Postoperative Pancreas

Published on 19/07/2015 by admin

Filed under Radiology

Last modified 22/04/2025

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Small free fluid, edema, and fat stranding in surgical bed with reactive subcentimeter lymph nodes in mesentery

Mild biliary dilatation, gastrojejunostomy thickening, and pancreatic duct dilatation due to anastomotic edema

Pancreatic duct stent (thin linear radiodensity) often placed during surgery (traversing pancreaticojejunostomy) to ↓ risk of pancreatic fistula

• Common complications

Pancreatic fistula: Leakage of amylase-rich fluid from pancreatic duct

– Focal fluid collection, ectopic gas, or hematoma directly adjacent to pancreaticojejunostomy

Abscess: Can be intrahepatic, in pancreatic bed, or in subphrenic, subhepatic, or retroperitoneal spaces

Gastrojejunostomy and hepaticojejunostomy leaks: Suspect when focal fluid collection or ectopic gas in close contiguity to anastomosis

Postoperative pancreatitis: Fluid, edema, and stranding centered in pancreatic remnant

Liver infarct: Wedge-shaped areas of hypodensity at periphery of liver

Postoperative hemorrhage: May be due to bleeding from gastroduodenal artery stump or due to structural abnormality (e.g., pseudoaneurysm)

Portomesenteric venous thrombosis

Anastomotic strictures: Suspect when progressive biliary or pancreatic ductal dilatation without obstructing tumor at anastomotic site

Delayed gastric emptying: Gastric remnant markedly dilated with large retained ingested material and fluid

Tumor recurrence: Differentiate linear postoperative scarring from nodular, mass-like tumor recurrence

CLINICAL ISSUES

• Whipple procedure mortality has dramatically fallen (was once ∼ 25%, and is now 1-3%)

• Morbidity for Whipple procedure remains considerable, with complications in ∼ 20% of patients

(Left) Graphic shows the Whipple (pancreaticoduodenectomy) procedure. Note the common bile duct margin , the pancreatic margin , and the intestinal margins .

(Right) This graphic depicts Whipple anatomy: Pancreaticojejunostomy , choledochojejunostomy , gastrojejunostomy or duodenojejunostomy , and cholecystectomy . The pylorus may be removed or preserved, depending on extent of disease and surgeon preference. Note the ligated gastroduodenal artery .

(Left) Axial CECT demonstrates a collection of fluid and gas immediately adjacent to the pancreaticojejunostomy in a patient with an elevated drain amylase, compatible with pancreatic fistula. Note the presence of a pancreatic duct stent .

(Right) Axial CECT in a patient with a fever after Whipple procedure demonstrates a thick-walled fluid collection in the right liver lobe with an internal air-fluid level, compatible with a postoperative hepatic abscess.

TERMINOLOGY

Synonyms

Definitions

•

IMAGING

General Features

• Best diagnostic clue

Post Whipple resection: Expected findings include gas in biliary tree, jejunal loop anastomosed to pancreatic neck, gallbladder usually resected

Post distal pancreatectomy: Expected findings include absent body and tail of pancreas; spleen often resected

• Location

• Surgical procedure determined by location and type of pathology

Whipple procedure most commonly performed for tumors of pancreatic head, uncinate, and proximal neck

– Classic Whipple procedure (pancreaticoduodenectomy) involves surgical removal of pancreatic head, gastric antrum, proximal duodenum, and gallbladder

– Pylorus-sparing Whipple procedure, which may theoretically have lower risk of bile reflux, retains pylorus and short segment of duodenum with creation of duodenojejunostomy

– 3 anastomoses created: Hepaticojejunostomy, pancreaticojejunostomy, and gastrojejunostomy (classic) or duodenojejunostomy (pylorus-sparing)

Distal pancreatectomy performed for tumors of distal pancreatic neck, body, and tail

– May be performed with splenectomy

– Can be performed with en bloc celiac axis resection for some pancreatic body tumors that invade celiac or hepatic artery

Central pancreatectomy performed for low-risk lesions (low malignant potential) in pancreatic neck/body

– Not used for higher risk lesions due to inadequate lymphadenectomy and ↑ risk of pancreatic fistula

Enucleation performed for lesions with low malignant potential that are small and exophytic (often utilized for insulinomas)

Frey procedure and Puestow procedure are both utilized for treatment of chronic pancreatitis

– Both result in lateral side-to-side pancreaticojejunostomy, with additional resection of portions of pancreatic head in Frey procedure

