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Clinical case: Horseshoe kidney transplantation
After reviewing this case you should be able to describe the following:
- How and why a horseshoe kidney develops embryologically? Where is such a kidney typically located and why? What does the “watershed” area of a horseshoe kidney mean?
- Why a transplanted kidney is typically placed in the iliac fossa rather than in the normal position for a kidney? How is it possible to do an end-to-end anastomosis of the renal arteries to the internal iliac artery and not cause ischemia in the pelvic and/or gluteal structures?
- Why immunosuppression was instituted in the patient. And what are the risks of immunosuppressants?
- What is the meaning of serum creatinine levels relative to kidney function?
- Why kidney transplant surgeons typically prefer to use a left donor kidney rather than a right one (although not in this case of a horseshoe kidney)?
This article is based on a case report published in the Journal "Case Reports in Surgery" in 2015, by Caroline C. Jadlowiec, Beata E. Lobel, Namita Akolkar, Michael D. Bourque, Thomas J. Devers, and David W. McFadden.
It has been modified and reviewed by Joel A. Vilensky PhD, Carlos A. Suárez-Quian PhD, Aykut Üren, MD.
Case description
History and investigations
A 30-year-old male had had his father’s right kidney implanted into his left iliac fossa when he was 19 years old (see Figure 1 for normal kidney anatomy).
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After 10 years of adequate functionality the transplanted kidney was rejected by the son’s immune system and the patient had to resume hemodialysis. A new transplant was needed and the son’s mother was the only available donor. However a magnetic resonance angiogram (MRA) revealed that the transplant procedure would be more complicated than normal because the mother had an asymptomatic horseshoe kidney (Figures 2).
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Intervention and management
The surgeons decided to approach the horseshoe kidney anteriorly from the left by entering the peritoneal cavity and mobilizing the descending colon. The horseshoe kidney was surgically transected through its watershed area (Figure 2). The left nephrectomy was accomplished with little hemorrhage (Figure 3A). The transected surface of the remaining right kidney was sutured close.
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The removed left half of the mother’s horseshoe kidney was implanted into the son’s right iliac fossa with an end-to-side anastomosis of the renal vein to the external iliac vein. Mother’s left kidney had two renal arteries, which were too far apart to make a common connection to an iliac artery so the superior artery was anastomosed end-to-end to the right internal iliac artery and the inferior vessel end-to-side to the right external iliac artery, The ureter was implanted into the bladder (Figure 4).
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Evolution
Immunosuppression was implemented in the son using a standard regiment. The mother had an uneventful recovery and was discharged on the fifth postoperative day. The son developed a DGF (delayed graft response), which is very common in kidney transplant surgery. The patient began diuresis on the eighth postoperative day and renal function was progressively achieved. Three months postoperative, renal function stabilized. At the end of the first year, serum creatinine was found to be 128 μmol/L (1.45 mg/dL). At two months postoperative, mother and son were in good health.
Surgical and anatomical considerations
Location and relations of the kidneys
Horseshoe kidneys occur in approximately 1 in 400-500 adults and are more frequently encountered in males (M:F; 2:1). When a potential kidney donor presents with vascular or urinary abnormalities such as a horseshoe kidney and there is no other suitable living donor, the only alternative may be to use a cadaver donation. But that process may entail long lists and waiting time, urgent surgery and poor compatibility. A continuing organ shortage in conjunction with large numbers of potential recipients sometimes requires using marginal donors or donors with vascular or urinary abnormalities. Use of kidneys from these donors compounds the difficulties of the surgical procedure.
Normally the human kidneys are situated in a retroperitoneal location, high in the abdominal cavity at a slightly oblique angle (Figure 1). Typically the right kidney is slightly lower than the left. The left is approximately at the T12-L3 level. Both kidneys are located directly inferior to the diaphragm with the right being posterior to the liver and the left being posterior to the spleen. The suprarenal (adrenal) gland is located on the superior pole of each kidney (Figure 1). However, when a kidney is not in its normal anatomical position as in a horseshoe kidney, the suprarenal glands are typically located in their normal anatomical position (Figure 5).
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The posterior abdominal wall forms the posterior relations of the kidneys. Specifically the muscles that form these relations include the:
- transversus abdominis
- quadratus lumborum
- psoas major
- and also the crus of the diaphragm (Figure 6)
The subcostal. iliohypogastric and ilioinguinal nerves also form posterior relationships of the kidney (Figure 6).
