Pre-operative precautions for donor nephrectomy
• The donor must retain one normal kidney. If one kidney is altered but not contraindicated for transplantation, the altered kidney is harvested. If both kidneys are normal, the kidney with less complicated vascular anatomy is removed (Sebastia et al., 2010).
• The left kidney is preferred for laparoscopic living donor nephrectomy because it has a longer renal vein and it is technically easier to remove (Sebastia et al., 2010).
• Surgeons also prefer kidneys with a single artery because both donor and recipient surgeries are less complicated and there is less risk for arterial thrombosis. Use of kidneys with inferior accessory polar arteries is avoided because of the risk for pyeloureteral damage if they are cut or thrombosed (Sebastia et al., 2010).
• Marginal donors such as the elderly and those with benign renal or non-renal disease are being widely accepted for donation (Kumar et al., 2003).
• Renal anomalies and diseases such as unilateral agenesis, horseshoe kidney, cortical atrophy, polycystic disease, medullary sponge kidney disease, and renal papillary necrosis exclude donation (Sebastia et al., 2010).
• Kidneys with renal ectopia or ureteropelvic junction stenosis may be transplanted if associated problems (eg, multiple arteries and veins in patients with renal ectopia) are resolved (Papanikolaou et al., 2007).
• Kidneys with unilateral small parenchymal scars and normal renogram results may be safely transplanted. Scarred kidneys are chosen for harvesting (Sebastia et al., 2010).
• However, long-term complications related to transplantation should be considered such as end-stage renal disease and gout (Lam et al., 2015).
Renal Assessment
Parenchymal Evaluation by CTA
The anatomic information collected includes the number, length, location, anatomic variants, and diseases of the donor kidneys and renal vasculature are listed below (Sebastia et al., 2010):
Location and length of kidneys
Number of renal arteries and veins
Types of accessory renal arteries (eg, hilar or polar)
Real orthogonal diameter of accessory arteries
Location and measurement of first arterial segmentary bifurcation
Location and measurement of the segmentary confluence of renal veins
Type of renal vein tributaries
Diameter and variants of renal vein tributaries
Presence of arterial diseases
Amount of perirenal fat
Number, location, and size of cysts, calculi, and angiomyolipoma (if present)
Number, location, size, and stage of tumor
Evaluation of upper urinary tract
Renal Arterial Anatomy and Variants
The anatomical knowledge of the renal arteries and its variations are of extreme importance for the surgeon who approaches the retroperitoneal region during the renal transplant surgeries (Deshpande et al., 2014).
In most individuals, a single renal artery supplies each kidney. However, renal artery variations are common. These variations are related to the embryological development of the kidneys. Arterial variants can be classified according to the origin, number and division pattern of the renal arteries (Perez et al., 2013).
Main renal arteries typically arise from the aorta at the level of the superior margin of the second lumbar vertebral body, slightly inferior the origin of the superior mesenteric artery. The RRA orifice is usually more superior and anterolateral than the left. Typically, the RRA has a long downward course to the relatively inferior right kidney, whereas the LRA has a more horizontal course to the superiorly located left kidney (Figure 3.1) (Turkvatan et al., -B- 2009).
The main renal arteries divide into anterior and posterior divisions that lie anterior and posterior to the renal pelvis. The anterior division branches into four segmental arteries including apical, upper, middle, and lower anterior. The apical and lower anterior segmental arteries supply the anterior and posterior surfaces of the upper and lower renal poles, and the upper and middle segmental arteries supply the remainder of the anterior surface (Turkvatan et al., -B- 2009).
The posterior division supplies a large portion of the blood flow to the posterior portion of the kidney. The segmental arteries course through the renal sinus and further subdivide into interlobar arteries (Figure 3.1) (Turkvatan et al., -B- 2009).
Figure (3.1): a. Coronal MIP image shows classic arterial anatomy with one renal artery to each kidney. The RRA has a downward course to the relatively inferior right kidney, whereas the LRA has a more horizontal course to the superiorly located left kidney
b. VR image show prehilar segmentation of RRA (white arrow)
c. MIP image show interlobar arteries (black arrows) (Quoted from Turkavatan et al., -A- 2009 ).
