DONOR
Laparoscopic nephrectomy has become the preferred surgical procedure for procuring kidneys from living donors.
The left kidney is preferred for laparoscopic nephrectomy in living donors because it is technically easier to remove and has a longer renal vein compared to the right kidney .
Multidetector computed tomographic angiography (MDCTA) is the modality of choice for preoperative evaluation of living renal donors and the radiologist is able to provide the surgeon with valuable information about abdominal anatomy ,
vascular pathways,
collecting system abnormalities,
the possible variants and the diseases,
before a potential renal surgery.
In our institution patients were examined using a multi-detector CT scanner (LightSpeed VCT 64,
GE Healthcare).
Scan parameters were: collimation 64×0.625 mm; slice thickness 5 mm; pitch 1.375; table speed/gantry rotation 55 mm; kV 140; and mA 240.
With a power injector,
100 ml of contrast medium (Ultravist 300) was injected in an antecubital vein at a flow rate of 4.0 mL/s.
We used a three-phase CT examination and the automatic bolus-tracking method:
- Arterial phase scan (scan was started after enhancement of the abdominal aorta at the level of the renal artery by 50 HU)
- Venous phase scan (automatically started 30 s after completion of the arterial phase scan)
- Delayed phase scan ( is done after an interval of 5-15 min)
In software analysis we used 2D (MPR,
MIP,
MinIP) and 3D reconstructions (VR).
RENAL VASCULATURE EVALUATION
- Renal arteries
Grafts with anatomic variants are still challenging problem to the surgeon.
Out of these variants,
multiple renal arteries are the most common. Fig. 2 Based on previous studies 75% living renal donor had a single renal artery and other 25% had bilateral vascular multiplicity.
All renal arteries must be reconstructed and prepared for safe anastomosis.
Recently,
there has been an increased use of kidneys with multiple arteries with excellent results. Anastomosis of two arteries close together on an aortic patch of a left-sided deceased donor kidney is relatively simple.
If they are more than 2 cm apart,
consideration could be given to perform two separate anastomoses.
Dual arteries to a right-sided kidney often make positioning of the kidney difficult without kinking one of the other artery.
Early arterial branching is also common anatomical variant.
It is essential to identify any prehilar branching that occurs within 2 cm of the origin of the renal artery from the abdominal aorta,
since most surgeons require at least a 2-cm length of renal artery before hilar branching to guarantee satisfactory control and anastomosis.
The use of donors with renal artery stenosis due to atherosclerosis and fibromuscular dysplasia is still controversial.
Fig. 1: MDCTA reveals insignificant parietal calcification on the origin of the left renal artery and 11mm from it.
Fibromuscular dysplasia (FMD) is an idiopathic,
segmental,
nonatherosclerotic,
and noninflammatory disease of the musculature of arterial walls,
leading to stenosis of small- and medium-sized arteries.
Bilateral FMD excludes donation.
Table 1
2. Renal veins
The renal vein is usually located anterior to the renal artery at the renal hilum.
The majority of left and right kidneys had just one renal vein that drains into the inferior vena cava (IVC) .
The right renal vein is shorter (2-4 cm) than the left (6-10 cm). The left donor kidney is preferred because the longer left renal vein facilitates venous anastomosis.
The right renal vein receives blood only from the right kidney.
The left renal vein collects the flow from the veins coming from the left kidney ,
left adrenal and gonadal veins and passes horizontally between the abdominal aorta and the superior mesenteric artery to reach the IVC
Venous variants can be: circumaortic left renal vein,
retroaortic left renal vein,
multiple veins ,
right-sided gonadal and adrenal drain and their existence must be included in the radiological report.
- Circumaortic left renal vein: In this anomaly,
the vein bifurcates and encircles the aorta,
with each limb entering the inferior vena cava apart.
- Retroaortic left renal vein is an anatomical variant where the left renal vein is located between the aorta and the vertebra and drains into the inferior vena cava.
In retrospective study performed at Johns Hopkins Hospital,
USA involving 654 potential renal donors circumaortic left renal vein was found in 7% of donors and retroaortic left renal vein was found in 2% of donors.
Table 2
3. Perinephric fat evaluation
Increased perirenal fat is associated with expanded operative complexity and operative time. Men exhibited larger volume of visceral and perirenal fat compared to women.
