Major pancreatic resections: normal postoperative findings and complications
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(1) To illustrate and describe the main types of pancreatic surgery; (2) to discuss the normal findings after pancreatic surgery; (3) to review the main complications and their radiological findings.
Despite the decreased postoperative mortality, morbidity still remains high resulting in longer hospitalisations and greater costs. Imaging findings following major pancreatic resections can be broadly divided into “normal postoperative alterations” and real complications. The former should regress within a few months whereas complications may be life-threatening and should be promptly identified and treated.
CT is the most effective postoperative imaging technique. MRI and fluoroscopy are used less often and only in specific cases such as assessing the gastro-intestinal function or the biliary tree. The most common normal postoperative findings are pneumobilia, perivascular cuffing, fluid collections, lymphadenopathy, acute anastomotic oedema and stranding of the peri-pancreatic/mesenteric fat. Imaging depicts the anastomoses and the new postoperative anatomy. It can also demonstrate early and late complications: pancreatic fistula, haemorrhage, delayed gastric emptying, hepatic infarction, acute pancreatitis of the remnant, porto-mesenteric thrombosis, abscess, biliary anastomotic leaks, anastomotic stenosis and local recurrence.
Radiologists should be aware of surgical procedures, postoperative anatomy and normal postoperative imaging findings to better detect complications and recurrent disease.
• Morbidity after pancreatic resections is high.
• CT is the most effective postoperative imaging technique.
• Imaging depicts the anastomoses and the new postoperative anatomy.
• Pancreatic fistula is the most common complication after partial pancreatic resection.
KeywordsPancreas Pancreatectomy Pancreaticojejunostomy Pancreaticoduodenectomy Postoperative complications
The morbidity and mortality of pancreatic surgery have decreased in the last decades thanks to improvements in both surgical technique and postoperative intensive care; the mortality rate originally described in the 1940 series by Whipple was about 25% , whereas nowadays mortality is lower than 1% in high-volume centres [2, 3].
Despite this improvement, morbidity still remains high, resulting in longer hospitalisations and greater hospital costs [4, 5, 6, 7, 8]. The most common complications following pancreatic surgery are pancreatic fistula (pancreatic fistula), haemorrhage, pancreatitis, porto-mesenteric venous thrombosis, delayed gastric emptying and anastomotic strictures. Among these, pancreatic fistula and delayed gastric emptying represent the most frequent complications [7, 8].
Imaging is not only essential in the preoperative assessment of these patients, but also plays a fundamental role in the postoperative setting to evaluate the presence of complications.
CT is the modality of choice in the postoperative setting, being able to detect and differentiate, even in the earliest phases, between normal and pathological findings. Other imaging techniques, like MRI with MR-cholangiopancreatogaphy (MRCP) sequences and fluoroscopy, are less useful and are used mainly for few specific indications .
In this article we will review the main types of major pancreatic resections and the resulting postoperative anatomy, normal findings in the early postoperative time and main post-surgical complications.
Different surgical procedures are performed based on the type of lesion and its location and can be broadly divided into resection and drainage procedures . The latter, however, will not be discussed in this review.
The most commonly performed resections are pancreaticoduodenectomy (pancreaticoduodenectomy) and distal pancreatectomy (distal pancreatectomy). Pancreaticoduodenectomy is performed for diseases involving the head of the pancreas, most commonly periampullary neoplasms, pancreatic head trauma and chronic pancreatitis [2, 6, 9].
In both types of pancreaticoduodenectomy the pancreatic remnant can be anastomosed to the stomach, thus creating a pancreatico-gastro anastomosis instead of a pancreaticojejunostomy. These two types of pancreatic anastomosis seem to have the same rate of complications, although a recent meta-analysis revealed that pancreatico-gastro anastomoses have a lower rate of pancreatic fistula .
In the first postoperative period no imaging is required unless complications are suspected.
As stated above, CT is the modality of choice to evaluate the postoperative patient, because it is widely available, fast and allows exploring the entire abdomen, with high spatial and contrast resolution. For these reasons it is able to clearly define the postoperative anatomy allowing identification of the anastomoses. It is also able to demonstrate para-physiological postoperative changes and early and late true complications such as pancreatic fistula, haemorrhage, acute pancreatitis of the remnant, abscess, aneurysms, biliary anastomotic stenosis and local recurrence [4, 6].
MR has similar performance to CT in postoperative conditions, but it is more expensive, time consuming, less available and requires greater compliance from the patient. As a consequence, MR with MRCP sequences is mainly performed to study the biliary and pancreatic ductal systems and anastomoses.
