June issue.indd

C.S. Zipitis T. Augustine A. Tavakoli R. Surange A. Agrawal H.N. Riad
Renal Transplant Unit, Manchester Royal Infirmary, Oxford Road, Manchester, M13 9WL, U.K.

Correspondence to: T. Augustine, Renal Transplant Unit, Manchester Royal Infirmary, Oxford Road, Manchester, M13 9WL, U.K. Email: titus.augustine@cmmc.nhs.uk

Case report

Discussion

References

Keywords: Renal transplant, horseshoe kidney, marginal kidney Surg J R Coll Edinb Irel., 1 June 2003, 160-163

Even though the number of patients awaiting renal transplant is rapidly increasing, the donor pool remains relatively stable. In an attempt to increase this pool, marginal kidneys and kidneys with congenital anatomical variations are being used. Horseshoe kidneys, being the most common renal fusion anomaly, can provide a useful solution to the ever-increasing gap between demand and supply. These kidneys have been successfully transplanted en bloc into a single recipient or, alternatively they have been divided and transplanted into 2 recipients. We report a case of the successful transplantation of an en bloc horseshoe kidney into a single recipient. To the best of our knowledge this is the first of its kind in the UK. The relevant literature is also reviewed with the aim of raising awareness about the necessity and promising outcomes of such transplants

CASE REPORT
A 39-year-old, Type I diabetic, female patient died of hypoxia following a hypoglycaemic episode. She had no known history of urinary tract infection, stones or congenital defects. Serum creatinine was 59µmol/L and urea 2.5mmol/L. At the time of organ procurement a horseshoe kidney was identified. The vascular anatomy consisted of six arteries and an equivalent number of veins, defying known classifications. The ureters and collecting systems were normal bilaterally, while the isthmus consisted of a broad band of apparently functional renal tissue. The kidney was removed en bloc (Figure 1) and a biopsy showed minor diabetes-related changes.

The recipient was a 33-year-old woman with end-stage renal failure secondary to reflux nephropathy and pyelonephritis. She had a previous transplant in 1983. This lasted until 1996 from which point continuous ambulatory peritoneal dialysis (CAPD) was started.

The donor aorta and the vena cava were closed distally with continuous sutures and the proximal parts anastomosed end-to-side to the recipient aorta and left common iliac vein, respectively. Arterial flow and perfusion were good. The ureters were spatulated, stented and joined to each other with sutures. The single double-barrelled ureter was then anastomosed to the dome of the bladder (Figure 2).

Recovery was uneventful. There was primary function and the 24-hour renogram showed good perfusion of the horseshoe kidney. Within four days the creatinine decreased to 79µmol/L. After three months, the ureteral stents were removed and we were pleased to note that her creatinine remained stable at 72µmol/L. The patient is maintained on a triple immunosuppressive regime consisting of Azathioprine, Prednisolone and Tacrolimus.

DISCUSSION
Although the number of patients awaiting transplantation is rapidly increasing, the donor pool remains static. According to the UK Transplant Database there were 1691 renal transplants in the UK last year while the number of patients awaiting renal transplantation was 4846.1 Over the last few years attempts have been made to increase this pool by using marginal kidneys and kidneys with congenital anatomical abnormalities. The most common anatomic variation of the kidney is the horseshoe kidney.^2-5

Horseshoe kidneys result from the fusion of the metanephric blastema across the midline at four to six weeks of gestation.

The normal medial rotation and the ascent from the pelvis are inhibited.⁶ The majority of renal fusion defects involve the lower poles. It has been suggested that the inferior mesenteric artery prevents upward migration of the fused kidney.

The incidence of horseshoe kidney is 1 in 400 in childhood and 1 in 600 to 1 in 800 in adult series.⁶ It is twice as common in males than it is in females. In addition to the association with other serious abnormalities, which may account for the discrepancy between childhood and adult series, horseshoe kidneys often have anomalous vasculature and ureteral abnormalities (e.g. ureteral duplication, ureterocoeles and ureteropelvic junction obstruction). The arterial anatomy of horseshoe kidneys has been classified by Graves:⁷

Type 3: middle and lower segment arteries arise directly from the aorta.

