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Postoperative CT in pancreas transplantation
Clinical Radiology xxx (2015) 1e9
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Postoperative CT in pancreas transplantation F.E. Powell a, S.J.F. Harper a, *, C.J. Callaghan a, A. Shaw b, E.M. Godfrey b, J.A. Bradley a, C.J.E. Watson a, G.J. Pettigrew a a
University Department of Surgery, and NIHR Comprehensive Biomedical Research Centre, Addenbrooke’s Hospital, Cambridge University Hospitals NHS Foundation Trust, Cambridge CB2 0QQ, UK b Department of Radiology, Addenbrooke’s Hospital, Cambridge University Hospitals NHS Foundation Trust, Cambridge CB2 0QQ, UK
art icl e i nformat ion Article history: Received 24 October 2014 Received in revised form 13 May 2015 Accepted 18 June 2015
AIM: To examine the usage and value of computed tomography (CT) following simultaneous pancreas and kidney (SPK) transplantation. MATERIALS AND METHODS: Indications for postoperative CT, key findings, and their influence on management were determined by retrospective analysis. RESULTS: Ninety-eight patients underwent 313 CT examinations. Common indications for the examinations included suspected intra-abdominal collection (31.1%) and elevated serum amylase/lipase (24.1%). CT findings most frequently showed non-specific mild inflammation (27.6%), a normal scan (17.1%) and fluid collections (16.3%). High capillary blood glucose (CBG) was associated with resultant CT demonstration of graft vascular abnormalities, but otherwise, particular clinical indications were not associated with specific CT findings. CONCLUSION: Clinical findings in patients with SPK transplants are non-specific. The pattern of abnormalities encountered is significantly different to those seen in native pancreatic disease and demands a tailored protocol. CT enables accurate depiction of vascular abnormalities and fluid collections, thus reducing the number of surgical interventions that might otherwise be required. Elevated CBG should prompt urgent CT to exclude potentially reversible vascular complications. Ó 2015 Published by Elsevier Ltd on behalf of The Royal College of Radiologists.
Introduction For patients with type I diabetes and end-stage renal failure, simultaneous pancreas and kidney (SPK) transplantation offers a survival advantage over deceased donor kidney transplantation alone (Fig 1)1,2; however, despite
* Guarantor and correspondent: S.J.F. Harper, Consultant Hepatobiliary and Transplant Surgeon, University Department of Surgery, Box 202, Addenbrooke’s Hospital, NIHR Comprehensive Biomedical Research Centre, Hills Road, Cambridge CB2 0QQ, UK. Tel.: þ44 1223 336975; fax: þ44 1223 762523. E-mail address: [email protected] (S.J.F. Harper).
improvements in surgical techniques and postoperative care, pancreas transplantation is associated with a higher complication rate and longer hospital stay than kidney transplantation alone.3,4 The clinical assessment of postoperative pancreas transplant recipients is often challenging and radiological evaluation is frequently performed5e7; however, the ideal technique and the indications for imaging are unclear, particularly when the pancreas is sited intra-peritoneally; ultrasound, for example, is often suboptimal due to gas within the overlying intestines obscuring the pancreas transplant. At Addenbrooke’s Hospital, computed tomography (CT) is the preferred graft imaging technique following pancreas
http://dx.doi.org/10.1016/j.crad.2015.06.086 0009-9260/Ó 2015 Published by Elsevier Ltd on behalf of The Royal College of Radiologists.
Please cite this article in press as: Powell FE, et al., Postoperative CT in pancreas transplantation, Clinical Radiology (2015), http://dx.doi.org/ 10.1016/j.crad.2015.06.086
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F.E. Powell et al. / Clinical Radiology xxx (2015) 1e9
Figure 1 Pancreas and kidney allograft outcomes. KaplaneMeier plots (with numbers at risk shown below): (a) actuarial pancreas and kidney allograft survival in SPK recipients (censored for death); (b) actuarial patient survival in SPK recipients.
transplantation. The present study reports the authors’ experience, focusing on the indications for imaging, the findings, and how CT influenced subsequent patient management; aspects that have not been previously reported.
Materials and methods Study population All patients undergoing SPK transplantation between 1 January 2005 and 1 August 2010 were included. Those receiving pancreatic grafts as part of multivisceral, modified multivisceral, or isolated pancreatic grafts were excluded. Post-transplant abdominopelvic CT performed on these patients at Addenbrooke’s Hospital were included if the primary indication was to image the pancreatic graft or to diagnose complications associated with it. Cases were excluded if they were performed for miscellaneous indications not related to the pancreas graft; performed following graft pancreatectomy; performed for drain or biopsy guidance only (following previous diagnostic CT); or were technically inadequate. Follow-up ended on 1 September 2010. Approval for the study was obtained from the Patient Safety Unit at Addenbrooke’s Hospital. The need for patient consent was waived.
Surgical implantation technique Pancreas grafts were implanted intra-peritoneally in the right iliac fossa with vascular reconstruction using a donor iliac artery ‘Y’ graft. Portal venous drainage was systemic via the inferior vena cava, with enteric exocrine drainage via a Roux-en-Y duodeno-enterostomy (Fig 2). A feeding jejunostomy was routinely placed, and an appendicectomy was performed in all recipients. Cholecystectomy was performed for those with gallstones or gallbladder polyps on ultrasonography performed during assessment. The kidney graft was placed extraperitoneally in the left iliac fossa.
Pancreatic imaging Pancreatic imaging was requested by senior clinicians in the transplant programme, according to perceived clinical need, in conjunction with biochemical markers of pancreatic function. CT was the primary imaging technique in pancreatic transplant recipients. Routine postoperative surveillance CT examination were not performed. If an intra-abdominal collection was suspected clinically, a single portal venous phase study was performed. A triple-phase study (unenhanced, early arterial and early venous phase) was performed in other cases unless contraindicated (e.g., anaphylaxis, poor renal function); oral contrast medium was not given routinely. Intravenous contrast medium comprised 100 ml iopamidol non-ionic contrast (Niopam 300, Bracco, High Wycombe, Bucks, UK). The unit has ready access to out-of-hours CT examinations; examinations are interpreted by senior radiology trainees with review by consultants routinely in working hours or out-of-hours as required.
Data collection and analysis Donor and recipient demographics, donor type, and patient and graft outcomes were obtained from a prospective database. All postoperative imaging was available via the hospital picture archiving and communications system (PACS). The clinical indication for each investigation was determined retrospectively from the electronic request form; when necessary, the primary indication was determined by case-note analysis. Key findings were recorded for each CT from the electronic report, including previously identified abnormalities in which a significant change had occurred. Where the request form suggested that the main indication was elevated blood glucose or serum amylase and/or lipase, contemporaneous biochemical values were recorded.
