Elucidating early CT after pancreatico-duodenectomy: a primer for radiologists
Pancreatico-duodenectomy (PD) represents the standard surgical treatment for resectable malignancies of the pancreatic head, distal common bile duct, periampullary region and duodenum, and is also performed to manage selected benign tumours and refractory chronic pancreatitis. Despite improved surgical techniques and acceptable mortality, PD remains a technically demanding, high-risk operation burdened with high morbidity (complication rates 40–50% of patients). Multidetector computed tomography (CT) represents the mainstay modality to rapidly investigate the postoperative abdomen, and to provide a consistent basis for an appropriate choice between conservative, interventional or surgical treatment. However, radiologists require familiarity with the surgically altered anatomy, awareness of expected imaging appearances and possible complications to correctly interpret early post-PD CT studies. This paper provides an overview of surgical indications and techniques, discusses risk factors and clinical manifestations of the usual postsurgical complications, and suggests appropriate techniques and indications for early postoperative CT imaging. Afterwards, the usual, normal early post-PD CT findings are presented, including transient fluid, pneumobilia, delayed gastric emptying, identification of pancreatic gland remnant and of surgical anastomoses. Finally, several imaging examples review the most common and some unusual complications such as pancreatic fistula, bile leaks, abscesses, intraluminal and extraluminal haemorrhage, and acute pancreatitis.
• Pancreatico-duodenectomy (PD) is a technically demanding surgery burdened with high morbidity (40–50%).
• Multidetector CT is the mainstay technique to investigate suspected complications following PD.
• Interpreting post-PD CT requires knowledge of surgically altered anatomy and expected findings.
• CT showing collection at surgical site supports clinico-biological diagnosis of pancreatic fistula.
• Other complications include biliary leaks, haemorrhage, abscesses and venous thrombosis.
KeywordsPancreatic carcinoma Pancreatico-duodenectomy Complications Pancreatic fistula Computed tomography (CT)
Pancreatico-duodenectomy (PD) represents the standard surgical treatment for tumours of the pancreatic head, distal common bile duct, periampullary region and duodenum, and is the only curative option for malignancies. Despite improved surgical techniques and perioperative care, PD remains a technically demanding, high-risk operation that includes complex resections and multiple anastomoses. In the last decade, at high-volume centres the postsurgical mortality after PD dropped below 2–3%. However, PD remains burdened with high morbidity, with complication rates approaching 40–50% of patients. Iatrogenic complications commonly result in prolonged hospitalisation, readmission (11–25% of discharged patients), need for reoperation (9%) or interventional procedures (14%). In descending order of frequency, the commonest postoperative adverse events are delayed gastric emptying (DGE), pancreatic fistula (PF), wound infections, biliary leakage, haemorrhage, abscesses, acute pancreatitis and intra-abdominal venous thrombosis [1, 2, 3].
Multidetector computed tomography (CT) currently represents the mainstay modality to investigate the postoperative abdomen, as it can rapidly and consistently detect iatrogenic complications, thus allowing a timely and appropriate choice between conservative, percutaneous or surgical treatment. As well presented by Mauri et al. , interventional radiology is increasingly used and very effective to treat most PD complications, allowing imaging-guided drainage of collections and biliary leaks, transarterial control of bleeding, venous interventions and percutaneous embolisation of postoperative fistulas via trans-drainage injection of ethanol or cyanoacrilic glue [4, 5, 6, 7, 8].
Unfortunately, interpretation of early postoperative CT imaging is generally challenging due to the surgically altered anatomy. Aiming to improve radiologists’ familiarity with postsurgical abdominal studies, this pictorial essay reviews and illustrates the expected postoperative CT appearances and the imaging features of typical and unusual post-PD complications [9, 10, 11].
Basics of pancreatico-duodenectomy
Most PDs are performed to manage resectable pancreatic ductal carcinoma, neuroendocrine and malignant intraductal papillary-mucinous neoplasms, cancers of the distal common bile duct (CBD), Vaterian ampulla and duodenum. Other indications include symptomatic chronic pancreatitis refractory to medical treatment and selected benign tumours not amenable to conservative surgery. The use of laparoscopy and robotic techniques is still limited in oncological pancreatic surgery [12, 13, 14].
Surgical reconstruction requires creation of: (1) an end-to-side anastomosis between the mobilised jejunal loop (MJL) and pancreatic duct [pancreatico-jejunostomy (PJS)]; (2) an end-to-side anastomosis between common hepatic duct and MJL [hepatico-jejunostomy (HJS)]; (3) either gastro-jejunostomy (GJS) in Whipple PD or duodeno-jejunostomy (DJS) in pylorus-preserving PD. Alternatively, some centres perform a variant technique (Fig. 1c), in which the PR and pancreatic duct are connected to the dorsal aspect of the stomach [pancreatico-gastrostomy (PGS)]. If required by venous invasion, experienced surgeons can also perform reconstructions or grafting of the superior mesenteric and portal veins [12, 13, 14].