At the level of the renal pyramids the interlobar arteries divide into arcuate arteries, which parallel the renal contour along the cortico-medullary junction. The actuate arteries give rise to multiple interlobular arteries. Also, the renal arteries give off inferior adrenal branches, capsular branches, and branches into renal pelvis and proximal ureter (Turkvatan et al., -B- 2009).
There are three types of renal arteries: hilar, which enter the kidney at the hilum; polar, which enter the kidney at the renal pole; and capsular, which surround the kidney (Fig 3.2 & 3.3) (Sebastia et al., 2010).
Figure (3.2): Coronal MIP from CTAin a 53.year-old female renal donor shows a dominant LRA (arrowhead) and lower polar accessory artery (arrow) (Quoted from Rastogi et al 2006).
Figure 3.3. Diagram of the kidney shows the course of the capsular, polar, and hilar arteries (Quoted form Sebastia et al., 2010).
Only 5% of kidneys contain three or more renal arteries, which are present in 4% and 1% of kidneys, respectively (Souza et al, 2015).
The presence of more than two arteries within a kidney is a contraindication for donation; donation is only possible if one of the three arteries is a small superior polar artery less than 2 mm in diameter. Such an artery may be sacrificed because the resultant volume of renal infarct does not substantially affect graft function. (fig.3.4 & 3.5 & 3.6) (Sebastia et al., 2010).
Figure (3.4) figure (3.5)
Figure: (3.4) Coronal VR image shows two accessory polar left renal arteries (arrow) that arise from the aorta at different levels (Quoted from Turkavatan et al., – A- 2009).
Figure (3.5): Coronal VR image shows four right renal arteries. The last originates from the right iliac artery and pierces the Lower pole of the right kidney directly (Quoted from Turkavatan et al., –A- 2009).
Figure (3.6): VR image shows the main renal arteries (thin arrows) and accessory renal arteries. The accessory arteries usually arise from the aorta or iliac arteries, between the levels of T11 and L4. The accessory renal artery (arrowheads) courses into the renal hilum. The polar arteries, a subgroup of accessory renal arteries, enter the renal parenchyma directly from the renal cortex (thick arrows) (Quoted from Hazirolan et al 2011).
When a kidney has two or more arteries with a separate aortic ostium, the vessel with the greatest diameter is considered to be the main renal artery and the others are considered accessories (Türkvatan et al ., –B- 2009).
Accessory arteries may originate above or below the main renal artery; when they originate from a low position, the origin may be near the aortic bifurcation or the iliac arteries (Sebastia et al., 2010).
When a kidney has two arteries ( figure 3.7), the length of the arteries before the segmentary bifurcation and the distance between the two arteries must be measured, and 3D volume-rendered images should be obtained. The surgeon evaluates these images and determines if side-to-side or end-to-side anastomosis of the arteries is possible (Fig 3.8) (Sebastia et al., 2010).
If end-to-side or side-to-side anastomosis is not possible, double arterial anastomosis is performed in the iliac artery of the recipient kidney (Fig 3.9) (Sebastia et al., 2010).
Fig (3.7) Gross anatomy of double right renal arteries and veins: A: Abdominal aorta, CT: Coeliac trunk, IRA: Inferior renal artery, IRV: Inferior renal vein, SMA: Superior mesenteric artery, SRA: Superior renal artery, SRV: Superior renal vein (Quoted from Mohamed et al., 2012).
Fig 3.8 Fig. 3.9
Figure 3.8 : Diagram shows end-to-side anastomosis in the recipient iliac artery. This procedure is performed when there is a short distance between the two donor renal arteries (Quoted from Sebastia et al., 2010).
Figure (3.9) Diagram shows double arterial anastomosis in the recipient iliac artery. This procedure is performed when there is a long distance between the two donor renal arteries (Quoted from Sebastia et al., 2010).
It also is necessary to measure the real orthogonal diameter of all renal arteries (Fig 3.10) (Sebastia et al., 2010).
Figure 3.10. Measurement of orthogonal diameter of renal arteries. (a) Coronal CT image shows the renal artery (arrows); image data are used to construct the orthogonal cross sections. (b) Orthogonal cross section shows the renal artery (arrow). Orthogonal cross sections may be used to measure real orthogonal diameter of the renal artery (Quoted from Sebastia et al., 2010).