Please cite this article in press as: Powell FE, et al., Postoperative CT in pancreas transplantation, Clinical Radiology (2015), http://dx.doi.org/ 10.1016/j.crad.2015.06.086
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Figure 2 Normal SPK anatomy. (a) Schematic diagram of typical SPK transplantation anatomy. (b) Arterial phase volume rendered coronal CT image demonstrating normal arterial anatomy of the transplanted pancreas. The large arrowhead indicates the donor Y-graft anastomosed to the right external iliac artery. The small arrowhead indicates the donor splenic artery and the small arrow the donor superior mesenteric artery. (c) Arterial phase coronal maximal intensity projection CT image demonstrating normal arterial anatomy following simultaneous PKT (same patient as in Figure 2a). Note the Y-graft anastomosed to the right external iliac artery and the donor renal artery anastomosed to the left external iliac artery. Surgical drains and a transplant ureteric stent are also in situ. (c) Sagittal reformatted 55-second delay curved CT image demonstrating normal venous anatomy following pancreatic transplantation. The large arrowhead indicates the donor portal vein that has been anastomosed to the inferior vena cava. The small arrowhead indicates the donor splenic vein and the small arrow the superior mesenteric vein.
The medical notes were reviewed to establish how often the imaging demonstrated positive findings requiring further intervention. Interventions were then categorised as follows: major (taken to theatre, ultrasound- or CT-guided drainage of collection, full anticoagulation, arterial angioplasty), minor (further investigations arranged, antibiotics, treatment for rejection, insertion of nasogastric tube, other, anticoagulation stopped, laxatives or enema/suppository), or no intervention required. KaplaneMeier analysis was used for patient and graft survival. Pancreatic graft survival was defined as the time from transplantation to graft pancreatectomy or return to insulin or oral hypoglycaemics. Kidney graft survival was defined as time from transplantation to return to dialysis. Cases were censored in the event of death with a functioning graft or end of follow-up. Categorical data were analysed using Fisher’s exact test. All statistical analyses were performed with GraphPad Prism 5 (GraphPad Software, La Jolla, CA, USA).
Results Demographics and graft outcomes Ninety-eight patients underwent SPK transplantation between 1 January 2005 and 1 August 2010. There were 70 men and 28 women with a mean (SD) age of 40 (8.2) years. Organs were recovered from both donation after brain death (DBD, n¼83) and donation after circulatory death (DCD, n¼15) donors; mean (SD) donor age was 34.6 (13.9) years. The median follow-up was 791 (range 31e2057) days. No cases were lost to follow-up. As a means of providing a context in which CT was performed, graft and patient survival are shown in Fig 1. Eleven pancreatic grafts failed (venous thrombosis in six; arterial thrombosis in two; rejection in two; autoimmune recurrence of diabetes mellitus in one), and five kidneys failed (acute or chronic rejection in four; venous thrombosis in one).
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F.E. Powell et al. / Clinical Radiology xxx (2015) 1e9
During the study period, 313 post-transplant abdominopelvic CT examinations were performed (median two examinations per patient; range 0e15). Ten patients did not undergo imaging at any stage during follow-up. Fifty-six CT examinations were excluded from further analysis for the following reasons: indication unrelated to the pancreas graft (n¼21); performed post-graft pancreatectomy (n¼16); performed for drain or biopsy guidance only (n¼14); or technically inadequate investigation (n¼5). Of the 257 CT examinations included in the study, the majority (n¼232, 90.3%) were performed during radiological “daytime” working hours (09.00e21.00), and 56.4% (n¼145) were performed during the index admission. Most CT studies were triple-phase (n¼157, 61.1%); enhanced single-phase, or dual-phase imaging was used in 33.5% (n¼86), and the remainder were unenhanced (usually due to renal impairment).
Indications and findings The indications for performing CT imaging are listed in Table 1, with suspected intra-abdominal collection and abnormal pancreatic biochemical indices being the most common. A wide variety of abnormalities were noted (see Table 1), but the commonest finding was non-specific mild intra-abdominal inflammation (27.6%), with no abnormality detected in 17.1%. Other findings were intra-abdominal fluid collections (16.3%); bowel abnormalities (12.8%); overt graft pancreatitis (7.8%); and vascular abnormalities (7%; Fig 3). More than one abnormality was unusual; two major
findings were identified on only 14 CT examinations (5.4%), and three abnormalities on two examinations (0.8%). To assess whether specific clinical indications for requesting imaging were associated with distinct abnormalities on CT, the relationship between four clinical scenarios was compared with the CT findings (Table 2). In addition to examining the relationship between clinical suspicion and CT detection of an intra-abdominal collection, imaging for patients with high capillary blood glucose (CBG) was likely to be performed to exclude graft thrombosis; for those with deranged pancreatic enzymes, to assess the degree of graft inflammation; and for those with abdominal pain or suspicion of obstruction, to confirm obstruction, perforation or other bowel abnormalities. Of the four indication/abnormality pairings examined, only high CBG was significantly associated with a higher than expected incidence of a particular CT abnormality, in that 21.4% of examinations performed for high CBG identified an arterial or vascular abnormality, whereas the incidence in CT examinations performed for all other indications was 4.2% (p<0.001). There was no association between abdominal pain and CT confirmation of bowel obstruction/ other bowel abnormalities (p¼0.061), between deranged pancreatic enzymes and pancreas inflammation (p¼0.102) and between clinical suspicion and CT demonstration of an intra-abdominal collection (p¼1). Although there was a significant association between high CBG and vascular abnormalities, the predictive value of CBG for vascular abnormalities remains low, because these were only present in approximately one-fifth of examinations performed for this indication (Table 2).