There are no relevant differences in complication patterns and rates between the three PD variants [14, 15]. General risk factors for increased morbidity include prolonged duration of surgery, significant intraoperative blood loss and high body-mass index (particularly regarding high-grade PF). The effect of advanced age is controversial: although overall complication rates are not substantially increased, mortality and risk of pneumonia are higher in elderly patients [16, 17, 18, 19, 20].
Early post-pancreatico-duodenectomy CT
Within the first 2 or 3 postoperative days after PD, the commonest indications for CT imaging include suspected early haemorrhage, peritonitis, physical and laboratory signs of systemic inflammation. Post-PD bleeding may be either intraluminal or extraluminal: the latter heralded by blood from drainage, nasogastric tube or abdominal incision site. On the other hand, the less common intraluminal haemorrhage manifests with haematemesis or melaena. In both situations, variable degrees of abdominal pain, signs of haemodynamic impairment and dropping haematocrit are present. Unfortunately, clinical and laboratory findings may not accurately reflect the true entity of bleeding [6, 21].
After the early postsurgical hospitalisation, the usual indications for CT imaging include suspected DGE with persistent need for nasogastric intubation, peripancreatic drainage yielding high-amylase fluid consistent with PF, increasing leucocyte count and C-reactive protein levels, as well as physical and laboratory signs of delayed haemorrhage. In our experience, surgeons increasingly think that physical findings, abdominal pain and distension are relatively insensitive and rely on routine postoperative CT imaging [6, 21].
Due to high prevalence of pleuropulmonary changes, we suggest to routinely include the lung bases in postsurgical abdomen/pelvis CT studies. Borrowing from experience after gastric surgery, oral administration of diluted water-soluble contrast medium (CM) a few minutes prior to CT has been suggested to improve identification of bowel loops and diagnostic confidence in the diagnosis or exclusion of anastomotic leaks. However, in the setting of PD surgery, most centres—including ours—discourage the use of oral CM, since it may cause beam-hardening artefacts and hamper detection of haemorrhage. Furthermore, recently operated patients are often unwell and not willing or able to swallow, particularly those with a distended stomach secondary to DGE [9, 10, 11].
Normal postsurgical findings after pancreatico-duodenectomy
Checklist for interpretation of early CT after pancreatico-duodenectomy (PD)
Report pleuropulmonary changes (such as atelectasis, pneumonia, pleural effusion) at lung bases
Particularly common in elderly patients
Externally draining tubes present?
Use thick-slab maximum-intensity projection (MIP) reconstructions
Report presence, number, course and distal tip position
- pancreatic remnant (body and tail)
- main pancreatic duct (MPD)
- either pancreatico-jejunostomy (PJS) or pancreatico-gastrostomy (PGS)
Best visualised in oblique-coronal images
Assess integrity, presence of internal or external trans-anastomotic stents
- mobilised jejunal limb
Identified by valvulae conniventes and tubular configuration on coronal images; mural oedema is generally normal
- hepatico-jejunostomy (HJS)
- either gastro-jejunostomy (GJS) or duodeno-jejunostomy (DJS)
- gastric dilatation
Pneumobilia and/or mild biliary tract dilatation are usually normal
Respectively after Whipple and pylorus preserving PD
Suggest delayed gastric emptying (optional fluoroscopy for confirmation)
Identify fluid collections and air
- surgical bed, abutting the PJS
- surrounding PR
Report as consistent with a clinical/laboratory diagnosis of pancreatic fistula (fat stranding, mild non-demarcated fluid, small lymphadenopathies are usually normal)
Suggest bile leakage
Suggest acute pancreatitis
Mild residual air within 3 days is usually normal Persistent or abundant pneumoperitoneum, diffuse ascites, enhancing peritoneal serosa suggest peritonitis from major anastomotic leakage
Search for bleeding
- intraluminal in jejunum
Use MIP reconstructions
Compare precontrast, arterial- and portal venous phase images
Always scrutinise the gastroduodenal artery “stump”
Assess patency of splenic, portal and mesenteric veins
For postoperative thrombosis, favoured by venous resections or graft insertion
Scrutinise laparotomic incision site
For fluid or abscess collections consistent with wound infection
Delayed gastric emptying
A dilated stomach with stagnant fluid and/or oral CM (Fig. 3) is the hallmark of DGE, which remains an unsolved problem after both classic and pylorus-preserving PD. Although a consensus definition is lacking, DGE with persistent need for nasogastric intubation occurs in 20-50% of patients, most often in the elderly, and may worsen the nutritional state and prolong hospitalisation. The exact mechanism is unknown, but likely involves loss or damage of autonomic innervation of the stomach, and may be decreased by special surgical techniques with subtotal stomach preservation and antecolic reconstruction [17, 27, 28].
