EUS-guided transmural cystgastrostomy or cystduodenostomy with a stent (for example, a lumen-apposing metal stent) is first line. It is as effective as surgery with shorter hospital stays, and it avoids the external pancreatic fistula that a percutaneous drain can leave behind. Before draining, exclude a pseudoaneurysm and a cystic neoplasm.

A "pseudocyst" in a patient who never had pancreatitis is a cystic neoplasm until proven otherwise.

Sterile and infected necrosis

Sterile necrosis. Prophylactic antibiotics do not prevent infection or death in severe or necrotizing pancreatitis, however extensive the necrosis. Give antibiotics only for suspected or proven infection (infected necrosis, cholangitis, pneumonia, bacteremia). Early enteral feeding by mouth, nasogastric tube, or nasojejunal tube, rather than TPN, preserves the gut barrier and lowers infectious complications.

Recognizing infection. Roughly a third of necrotizing pancreatitis becomes infected, usually after the first 7–10 days (typically weeks 2–4). Clues are new fever, a rising WBC, or clinical deterioration with new or worsening organ failure. Gas bubbles within a necrotic collection on CT are nearly diagnostic, and CT-guided FNA is rarely needed.

Treatment. Start an antibiotic that penetrates necrotic tissue: a carbapenem, or a fluoroquinolone plus metronidazole as an alternative. In a stable patient, postpone any procedure for about 4 weeks so the necrosis can liquefy and wall off. Early debridement of soft, unencapsulated necrosis increases bleeding, organ failure, and death.

Vascular and ductal complications

Splenic vein thrombosis. The splenic vein runs along the posterior pancreas, so inflammation can thrombose it. The result is left-sided (sinistral) portal hypertension: isolated gastric fundal varices and splenomegaly, with a normal liver and normal portal pressure. Bleeding gastric varices are cured by splenectomy, which removes the inflow feeding them; asymptomatic thrombosis is observed.

Pseudoaneurysm. Pancreatic enzymes digest nearby arterial walls. The splenic artery is involved most often, followed by the gastroduodenal and pancreaticoduodenal arteries. The pseudoaneurysm can rupture into a pseudocyst, the retroperitoneum, the bowel, or the pancreatic duct. Suspect it when a pseudocyst suddenly enlarges or the hemoglobin falls without an obvious source. Diagnose with CT angiography and treat with angiographic coil embolization, reserving surgery for failure.

Hemosuccus pancreaticus. A pseudoaneurysm bleeding into the pancreatic duct drains through the ampulla of Vater, causing intermittent melena or hematemesis, often with epigastric pain, in a patient with chronic pancreatitis or a pseudocyst. Endoscopy may be normal between bleeds or show blood at the papilla; CT angiography and embolization follow.

Pancreatic ascites and pleural effusion. A disrupted pancreatic duct or a leaking pseudocyst can fill the peritoneum or, through the diaphragm, the (usually left) pleural space. The fluid has a very high amylase (often >1,000 U/L), protein >3 g/dL, and a low SAAG. Management is bowel rest with nutritional support, octreotide, drainage by paracentesis or thoracentesis, and ERCP with a pancreatic duct stent to bridge the leak; surgery is for refractory cases.

Post-ERCP pancreatitis. This is the most common complication of ERCP, occurring in roughly 3–10% of procedures. A single 100-mg rectal dose of indomethacin (or diclofenac) around the procedure lowers the risk. High-risk patients (young women, suspected sphincter of Oddi dysfunction, difficult cannulation) also receive aggressive lactated Ringer's hydration and a prophylactic pancreatic duct stent.

Pancreatic cystic lesions

Workup. MRI with MRCP shows morphology and whether the cyst communicates with the pancreatic duct. EUS with FNA is added when features are concerning. Cytology is specific but insensitive, so cyst-fluid chemistry carries much of the weight:

Serous cystadenoma. Seen in older women (around their 60s), often in the head. It is a microcystic "honeycomb" lesion with a central stellate scar that may calcify in a sunburst pattern, and it is associated with von Hippel–Lindau disease. CEA and amylase are both low. Malignant potential is negligible, so it is observed and resected only for symptoms or diagnostic doubt.

Mucinous cystic neoplasm (MCN). Occurs almost exclusively in women aged 40–50. It is a solitary cyst in the body or tail with ovarian-type stroma, sometimes peripheral eggshell calcification, and no communication with the duct. CEA is high and amylase low. MCN is premalignant, so fit patients undergo resection, usually distal pancreatectomy.

Intraductal papillary mucinous neoplasm (IPMN). A mucin-producing tumor that grows inside the ducts of adults in their 60s–70s, most often in the head. Because it communicates with the duct, both CEA and amylase are high. At endoscopy, a "fish-mouth" papilla extruding mucin is the classic sign of main-duct disease.

• Main-duct IPMN (main duct ≥5 mm) carries a high cancer risk; a duct ≥10 mm is resected, while 5 to 9 mm prompts EUS.
• Branch-duct IPMN is followed with MRI or EUS.
• Worrisome features (cyst ≥3 cm, enhancing mural nodule, thickened wall, main duct 5–9 mm, rising CA 19-9, rapid growth) call for EUS-FNA.
• High-risk stigmata (obstructive jaundice, enhancing nodule ≥5 mm, main duct ≥10 mm) call for resection.

Solid pseudopapillary neoplasm. A solid and cystic tumor of young women with low-grade malignant potential; it is resected. Together these give the mnemonic "grandmother, mother, daughter": serous (older, benign), mucinous (middle-aged, premalignant), solid pseudopapillary (young, low-grade malignant).