Renal vessels and their locations
Theoretically, each kidney receives a single artery directly from the aorta, but in many cases, the kidneys receive more than a single artery. Similarly, each kidney is typically drained by a single vein that drains into the inferior vena cava (Figure 1). The right renal artery passes posterior to the inferior vena cava and the left renal vein passes anterior to the aorta. This relationship is very useful for obtaining orientation in radiologic imaging, especially CT and ultrasound images.
Learn more about the kidney and related structures through these great resources!
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Objective explanations
Objectives
After reviewing this case you should be able to describe the following:
- How and why a horseshoe kidney develops embryologically? Where is such a kidney typically located and why? What does the “watershed” area of a horseshoe kidney mean?
- Why a transplanted kidney is typically placed in the iliac fossa rather than in the normal position for a kidney? How is it possible to do an end-to-end anastomosis of the renal arteries to the internal iliac artery and not cause ischemia in the pelvic and/or gluteal structures?
- Why immunosuppression was instituted in the patient. And what are the risks of immunosuppressants?
- What is the meaning of serum creatinine levels relative to kidney function?
- Why kidney transplant surgeons typically prefer to use a left donor kidney rather than a right one (although not in this case of a horseshoe kidney)?
Horseshoe kidney development: Location and characteristics
The kidneys develop from the interaction between the ureteric bud (derived from the mesonephric duct), and the metanephros, which is the most caudal part of the nephrogenic cord. Kidney development begins early in the fourth week of gestation and between weeks 6-8, the lobulated embryonic kidneys ascend from the pelvic region along the posterior abdominal wall to their adult location. During their ascent the kidneys obtain their blood supply sequentially from vessels that are nearest to them. First, from the median sacral artery, then from the common iliac and inferior mesenteric arteries, and finally from the aorta.
If during their ascent the developing kidneys join in the midline, a horseshoe kidney will result. The left and right kidneys are then connected by an isthmus of either functioning renal parenchyma, or fibrous tissue. In the vast majority of cases the fusion is between the lower poles of the kidneys (90%). If the kidneys are connected by fibrous tissue, the horseshoe kidney will have a watershed zone that is poorly vascularized and can serve as a region for transection as in this case. Usually, the ascent of a horseshoe kidney is halted by the inferior mesenteric artery as illustrated in Figure 2. Since adrenal glands embryonically are not related to kidneys, their development and location are not affected by the malformations of horseshoe kidneys.
Position of an implanted kidney and end-to-end anastomosis
When a patient has non-functioning kidneys and is getting a donor kidney, removing one of the non-functioning kidneys add complexity and risk to the procedure. It is much easier to place the donated kidney into the roomy iliac fossa (much roomier than the natural location of the kidneys, which is surrounded by viscera) where there is also easy access to the urinary bladder and the blood via the common, external, and internal iliac arteries.
Fortunately, in the pelvic region there is ample collateral circulation especially across the midline; thus, the surgeons in this case were able to do an end-to-end anastomosis between one of the renal arteries and the right internal iliac artery because the left vessel of the same name supplied sufficient blood to all of the pelvic viscera via the midline anastomoses.
Immunosuppression and transplantation
Deliberately induced immunosuppression is done in patients after donor implant to prevent their body from rejecting the transplanted organ. It is also done in treating various other conditions especially autoimmune diseases such as rheumatoid arthritis and Crohn’s disease. Immunosuppression can result in increased susceptibility to opportunistic infections and cancer.
Serum creatinine
Creatinine is a chemical that circulates in the blood and that is derived from muscle metabolism. The kidneys remove most of the creatinine from circulation, and it is then excreted as part of urine. Normal creatinine levels in the blood are approximately 0.6 to 1.2 (mg/dl) in adult males and 0.5 to 1.1 (mg/dl) in adult females. Chronically increased levels reflect poor kidney function.
Preference of the left kidney in transplantation
As implicated in the above discussion, the left kidney has a relatively long vein and the right kidney has a relatively long artery (Figure 7). Veins are more difficult to suture securely because their walls are thinner and contain less smooth muscle than arteries. All else being equal, a surgeon would thus prefer to have more vein than artery, and that is the reason left donor kidneys are preferred.
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During this procedure left adrenal vein and left gonadal vein, both of which are tributaries of the left renal vein, are ligated and cut. However, left adrenal gland and left ovary or testis do not suffer any significant pathological consequences due to collateral circulations.
Clinical case: Horseshoe kidney transplantation: want to learn more about it?
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