Perirenal fat on the left side was consistently greater compared to the right side in both genders.
BMI is known to be a poor marker of visceral fat volume and is also a poor marker of perirenal fat volume.
4. Upper urinary tract evaluation
Presence of severe hydronephrosis,
papillary necrosis,
medullary sponge kidney,
and transitional cell tumors permit direct exclusion from kidney donation
5. Nephrolithiasis evaluation
Previously,
donors with detection of kidney stone prior to donation were not considered ideal candidates because of the presumed risk of donor morbidity from possible stone formation in the solitary remaining kidney and potential recipient morbidity from obstruction attributable to a ‘donor-gifted’ stone.
The new guidelines recommend that in the absence of a significant metabolic abnormality,
kidnys with stone less than 4 mm could be left in situ and the kidney can be safely transplanted.
Stone in the kidney (size 4-12mm) can be managed at the time of transplantation with Ex vivo ureteroscopy and this technique can safely return a stone-free kidney before transplantation.
Multiple stone in one kidney or bilateral stone disease are contraindication for renal donors.
6. Evaluation of renal parenchyma
Evaluation includes the number,
length Fig. 3
Fig. 3
location,
anatomic variants,
and diseases of the donor kidneys.
Renal anomalies and diseases such as unilateral agenesis, significant unilateral atrophy horseshoe kidney,
cortical atrophy,
polycystic disease,
medullary sponge kidney disease.
Renal Masses:
- The presence of simple cyst (Bosniak 1) and small angiomyolipomas (<5 mm) does not exclude kidney donation.
- Renal cell carcinoma (RCC) was previously considered as contraindicationis for transplantation but a recent studies suggest that kidneys with small incidental tumors ,
after appropriate removal of the lesion and careful pathological examination could be considered for transplantation with a very low risk of recurrent disease.
RECIPIENTS
In presurgical evaluation of potential kidney transplant recipients,
MDCT angiographia is an imaging technique that allows rapid and noninvasive exploration of the vascular and extravascular system.
The radiological report should indicate
- existing calcification of the aortoilic segment;
- deviation from the normal diameter of the aorto-iliac segment in terms of stenotic and aneurysmal disease;
- deep venouse thromboses;
- active malignancy;
- infection.
1.Detection of iliac-artery calcifications
to perform the arterial anastomosis,
a site without significant arteriosclerosis must be chosen since calcification itself makes vessels less amenable to anastomosis,
and the atherosclerotic process can lead to luminal stenosis,
compromising graft perfusion.
Fig. 4: Presurgical evaluation of potential kidney transplant recipients( a), (c) CT image shows massive parietal calcifications of the infrarenal abdominal aorta and both common and internal iliac artery. Both external iliac arteries are free of parietal calcifications. (b) Contrast-enhanced CT shows small atrophic kidneys bilaterally, consistent with end-stage renal disease.
2. Aortoiliac Caliber
- In men,
the common iliac artery normally averages 1.2 ± 0.2 cm,
whereas in women it is smaller,
averaging 1.0 ± 0.2 cm,
an aneurysm is generally present if the artery measures >1.85 cm in males and >1.5 cm in females.
- The internal iliac artery in both genders averages 0.54 ± 0.15 cm and diameter more than 0.8 cm is likely aneurysmal.
- The normal diameter of the abdominal aorta is regarded to be less than 3.0 cm.
3.
Deep venous thromboses
4. Active malignancy
Patients with chronic kidney disease both those who were on long-term dialysis and those who were not have a higher-than-normal cancer risk.
The liver,
bladder,
and kidney cancers are the three most frequent in male ESRD patients on dialysis and the bladder,
kidney,
and breast cancers were the three most frequent in female ESRD patients on dialysis.
5.Evaluate the native kidneys and urinary tract
Native nephrectomy is recommended before transplantation (unilateral or bilateral) in patients with autosomal polycystic kidney disease Fig. 11 and when space for the transplant kidney is insufficient.
*In retrospective study of 179 transplant candidates, CTA demonstrated findings that altered their care and tretman was changed in 41 patient.
CTA is relatively safe,
is cost-effective,
and has the potential to increase graft and patient survival
Fig. 5: Volume-rendered image.