Table 1 Computed tomography (CT) indications and findings post-simultaneous pancreas and kidney (SPK) transplantation. Findings
Non-specific, mild intra-abdominal inflammation Normal Abnormality unchanged Intra-abdominal fluid collection Bowel abnormalitiesa Pancreatitis Vascular abnormalitiesb Other abnormalitiesc Haematoma or bleeding Total number of findings
Indication (n¼257 scans) Suspected intra-abdominal collection (n¼80)
Raised serum amylase and/or lipase (n¼62)
High capillary blood glucose (n¼42)
Abdominal Reassessment Suspected Suspected Other Total pain (n¼15) bleeding bowel (n¼8) (% of all (n¼27) (n¼12) obstruction scans) (n¼11)
27 (33.8)
12 (19.4)
9 (21.4)
12 (44.4)
2 (13.3)
3 (25)
2 (18.2)
4 71 (27.6) (44.4)
2 (2.5) 10 (12.5)
23 (37.1) 9 (14.5)
10 (23.8) 3 (7.1)
4 (14.8) 1 (3.7)
3 (20) 3 (20)
1 (8.3) 0 (0)
1 (9.1) 0 (0)
0 (0) 0 (0)
44 (17.1) 26 (10.1)
13 (16.3)
4 (6.5)
5 (11.9)
6 (22.2)
6 (40)
2 (16.7)
3 (27.3)
42 (16.3)
13 (16.3) 10 (12.5) 1 (1.3)
3 (4.8) 8 (12.9) 4 (6.5)
5 (11.9) 0 (0) 9 (21.4)
4 (14.8) 2 (7.4) 3 (11.1)
0 (0) 0 (0) 0 (0)
1 (8.3) 0 (0) 1 (8.3)
5 (45.5) 0 (0) 0 (0)
3 (33.3) 2 (25) 0 (0) 0 (0)
7 (8.8) 0 (0)
5 (8.1) 0 (0)
1 (2.4) 2 (4.8)
0 (0) 0 (0)
1 (6.7) 0 (0)
0 (0) 4 (33.3)
1 (9.1) 0 (0)
0 (0) 0 (0)
15 (5.8) 6 (2.3)
83
68
44
32
15
12
12
9
275
33 (12.8) 20 (7.8) 18 (7)
a Significant small or large bowel wall thickening n¼10, small bowel obstruction n¼5, ileus n¼13, possible perforation n¼3, suspected intussusception n¼1, possible Roux-loop ischaemia n¼1. b Venous thrombosis n¼6, arterial thrombosis n¼6, venous or arterial stenosis or narrowing n¼6. c Kidney/bladder changes n¼6, resolving haematoma n¼1, poor enhancement of transplant gland but no obvious vascular abnormality n¼2, gynaecological abnormalities n¼2, abdominal wall hernia n¼1, liver haematoma n¼1, anterior abdominal wall collection n¼1, suspected gastrointestinal bleeding n¼1.
Please cite this article in press as: Powell FE, et al., Postoperative CT in pancreas transplantation, Clinical Radiology (2015), http://dx.doi.org/ 10.1016/j.crad.2015.06.086
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Figure 3 Vascular complications on postoperative CT following SPK transplantation. (a) Arterial phase axial CT image demonstrating complete thrombosis of the donor SMA (arrow). In this case the Y-graft has been anastomosed to the right common iliac artery; (b) 55 second delay axial CT image demonstrating non-occlusive thrombosis of the donor SMV (arrow). (c) Unenhanced axial CT image demonstrating high attenuation material within the distended donor portal vein (arrow), highly suspicious for occlusive thrombus; (c) 55 second delay axial CT image at the same level demonstrating a complete lack of enhancement within the portal vein confirming occlusive thrombus.
Changes to management The majority (n¼150, 58.4%) of CT studies did not prompt further intervention. Only 15.6% resulted in a major change intervention; 26.1% led to a minor intervention (Table 3). Those patients who underwent laparotomy as a result of CT were the most informative because they provided an opportunity to validate the CT findings. The most common indication for laparotomy was the demonstration on CT of either arterial or venous compromise (Table 3). Of these nine patients, pancreas graft thrombosis or infarction was confirmed at laparotomy in six. In two patients, no vascular abnormality was detected, and in one patient, it was impossible to visualise the venous anatomy. Six graft
pancreatectomies were performed as a consequence. Of the three gastrointestinal perforations diagnosed on CT imaging, two were visualised at laparotomy, and in the third case, the precise location of a probable perforation could not be identified. In the remainder, the CT findings were confirmed in all patients who underwent laparotomy. Crucially, the majority of studies provided reassurance to the transplant team and avoided the need for diagnostic laparotomy. Major interventions were required more frequently when the initial clinical indication was suspected bowel obstruction (45.5% versus 14.2%, p¼0.016), and less frequently when an intra-abdominal collection was suspected (8.7% versus 18.6%, p¼0.043; Table 4).
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Table 2 Association between clinical indications and computed tomography (CT) findings. Intra-abdominal collections Suspected intraCollection not abdominal collection suspected(n¼177) (n¼80) Collection 13 (16.3%) 29 (16.4%) identified Not identified 67 (83.8%) 148 (83.6%) High capillary blood glucose and vascular abnormalities High capillary blood Capillary blood glucose glucose (n¼42) normal (n¼215) Vascular 9 (21.4%) 9 (4.2%) abnormality identifieda Not identified 33 (78.6%) 206 (95.8%) Obstruction/abdominal pain and bowel abnormalities Suspected obstruction Obstruction not suspected, or abdominal pain no abdominal pain (n¼219) (n¼38) Bowel 9 (23.7%) 24 (11%) abnormality identifiedb Not identified 29 (76.3%) 195 (89%) Elevated serum amylase/lipase and pancreatitis Raised serum amylase Amylase/lipase and/or lipase (n¼62) normal (n¼195) Pancreatitis 8 (12.9%) 12 (6.2%) identified Not identified 54 (87.1%) 183 (93.8%) a Venous thrombosis n¼6, arterial thrombosis n¼6, venous or arterial stenosis or narrowing n¼6. b Significant small or large bowel wall thickening n¼10, small bowel obstruction n¼5, ileus n¼13, possible perforation n¼3, suspected intussusception n¼1, possible Roux-loop ischaemia n¼1.
Table 3 Interventions required post-computed tomography (CT). Subsequent interventions Major intervention required Laparotomya Ultrasound- or CT-guided collection drainage Full anticoagulation Arterial angioplasty Minor intervention required Further investigations arrangedb Antibiotics Treatment for rejection (IV methylprednisolone or anti-thymocyte globulin) Insertion of NG tube Otherc Anticoagulation stopped Laxatives or enema/suppository No intervention required a
Number of CT examinations (%) 40 23 11 5 1 67 34 8 8
(15.6%) (8.9) (4.3) (1.9) (0.4) (26.1%) (13.2) (3.1) (3.1)
6 6 3 2 150
(2.3) (2.3) (1.2) (0.8) (58.4%)
Indications for re-laparotomy: vascular abnormality (9), small bowel obstruction (5), perforation (3), collection (3), intra-abdominal haematoma (2), possible collection and peripancreatic induration (1). b Renal biopsy (16), pancreatic biopsy (5), angiogram (5), white-cell scan (3), gastroscopy (2), transabdominal and transvaginal ultrasound examinations (2), methylene blue via feeding jejunostomy (1). c Intravenous fluids for pancreatitis on CT (1), urinary catheterisation (1), nil by mouth and started on erythromycin (1), removal of inadvertentlyretained stent (1), correction of coagulopathy to control minor gastrointestinal blood loss (1) and drain removal (1).
