Vascular Challenges in Horseshoe Kidney Transplantation: A Case Report

Introduction

GRAFTS BENCHING AND SPLITTING TECHNIQUE:

There are 2 ways of transplanting HK: whole, en bloc or in up to 2 separate split fragments. The main problems to be overcome when preparing HKs for transplantation are vascular complexity and urinary tract malformations.

There is no single technique for splitting HKs. The division of the isthmus must be planned first. Before dividing, the surgeon should confirm that both split fragments have separate urinary collecting systems and viable adequate vasculature. In living donors, this can be done using noninvasive methods, such as urinary computed tomography (CT) or magnetic resonance imaging or scintigraphy. These techniques can also visualize the vasculature. In the case of deceased donor kidneys, dyes, such as methylene blue, should be injected into the ureters to confirm the structure of the urinary collecting system [8]. Ureterography after contrast injection into the ureters and direct X-ray is the other method of confirmation [8]. Indocyanine green with a fluorescence detector can be used to visualize the vasculature of separate fragments during bench preparation of the graft.

Division can be performed with a scalpel or harmonic scalpel to minimize the risk of bleeding from the incision site. Division with a stapler gastrointestinal anastomosis in a living donor has also been reported [7]. Prior to division in living donors, the supplying arteries should be clamped or ligated to make a safe incision in the ischemic area. This also avoids leaving a necrotic part of the HK in the donor. The incision site can be sutured with absorbable sutures −1 or 2 running sutures, or single sutures. De Pablos-Rodríguez et al reported [9] that the isthmus site was also sutured with hem-o-locks.

Supplying blood vessels can be anastomosed separately, reconstructed to a common trunk, or reconstructed on a single aortic patch in case of the inflow. If reconstruction is required, particularly, matching the length of a vein to the length of an artery, it can be achieved with elongation of the donor’s inferior vena cava.

Case Report

DONOR:

The donor was 36-year-old man with confirmed brain death triggered by onset of intracerebral bleeding. Brain death was confirmed on the fourth day of hospitalization in the Intensive Care Unit.

The donor had a normal weight (body mass index=24.7 kg/m2), hearing impairment, and no other confirmed chronic diseases. His blood type was B Rh (+), and he was HIVab (-), HBsAg (-), HCVab (-), HBc (-), CMV IgG (+), CMV IgM (-), VDRL (-), Toxoplasma IgG (+), and IgM (-). Tumor marker tests were within normal limits. Laboratory parameters of the donor are shown in Table 1. Vital parameters were stable, with noradrenaline infusion 0.02 μg/kg/min. Diuresis was maintained at 100 mL/h.

Procurement was performed within a day after donor registration on the fifth day of hospitalization. An amount of 25 000 UI of unfractionated heparin was administered intravenously prior to in situ perfusion. Perfusion was performed with Store Protect Plus by the aorta and superior mesenteric vein in amounts of 4000 mL and 1000 mL, respectively. The HK was procured en bloc and stored in University of Wisconsin (UW) Store Protect Plus under static cold storage (4°C).

SPLITTING PROCEDURE OF THE HK:

An isthmus was made up of the fused lower poles. The kidney had a vascular supply of a total of 7 arteries and 2 veins (Figure 1), accompanied by 2 ureters. Methylene blue was injected into each ureter to confirm that both fragments had separate urinary collecting ducts. The splitting procedure started with removing the excess fat tissue and 2 adrenal glands from the upper poles. The isthmus was then incised with a scalpel. The incision sites were sutured with 2 PDS 4-0 running sutures. The fragment of the donor aorta was incised longitudinally in the midline with the scissors. The portion of the donor vena cava inferior was divided in the similar way, between the HK fragments. The right kidney arterial supply was reconstructed to produce 2 separate patches: the upper with 2 arteries and the lower with 1 artery. The upper patch in addition was reconstructed from 2 single patches, due to the long distance between the arteries in the donor’s aorta. The patches were connected with a Prolene 5-0 running suture. The right renal vein was extended with the donor vena cava inferior patch. Reconstruction was performed with 2 Prolene 5-0 running sutures. In the left kidney, the 2 patches were sutured together with the additional barrel anastomosis. The barrel patch was constructed within a Prolene 5-0 running suture. The left vein was single and did not require reconstruction. The kidneys were then perfused with Ringer’s lactate to visualize possible leaks. The leakage sites were then sutured with single non-absorbable Prolene 5-0 sutures. The time-zero biopsy was taken from each kidney at the upper pole. The biopsy site was sutured with a single “z-fashion” PDS 4-0 suture. Backtable preparation lasted 3 h. Prepared kidneys grafts were stored in Belzer UW solution and kept under static cold storage conditions until transplantation. Each kidney was flushed with approximately 200 to 300 mL of Ringer’s lactate right before surgery.