For safe recipient arterial graft anastomosis, arterial diameters must be at least 3 mm. In arteries smaller than 3 mm, anastomosis is difficult, and there is a high incidence of thrombosis within these arteries. There are three renal artery measurements that must be taken (Sebastia et al., 2010) :
A. The distance between the right arterial origin and the first segmentary bifurcation
B. The distance between the right inferior vena cava (IVC) margin and the first segmentary bifurcation,
C. The distance between the left arterial origin and the first segmentary bifurcation (Fig 3.11).
If the course of the renal arteries is horizontal, the axial plane should be used to determine these measurements. If the arteries have a cranial-caudal course, which is more common, coronal reformation should be used (Sebastia et al., 2010).
Figure 3.11. Diagram shows the renal artery measurements that must be taken. A= the distance between the right arterial origin and the first segmentary bifurcation, B= the distance between the right IVC margin and the first segmentary bifurcation, C = the distance between the left arterial origin and the first segmentary bifurcation (Quoted from Sebastia et al., 2010).
In the right kidney, early segmentary arterial branching is defined as segmental branching behind the IVC (retrocaval branching) or when it occurs 1 cm from the right IVC margin. Early segmentary arterial branching is present in 10%–12% of cases (Fishman et al., 2004).
Working behind the IVC is difficult because of the possibility of injuring a large vessel. In terms of surgery, a segmentary bifurcation behind the IVC is considered a double artery because it usually is not possible to safely section the common trunk (Fig 3.12) (Sebastia et al., 2010).
In the left kidney, early segmentary arterial branching is defined as segmental branching less than 1–1.5 cm from the origin of the LRA (Fig 3.13). Expert surgeons require at least 1 cm of main renal artery in order to clamp and properly anastomose the artery in the recipient (Sebastia et al., 2010).
Fig (3.12) fig. 3.13
Figures 3.12 & 3.13. (3.12) Early segmental (retrocaval) branching of the RRA. Volume-rendered CT image (posterior view) shows retrocaval segmental branching of the RRA (arrow) and the IVC. (3.13). Early segmental branching of the LRA. Curved coronal thin-section MIP image shows segmental bifurcation of the LRA (arrow) 1 cm from the aorta (Quoted from Sebastia et al., 2010).
Regardless of the distance from the arterial bifurcation to the aorta, the radiologist’s report must include information about intra- or extra-hilar arterial segmental bifurcation. Inferior phrenic, adrenal, and capsular arteries may be mistaken for early prehilar branching of the renal artery (Sebastia et al., 2010).
Arteries that enter the kidney at the poles are called polar arteries. It is possible to estimate the renal parenchyma that is supplied by the polar arteries on the basis of vessel size; thus, small vessels (those with a diameter of 2 mm or less) may be cut or thrombosed, producing a graft infarct with a volume of less than 10% (Satyapal et al., 2001).
In some cases, the surgeon may clamp a polar artery to determine the amount of parenchyma it supplies before deciding to cut the artery (Sebastia et al., 2010).
Because of their low attenuation, small polar arteries usually are not visible on thick-section MIP images or volume-rendered reconstructions; for this reason, it is important to review thin-section axial images for these small polar arteries (Sebastia et al., 2010).
The best reconstructions use curved planes and thin-section MIP drawn across these arteries (Fig 3.14) (Rastogi et al., 2006).
If small polar arteries are not reported, they may be accidentally cut, which can cause uncontrolled arterial bleeding and renal infarct (Sebastia et al., 2010).
Figure (3.14): Accessory polar arteries. Curved coronal thin-section MIP image shows bilateral superior accessory polar arteries (arrowheads) (Quoted from Sebastia et al., 2010)
Accessory renal polar arteries have been reported arising from the iliac, superior and inferior mesenteric, celiac, middle colic, lumbar, gonadal, and middle sacral arteries, as well as the contra-lateral artery (Figs 3.15 , 3.16) (Pozniak et al., 1998).
Figure (3.15) Inferior bilateral polar arteries. Curved coronal thin-section MIP image shows bilateral inferior polar arteries (arrows) arising from the LRA. These accessory arteries supply the inferior poles of both kidneys (Quoted from Sebastia et al., 2010).