Value of repeated CT The majority of patients had more than one CT examination, and approximately two-thirds were performed within 28 days of transplantation (Fig 4a). The chronology of examinations in individual patients showed that imaging was frequently clustered in relatively short time periods (Fig 4b), usually due to persisting symptoms and clinical uncertainty. Of the 157 studies performed in the first 28 days, 79 were performed as the first examination and 78 as repeat examination. The first examination led to a major intervention in 17 patients (21.5%); of the 78 repeat examination, only eight (10.3%) resulted in a major intervention (p¼0.080), whilst 69.2% (n¼54) led to no intervention, and 20.5% (n¼16) to a minor intervention. These findings, therefore, suggest that repeat CT is less likely to yield positive findings.
Discussion Despite improvements in surgical techniques and immunosuppression regimens, complications after SPK transplantation are common and include vascular complications, graft rejection, gastrointestinal and graft haemorrhage, pancreatitis and peripancreatic collections. Distinguishing clinically between these complications is often difficult, because they frequently present as a common syndrome that involves non-specific abdominal pain, graft tenderness, pyrexia, and elevated blood glucose and/or pancreatic enzymes. CT evaluation improves diagnostic accuracy, but the precise indications for imaging remain unclear. The present study highlights that CT can direct the team where interventions are required and, of equal importance, provide reassurance to the clinicians in this complex patient group, thus avoiding unnecessary surgery. Of the various imaging techniques available, ultrasonography of the pancreas transplant has been suggested as a first-line investigation,8 although accurate assessment may be limited by obscuration from overlying bowel gas where the pancreas is intraperitoneal. Magnetic resonance Table 4 Computed tomography (CT) indication and subsequent major management changes. Major intervention (%) Suspected intra-abdominal collection (n¼80) Elevated serum amylase and/or lipase (n¼62) High capillary blood glucose (n¼42) Abdominal pain (n¼27) Reassessment of previous findings (n¼15) Suspected bleeding (n¼12) Suspected bowel obstruction (n¼11) Other (n¼8) Total
Minor/no intervention (%)
7 (8.7)
73 (91.3)
7 (11.3)
55 (88.7)
9 (21.4)
33 (78.6)
5 (18.5) 2 (13.3)
22 (81.5) 13 (86.7)
4 (33.3) 5 (45.5)
8 (66.7) 6 (54.5)
1 (12.5) 40 (15.6)
7 (87.5) 217 (84.4)
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Figure 4 Timeline of CT examinations performed for individual patients. (a) Bar graph depicting number of CT examinations performed in specified periods after SPK transplantation. (b) Timeline depicting when CT examinations were performed on each patient. Symbols represent an individual CT and for ease of visualisation, where multiple examinations were performed on the same patient. These are connected by a horizontal line. Of the 98 patients, 10 had no examinations performed.
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imaging (MRI) including magnetic resonance angiography (MRA) has been suggested as the reference standard for visualising graft vasculature and parenchyma of the gland,9e12 but CT may identify infective and bowel-related complications more readily13e15 and is the preferred option in Addenbrooke’s Hospital. In addition, CT imaging is faster; an important factor if patients are acutely unwell. The present findings concur with previous publications reporting that a wide variety of abnormalities are identified by CT.16 Previous publications have not reported whether specific clinical scenarios are associated with distinct CT findings; equally, the impact of the CT on patient management has not been assessed in detail. One study has reported that routine CT examinations performed in the first week after pancreas transplantation may allow graft salvage by prompting anticoagulation when partial venous thrombosis is identified,17 but patient numbers were small and more than one-quarter of all grafts in that study were removed due to thrombosis. The present demonstration that high CBG is associated with thrombosis on CT imaging and the possible association with deranged pancreatic enzymes and CT confirmation of pancreatic inflammation, indicates that it is not possible to reliably distinguish different pathologies in the postoperative pancreas transplant patient on clinical assessment alone; the predictive value of the clinical findings for the final (CT) diagnosis was very poor. Moreover, the extent to which reporter bias is responsible for the association between clinical indication and CT finding requires consideration. CT imaging of postoperative pancreas recipients was not performed routinely, but only when clinically indicated; as such, the radiologist is guided by the clinical context. For example, the possible correlation of high serum amylase/lipase levels with graft pancreatitis on CT is unsurprising, but current models for scoring severity of native pancreatitis18 is not applicable to pancreas transplants in our experience. Thus the distinction between mild, non-specific inflammation and overt graft pancreatitis is subtle and operator dependent. Against this, identifying graft vascular thrombus on CT is likely less prone to observer variation and hence its correlation with high blood glucose levels (an equally distinct clinical measurement) is difficult to ascribe solely to undue weighting on the clinical information provided. One of the limitations of the present study is its retrospective nature, as this undoubtedly introduces a degree of subjectivity. In particular, the specific indication for performing a particular CT study, can, in some instances, be difficult to ascertain. Similarly, one could argue that the present classification of interventions was an arbitrary distinction; however, this distinction is appropriate in that reasonable doubt exists as to whether, for minor interventions, the management would have differed if the CT examination had not been performed. Notably in this respect, many of those cases of minor change depended on either a normal or minimally abnormal result to dictate change; in essence, CT is used to exclude structural or vascular abnormalities before, for example, graft biopsy is performed. Indeed, the greatest benefit of CT is prevention
of unnecessary laparotomy, but this is difficult to quantify retrospectively. A prospective study whereby the clinician documents the perceived impact on management at the time of CT may resolve this. Finally, the retrospective nature of the study also prohibits a definitive assessment of how essential CT was in prompting major changes in management, because it is not possible to state with confidence that the same treatment option would not have been followed if CT were unavailable. In this regard, two patients underwent laparotomy and subsequent removal of a thrombosed pancreas graft based on clinical findings alone. The present study is the first to attempt to correlate the clinical indications for performing postoperative CT following SPK transplantation with the CT findings and the impact on patient management. Despite demonstrating an association between specific clinical conditions and distinct abnormalities on subsequent CT imaging, a large number of examinations are performed in this complex group, which prove normal. Despite this, the key correlation between elevated CBG and potentially reversible vascular complications, demonstrated in this study, suggests this indication should carry greater weight in deciding whether to perform a CT examination in clinical practice. This is important, as a greater understanding of the clinical scenarios following SPK transplantation may allow for more selective use of imaging in this challenging group of patients.
Acknowledgements The authors thank Stephanie Smith and Julia Ertner for maintaining the prospective SPK database.
