Simultaneous Pancreas-Kidney Transplant Complicated by Kidney Allograft Torsion and Pseudoaneurysms of the Y-Allograft: A Case Report and Review of the Literature

Background We report and review the literature of two rare complications of simultaneous pancreas-kidney transplantation (SPKT) occurring in one patient. Case Report. A 39-year-old man with dialysis-dependent kidney failure secondary to type 1 diabetes mellitus underwent successful SPKT in October 2018. Three months later, he presented with an acute kidney injury (AKI) and returned to dialysis. Kidney scintigraphy showed a central photopenic region, and angiograms showed absent flow in the kidney transplant artery without treatable thrombus and the incidental finding of two pseudoaneurysms of the pancreatic Y-graft. He remained dialysis-dependent for three weeks before spontaneous partial recovery of allograft function; repeat kidney scintigraphy showed significant improvement in perfusion. However, in April 2019 he was readmitted with a sudden deterioration in kidney allograft function again necessitating haemodialysis. Repeat imaging confirmed that the kidney allograft had shifted from the left iliac fossa to the midline. He underwent surgical exploration, during which torsion of the kidney allograft was confirmed and a nephropexy was performed. The kidney allograft was originally implanted in the left retroperitoneum via a midline transperitoneal approach, which likely predisposed it to torsion. The pseudoaneurysms of the pancreatic Y-graft were managed conservatively, and surveillance imaging demonstrated that they remained stable in size. The patient regained reasonable kidney allograft function (estimated glomerular filtration rate, eGFR, of 45 mL/min) and maintained normal pancreatic allograft function. Conclusion Kidney allograft torsion should be considered post-SPKT in patients with AKI and absent arterial flow. Although most case reports describe surgical management of pseudoaneurysms post-SPKT, our case demonstrates successful conservative management.


Introduction
SPKT is an established treatment option for patients with type 1 diabetes who are dialysis-dependent.Tere were 38 SPKT recipients in Australia in 2019 [1].Although SPKT ofers numerous benefts, including improved patient survival; recipients tend to experience surgical complications at a relatively higher rate in comparison to kidneyonly recipients, without impact on longer-term allograft function [2][3][4].
We describe and review the literature of two rare complications of SPKT occurring in the same patient: torsion of the kidney allograft and pseudoaneurysms of the pancreatic Y-graft.

Case Presentation
A 39-year-old man with kidney failure secondary to type 1 diabetes mellitus received a simultaneous pancreas-kidney transplant in October 2018 after four years on haemodialysis.Via a transperitoneal approach, the donor's left kidney was placed in the left iliac fossa.Te single transplant renal artery was anastomosed end-to-side to the left external iliac artery; the single transplant renal vein was anastomosed to the left external iliac vein, and the transplant ureter to the recipient's bladder.Te donor pancreas was vascularised via a Y-graft from the donor splenic and superior mesenteric arteries to the recipient's right common iliac artery; the donor portal vein anastomosed to the recipient's inferior vena cava.Te donor duodenum was anastomosed to the recipient's jejunum for exocrine drainage.
Postoperatively, he returned to theatre on day 0 posttransplant.A repeat laparotomy demonstrated bleeding around the venous anastomosis of the kidney allograft and a small branch of the inferior vena cava (IVC), with haemostasis being achieved.
Te patient made an excellent recovery and was discharged two weeks post-transplant on triple immunosuppressive therapy: tacrolimus, mycophenolate, and prednisolone.Prior to discharge, he was euglycaemic with a creatinine of 94 μmol/L and lipase of 33 U/L.A contrast computed tomography (CT) scan performed on day 22 post-SPKT showed patent transplant vessels of both the pancreatic and kidney allografts with no abnormalities of the vasculature.No abnormal positioning of either allograft was noted.
He presented three months later (day 95 post-transplant) with AKI -creatinine 403 μmol/L and lactate dehydrogenase of 2301 U/L.He was asymptomatic.Tree days prior to admission, his creatinine had been 104 μmol/L.He remained euglycaemic with a normal lipase.Kidney scintigraphy showed a central photopenic region (Figure 1), and subsequent angiography confrmed minimal fow in the transplant renal artery with a nonperfused kidney allograft and no thrombus amenable to intervention.Torsion of the vessels was not observed at the angiogram.A further contrast CT scan demonstrated no diferential enhancement of the transplant kidney between the arterial and portal venous phases, and the diagnosis was presumed kidney allograft loss secondary to infarction.Te placement of the kidney allograft was not commented on.
Te CT also revealed the development of two pseudoaneurysms of the superior iliac artery of the Y-graft (Figure 2) measuring 12 × 4 mm and 3 mm, respectively.
Extensive investigation looking for infection and vasculitis (including blood cultures, antineutrophil cytoplasmic antibodies, antinuclear antibody, extractable nuclear antigen antibodies, and an antiphospholipid antibody screen) as potential causes of the pseudoaneurysms returned negative results and a decision was made to opt for conservative management.Te creatinine peaked at 766 μmol/L and he was re-established on haemodialysis and discharged to home.
Te patient underwent 11 sessions of haemodialysis over 3 weeks.A repeat kidney scintigraphy was performed after he reported increasing urine output and this revealed improvement in kidney perfusion with no evidence of vascular insult (Figure 3).
He was trialled of dialysis and achieved a baseline creatinine of 250 μmol/L.Pancreatic allograft function remained stable throughout this time.Mobility of the kidney allograft was suspected to be the underlying cause and a semiurgent nephropexy was planned.However, one day prior to his planned surgery, he represented on day 158 posttransplant, again with AKI (creatinine 532 μmol/L from 249 μmol/L two days prior).A third nuclear scan was performed, this time demonstrating reduced perfusion of the kidney allograft with displacement from the left iliac fossa to the central abdomen (Figure 4).
He received a single session of haemodialysis before undergoing urgent surgical correction with nephropexy.Tis involved surgical fxation of the kidney allograft by creating an extraperitoneal pocket to place the kidney behind the retroperitoneum.A biopsy showed acute tubular necrosis with no evidence of rejection.
Te patient has since maintained reasonable allograft function with a baseline creatinine 170 μmol/L (eGFR of 45 mL/min).His pancreatic function remains stable, with no insulin requirement and normal lipase levels.An ultrasound of the pancreatic allograft at 19 months posttransplant revealed that the pseudoaneurysm was not larger at 6.5 × 5.9 mm in size; the smaller pseudoaneurysm could not be visualised.A CT with contrast at 25 months posttransplant demonstrated a pancreatic transplant of normal appearance.Regular imaging surveillance of the pseudoaneurysms will continue at 6-12 monthly intervals, or earlier in the event of symptoms.