Located in variable positions according to surgeons’ preference, the GJS (Fig. 3c) is best viewed in the coronal orientation and sometimes indicated by metallic stapling along the gastric suture. Traditionally, contrast fluoroscopic studies were use to assess position, patency and integrity of the GJS (Fig. 2d) and to detect delayed or absent emptying of the residual stomach consistent with DGE (Fig. 3d) [10, 11, 22].
Postoperative pancreatic fistula
Defined by leaking pancreatic secretions at the PJS, PF represents the single most important cause of post-PD morbidity with an overall incidence of 17–30%. PF is more frequent in obese individuals and following PD for ampullary and duodenal cancers rather than for pancreatic tumours [19, 28, 29, 30, 31]. Patients with “soft” pancreatic texture reflecting fatty infiltration are more prone to develop PF. At CT, an increased risk of PF may be predicted by high visceral fat area, low attenuation of abdominal viscera and paraspinal muscles, large pancreatic volume and small (<3 mm) pancreatic duct calibre [32, 33, 34, 35, 36].
According to the International Study Group on PF, this condition is diagnosed on the basis of “any measurable output from peripancreatic drainage on or after postoperative day 3 with amylase content >3 times the serum amylase”, alternatively at reoperation or percutaneous drainage. In the recent 2016 re-definition, grade A is now termed “biochemical leak” and no longer considered a true PF. The clinically significant grades B and C PF are respectively defined as “requiring modification in postoperative management (drainage left in place >3 weeks or repositioned through endoscopic or percutaneous procedures)” and “requiring reoperation or causing single or multiple organ failure”. Whereas the overall PF-related mortality is approximately 1%, grade C is associated with 25.7% mortality . Importantly, even low-grade PF is strongly associated with a higher incidence of reoperation and of other non-fistulous complications (incidence 51% versus 21% in patients without PF) such as pancreatitis, abscess formation, haemorrhage, bile leakage, wound and systemic infection [19, 29, 30, 31].
The above-mentioned clinico-biological criterion diagnoses PF on average 7 days after PD with 70–75% sensitivity, but is not sufficiently reliable in the early postoperative period. Unfortunately, PF may be clinically silent or manifest after discharge or resumption of oral feeding: therefore, the use of CT is valuable to decrease the occurrence of occult or delayed PF .
The majority (90%) of PF occurrences can be managed non-surgically with parenteral nutrition, octreotide and antibiotics until fistula closure, plus percutaneous drainage of major biliary collections and abscesses. Small collections that are not amenable to aspiration should be considered as probable PF and monitored until resolution [5, 8, 23, 29].
The other important post-PD complications include postoperative haemorrhage (4–16% incidence), wound infection, intra-abdominal and hepatic abscesses (3–8%), biliary leakage (1–5%), acute pancreatitis of the PR (2–3%), thrombosis of the portal or superior mesenteric veins (particularly after complex venous reconstructions) and visceral ischaemia (below 1%) [28, 30].
Leakage of bile primarily results from technical failure of the HJS. Although CT cannot assess for sure whether fluid leaks from the PJS or HJS, biloma is suggested by a homogeneous, non-enhancing water-attenuation collection, which generally lies in the subhepatic space or right hemiabdomen (Figs. 8 and 9) [10, 11, 22].
Post-PD haemorrhage accounts for almost one-third of the in-hospital mortality. Early bleeding develops within 24 h from surgery, is generally severe and most usually results from inadequate ligation of the gastroduodenal artery (GDA). Less common sites of bleeding include the common hepatic, right gastric and peripancreatic arteries. Conversely, the more frequent late bleeding occurs after a variable delay (median 33 days, up to 10 weeks) and is preceded by PF, anastomotic leak or intra-abdominal sepsis in approximately one-half of cases [6, 21, 28].
Rapid CT imaging diagnosis is crucial to dictate and guide transarterial embolisation, which is increasingly preferred as first-line treatment with 75–85% success rates [5, 6, 7, 21]. Selective embolisation of pseudoaneurysms (Fig. 13b-f) is associated with a higher recurrence of bleeding compared to endovascular trapping of the hepatic artery .
Occasionally, ischaemia of the liver, stomach and/or spleen may develop after PD secondary to either inadvertent injury, ligation or clamping of the hepatic artery or celiac trunk during surgical dissection, or impaired visceral perfusion in patients with pre-existing conditions such as atherosclerosis, median arcuate ligament compression or fibromuscular dysplasia. Preoperative recognition and appropriate management of underlying haemodynamically significant arterial strictures is beneficial to prevent these lethal (50–83% mortality) complications [28, 41, 42, 43]. The resulting CT appearances include devascularisation of the gastric wall or left liver lobe [9, 10, 11].
Following PD, multidetector CT rapidly provides a comprehensive visualisation of the operated abdominal compartment, and represents a consistent basis for triage of iatrogenic complications and correct choice between conservative, interventional or surgical treatment. Understanding the surgically altered anatomy and awareness of expected postoperative appearances is crucial to correctly recognise and classify complications.
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