Figure 1: The procured horseshoe kidney. A: Inferior Vena Cava; B: Renal Arteries; C: Aorta; D: Hypoperfused area in the isthmus due to inadvertent ligation of a small artery supplying the isthmus; E: Ureters; F: Isthmus

However, frequently occurring variations in anatomy, nicely illustrated by the kidney we have used, preclude a proper classification.

If a congenital defect is identified, the donor family should be questioned by the organ procurement coordinators regarding any history of urinary tract infections, pyelonephritis, stones or haematuria⁸ due to the high incidence of vesicoureteral reflux, hydronephrosis, urine stasis, nephrolithiasis and upper tract infections in those with horseshoe kidneys.⁶ Furthermore, identification of problems can lead to early intervention e.g. ureteropyeolostomy for a stenotic ureteropelvic junction. It should, however, be born in mind that nearly a third of patients with horseshoe kidneys remain asymptomatic.

Renal carcinoma has been associated with horseshoe kidneys. About half of these are hypernephromas with renal pelvic tumours and Wilms’s tumour each accounting for 25% of the total. The incidence of Wilm’s tumour is more than twice that expected in the general population. Furthermore, a large number of these cancers appear to have arisen in the isthmus such that investigators have suggested that teratogenic factors are responsible for abnormal migration of nephrogenic cells that form an isthmus, leading to horseshoe shape and the increased potential of carcinoma development in this portion of the kidney.9 As for the increased incidence of renal pelvic tumours, these have been put down to the increased occurrence of chronic infection, obstruction, and stone formation.6 We are not aware of any report of carcinoma in a transplanted horseshoe kidney but this may change in the future as the number of such kidney transplants will increase, and with these patients being immunosuppressed their chances of developing malignancy will be higher.

Although common, there is relative inexperience in transplantation of horseshoe kidneys. ^8,10-14 Politano performed the first successful transplantation of a horseshoe kidney in the early 1960s, when he successfully implanted the right half of a horseshoe kidney into the monozygotic twin of the donor. Nelson published the first documented case of a horseshoe kidney transplant in 1975.¹⁵ The most recent, and probably sole worldwide survey of horseshoe kidney transplantation reports 23 en bloc and 57 divided transplantations. ¹⁶ Furthermore, although there have been three split horseshoe kidney transplantations in the UK there is currently, to the best of our knowledge, no report of an en block transplant procedure.

Figure 2: Diagrammatic representation of the transplanted horseshoe kidney. A: Recipient Aorta; B: Donor aorta closed distally with continuous sutures and anastomosed end-to-side to recipient aorta; C: Donor vena cava closed distally with continuous sutures and anastomosed end-to-side to recipient left common iliac vein; D: Hypoperfused area in the isthmus secondary to accidental damage of one of the renal arteries; E: The ureters were spatulated, stented and joined to each other with sutures; F: Urinary bladder; G: Ureteric stent

Although a recent study supports that more than 90% of surgeons would transplant horseshoe kidneys if one was offered to them, it is known that more than 20% of these kidneys are discarded. ^13,16,17 Reasons quoted for this are complex vascular anatomy, injury to the urinary collecting system and lack of suitable recipients. ¹⁶

It is important to note that despite the obvious anatomical anomalies, horseshoe kidneys are histologically normal and should, therefore, function well after transplantation. This is supported by data from Stroosma et al (2001). ¹³ In this article, eight horseshoe kidneys transplanted en bloc and 26, which were split and transplanted into 47 recipients, were compared with 110 transplants in a control group. No significant differences were found either in the short- or long-term post-transplant results. Furthermore, no difference was noted between results from en bloc or spit horseshoe kidneys. ^13,18

There are interesting individual reports in the literature such as a successful pancreas transplantation combined with a split horseshoe kidney, and the use of a horseshoe kidney as a renal transplant from a living donor. ^19,20

In conclusion, we have described a case of successful horseshoe kidney transplantation. This is the first reported horseshoe kidney to be transplanted en bloc in the UK. Although a number of reports have appeared in the literature over the last 27 years, describing the successful outcome of transplantations involving horseshoe kidneys, surgeons are still sceptical about their use. This has led to an unacceptably high number of these kidneys being discarded at a time when the number of patients awaiting renal transplantation is rapidly increasing. We, as others have done before us, strongly support the use of horseshoe kidneys for transplantation as they have been shown to be as effective as normal kidneys, thus, posing as a possible solution to the ever-increasing gap between demand for and supply of donated kidneys.

