With laproscopic nephrectomy becoming the norm,
it is crucial to be meticulous in reporting as intraoperative visibility is limited.
WHICH KIDNEY IS BETTER FOR DONATION
- Left renal vein(7.5 cm) is longer than the right(2.5 cm) making surgery simpler (Figure 1)
- Even left kidneys with one or two accessory arteries or veins are preferred over right (1)
- If one kidney is abnormal but not contraindicated for transplantation,
the abnormal kidney is harvested
- If both the kidneys are normal the one with less complicated vascular anatomy is chosen
NORMAL ANATOMY
Fig. 1: Renal vascular anatomy
References: V Baliyan, Department of Radiology, AIIMS, New Delhi
- Renal arteries arise 1cm below superior mesenteric artery at L2 level (2)
- 1/4th individuals have double renal arteries and some of them have three or more
- Accessory arteries are considered to be persistent embryonic lateral splanchnic arteries(2)
- Right renal vein generally does not have any tributaries although right adrenal vein (30%) right gonadal vein (7%) ,
right lumbar and hemiazygos veins (3%) may drain into it in a small percentage of cases
- The left gonadal,
adrenal ,
lumbar and hemiazygos veins typically drain into left renal vein(3)
PRETRANSPLANT DONOR EVALUATION:
MDCT ANGIOGRAPHY
- Prior to development of MDCT technique Digital Subtraction Angiography(DSA) was considered the investigation of choice for evaluation of vascular anatomy of the donor
- Currently MDCT has replaced DSA for this indication
- MDCT can deliniate the fine details of vascular anatomy with the help of 3-D Multiplanar reconstructions and submillimeter slice reconstruction
While reporting one must focus on the following aspects of renal anatomy and evaluate each in detail
1. STRUCTURAL AND PARENCHYMAL ABNORMALITIES
2. ARTERIAL ANATOMY AND VARIATIONS
3.
RENAL ARTERY DISEASES
4.
VENOUS ANATOMY AND VARIATIONS
5.
PELVIURETERIC EVALUATION
6.
OTHER FINDINGS LIKE CALCULI AND INCIDENTAL MASSES
1.STRUCTURAL AND PARENCHYMAL ABNORMALITIES
Kidneys are evaluated for size,
congenital and acquired anomalies and findings which contraindicate transplantation.
Absolute contraindications |
Relative contraindications(if other things are favourable) |
- Unilateral agenesis (naturally) (Figure 2)
- Horseshoe kidney (Figure 3)
- Polycystic disease (Figure 4)
- Renal papillary necrosis
- Sponge kidney
|
- Renal ectopia (Figure 5)
- PUJ obstruction
- Unilateral small parenchymal scars(harvested if normal function on nuclear scan ; scarred kidney is harvested)
|
Fig. 2: AGENESIS: Coronal CECT showing left renal agenesis
References: Department of Radiology, All India Institute of Medical Sciences, New Delhi,2012
Fig. 3: HORSESHOE KIDNEY: VRT showing medially oriented lower renal poles joining together just below Inferior mesentric artery suggestive of horseshoe kidney
VRT:Volume rendered technique
References: Department of Radiology, All India Institute of Medical Sciences, New Delhi,2012
Fig. 4: ADULT POLYCYSTIC KIDNEY DISEASE
References: Department of Radiology, All India Institute of Medical Sciences, New Delhi,2012
Fig. 5: Coronal MPR and VRT images show a malrotated ectopic right kidney. This serves as a relative contraindication
References: Department of Radiology, All India Institute of Medical Sciences, New Delhi,2012
2.ARTERIAL ANATOMY AND VARIATIONS
- Seventy-one percent of kidneys have one artery
- 24% have two arteries
- Only 5% have three or more arteries -absolute contraindicationfor donation (Figure 6)
Fig. 6: MULTIPLE ARTERIES: Coronal MIP image showing three hilar arteries supplying the right kidney; MIP: Maximum intensity projection
References: Department of Radiology, All India Institute of Medical Sciences, New Delhi,2012
ACCESSORY ARTERY
- When a kidney has two arteries the one with the larger diameter is considered main and the other one accessory
- Distance between the two arteries (helps the surgeon locate the second artery easily) (4)
- Accessory arteries can be of three types hilar,
polar and capsular(Figure 7,8)
Fig. 7: ACCESSORY HILAR ARTERY :MIP and VRT images showing bilateral accessory hilar arteries
References: Department of Radiology, All India Institute of Medical Sciences, New Delhi,2012
- Inferior polar arteries supply the pelvis and upper ureter which if inadvertently damaged may lead to irreversible pyeloureteral damage(3)
*PEARLS
Polar arteries may be sacrificed if their diameter is less than 2mm without much risk of damage to the kidney (Figure 8)
Fig. 8: POLAR ARTERY: Coronal MIP showing right superior polar artery with a significant diameter
References: Department of Radiology, All India Institute of Medical Sciences, New Delhi,2012
- Small accessory arteries may only be picked up on thin section axial images therefore it is important to review the source images in addition to MIP and VRT images.