Other imaging modalities, such as fluoroscopy, can provide information in relation to specific questions such as the evaluation of gastrointestinal function or of the hepatico- and pancreatico-anastomosis.
To evaluate resected patients in the first postoperative period, we use a multiphase technique including a non-contrast scan, useful to recognise hyperdense materials (clips, stents or blood), followed by a late arterial phase (bolus tracking, 200 HU threshold, 15 s delay) and a venous phase (60 s delay after the threshold has been reached). Patients receive 1.5 ml/kg of high-concentration nonionic contrast material, at a rate of 3–4 ml/s, followed by a 50-ml saline bolus.
The MRI acquisition protocol in the postoperative setting at our institution is based on multiplanar T1- and T2-weighted sequences with and without fat saturation, diffusion-weighted images and 3D MRCP acquisitions. Multiphase acquisitions after the administration of hepatospecific contrast agent are performed; when clinically indicated, a late scan in the excretory phase is performed to evaluate the biliary system.
These protocols allow studying the pancreatic parenchyma and the entire abdomen to identify all possible complications.
Normal postoperative findings
Pancreaticojejunostomy: a jejunal loop is anastomosed to the right of the pancreatic remnant, anteriorly to the superior mesenteric artery (Fig. 5).
Pancreaticogastrostomy: the pancreas remnant is anastomosed with the posterior wall of the stomach (Fig. . 6).
Gastro-/duodenojejunostomy: gastrojejunostomy usually is located anteriorly and on the right of the pancreatic remnant. Duodenojejunostomy is usually located in the right upper quadrant of the abdomen (Fig. 1).
In the first postoperative period CT may show a series of findings that should be regarded as “normal” physiological temporary consequences of surgery. Among these, the most common are pneumobilia, perivascular cuffing, fluid collections, lymphadenopathies, acute anastomotic oedema, peripancreatic fat stranding and presence of stents and free air [2, 4, 6, 16].
Acute anastomotic oedema
Stranding of the peripancreatic fat
Postoperative pancreatic fistula
Pancreatic fistula is the most common complication after partial pancreatic resection, occurring between 10% and 30% of cases, and it is associated with increased length of hospital stay, costs and mortality [7, 18, 19, 20]. According to the ISGPF (International Study Group of Pancreatic Fistula) definition, pancreatic fistula is “the presence of drainage fluid on the third postoperative day or later, with an amylase content greater than three times the upper normal serum value” . Pancreatic fistula represents the failure of healing/sealing of the pancreatic anastomosis in pancreaticoduodenectomy or a parenchymal leak from the raw resection margin in distal pancreatectomy [7, 18, 22]. The major risk factors are a small-calibre main pancreatic duct (diameter < 3 mm), a soft parenchymal texture and intraoperative bleeding [6, 7]. Imaging studies, especially CT, can confirm the clinical suspicion of pancreatic fistula. Imaging acquisition should be guided by clinical signs and symptoms and laboratory data as the diagnostic criteria mentioned above are fulfilled.
Delayed gastric emptying (DGE)
Hepatic infarction is a rare event, with a prevalence of 1% [8, 30]. Infarction is uncommon because of the dual hepatic blood supply from the hepatic artery and portal vein and it can be due to an insult to the hepatic artery or portal vein. However, the presence of a pre-existing severe stenosis of the superior mesenteric artery or the caeliac trunk is a significant risk factor that can lead to infarction  even without any intraoperative arterial trauma or venous impairment [6, 31].The imaging appearance of an hepatic infarction could be due to ischaemia of the biliary tree that has an almost exclusive arterial blood supply, thus being more sensitive to arterial lesions during surgery . The left hepatic lobe is more commonly affected following a trauma during the dissection of the hepatic artery and the caeliac trunk. The inadvertent sacrifice of a right hepatic artery arising from the superior mesenteric artery (replaced right hepatic artery) may lead to a selective infarction of the right lobe [6, 33].
Portal vein and superior mesenteric vein thrombosis (SMV)
Biliary anastomotic leaks
Radiologists should be aware of surgical procedures, postoperative anatomy and normal postoperative imaging findings to better detect complications and recurrent disease. This does not only apply to those working in referral centres for pancreatic diseases or oncology, but also to general radiologists, who may encounter patients who underwent previous resections in their clinical practice. CT is the best imaging tool to depict the early and late “normal” postoperative findings and the complications, because of its speed and spatial and contrast resolution, coupled with post-processing capabilities, that increase the diagnostic confidence. MR can provide similar information, but in the early postoperative period it is less used because usually less readily available, requiring longer examination times and greater compliance from the patient, and more expensive.
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