Fig. (3.16) Accessory polar artery arising from the left gonadal artery. Coronal thin-section MIP image shows a small inferior polar artery (arrow) arising from the left gonadal artery (arrowheads) (Quoted from Sebastia et al., 2010).
These inferior polar arteries are important because they provide vessels to the upper urinary tract. An unnoticed section of an inferior polar artery may lead to graft pyeloureteral necrosis with secondary stenosis or urinary tract leakage. When preservation of a small inferior polar artery is not feasible, the surgeon may consider anastomosing the donor renal pelvis to the recipient ureter (pyelo-ureteral anastomosis) (Sebastia et al., 2010).
Capsular arteries, tiny vessels that perfuse the renal capsule, may arise from the main renal artery, branch renal arteries, or other retroperitoneal vessels. It may be difficult to distinguish capsular arteries from polar arteries. Capsular arteries tend to be smaller than polar arteries, and they course tangentially to the renal margin rather than extend directly into the renal parenchyma, as do polar arteries (Fig 3.17) (Uflacker et al., 2006).
Figure 3.17. Right superior capsular artery. Curved coronal thin-section MIP image shows the capsular artery coursing tangentially to the renal margin (arrows) (Quoted from Sebastia et al., 2010).
Mesenteric, pancreatic, adrenal, and capsular arterial branches may simulate polar arteries. The renal poles should be viewed in thin axial sections to determine if the artery enters the kidney, a finding known as the polar artery sign. If the artery enters the superior renal pole, the polar arteries may be accurately identified (Fig 3.18) (Sebastia et al., 2010).
Figure 3.18. The polar artery sign. Axial thin-section MIP image shows an artery entering the superior renal pole (arrow), a finding indicative of a polar artery (Quoted from Sebastia et al., 2010).
Renal Artery Diseases
Renal artery atherosclerosis generally occurs at the origin or proximal aspect of the renal artery in older patients with typical cardiovascular disease risk factors. With the increasing acceptance of older donors in the past few years, renal artery atherosclerotic disease is increasingly encountered (Sebastia et al., 2010).
In patients with unilateral renal artery atherosclerotic plaque, the atheromatous kidney may be harvested, with end-arterectomy or resection of the affected segment performed during bench surgery (Sebastia et al., 2010).
Calcified plaque does not allow a vessel to close properly when clamped and may cause laceration of the intima of both the renal artery and the aorta, which may lead to life-threatening bleeding; it is important to differentiate calcified plaque from soft plaque and to alert the surgeon to its presence (Sebastia et al., 2010).
The presence of bilateral atherosclerotic renal artery disease rules out donation (Fig 3.19) (Costa and Horta., 2014).
Figure 3.19. Bilateral renal artery atheromatous disease. Curved coronal thin-section MIP image shows two right renal arteries. The lower right artery demonstrates proximal stenosis (arrow), and calcified plaque (arrowhead) is seen in the ostium of the LRA. Diffuse calcification also is seen in the infra-renal abdominal aorta. The presence of bilateral renal artery atheromatous disease excludes donation (Quoted from Sebastia et al., 2010).
Fibromuscular dysplasia (FMD) is an idiopathic, segmentary, non-inflammatory and non-atherosclerotic disease that can affect small- and medium-caliber arteries, commonly in female (Varennes et al, 2015).
Asymptomatic FMD is discovered in 2%–6% of living renal donors at the time of donor evaluation (Blondin et al., 2010).
Little is known of the long-term follow-up of these patients. CT findings of FMD are characteristic and include a “string-of-beads” appearance, focal stenosis, and aneurysms, usually in the mid or distal main renal artery and segmentary renal arteries (Sanidas et al, 2015).
If findings are clear at multidetector CT, FMD may be accurately diagnosed. However, if there is doubt, angiography is performed (Sebastia et al., 2010).
If a unilateral segment of FMD is found, the affected kidney may be chosen and the affected segment replaced with a graft (biologic or synthetic) (Fig 3.20). Bilateral FMD excludes donation (Sebastia et al., 2010).
At helix imaging, respiratory movements that mimic atherosclerotic disease or FMD in the renal arteries may be seen, a finding known as respiratory artifact (Fig 3.21). Angiography is required if doubt persists (Sebastia et al., 2010).