- Sometimes renal artery may have atypical branches like inferior phrenic artery which normally arises from the aorta (Figure 9)
Fig. 9: VARIANT INFERIOR PHRENIC ARTERY: VRT AND MIP images showing right inferior phrenic artery arising from right renal artery(arrow).It normally arises from aorta.
References: Department of Radiology, All India Institute of Medical Sciences, New Delhi,2012
PREHILAR BRANCHING
Implication : Surgery behind IVC is technically difficult and surgeons require at least 1 cm of renal artery for clamping and anastomosing the artery in the recipient
Measurements to be made
- Length of each of the artery before bifurcation
- Right side -branching point of renal artery is at a distance less than 1 cm from the IVC margin (x in Figure 10)
- Left side - branching point of renal artery is at a distance less than 1-1.5 cm from the lateral aortic margin (y in Figure 10)(5)
(Figure 10,11,12)
Fig. 10: PREHILAR BIFURCATION:
x=distance of right renal artery from right IVC margin
y=distance of left renal artery from left aortic margin
If x is less than 1 cm or y is less than 1-1.5 cm it is called as prehilar bifurcation
References: V Baliyan, Department of Radiology, AIIMS, New Delhi
Fig. 11: PREHILAR POLAR ARTERY: MIP and VRT images showing right accessory polar artery arising as a prehilar branch
References: Department of Radiology, All India Institute of Medical Sciences, New Delhi,2012
Fig. 12: MIP image showing right accessory hilar artery and left perhilar bifurcation
References: Department of Radiology, All India Institute of Medical Sciences, New Delhi,2012
3.
RENAL ARTERY DISEASES
Absolute contraindications
|
|
|
Relative contraindications
|
|
|
- Bilateral atherosclerotic involvement
|
- Unilateral atherosclerotic involvement (harvested if endarterectomy is performed)
- Unilateral FMD(harvested if grafting is performed)
|
|
Table 2
- Fibromuscular dysplasia (FMD) is a disease affecting young women with a string-of-beads appearance
- FMD affects mid or distal main renal artery (Figure 13,14)
- Atherosclerosis causes ostial stenosis (Figure 15)
Fig. 13: Renal artery stenosis due to atherosclerosis causes ostial narrowing while Fibromuscular dysplasia(FMD)causes a "string of beads" appearance in mid and distal renal artery
References: V Baliyan, Department of Radiology, AIIMS, New Delhi
Fig. 14: FIBROMUSCULAR DYSPLASIA: MIP image showing "string of beads" appearance in mid and distal right renal artery
References: Department of Radiology, All India Institute of Medical Sciences, New Delhi,2012
Fig. 15: RENAL ARTERY STENOSIS: MIP and VRT images show ostial narrowing in right renal artery due to atherosclerosis
References: Department of Radiology, All India Institute of Medical Sciences, New Delhi,2012
*PEARLS
Arterial anatomy may rarely be doubtful in which case conventional angiography may be advised.