Histopathological examination of the time-zero of the both grafts has shown mild arteriosclerosis and mild arteriole hyalinization (Remuzzi score=2). Table 1 presents the data regarding the donor and the procurement. Figures 2 and 3 present separate reconstructed kidney grafts after splitting.

Recipients were selected based on waiting list and human leukocyte antigen (HLA) matching from first and sixth place, respectively. Disqualification of the candidates between was based on expired qualification testing (1 patient), expected surgical difficulties (2 patients), and malignancy found in left kidney in CT scan (1 patient).

RECIPIENT 1:

The patient was a 64-year-old-man with end-stage kidney disease secondary to diabetes mellitus type 1, which was well-controlled with multiple dose insulin injections of average 36 IU per day and continuous glucose monitoring. Nevertheless, the patient had multiple vascular complications of diabetes mellitus type 1. The patient had chronic coronary artery disease, with a history of acute coronary syndrome of the anterolateral wall in 2003, which was addressed with percutaneous coronary intervention (PCI) and stenting. A year before transplant, 4 PCIs were performed. The first was with plain old balloon angioplasty of the left anterior descending artery; the second with balloon angioplasty of left anterior descending artery with drug-eluting balloons SeQuent Please NEO 2.5/35 mm. The third PCI included plain old balloon angioplasty of diagonal and marginal branches of the left coronary artery. The last procedure involved the right coronary artery, with implantation of a drug eluting stent. The last procedure was performed 12 months before transplantation, and the patient remained on single-drug antiplatelet therapy of 75 mg of acetylsalicylic acid. In pre-transplant evaluation, the patient had heart failure with preserved ejection fraction (55%) and enlarged left atrium (left atrium volume index 47 mL/m², left atrium area 25.1 cm²). Radiological examination showed ischemic lesions in the left cerebellar hemisphere. Moreover, the patient had retinopathy, with a history of photocoagulation 18 years before transplant and cataract surgery. Additionally, the patient had arterial hypertension, hyperlipidaemia, hyperuricaemia, spondylarthritis, left inguinal hernia, and hernia of the linea alba.

Peritoneal dialysis was started 16 months before transplantation by means of a Tenckhoff catheter. There was a single incident of catheter exit-site infection with Staphylococcus aureus 5 months before the transplant.

At admission, the patient was in overall good condition, with no signs of infection, and had 500 to 900 mL of diuresis. Preoperative laboratory blood test results are shown in Table 2.

HLA compliance was 2/6 in HLA-A, -B and -DR. Preformed reactive antibodies activity was 0%.

Immunosuppression was induced with 20 mg of basiliximab prior to kidney transplantation, in accordance with the local induction protocol.

On August 13, 2024, the right kidney graft was implanted on the left pelvic plate with end-to-side anastomoses to the external iliac vein and 2 arterial anastomoses to the external iliac artery using medial and lateral running suture Prolene 5-0. The lower part of the posterior and inferior segments had visibly worse perfusion. The ureterovesical anastomosis was made using a PDS 4-0 running suture, with the implantation of a 6-mm double-J catheter. Redon drainage was placed along the kidney close to the anastomoses. The Tenckhoff catheter was removed after the transplant and closing of the muscle fascia, subcutaneous layer, and skin with PDS 1-0 loop, PDS 3-0, and Monosyn 3-0 running sutures, respectively. Blood loss was estimated at 150 mL. The operation lasted 2.5 h, anastomoses time was 73 min, and cold ischemia time of kidney was 12 h 33 min (753 min). Standard 3-drug regimen of immunosuppression consisted of tacrolimus, mycophenolate mofetil, and glucocorticosteroids.