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16. Dachman AH, Newmark GM, Thistlethwaite Jr JR, et al. Imaging of pancreatic transplantation using portal venous and enteric exocrine drainage. AJR Am J Roentgenol 1998;171:157e63. 17. Grabowska-Derlatka L, Grochowiecki T, Jakimowicz T, et al. Usefulness of 16-row multidetector computed tomography with volume rendering and maximum intensity projection reconstruction as a monitor pancreatic graft vessel patency during the early postoperative period. Transplant Proc 2009;41:3154e5. 18. Balthazar EJ. Acute pancreatitis: assessment of severity with clinical and CT evaluation. Radiology 2002;223:603e13.
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Postoperative CT in pancreas transplantation F.E. Powell a, S.J.F. Harper a, *, C.J. Callaghan a, A. Shaw b, E.M. Godfrey b, J.A. Bradley a, C.J.E. Watson a, G.J. Pettigrew a a
University Department of Surgery, and NIHR Comprehensive Biomedical Research Centre, Addenbrooke’s Hospital, Cambridge University Hospitals NHS Foundation Trust, Cambridge CB2 0QQ, UK b Department of Radiology, Addenbrooke’s Hospital, Cambridge University Hospitals NHS Foundation Trust, Cambridge CB2 0QQ, UK
art icl e i nformat ion Article history: Received 24 October 2014 Received in revised form 13 May 2015 Accepted 18 June 2015
AIM: To examine the usage and value of computed tomography (CT) following simultaneous pancreas and kidney (SPK) transplantation. MATERIALS AND METHODS: Indications for postoperative CT, key findings, and their influence on management were determined by retrospective analysis. RESULTS: Ninety-eight patients underwent 313 CT examinations. Common indications for the examinations included suspected intra-abdominal collection (31.1%) and elevated serum amylase/lipase (24.1%). CT findings most frequently showed non-specific mild inflammation (27.6%), a normal scan (17.1%) and fluid collections (16.3%). High capillary blood glucose (CBG) was associated with resultant CT demonstration of graft vascular abnormalities, but otherwise, particular clinical indications were not associated with specific CT findings. CONCLUSION: Clinical findings in patients with SPK transplants are non-specific. The pattern of abnormalities encountered is significantly different to those seen in native pancreatic disease and demands a tailored protocol. CT enables accurate depiction of vascular abnormalities and fluid collections, thus reducing the number of surgical interventions that might otherwise be required. Elevated CBG should prompt urgent CT to exclude potentially reversible vascular complications. Ó 2015 Published by Elsevier Ltd on behalf of The Royal College of Radiologists.
Introduction For patients with type I diabetes and end-stage renal failure, simultaneous pancreas and kidney (SPK) transplantation offers a survival advantage over deceased donor kidney transplantation alone (Fig 1)1,2; however, despite
* Guarantor and correspondent: S.J.F. Harper, Consultant Hepatobiliary and Transplant Surgeon, University Department of Surgery, Box 202, Addenbrooke’s Hospital, NIHR Comprehensive Biomedical Research Centre, Hills Road, Cambridge CB2 0QQ, UK. Tel.: þ44 1223 336975; fax: þ44 1223 762523. E-mail address: [email protected] (S.J.F. Harper).
improvements in surgical techniques and postoperative care, pancreas transplantation is associated with a higher complication rate and longer hospital stay than kidney transplantation alone.3,4 The clinical assessment of postoperative pancreas transplant recipients is often challenging and radiological evaluation is frequently performed5e7; however, the ideal technique and the indications for imaging are unclear, particularly when the pancreas is sited intra-peritoneally; ultrasound, for example, is often suboptimal due to gas within the overlying intestines obscuring the pancreas transplant. At Addenbrooke’s Hospital, computed tomography (CT) is the preferred graft imaging technique following pancreas
http://dx.doi.org/10.1016/j.crad.2015.06.086 0009-9260/Ó 2015 Published by Elsevier Ltd on behalf of The Royal College of Radiologists.
Please cite this article in press as: Powell FE, et al., Postoperative CT in pancreas transplantation, Clinical Radiology (2015), http://dx.doi.org/ 10.1016/j.crad.2015.06.086
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Figure 1 Pancreas and kidney allograft outcomes. KaplaneMeier plots (with numbers at risk shown below): (a) actuarial pancreas and kidney allograft survival in SPK recipients (censored for death); (b) actuarial patient survival in SPK recipients.
transplantation. The present study reports the authors’ experience, focusing on the indications for imaging, the findings, and how CT influenced subsequent patient management; aspects that have not been previously reported.
Materials and methods Study population All patients undergoing SPK transplantation between 1 January 2005 and 1 August 2010 were included. Those receiving pancreatic grafts as part of multivisceral, modified multivisceral, or isolated pancreatic grafts were excluded. Post-transplant abdominopelvic CT performed on these patients at Addenbrooke’s Hospital were included if the primary indication was to image the pancreatic graft or to diagnose complications associated with it. Cases were excluded if they were performed for miscellaneous indications not related to the pancreas graft; performed following graft pancreatectomy; performed for drain or biopsy guidance only (following previous diagnostic CT); or were technically inadequate. Follow-up ended on 1 September 2010. Approval for the study was obtained from the Patient Safety Unit at Addenbrooke’s Hospital. The need for patient consent was waived.
Surgical implantation technique Pancreas grafts were implanted intra-peritoneally in the right iliac fossa with vascular reconstruction using a donor iliac artery ‘Y’ graft. Portal venous drainage was systemic via the inferior vena cava, with enteric exocrine drainage via a Roux-en-Y duodeno-enterostomy (Fig 2). A feeding jejunostomy was routinely placed, and an appendicectomy was performed in all recipients. Cholecystectomy was performed for those with gallstones or gallbladder polyps on ultrasonography performed during assessment. The kidney graft was placed extraperitoneally in the left iliac fossa.
Pancreatic imaging Pancreatic imaging was requested by senior clinicians in the transplant programme, according to perceived clinical need, in conjunction with biochemical markers of pancreatic function. CT was the primary imaging technique in pancreatic transplant recipients. Routine postoperative surveillance CT examination were not performed. If an intra-abdominal collection was suspected clinically, a single portal venous phase study was performed. A triple-phase study (unenhanced, early arterial and early venous phase) was performed in other cases unless contraindicated (e.g., anaphylaxis, poor renal function); oral contrast medium was not given routinely. Intravenous contrast medium comprised 100 ml iopamidol non-ionic contrast (Niopam 300, Bracco, High Wycombe, Bucks, UK). The unit has ready access to out-of-hours CT examinations; examinations are interpreted by senior radiology trainees with review by consultants routinely in working hours or out-of-hours as required.