(A) (B)
Figure 3.20 (A & B). Bilateral renal artery FMD. (a) Coronal VR CT image shows beading of the middle segment of the left main renal artery (arrow), a finding known as the string-of-beads sign, which is indicative of FMD. (b)Intra-operative photograph shows replacement of the damaged artery with a cryo-preserved graft (arrow) ( Quoted from Sebastia et al., 2010).
Figure 3.21. Respiratory artifact. Axial thin-section MIP image shows pseudo-thickening of the LRA (arrow) due to respiratory movement. The LRA was normal at angiography (not shown) (Quoted from Sebastia et al., 2010).
Renal Veins
Occurrence of multiple renal veins are relatively common, and several authors have reported large numbers of venous variations resulting from embryonic developmental errors .The renal veins present fewer variations than do the renal arteries, and multiple renal veins are more common on the right side than on the left side (Aragão et al, 2015).
The renal veins usually lie anterior to the renal artery at the renal hilum with average lengths about 6.8–7.5 cm on the left and 2.5–2.6 cm on the right side. The left renal vein usually passes between the aorta and the superior mesenteric artery (Figure 3.22), to enter the medial side of inferior vena cava. The right renal vein enters the lateral side of the inferior vena cava typically at the level of first lumbar vertebra and usually receives no tributaries (Turkvatan et al., -B- 2009).
Figure (3.22): Axial MIP image shows normal renal veins. The left renal vein that passes between anterior to the aorta (Ao) and posterior to the superior mesenteric artery (arrow) and that enters the medial side of inferior vena cava (IVC). The right renal vein, which is shorter than the left, enters the lateral side of the inferior vena cava (quoted from Turkavatan et al., -A- 2009).
The number, course, and length of main renal veins and their tributaries must be detailed in the radiologist’s report. Double and triple veins usually are seen in the right kidney and are present in 15% of donors (Fig 3.23 & 3.24 & 3.25) (Kawamoto et al., 2006).
Figure 3.23. Right double renal vein. Curved coronal thin-section MIP image shows two right renal veins (arrows) (quoted from Sebastia et al., 2010).
Figure (3.24) multiple supernumerary right renal veins in 27-year-old female voluntary kidney donor. Coronal oblique MIP (a) and anterior oblique volume rendered (b) images show four right renal veins (arrows) (quoted from Kumar et al., 2010).
Figure 3.25: Dissection of right part of the abdominal cavity showing the right renal vessels. (IVC; inferior vena cava, RK; right kidney, RA; RRA, URV; upper renal vein, MRV; middle renal vein, LRV; lower renal vein, U; ureter) (Quoted from Satheesha et al., 2012).
Three main renal venous measurements must be taken:
A. The distance between the segmentary confluence of the right renal vein and the IVC
B. The distance between the segmentary confluence of the left renal vein and the IVC
C. The distance between the confluence of the left renal vein and the left margin of the aorta (Fig 3.26).
Figure 3.26. Diagram shows the renal vein measurements that must be taken.
A = the distance between the segmentary confluence of the right renal vein and the IVC,
B= the distance between the segmentary confluence of the left renal vein and the IVC,
C = the distance between the confluence of the left renal vein and the left margin of the aorta (Quoted from Sebastia et al., 2010).
The circum-aortic and retro-aortic veins (present in 6% and 3% of donors, respectively) are the most common major venous variants in the left kidney and are related to the embryologic development of the IVC (Figs 3.27 & 3.28 & 3.29 & 3.30 & 3.31) (Chai et al., 2008).
Figure (3.27) Left circumaortic renal vein. Axial thin-section MIP image shows the retroaortic (arrow) and preaortic (arrowhead) components of the left circumaortic renal vein (Quoted from Sebastia et al., 2010).
Figures 3.28. Left retroaortic renal vein. Axial thin-section MIP image shows the course of the left retroaortic renal vein (arrow) (Quoted from Sebastia et al., 2010).
Figure (3.29): Axial (a) and VR (b) images show retro-aortic left renal vein (LRV). A second small right renal vein (arrow) is seen in image B. (RRV right renal vein, IVC inferior vena cava) ( Quoted from Turkavatan et al., – A- 2009).