REFERENCES
1. UK Transplant Data Registry. Bristol, 2002 (www.uktransplant.org.uk)
2. Kumar A, Mandhani A, Verma BS et al. Expanding the living related donor pool in renal transplantation: use of marginal donors. J Urol 2000; 163: 33
3. Langle F, Sauther T, Grunberger T et al. Impact of donor age on graft function in living-related kidney transplantation. Transplant Proc 1992; 24: 2725
4. Sumrani N, Delaney V, Ding ZK et al. Renal transplantation from elderly living donors. Transplantation 1991; 51: 305
5. Merkel FK. Transplantation of small en bloc kidneys including a horseshoe kidney from donors aged 2 to 60 months to adult recipients: a 13-year experience. Transplant Proc 2001; 133: 3783
6. Bauer SB, Perlmutter AD, Retik AB: Anomalies of the upper urinary tract. In: Cambell’s Urology, 6th ed, 1992. Edited by Walsh PC, Retik AB, Stamey TA, Vaughan ED Jr. Philadelphia: WB Saunders Co, vol 2, chapt 34, pp1376-81
7. Graves FT. The arterial anatomy of the congenitally abnormal kidney. Brit J Surg 1969; 56: 533
8. Ratner LE, Zibari G. Strategies for the successful transplantation of the horseshoe kidney. J Urol 1993; 150: 958
9. Neville H, Ritchey ML, Shamberger RC et al. The occurrence of Wilms tumor in horseshoe kidneys: a report from the National Wilms Tumor Study Group (NWTSG). J Pediatr Surg 2002; 37(8): 1137
10. Klan R, Hirner A, Fielder U, Offermann G. Transplantation of a horseshoe kidney en bloc: report of a case. J Urol 1988; 139: 571
11. Perumalla C, Lawen JG, MacDonald AS. Transplantation of a horseshoe kidney into two recipients after separation. Br J Urol 1996; 78: 145
12. Shen GK, Salvatierra O Jr, Dafoe DC, Alfrey EJ. Use of split horseshoe kidney for transplantation. Surg 1998; 123(4): 475
13. Stroosma OB, Smits JMA, Schurink GWH et al. Horseshoe kidney transplantation within the eurotransplant region. A case control study. Transplantation 2001; 72: 1930
14. Uzzo RG, Hsu THS, Goldfarb DA et al. Strategies for transplantation of cadaveric kidneys with congenital fusion anomalies. J Urol 2001; 165: 761
15. Nelson RP, Palmer JM. Use of horseshoe kidney in renal transplantation: technical aspects. Urol 1975; 6: 357
16. Stroosma OB, Schurink GWH, Smits JMA, Kootstra G. Transplanting horseshoe kidneys: a worldwide survey. J Urol 2001; 166: 2039
17. Stroosma OB, Wilhelmus G, Schurink H, Kootstra G. Current opinions in horseshoe kidney transplantation. Transpl Int 2002; 15: 196
18. Stroosma OB, Scheltinga MRM, Stubenitsky BM, Kootstra G. Horseshoe kidney transplantation: an overview. Clin Transplantation 2000; 14: 515
19. White JC, Shaver TR, Kocandrle V. Simulatneous kidney-pancreas transplantation using a horseshoe kidney. Transplant Int 1993; 6: 302
20. Inoue S, Imai K, Kuzuhara O, Ootubo O, Yanada A. Use of horseshoe kidney as renal transplant from living donor: its surgical feasibility and pitfalls. Transplant Proc 2000; 32: 1586

Case Report

Horseshoe kidney transplantation