Data collection and analysis Donor and recipient demographics, donor type, and patient and graft outcomes were obtained from a prospective database. All postoperative imaging was available via the hospital picture archiving and communications system (PACS). The clinical indication for each investigation was determined retrospectively from the electronic request form; when necessary, the primary indication was determined by case-note analysis. Key findings were recorded for each CT from the electronic report, including previously identified abnormalities in which a significant change had occurred. Where the request form suggested that the main indication was elevated blood glucose or serum amylase and/or lipase, contemporaneous biochemical values were recorded.
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Figure 2 Normal SPK anatomy. (a) Schematic diagram of typical SPK transplantation anatomy. (b) Arterial phase volume rendered coronal CT image demonstrating normal arterial anatomy of the transplanted pancreas. The large arrowhead indicates the donor Y-graft anastomosed to the right external iliac artery. The small arrowhead indicates the donor splenic artery and the small arrow the donor superior mesenteric artery. (c) Arterial phase coronal maximal intensity projection CT image demonstrating normal arterial anatomy following simultaneous PKT (same patient as in Figure 2a). Note the Y-graft anastomosed to the right external iliac artery and the donor renal artery anastomosed to the left external iliac artery. Surgical drains and a transplant ureteric stent are also in situ. (c) Sagittal reformatted 55-second delay curved CT image demonstrating normal venous anatomy following pancreatic transplantation. The large arrowhead indicates the donor portal vein that has been anastomosed to the inferior vena cava. The small arrowhead indicates the donor splenic vein and the small arrow the superior mesenteric vein.
The medical notes were reviewed to establish how often the imaging demonstrated positive findings requiring further intervention. Interventions were then categorised as follows: major (taken to theatre, ultrasound- or CT-guided drainage of collection, full anticoagulation, arterial angioplasty), minor (further investigations arranged, antibiotics, treatment for rejection, insertion of nasogastric tube, other, anticoagulation stopped, laxatives or enema/suppository), or no intervention required. KaplaneMeier analysis was used for patient and graft survival. Pancreatic graft survival was defined as the time from transplantation to graft pancreatectomy or return to insulin or oral hypoglycaemics. Kidney graft survival was defined as time from transplantation to return to dialysis. Cases were censored in the event of death with a functioning graft or end of follow-up. Categorical data were analysed using Fisher’s exact test. All statistical analyses were performed with GraphPad Prism 5 (GraphPad Software, La Jolla, CA, USA).
Results Demographics and graft outcomes Ninety-eight patients underwent SPK transplantation between 1 January 2005 and 1 August 2010. There were 70 men and 28 women with a mean (SD) age of 40 (8.2) years. Organs were recovered from both donation after brain death (DBD, n¼83) and donation after circulatory death (DCD, n¼15) donors; mean (SD) donor age was 34.6 (13.9) years. The median follow-up was 791 (range 31e2057) days. No cases were lost to follow-up. As a means of providing a context in which CT was performed, graft and patient survival are shown in Fig 1. Eleven pancreatic grafts failed (venous thrombosis in six; arterial thrombosis in two; rejection in two; autoimmune recurrence of diabetes mellitus in one), and five kidneys failed (acute or chronic rejection in four; venous thrombosis in one).
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During the study period, 313 post-transplant abdominopelvic CT examinations were performed (median two examinations per patient; range 0e15). Ten patients did not undergo imaging at any stage during follow-up. Fifty-six CT examinations were excluded from further analysis for the following reasons: indication unrelated to the pancreas graft (n¼21); performed post-graft pancreatectomy (n¼16); performed for drain or biopsy guidance only (n¼14); or technically inadequate investigation (n¼5). Of the 257 CT examinations included in the study, the majority (n¼232, 90.3%) were performed during radiological “daytime” working hours (09.00e21.00), and 56.4% (n¼145) were performed during the index admission. Most CT studies were triple-phase (n¼157, 61.1%); enhanced single-phase, or dual-phase imaging was used in 33.5% (n¼86), and the remainder were unenhanced (usually due to renal impairment).
Indications and findings The indications for performing CT imaging are listed in Table 1, with suspected intra-abdominal collection and abnormal pancreatic biochemical indices being the most common. A wide variety of abnormalities were noted (see Table 1), but the commonest finding was non-specific mild intra-abdominal inflammation (27.6%), with no abnormality detected in 17.1%. Other findings were intra-abdominal fluid collections (16.3%); bowel abnormalities (12.8%); overt graft pancreatitis (7.8%); and vascular abnormalities (7%; Fig 3). More than one abnormality was unusual; two major
findings were identified on only 14 CT examinations (5.4%), and three abnormalities on two examinations (0.8%). To assess whether specific clinical indications for requesting imaging were associated with distinct abnormalities on CT, the relationship between four clinical scenarios was compared with the CT findings (Table 2). In addition to examining the relationship between clinical suspicion and CT detection of an intra-abdominal collection, imaging for patients with high capillary blood glucose (CBG) was likely to be performed to exclude graft thrombosis; for those with deranged pancreatic enzymes, to assess the degree of graft inflammation; and for those with abdominal pain or suspicion of obstruction, to confirm obstruction, perforation or other bowel abnormalities. Of the four indication/abnormality pairings examined, only high CBG was significantly associated with a higher than expected incidence of a particular CT abnormality, in that 21.4% of examinations performed for high CBG identified an arterial or vascular abnormality, whereas the incidence in CT examinations performed for all other indications was 4.2% (p<0.001). There was no association between abdominal pain and CT confirmation of bowel obstruction/ other bowel abnormalities (p¼0.061), between deranged pancreatic enzymes and pancreas inflammation (p¼0.102) and between clinical suspicion and CT demonstration of an intra-abdominal collection (p¼1). Although there was a significant association between high CBG and vascular abnormalities, the predictive value of CBG for vascular abnormalities remains low, because these were only present in approximately one-fifth of examinations performed for this indication (Table 2).