Figure (3.30): Volume-rendered coronal image displaying a circumaortic renal vein. Note how the anterior branch (white thick arrow) forms a ring. The left gonadal vein (black arrowheads) joins the anteroinferior aspect of the ring. The posterior branch (white thin arrows) surrounds the posterior aspect of the aorta to finally reach the IVC. The right gonadal vein (white arrowheads) joins the IVC directly (Quoted from Perez et al 2013).
Figure (3.31): Coronal VR image shows a circumaortic left renal vein with retroaortic (R) and preaortic (P) components. An accessory LRA (arrow) which entering hilum of the kidney is present (Quoted from Turkavatan et al 2009 –A-).
Figure 3.32. Late segmentary confluence of the right renal vein. Curved coronal thin-section MIP image shows the confluence of the segmentary veins (arrow), which is located 1 cm from the IVC (Quoted from Sebastia et al., 2010).
Right renal vein late segmental confluence occurs less than 1–2 cm from the IVC (Fig 3.32). Because this vein usually is short, the left kidney is preferred for donation because its main vein is longer than that in the right kidney. Left renal vein late segmental confluence occurs less than 1.5–2 cm from the left aortic margin (Fig 3.33 & 3.34) (Sebastia et al., 2010).
Figure 3.33. Late segmentary confluence of the left renal vein. Axial thin-section MIP image shows late segmentary confluence of the left renal vein (arrow) near the left aortic margin. Two segmentary veins (arrowheads) also are seen (Quoted from Sebastia et al., 2010).
figure 3.34 (A)
Figure 3.34 (B)
Figure (3.34): Late venous confluence of left renal vein in 27-year-old male voluntary kidney donor. Curved coronal MIP (A) and anterior oblique VR (B) images show late venous confluence of LRV (thick white arrows). MIP image also shows two renal veins on right side (thin arrow). Left adrenal gland and adrenal vein are also nicely seen (Quoted from Kumar et al 2010).
In contrast to retro-caval arterial segmentary bifurcation, the main renal vein may be cut in front of the aorta without much difficulty. Veins are connected and supportive; if one segmental vein or double renal vein is cut and ligation performed, small collateral vessels develop between the veins and redirect the flow, thus preventing renal infarct from occurring (Sebastia et al., 2010).
Renal Vein Tributaries
Reliable visualization and knowledge of the location and diameter of renal vein tributaries are important because of the limited visual field of laparoscopic nephrectomy and for prevention of hemorrhagic complications during surgery. In most cases, the right renal vein has no venous tributaries. The right adrenal vein drains into the right renal vein in 30% of cases, the right gonadal vein drains into the right renal vein in 7% of cases, and the retroperitoneal vessels (the lumbar and hemiazygos veins) drain into the right renal vein in 3% of cases (Sebastia et al., 2010).
The left renal vein typically has several major venous tributaries (Fig 3.35). The left adrenal vein joins the left renal vein superiorly, just lateral to the adjacent vertebral body. The inferior phrenic and capsular veins typically join the left adrenal vein before its union with the renal vein (Anderson et al., 2008).
The left gonadal vein joins the left renal vein inferiorly, just lateral to the adrenal vein (Sebastia et al., 2010).
Figure 3.35. Diagram (sagittal view) shows the left renal vein tributaries (Quoted from Sebastia et al., 2010).
A gonadal vein with a diameter larger than 5 mm should be reported because the surgeon may need to use an alternate sectioning technique (eg, staples or plastic clips rather than cautery) (Fig 3.36) (Türkvatan et al., –B- 2009).
Figure (3.36): Sagittal thin-section MIP image shows the left gonadal vein which is large, with a diameter of 9 mm (arrow) draining into the inferior margin of the LRV (*). The hemiazygos vein (arrowheads) also drains into the superior margin of the left renal vein (Quoted from Sebastia et al 2010).
The left gonadal vein may be a double vein, or it may split at the confluence with the left renal vein, a finding seen in 15% of cases. Segmentary renal veins may drain directly into the gonadal vein. Retroperitoneal (lumbar, ascending lumbar, and hemiazygos) veins enter the left renal vein just lateral to the aorta along its posterior aspect. Again, a prominent lumbar vein with a diameter larger than 5 mm should be reported to ensure an appropriate surgical approach (Türkvatan et al., -B- 2009).
The segmental renal, gonadal, ascending lumbar, and hemiazygos veins may drain directly into the lumbar veins (Fig 3.37) (Kawamoto et al., 2006).