Laparoscopic technique is increasingly utilized at high-volume surgical centers (distal pancreatectomy > Whipple procedure)

CT Findings

• Normal findings immediately after Whipple procedure

Small free fluid, edema, and fat stranding in surgical bed with reactive subcentimeter lymph nodes in mesentery

Pneumobilia is an expected finding after Whipple procedure due to hepaticojejunostomy

Mild biliary dilatation frequently present due to anastomotic edema at hepaticojejunostomy

Thickening at gastrojejunostomy due to edema

Mild pancreatic duct dilatation due to anastomotic edema at pancreaticojejunostomy

Pancreatic duct stent (thin linear radiodensity) often placed during surgery (traversing pancreaticojejunostomy) to ↓ risk of pancreatic fistula

– Will eventually pass into bowel over time on its own

Small free air expected for 14 days after surgery

• Complications

Pancreatic fistula

– Leakage of amylase-rich fluid from pancreatic duct (either at pancreaticojejunal anastomosis or at site of parenchymal injury)

– Should be suspected when focal fluid collection, greater than expected ectopic gas, or hematoma identified directly adjacent to pancreaticojejunostomy

Fluid and gas may be visualized in direct contiguity with suture line

Abscess

– Rim enhancing fluid collection ± internal ectopic gas

– Abscesses following Whipple may be intrahepatic, in surgical bed, or in subphrenic, subhepatic, or retroperitoneal spaces

– Abscesses following distal pancreatectomy are typically in left subphrenic or left subhepatic spaces

Gastrojejunostomy and hepaticojejunostomy leaks

– Both are uncommon complications, but hepaticojejunostomy leaks are more common

– Should be suspected in acute setting when focal fluid collection visualized in close contiguity to anastomosis (usually with greater than expected ectopic gas)

Postoperative pancreatitis

– May be difficult to distinguish from normal postoperative inflammation in surgical bed

– Suspect pancreatitis when fluid, edema, and fat stranding are disproportionately centered in pancreatic remnant (rather than surgical bed as a whole)

Liver infarct

– Uncommon due to dual blood supply of liver

– Patients often have underlying vascular compromise (atherosclerosis, median arcuate ligament syndrome, etc.) that may be exacerbated by surgical complications, hypotension, etc.

– Infarcts appear as wedge-shaped areas of hypodensity at periphery of liver

Postoperative hemorrhage

– May be due to bleeding from gastroduodenal artery stump (first 24 hours after surgery) or due to structural abnormality (pseudoaneurysm, vascular erosion) usually after 5th postoperative day

– Hemorrhage usually in surgical bed, but can be intraluminal (usually within stomach or right upper quadrant jejunal loops near anastomosis)

– Look for evidence of active extravasation or pseudoaneurysm: Acquisition of arterial phase CECT images critical if bleed is suspected

Portomesenteric venous thrombosis

– Increasingly common due to complex vascular reconstructions and use of venous interposition grafts

– Superior mesenteric vein (SMV) thrombosis easier to overlook on axial images compared to coronal reconstructions

Postoperative pseudocyst

– Commonly seen after distal pancreatectomy, with loculated fluid collection immediately abutting suture line along distal aspect of pancreatic remnant

Anastomotic strictures

– Can occur at either pancreaticojejunostomy or hepaticojejunostomy

– Suspect stricture in setting of progressive biliary or pancreatic ductal dilatation without evidence of obstructing recurrent tumor at anastomotic site

– Biliary anastomotic stricture may be associated with imaging signs of cholangitis (hyperenhancement and thickening of bile duct remnant, heterogeneous perfusion of liver parenchyma)

Delayed gastric emptying

– Very common complication of unknown etiology that can be suggested when gastric remnant appears markedly dilated with large amount of retained ingested material and fluid

Tumor recurrence

– Normal postoperative fibrosis and scarring typically appears linear (not mass-like), and is often located posterior to SMA/SMV (in Whipple procedure)

– Tumor recurrence usually appears nodular and mass-like and may narrow or occlude adjacent vessels

Imaging Recommendations

• Best imaging tool

CECT is best for suspected postoperative complications

Intraoperative US to detect nonpalpable lesions and guide intraoperative approach and plane of resection

CECT of chest, abdomen, and pelvis for suspected postoperative complications

Secretin-enhanced MR to detect postoperative stricture of pancreatic duct anastomosis