Table 1 Computed tomography (CT) indications and findings post-simultaneous pancreas and kidney (SPK) transplantation. Findings
Non-specific, mild intra-abdominal inflammation Normal Abnormality unchanged Intra-abdominal fluid collection Bowel abnormalitiesa Pancreatitis Vascular abnormalitiesb Other abnormalitiesc Haematoma or bleeding Total number of findings
Indication (n¼257 scans) Suspected intra-abdominal collection (n¼80)
Raised serum amylase and/or lipase (n¼62)
High capillary blood glucose (n¼42)
Abdominal Reassessment Suspected Suspected Other Total pain (n¼15) bleeding bowel (n¼8) (% of all (n¼27) (n¼12) obstruction scans) (n¼11)
27 (33.8)
12 (19.4)
9 (21.4)
12 (44.4)
2 (13.3)
3 (25)
2 (18.2)
4 71 (27.6) (44.4)
2 (2.5) 10 (12.5)
23 (37.1) 9 (14.5)
10 (23.8) 3 (7.1)
4 (14.8) 1 (3.7)
3 (20) 3 (20)
1 (8.3) 0 (0)
1 (9.1) 0 (0)
0 (0) 0 (0)
44 (17.1) 26 (10.1)
13 (16.3)
4 (6.5)
5 (11.9)
6 (22.2)
6 (40)
2 (16.7)
3 (27.3)
42 (16.3)
13 (16.3) 10 (12.5) 1 (1.3)
3 (4.8) 8 (12.9) 4 (6.5)
5 (11.9) 0 (0) 9 (21.4)
4 (14.8) 2 (7.4) 3 (11.1)
0 (0) 0 (0) 0 (0)
1 (8.3) 0 (0) 1 (8.3)
5 (45.5) 0 (0) 0 (0)
3 (33.3) 2 (25) 0 (0) 0 (0)
7 (8.8) 0 (0)
5 (8.1) 0 (0)
1 (2.4) 2 (4.8)
0 (0) 0 (0)
1 (6.7) 0 (0)
0 (0) 4 (33.3)
1 (9.1) 0 (0)
0 (0) 0 (0)
15 (5.8) 6 (2.3)
83
68
44
32
15
12
12
9
275
33 (12.8) 20 (7.8) 18 (7)
a Significant small or large bowel wall thickening n¼10, small bowel obstruction n¼5, ileus n¼13, possible perforation n¼3, suspected intussusception n¼1, possible Roux-loop ischaemia n¼1. b Venous thrombosis n¼6, arterial thrombosis n¼6, venous or arterial stenosis or narrowing n¼6. c Kidney/bladder changes n¼6, resolving haematoma n¼1, poor enhancement of transplant gland but no obvious vascular abnormality n¼2, gynaecological abnormalities n¼2, abdominal wall hernia n¼1, liver haematoma n¼1, anterior abdominal wall collection n¼1, suspected gastrointestinal bleeding n¼1.
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Figure 3 Vascular complications on postoperative CT following SPK transplantation. (a) Arterial phase axial CT image demonstrating complete thrombosis of the donor SMA (arrow). In this case the Y-graft has been anastomosed to the right common iliac artery; (b) 55 second delay axial CT image demonstrating non-occlusive thrombosis of the donor SMV (arrow). (c) Unenhanced axial CT image demonstrating high attenuation material within the distended donor portal vein (arrow), highly suspicious for occlusive thrombus; (c) 55 second delay axial CT image at the same level demonstrating a complete lack of enhancement within the portal vein confirming occlusive thrombus.
Changes to management The majority (n¼150, 58.4%) of CT studies did not prompt further intervention. Only 15.6% resulted in a major change intervention; 26.1% led to a minor intervention (Table 3). Those patients who underwent laparotomy as a result of CT were the most informative because they provided an opportunity to validate the CT findings. The most common indication for laparotomy was the demonstration on CT of either arterial or venous compromise (Table 3). Of these nine patients, pancreas graft thrombosis or infarction was confirmed at laparotomy in six. In two patients, no vascular abnormality was detected, and in one patient, it was impossible to visualise the venous anatomy. Six graft
pancreatectomies were performed as a consequence. Of the three gastrointestinal perforations diagnosed on CT imaging, two were visualised at laparotomy, and in the third case, the precise location of a probable perforation could not be identified. In the remainder, the CT findings were confirmed in all patients who underwent laparotomy. Crucially, the majority of studies provided reassurance to the transplant team and avoided the need for diagnostic laparotomy. Major interventions were required more frequently when the initial clinical indication was suspected bowel obstruction (45.5% versus 14.2%, p¼0.016), and less frequently when an intra-abdominal collection was suspected (8.7% versus 18.6%, p¼0.043; Table 4).
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Table 2 Association between clinical indications and computed tomography (CT) findings. Intra-abdominal collections Suspected intraCollection not abdominal collection suspected(n¼177) (n¼80) Collection 13 (16.3%) 29 (16.4%) identified Not identified 67 (83.8%) 148 (83.6%) High capillary blood glucose and vascular abnormalities High capillary blood Capillary blood glucose glucose (n¼42) normal (n¼215) Vascular 9 (21.4%) 9 (4.2%) abnormality identifieda Not identified 33 (78.6%) 206 (95.8%) Obstruction/abdominal pain and bowel abnormalities Suspected obstruction Obstruction not suspected, or abdominal pain no abdominal pain (n¼219) (n¼38) Bowel 9 (23.7%) 24 (11%) abnormality identifiedb Not identified 29 (76.3%) 195 (89%) Elevated serum amylase/lipase and pancreatitis Raised serum amylase Amylase/lipase and/or lipase (n¼62) normal (n¼195) Pancreatitis 8 (12.9%) 12 (6.2%) identified Not identified 54 (87.1%) 183 (93.8%) a Venous thrombosis n¼6, arterial thrombosis n¼6, venous or arterial stenosis or narrowing n¼6. b Significant small or large bowel wall thickening n¼10, small bowel obstruction n¼5, ileus n¼13, possible perforation n¼3, suspected intussusception n¼1, possible Roux-loop ischaemia n¼1.
Table 3 Interventions required post-computed tomography (CT). Subsequent interventions Major intervention required Laparotomya Ultrasound- or CT-guided collection drainage Full anticoagulation Arterial angioplasty Minor intervention required Further investigations arrangedb Antibiotics Treatment for rejection (IV methylprednisolone or anti-thymocyte globulin) Insertion of NG tube Otherc Anticoagulation stopped Laxatives or enema/suppository No intervention required a
Number of CT examinations (%) 40 23 11 5 1 67 34 8 8
(15.6%) (8.9) (4.3) (1.9) (0.4) (26.1%) (13.2) (3.1) (3.1)
6 6 3 2 150
(2.3) (2.3) (1.2) (0.8) (58.4%)
Indications for re-laparotomy: vascular abnormality (9), small bowel obstruction (5), perforation (3), collection (3), intra-abdominal haematoma (2), possible collection and peripancreatic induration (1). b Renal biopsy (16), pancreatic biopsy (5), angiogram (5), white-cell scan (3), gastroscopy (2), transabdominal and transvaginal ultrasound examinations (2), methylene blue via feeding jejunostomy (1). c Intravenous fluids for pancreatitis on CT (1), urinary catheterisation (1), nil by mouth and started on erythromycin (1), removal of inadvertentlyretained stent (1), correction of coagulopathy to control minor gastrointestinal blood loss (1) and drain removal (1).