4. VENOUS ANATOMY AND VARIATIONS
- Double and triple renal veins are quite common (Figure 16,17)
Fig. 17: TRIPLE RENAL VEINS: MIP and VRT images showing three renal veins on the right side
References: Department of Radiology, All India Institute of Medical Sciences, New Delhi,2012
Fig. 16: DOUBLE RENAL VEINS: MIP image shows two renal veins on right side
References: Department of Radiology, All India Institute of Medical Sciences, New Delhi,2012
- It is important to report a gonadal or a lumbar vein with >5mm diameter (Figure 18)
- Implication : may require alternate sectioning techniques
- Circumaortic and retroaortic veins occur in 7% and 2-3%individuals respectively (6)
- Implication : surgery must be open rather than laparoscopic(3,5)(Figure 19,20,21)
Fig. 19: Diagram showing normal course of left renal vein anterior to aorta(A), circumaortic course(B) and retroaortic course(C)
References: V Baliyan, Department of Radiology, AIIMS, New Delhi
Fig. 20: CIRCUMAORTIC RENAL VEIN
References: Department of Radiology, All India Institute of Medical Sciences, New Delhi,2012
Fig. 21: RETROAORTIC RENAL VEIN: Oblique and Coronal MPRs show retroaortic and obliquely downward course of left renal vein; MPR: multiplanar reconstruction
References: Department of Radiology, All India Institute of Medical Sciences, New Delhi,2012
- IVC anomalies like double and left sided IVC may pose a special challenge at surgery and anatomy must be described in detail (Figure 22,23) (7)
Fig. 22: DOUBLE IVC: right IVC and left IVC shown by arrow and arrowhead respectively
References: Department of Radiology, All India Institute of Medical Sciences, New Delhi,2012
Fig. 23: MIP and VRT images showing right IVC(arrow) continuing upward from the right renal vein. Left IVC(arrowhead) is draining the lower limb and left renal vein
References: Department of Radiology, All India Institute of Medical Sciences, New Delhi,2012
- Late segmental confluence of the right renal vein occurs less than 1-2 cm from IVC(x in Figure 24) while of the left renal vein occurs less than 1.5-2 cm from the aortic margin(y in Figure 24).
- Implication : not much problematic as vein may be cut in front of the aorta without much hassle (Figure 25)
Fig. 24: LATE SEGMENTAL CONFLUENCE: x=distance from right renal vein confluence to right IVC margin; y=distance from left renal vein confluence to left aortic margin
x less than 1-2 cm and y less 1.5-2 cm than is called as late segmental confluence of renal veins
References: Department of Radiology, All India Institute of Medical Sciences, New Delhi,2012
*PEARLS
Even if a segmental or double vein is cut chances of infarct are less as collateral formation occurs readily with veins.
However knowledge of these variations help the surgeon to be prepared beforehand and avoid accidental hemorrhage
5.PELVIURETERIC EVALUATION
Transplanted with care |
Absloute contraindications |
- Ureteric duplication(ureters are never separated to avoid ischemic damage) (Figure 26)
- Pelviureteric junction obstruction
|
- Severe hydronephrosis
- Papillary necrosis
- Transitional cell carcinomas
|
Table 3
Fig. 26: PARTIAL DUPLICATION OF RIGHT URETER
References: Department of Radiology, All India Institute of Medical Sciences, New Delhi,2012
6.OTHER FINDINGS
Renal calculi
- All prospective donors with calculi undergo workup for possible metabolic disease
- Asymptomatic donors with calculi less than 4 mm can safely be harvested(Figure 27)
Fig. 27: SMALL RENAL CALCULUS: can be transplanted without calculus removal
References: Department of Radiology, All India Institute of Medical Sciences, New Delhi,2012
- Calculi > 5mm or multiple stones cannot be harvested until the stones are removed(Figure 28)(8)
Fig. 28: MULTIPLE CALCULI: must be removed prior to transplantation
References: Department of Radiology, All India Institute of Medical Sciences, New Delhi,2012
Incidental masses
Best phase for evaluation of masses is nephrographic phase (renal parenchyma enhances uniformly)
- Bosniak type 1 cysts (Figure 29) and small angiomyolipomas <5mm are safely harvested
Fig. 29: BOSNIAK TYPE 1 CYST: can be transplanted
References: Department of Radiology, All India Institute of Medical Sciences, New Delhi,2012
- Small fat poor angiomyolipomas and those >5 mm may be transplanted after excision (Figure 30,31)
Fig. 30: ANGIOMYOLIPOMA (fat density lesion in right kidney): must be excised prior to transplantation
References: Department of Radiology, All India Institute of Medical Sciences, New Delhi,2012
Fig. 31: ANGIOMYOLIPOMA: T1W image shows hyperintense lesion in rigt kidney corresponding to CT in Figure 26
References: Department of Radiology, All India Institute of Medical Sciences, New Delhi,2012
- Oncocytomas: kidneys may be transplanted after excision (Figure 32)
Fig. 32: RENAL ONCOCYTOMA: well defined lesion in the left kidney showing arterial enhancement and washout on delayed phase
References: Department of Radiology, All India Institute of Medical Sciences, New Delhi,2012
- Small Renal cell carcinomas do not have a high recurrence rate owing to which kidneys containing them may be considered for transplantation after excision has been performed with informed consent of the recipient (27)