Blood flow within the graft was controlled with ultrasound sonography, with Doppler ultrasound 4 h after surgery and in following days. On postoperative day (POD) 0, one kidney artery was visualized with a high pulse range, with Vmax=207 cm/s and Vmin 28 cm/s. The vein was patent, and the pelvicalyceal system was not dilated. On POD 1, two graft arteries were visualized. The proximal artery had a high pulse range, with Vmax=140 cm/s and Vmin=18 cm/s. The distal artery had high resistance flow, with Vmax=225 cm/s and no diastolic flow. On POD 2, the proximal artery had a high pulse range, with Vmax=395 cm/s and Vmin=15 cm/s. The distal artery had a high resistance flow, with Vmax=185 cm/s and no diastolic flow. Parenchymal flow was visible with low resistance, except the lower renal pole, where no diastolic flow was visible. On POD 7, the proximal artery had a high pulse range with Vmax=176 cm/s and Vmin=23 cm/s. The distal artery had high resistance flow, with Vmax=55 cm/s and no diastolic flow. Parenchymal resistance indexes were increased in some parts of the kidney: pulsatility index=1.49–2.06 and resistive index=0.73–0.88. In all ultrasound sonography examinations, fluid collections were stable in comparison to POD 0.

On POD 12, the Redon drain was removed. Postoperative diuresis and laboratory parameters are shown in Figure 4. The patient was discharged on POD 15. The double-J catheter was removed 3 weeks after transplantation. At the 2-month follow-up, the patient had satisfactory graft function, with no need for dialysis and no episodes of acute rejection. On February 14, 2025 (POD 185), the serum creatinine and potassium levels were 1.49 mg/dL and 4.74 mmol/L, respectively.

RECIPIENT 2:

The patient was a 65-year-old man with end-stage kidney disease secondary to tubule-interstitial aseptic inflammation. Other comorbidities included arterial hypertension, diabetes mellitus type 2, overactive bladder treated with botulinum, Barrett esophagus, macular degeneration of the right eye, laparoscopic cholecystectomy, and history of extensive multiorgan trauma in 1983 and 1995. Peritoneal dialysis started 5 months prior to transplantation, by means of a Tenckhoff catheter.

On admission, the patient was in overall good condition and had 500 mL of diuresis. Preoperative laboratory blood test results are shown in Table 2.

HLA compliance was 2/6 in HLA-A, -B, and -DR. The performed reactive antibodies activity was 0%. Immunosuppression was induced with 20 mg of basiliximab before kidney transplantation, in accordance with the local induction protocol. One unit of packed cells were transfused prior to kidney transplantation.

On August 13, 2024, the left kidney graft was implanted on the right pelvic plate with end-to-side anastomoses to the external iliac vein and external iliac artery using Prolene 5-0. Ureterovesical anastomosis was made using PDS 4-0, with implantation of a 6-mm double-J catheter. Redon drainage was placed close to the anastomoses, along the kidney graft. The Tenckhoff catheter was removed after closing of the muscle fascia, subcutaneous layer, and skin with PDS 1-0 loop, PDS 3-0, and Monosyn 3-0 running sutures, respectively. Blood loss was estimated at 150 mL. The operation lasted 2 h 35 min, vascular anastomoses time was 45 min, and cold ischemia time of kidney was 20 h 0 min (1200 min). Figure 5 shows the left kidney graft after reperfusion.

Blood flow within the graft was controlled with ultrasound sonography, with Doppler ultrasound 6 h after surgery and in following days. On POD 0, three graft arteries were visualized, all with correct flow, although not calculated. Parenchymal perfusion was even in the whole graft. The renal vein was patent, and the pelvicalyceal system was not dilated. On POD 3 and POD 9, all 3 arteries were visualized, with similar description as on POD 0. Unfortunately, flow velocity and resistance were not calculated.