These renal vein tributaries are small and travel in many directions, presenting a challenge that requires the use of multiple workstation tools; curved planes are particularly useful for following the course of these tributaries.
Figure 3.37. Left lumbar and hemiazygos veins. Sagittal thin-section MIP image shows the lumbar vein (arrow)—which is large, with a diameter of 7 mm—draining into the posterior aspect of the left renal vein (*). The hemi-azygos vein (arrowhead) also drains into the superior aspect of the lumbar vein before anastomosing with the posterior margin of the left renal vein (*) (Quoted from Sebastia et al., 2010).
It is difficult to determine whether a small vein which is connected to the left renal vein, courses posterior to the aorta, and drains into the IVC should be defined as the retroaortic component of a circum-aortic renal vein or as a communication of a retroperitoneal vein—such as the lumbar and ascending lumbar veins—with the IVC by way of a small venous collateral vessel (Fig 3.38) (Kawamoto et al., 2005).
They defined such a vessel as a retro-aortic component of the circum-aortic vein when it is larger than the lumbar vein and as a small lumbar branch when it is similar to or smaller than the lumbar vein (Kawamoto et al., 2005).
These small posterior branches do not affect the surgical approach.
Figure 3.38. Ascending lumbar vein. Coronal volume-rendered image shows the large ascending lumbar vein (arrow) draining into the inferior aspect of the left renal vein. This ascending lumbar vein is connected to a collateral vein (arrowhead) that anastomoses to the IVC. It is difficult to differentiate these vessels from a small left retroaortic renal vein (Quoted from Sebastia et al., 2010).
Perirenal Fat
Kidneys that are to be transplanted must have all perirenal fat removed, a procedure that usually is performed at the time of harvesting. Large amounts of perirenal fat make surgery difficult and obscure anatomic landmarks (Sebastia et al., 2010).
Anderson et al., 2008 reported an association between the surgical time and the amount of perirenal fat present. Radiologists must measure perirenal fat and alert the urologist if a large amount of fat is present because it can lead to increased surgical complexity and time. Men tend to have more perirenal fat than women, and surgery in overweight men generally is difficult.
Nephrolithiasis
Due to its high sensitivity, multidetector CT is able to depict more small renal calculi in asymptomatic patients than techniques such as angiography and urography. Some authors report that most nephro and urolithiasis are depicted on arterial phase images (Türkvatan et al., -B- 2009).
Detection of lithiasis is important to determine if a renal stone must be treated before the kidney is removed or if it requires no treatment at all. In asymptomatic donors, a kidney with small calculi (<4 mm) may be safely harvested, particularly if calculi are located in the lower inferior pole and the donor has no history of lithiasis or metabolic disease (Fig 3.39) (Martin et al., 2007).
It is important to monitor the recipient for development of obstructive transplant stones.
Figure 3.39. Nephrolithiasis. Unenhanced axial CT image shows a small (2-mm) caliceal calculus in the right kidney (arrow). This kidney may be safely transplanted (Quoted from Sebastia et al., 2010).
Contraindications for transplantation of donors with urolithiasis are single stone < 5 mm, multiple unilateral stones, bilateral renal stones, infection stones, Uncorrectable metabolic abnormality (e.g. cystinuria) or lack of access to emergency urology expertise after donation (Olsburgh et al., 2013).
The donation is postponed till the calculi are removed and metabolic analysis is performed. Ex vivo ureteroscopy lithotripsy and extracorporeal shock wave lithotripsy are feasible and may render a stone-bearing kidney stone free without compromising ureteral integrity or renal allograft function (Trivedi et al., 2007).
Renal Masses
The presence of simple renal cysts does not exclude kidney donation (Simms et al., 2014).
It is important to evaluate the characteristics of the cyst to determine if a solid mass is present. Simple, even large, cysts may be easily excised, a procedure that does not increase morbidity for the transplant recipient (Grotemeyer et al., 2009).
Small indeterminate masses that are hypoattenuating at multidetector CT must be evaluated at ultra-sonography and characterized as cystic or solid. Kidneys with small angiomyolipomas (<5 mm) may be safely transplanted because these masses are slow growing and do not cause morbidity (Fig 3.40) (Sebastia et al., 2010).