Discussion
Tis is the frst case report to describe two rare complications of SPKT -kidney allograft torsion and pseudoaneurysms of the Y-allograft -occurring in one patient.
Kidney torsion is an uncommon cause of allograft failure and requires a high degree of diagnostic suspicion due to its nonspecifc symptomatology and variable timing of presentation.At the time of writing, there were26 published cases of kidney transplant torsion, 18 of which involved SPKT with intraperitoneal placement of the kidney.Tese are summarised in Table 1.
Among the SPKT recipients, for whom the kidney allograft is typically placed intraperitoneally, the timing of the occurrence of kidney allograft torsion was highly variable, ranging from the early postoperative period to ten years post-transplant [7,11].Interestingly, of the 8 kidney transplants performed without pancreatic transplantation, 3 of these allografts were placed extraperitoneally and experienced torsion in the early postoperative period [14][15][16].

2
Case Reports in Nephrology Some clinicians have proposed that intraperitoneal placement increases the risk of mobility with subsequent torsion and recommend that prophylactic nephropexy should be performed for patients who require an intraperitoneal kidney transplant [12,21].Kidney allograft torsion results in a high rate of allograft loss, with only 58% of allografts salvaged (15 of 26) [7,8,[11][12][13][14][15][16][17][18][19][20][21].Successful management depends on rapid diagnosis and surgical correction to limit ischaemic time and, as in our case, can result in a favourable allograft outcome.
Pseudoaneurysm development is a rare complication of SPKT and can present as a medical emergency.Patients may present with rupture leading to signifcant haemodynamic instability necessitating urgent intervention [22][23][24].Asymptomatic presentations such as in our patient are infrequently described [25][26][27][28].Proposed aetiologies for pseudoaneurysm development include infection, vascular damage during transplantation, pancreatitis, and as a complication of biopsy [28][29][30][31].Pseudoaneurysms developing in the setting of previous failed pancreas allografts have also been described [31].Te aetiology of our patient's pseudoaneurysms remains uncertain.We hypothesise that they may have developed as a consequence of vascular injury given the need for a second laparotomy to establish haemostasis.
Te current literature guiding management of this uncommon complication comprises case reports and small case series.Most centres reporting their outcomes of pseudoaneurysms describe management via surgical intervention and, in more recent times, an endovascular approach [26,[31][32][33].Of the three case reports describing patients with asymptomatic pseudoaneurysms, one patient went on to develop haemorrhage in the setting of anticoagulation and required endovascular intervention, and one underwent surgical exploration due to the large size of the pseudoaneurysm (8 cm) with the fnal patient declining intervention [26][27][28].Our patient, for whom no infective cause for the pseudoaneurysms could be identifed, remains  asymptomatic following a conservative approach at 40 months post-transplant, and imaging (ultrasound and CT with contrast) indicates that the pseudoaneurysms have remained stable in size, though ongoing surveillance will continue.For our case, conservative management with regular imaging surveillance was felt to be a reasonable option due to the relatively small size of the pseudoaneurysms, lack of clinical symptoms, and absence of an identifed aetiology that clearly warranted intervention, such as infection.
In conclusion, kidney allograft torsion, though rare, is an important diferential in SPKT recipients with AKI.Swift diagnosis increases the likelihood of allograft salvage, as operative correction is essential.Some transplant specialists recommend prevention via nephropexy [12].Our case is notable in that there were two signifcant   4 Case Reports in Nephrology Case Reports in Nephrology kidney torsion events both requiring haemodialysis.Te frst episode resolved spontaneously, and the second required surgical correction.Te occurrence of pseudoaneurysms following SPKT is also unusual, and its management in the literature is variable.Our case is diferent in a number of aspects, but particularly in our decision to opt for conservative management in light of his asymptomatic presentation.

Figure 2 :
Figure 2: Contrast computed tomography scan of the abdomen showing one of the two pseudoaneurysms of the superior artery of the Y-graft.

Figure 1 :
Figure 1: Kidney scintigraphy on day 95 post-transplantation demonstrating a central photopenic region, suggesting absent perfusion of the kidney allograft.

Figure 4 :
Figure 4: Kidney scintigraphy performed on day 158 post-transplant showing displacement of the transplant kidney to the midline, still with some perfusion present.

Figure 3 :
Figure 3: Kidney scintigraphy performed on day 115 post-transplantation demonstrating a return of perfusion to the kidney allograft.

Table 1 :
Summary table of published cases of kidney allograft torsion.