Biliary scintigraphy or MR with hepatobiliary agents (i.e., Eovist) may be helpful if biliary leak is suspected

PET/CT for diagnosis of local recurrence and distant metastases

• Protocol advice

Multiplanar CECT

DIFFERENTIAL DIAGNOSIS

Normal Jejunal Loop

• Jejunum in right upper quadrant may be collapsed and confused for postoperative abscess or hematoma

Rim-Enhancing Hepatic Metastases

• May appear similar to rim-enhancing hepatic abscesses

• Biopsy may be required if distinction between infection and metastases is not clinically or radiographically apparent

Postoperative Fat Necrosis in Mesentery or Greater Omentum

• Mass with internal mixed attenuation and fat density, which may be mistaken for tumor recurrence or abscess

• Fat density within mass is key to diagnosis

• May be more common in procedures performed with laparoscopic technique

PATHOLOGY

Staging, Grading, & Classification

• Small fluid collections in pancreatic bed are an expected finding and usually do not require therapy

Gross Pathologic & Surgical Features

• Whipple resection may be performed with pylorus-sparing technique in order to reduce potential complication of “dumping syndrome”

CLINICAL ISSUES

Presentation

• Most common signs/symptoms

Most common immediate complications include

– Intraabdominal abscess (6%), postoperative hemorrhage (4%), pancreatic fistula (6-14%), biliary leak (3.7%), pancreatitis (27%), portomesenteric venous thrombosis (17%), and pulmonary embolus

Pancreatic fistula defined as drain fluid amylase level 3x > serum amylase level on 3rd postoperative day (or > 50 cc amylase-rich fluid from drains per day)

– Single most common cause of poor outcomes after Whipple procedure and strongly associated with multiple other complications, including abscess, hemorrhage, sepsis, and delayed gastric emptying

– Mortality rates after fistula were once ∼ 40%, but have now fallen to < 5%

Most common delayed complications following Whipple procedure include: Anastomotic stricture at biliary (8.2% at 5 years) or pancreatic (4.6% at 5 years) anastomosis, pseudocyst formation from pancreatic leak, and delayed gastric emptying (∼ 50%)

– Pancreatic duct strictures can result in pancreatic exocrine or endocrine insufficiency due to parenchymal atrophy

– Delayed gastric emptying is clinically defined as persistent need for nasogastric tube after surgery

Now most common postoperative complication, but usually resolves spontaneously

• Other signs/symptoms

Natural History & Prognosis

• Whipple procedure morbidity and mortality have dramatically fallen

Mortality rate was once ∼ 25%, and is now 1-3%, despite pancreatic surgeries increasingly being performed for tumors previously considered unresectable

Decline in mortality mostly attributable to tertiary centers performing high volumes of pancreatic surgery, refinements of surgical technique, and increasing use of imaging to identify complications and guide percutaneous treatment

Patients at high-volume centers have ↓ morbidity and mortality compared to low-volume centers

Morbidity for Whipple procedure remains considerable, with complications in ∼ 20% of patients

• Distal pancreatectomy widely thought to be safer than Whipple procedure, but complication rate as high as 37%

Treatment

• Pancreatic fistulas usually treated conservatively with drainage of fluid collections, antibiotics, and parenteral nutrition (surgery only considered for large pancreaticojejunal anastomotic dehiscence)

Octreotide may be helpful by ↓ pancreatic secretions

80% of pancreatic fistulas heal with conservative management

Repeat surgery only necessary in a small % of patients

• Postoperative fluid collections (abscess or biloma), particularly when sizeable (> 3 cm), are usually treated with percutaneous drainage

• Postoperative hemorrhage is usually treated with emergent angiographic embolization (or rarely surgery)

• Postoperative portomesenteric venous thrombosis is treated with systemic anticoagulation

• Hepaticojejunostomy bile leaks are usually treated conservatively with percutaneous drainage

• Anastomotic strictures are initially treated nonoperatively with balloon dilatation

• Percutaneous biliary drainage with stenting for postoperative biliary strictures

• Surgical revision of stricture of pancreatic duct and jejunal anastomosis

DIAGNOSTIC CHECKLIST

Consider

• Differentiate normal postoperative findings (ectopic gas, fluid/edema in surgical bed, collapsed loops of jejunum in right upper quadrant) from true complications

• Differentiate normal postoperative fibrosis (linear induration posterior to SMA and SMV with no mass effect) from true tumor recurrence, which is nodular and mass-like