Figure 3.40. Renal angiomyolipoma. Unenhanced axial CT image shows a small (4-mm) hypoattenuating mass (arrow) in the right kidney, a finding indicative of angio-myolipoma. The presence of this small angiomyolipoma does not exclude transplantation (Quoted from Sebastia et al., 2010).
Small, fat-poor angiomyolipomas masquerading as renal cell carcinoma and larger angiomyolipomas (> 5 mm) may be locally excised (Sener et al., 2009).
Transplantation of donor kidneys with a small renal cell carcinoma is controversial (figure 3.41). Urologic oncologists should have discussions with transplant surgeons about kidney transplantation in selected recipients after ex vivo excision of small masses from selected donors (Ogawa et al., 2015).
Figure 3.41. Renal cell carcinoma (a) Coronal reformatted CT image shows a 9-mm renal cell carcinoma in the left kidney (arrow). Two cysts (arrowheads) also are seen. (b)Intra-operative photograph shows removal of the tumor (arrow) (Quoted from Sebastia et al., 2010).
As reported in some small studies, because renal cell carcinoma is associated with a low risk for recurrence (it recurs in <2% of recipients) and an even lower risk for transmission to the contra-lateral kidney and other organs, kidneys with small renal cell carcinoma may be considered for local excision and transplantation if the recipient is informed of the risks and consents to the procedure (Mitsuhata et al., 2007).
Upper Urinary Tract Assessment
Some upper urinary tract anomalies such as severe hydronephrosis, papillary necrosis, medullary sponge kidney, and transitional cell tumors warrant direct exclusion from kidney donation. Complete and partial ureteral duplication and obstruction of the ureteropelvic junction are not absolute contraindications for donation; each case should be carefully evaluated (Sebastia et al., 2010).
Delayed topograms acquired in the excretory phase adequately depict the pelvicaliceal system and ureters and require less radiation than delayed phase multidetector CT images (Huang et al., 2006). Most of the recently published studies report good results with the use of delayed topograms obtained in the excretory phase (Huang et al., 2006).
If excretory topogram results are unclear, conventional abdominal radiography is immediately performed. Conventional abdominal radiography is more useful than excretory phase CT for differentiation of partial and complete ureteral duplication because it allows dynamic visualization of ureters (Sebastia et al., 2010).
Complete or partial ureteral duplication occurs in 1% of the general population. Coronal nephrographic reformatted images of the kidneys may depict a double or forked upper urinary system, which is recognizable by the presence of normal parenchyma between the pelvicaliceal systems (Fig 3.42) (Sebastia et al., 2010).
Figure 3.42. Bilateral partial ureteral duplication. (a)Coronal reformatted CT image shows normal parenchyma between the two pyeloureteral systems (arrows), a finding characteristic of two upper urinary tract systems. (b) Delayed excretory topogram shows bilateral partial ureteral duplication (Quoted from Sebastia et al., 2010).
To preserve ureteral circulation, the surgeon must take care not to separate the ureters during removal, even in cases of complete ureteral duplication. It is difficult to differentiate extrarenal pelvis from mild ureteropelvic junction obstruction in patients with pelvic ectasia; acquisition of a diuretic renogram may help determine if obstruction is present. (Sebastia et al., 2010).
Because ischemic ureteral problems may worsen obstruction in patients with mild ureteropelvic junction obstruction, kidney transplantation may be feasible by suturing the donor pelvis to the recipient ureter (Sebastia et al., 2010).
Absolute and relative contraindications for transplantation (modified from Sebastia et al., 2010)
Absolute contraindications
• Congenital anomalies as horseshoe kidney and crossed fused actopia
• Renal diseases such as cortical atrophy, polycystic disease, medullary sponge kidney disease, and renal papillary necrosis
• Bilateral FMD
• Uncorrectable coagulopathy
• Diabetes Mellitus
Relative contraindications
• Elderly donors
• Benign tumors (e.g. angiomyolipoma)
• Small resectable malignancies (controversial)
• Non-renal disease ( e.g cardiovascular)
• Multiple accessory arteries
• Renal scars
• Simple renal ectopia and pelviureteric junction stenosis
• Renal stones (single, small sized > 4 mm, non-obstructing, lower calyceal in position)