A standard regimen of immunosuppression was administered with tacrolimus, mycophenolate mofetil, and glucocorticosteroids. In the postoperative period, high glycemia levels were observed, and the patient was treated with insulin injections. Post-transplant diabetes was diagnosed. On POD 2, the patient reported dysuria symptoms, accompanied by the increase of C-reactive protein. Empiric treatment with ceftriaxone was started, resulting in a reduction of symptoms and C-reactive protein level in the following days. Ceftriaxone was continued for 7 days. Urine cultures collected prior to ceftriaxone administration were negative. On POD 8, one unit of packed cells were infused due to anemia, with increase of hemoglobin concentration from 7.8 mg/dL to 10.1 mg/dL. On POD 9, Redon drainage was removed and co-trimoxazole prophylaxis was added to treatment.

Postoperative diuresis and laboratory parameters are shown in Figure 4. The patient was discharged on POD 10. The double-J catheter was removed 3 weeks after transplantation. At the 2-month follow-up, the patient had satisfactory graft function, with no need for dialysis and no episodes of acute graft rejection. On January 7, 2025 (POD 147), the serum creatinine and potassium levels were 1.6 mg/dL and 4.07 mmol/L, respectively.

Discussion

Due to the constant shortage of kidney grafts, HKs are a viable option for transplantation. However, vascular and urinary abnormalities can make these organs unsuitable for transplantation. Data on HKs transplantation and post-transplantation outcomes demonstrate the usefulness and safety of this method. The 2000 report by Stroosma et al [8] on cases from 1975 to 1998 presented 21 HKs divided and transplanted into 38 recipients and 10 HKs transplanted en bloc. The follow-up was 22 months, 41% of the transplanted kidneys achieved immediate graft function, and 46% had delayed graft function. Non-function was observed in 6 cases, due to thrombosis or acute rejection. A case-control study by the same authors compared 26 split HKs transplanted into 47 recipients and 8 HKs transplanted en bloc, with 110 transplants in the control group [5]. The differences in 1-year and 5-year graft survival were not significant between the 3 groups, with or without censoring for immunological failure. The authors noted 6 cases of bleeding from the division site. Up to 2021, a total of 131 cases of HKs transplantation were reported, of which 53 HKs were transplanted to a single recipient [10], and 78 HKs were divided and transplanted into 131 recipients [10]. The authors did not observe any wound infections, urine leakage, vascular thrombosis, lymphocele, or hydronephrosis in this case series. At the time of the 36-month follow-up, the mean serum creatinine level was 1.8 mg/dL. The authors reported that patient and graft survival were 100% during this follow-up period. Our follow-up period was 6 months. The function of organs in both recipients was satisfactory. Despite the lack of recent laboratory parameters, the patients were under the care of the transplant clinic. During the last visits at the end of February, the patients did not present any signs of graft function impairment. What is more important, we did not observe any short-term complications, such as primary non-function, delayed graft function, and arterial or venous thrombosis. Vascular complications were our main concern, due to complex arterial vasculature. Based on previously mentioned data, we expect regression of organ function in a similar pace as in other types of grafts. The relatively small number of HK transplantation cases reported so far may be due to the small number of potential donors with HK found during procurement.

Conclusions

In our case, we decided to divide the HK and perform vascular reconstruction. We divided the HK with a scalpel and sutured both grafts with PDS 2-0 absorbable sutures. We did not observe any bleeding from the incision sites, urinary leakage, or stricture. The function of both kidney grafts was still satisfactory at the time of this report. Vascular and urinary abnormalities can make these organs unsuitable for transplantation and require complex vascular reconstruction and experienced personnel, which is what makes this procedure promising yet difficult. The small number of HKs and the variety of HK anatomy leads to a lack of experience in HK transplantation. Moreover, there are no statements or recommendations regarding splitting techniques and consistent methods of confirming exact HK anatomy prior to procurement. The presented case and the data reported so far show that HK transplantation can be a safe method of kidney transplantation and expand the number of available organs.