Value of repeated CT The majority of patients had more than one CT examination, and approximately two-thirds were performed within 28 days of transplantation (Fig 4a). The chronology of examinations in individual patients showed that imaging was frequently clustered in relatively short time periods (Fig 4b), usually due to persisting symptoms and clinical uncertainty. Of the 157 studies performed in the first 28 days, 79 were performed as the first examination and 78 as repeat examination. The first examination led to a major intervention in 17 patients (21.5%); of the 78 repeat examination, only eight (10.3%) resulted in a major intervention (p¼0.080), whilst 69.2% (n¼54) led to no intervention, and 20.5% (n¼16) to a minor intervention. These findings, therefore, suggest that repeat CT is less likely to yield positive findings.
Discussion Despite improvements in surgical techniques and immunosuppression regimens, complications after SPK transplantation are common and include vascular complications, graft rejection, gastrointestinal and graft haemorrhage, pancreatitis and peripancreatic collections. Distinguishing clinically between these complications is often difficult, because they frequently present as a common syndrome that involves non-specific abdominal pain, graft tenderness, pyrexia, and elevated blood glucose and/or pancreatic enzymes. CT evaluation improves diagnostic accuracy, but the precise indications for imaging remain unclear. The present study highlights that CT can direct the team where interventions are required and, of equal importance, provide reassurance to the clinicians in this complex patient group, thus avoiding unnecessary surgery. Of the various imaging techniques available, ultrasonography of the pancreas transplant has been suggested as a first-line investigation,8 although accurate assessment may be limited by obscuration from overlying bowel gas where the pancreas is intraperitoneal. Magnetic resonance Table 4 Computed tomography (CT) indication and subsequent major management changes. Major intervention (%) Suspected intra-abdominal collection (n¼80) Elevated serum amylase and/or lipase (n¼62) High capillary blood glucose (n¼42) Abdominal pain (n¼27) Reassessment of previous findings (n¼15) Suspected bleeding (n¼12) Suspected bowel obstruction (n¼11) Other (n¼8) Total
Minor/no intervention (%)
7 (8.7)
73 (91.3)
7 (11.3)
55 (88.7)
9 (21.4)
33 (78.6)
5 (18.5) 2 (13.3)
22 (81.5) 13 (86.7)
4 (33.3) 5 (45.5)
8 (66.7) 6 (54.5)
1 (12.5) 40 (15.6)
7 (87.5) 217 (84.4)
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Figure 4 Timeline of CT examinations performed for individual patients. (a) Bar graph depicting number of CT examinations performed in specified periods after SPK transplantation. (b) Timeline depicting when CT examinations were performed on each patient. Symbols represent an individual CT and for ease of visualisation, where multiple examinations were performed on the same patient. These are connected by a horizontal line. Of the 98 patients, 10 had no examinations performed.
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F.E. Powell et al. / Clinical Radiology xxx (2015) 1e9
imaging (MRI) including magnetic resonance angiography (MRA) has been suggested as the reference standard for visualising graft vasculature and parenchyma of the gland,9e12 but CT may identify infective and bowel-related complications more readily13e15 and is the preferred option in Addenbrooke’s Hospital. In addition, CT imaging is faster; an important factor if patients are acutely unwell. The present findings concur with previous publications reporting that a wide variety of abnormalities are identified by CT.16 Previous publications have not reported whether specific clinical scenarios are associated with distinct CT findings; equally, the impact of the CT on patient management has not been assessed in detail. One study has reported that routine CT examinations performed in the first week after pancreas transplantation may allow graft salvage by prompting anticoagulation when partial venous thrombosis is identified,17 but patient numbers were small and more than one-quarter of all grafts in that study were removed due to thrombosis. The present demonstration that high CBG is associated with thrombosis on CT imaging and the possible association with deranged pancreatic enzymes and CT confirmation of pancreatic inflammation, indicates that it is not possible to reliably distinguish different pathologies in the postoperative pancreas transplant patient on clinical assessment alone; the predictive value of the clinical findings for the final (CT) diagnosis was very poor. Moreover, the extent to which reporter bias is responsible for the association between clinical indication and CT finding requires consideration. CT imaging of postoperative pancreas recipients was not performed routinely, but only when clinically indicated; as such, the radiologist is guided by the clinical context. For example, the possible correlation of high serum amylase/lipase levels with graft pancreatitis on CT is unsurprising, but current models for scoring severity of native pancreatitis18 is not applicable to pancreas transplants in our experience. Thus the distinction between mild, non-specific inflammation and overt graft pancreatitis is subtle and operator dependent. Against this, identifying graft vascular thrombus on CT is likely less prone to observer variation and hence its correlation with high blood glucose levels (an equally distinct clinical measurement) is difficult to ascribe solely to undue weighting on the clinical information provided. One of the limitations of the present study is its retrospective nature, as this undoubtedly introduces a degree of subjectivity. In particular, the specific indication for performing a particular CT study, can, in some instances, be difficult to ascertain. Similarly, one could argue that the present classification of interventions was an arbitrary distinction; however, this distinction is appropriate in that reasonable doubt exists as to whether, for minor interventions, the management would have differed if the CT examination had not been performed. Notably in this respect, many of those cases of minor change depended on either a normal or minimally abnormal result to dictate change; in essence, CT is used to exclude structural or vascular abnormalities before, for example, graft biopsy is performed. Indeed, the greatest benefit of CT is prevention
of unnecessary laparotomy, but this is difficult to quantify retrospectively. A prospective study whereby the clinician documents the perceived impact on management at the time of CT may resolve this. Finally, the retrospective nature of the study also prohibits a definitive assessment of how essential CT was in prompting major changes in management, because it is not possible to state with confidence that the same treatment option would not have been followed if CT were unavailable. In this regard, two patients underwent laparotomy and subsequent removal of a thrombosed pancreas graft based on clinical findings alone. The present study is the first to attempt to correlate the clinical indications for performing postoperative CT following SPK transplantation with the CT findings and the impact on patient management. Despite demonstrating an association between specific clinical conditions and distinct abnormalities on subsequent CT imaging, a large number of examinations are performed in this complex group, which prove normal. Despite this, the key correlation between elevated CBG and potentially reversible vascular complications, demonstrated in this study, suggests this indication should carry greater weight in deciding whether to perform a CT examination in clinical practice. This is important, as a greater understanding of the clinical scenarios following SPK transplantation may allow for more selective use of imaging in this challenging group of patients.
Acknowledgements The authors thank Stephanie Smith and Julia Ertner for maintaining the prospective SPK database.
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