The end of the donor kidney vein is attached to the side of the external iliac vein (black aroww). The cut end of the donor renal artery is attached to the side of the external iliac artery (blue aroww)
COMPLICATIONS OF RENAL TRANSPLANTATION:
Renal transplantation complications may be:
1.Vascular: renal artery stenosis and thrombosis,
arteriovenous fistula,
pseudoaneurysms,
infarction;
2.Urologic: ureteral obstruction,
peritransplantation fluid collections (hematoma,
seroma,
lymphocele,
and abscess formation);
3.Nephrogenic: acute tubular necrosis,
graft rejection,
neoplasms,
infection.
Vascular comlications:
1.RENAL ARTERY STENOSIS is the narrowing of the renal arteries and is the most common vascular complication in renal transplant patients.
It occurs most frequently in the first 6 months within 1 cm of the anastomosis.
Patients usually present with refractory hypertension and flash pulmonary edema.
Early detection and correction,
reduce patients morbidity and allograft dysfunction.
Fig. 6: A 50-yr-old woman developed end-stage renal disease secondary to glomerular disease in systemic lupus erythematosus that had been diagnosed 14 year before. 7 months previously, she had undergone a living-related renal transplantation to the right iliac fossa.(a) Coronal enhanced MDCT images shows normal sized transplanted kidney implanted in the right iliac fossa. (b) Coronal enhanced CT image demonstrates a proximal stenosis of the transplant kidney artery (c) there is two wedged-shaped area of low attenuation in the right kidney, consistent with infarction (d) 3 D reconstructed MDCT demonstrated -correctly positioned double J stent
2.RENAL ARTERY THROMBOSIS
Acute renal artery thrombosis is a severe complication of renal transplantation that can result in graft loss if not detected early and usually presents with sudden onset oliguria or anuria accompanied by pain and tenderness over the graft site.
Renal artery thrombosis may result from hyperacute rejection,
anastomotic occlusion,
arterial kinking Fig. 7 ,
or intimal flap.
Fig. 7: CT angiography of the transplant renal showing an acute angled kink of the transplant renal artery
3.SEGMENTAL INFARCTION
Segmental infarction results from thrombosis of the intrarenal arterial branches. Fig. 6
4.
ARTERIOVENOUS FISTULA AND PSEUDOANEURYSM
Percutaneous biopsy is commonly performed in transplant recipients when rejection is suspected and this invasive procedure is not without risk.
Biopsy-induced arterial injury may result in arteriovenous fistula,
pseudoaneurysm,
arteriocalyceal fistula and rarely arterial thrombosis.
The prevalence of extrarenal arterial pseudoaneurysm after renal transplantation is less than 1%.
- Extrarenal pseudoaneurysm is directly related to arterial anastomosis surgery and,
rarely,
to infectious causes.
- It is usually is asymptomatic but can occasionally cause renal dysfunction or compression of adjacent structures .When these pseudoaneurysms become large,
they must be surgically removed to avoid spontaneous rupture.
Fig. 8: In the right iliac fossa, the site of previously transplanted kidnay demonstrates to liquid collection, 54x45mm within pseudoaneurysm arising from AIE* in graft kidney.
*AIE (artery iliaca externa)
Urologic complications
1.
URINARY OBSTRUCTION
Urinary obstruction occurs in approximately 2% of transplantations and almost always within the first 6 months after the procedure.
The most common causes are stricture in the distal third of the ureter,
oedema at the anastomotic site,
a blood clot within the ureter or bladder,
and perinephric fluid collections.
Fig. 9: 20mm from insertion in the urinary bladder, ureter show significant narowing of 1mm because of periureteral fibrosis that generate moderate ureterohydronephrosis of the graft.
2.
PERITRANSPLANTATION FLUID COLLECTIONS
Postoperative fluid collections are common after transplantation and includes: hematomas,
urinomas,
lymphoceles,
and abscesses.
-HEMATOMAS
Small peritransplantation fluid collections seen immediately after transplantation are most likely hematomas or seromas,
and should be considered a normal sequela.
Size,
location,
and growth determine the significance of a hematoma.
They appear as a fluid collection with hyperattenuating areas on unenhanced CT.
Older hematomas may appear as heterogeneous fluid collections with liquefied serous components.
-URINOMAS
Urinomas are usually caused by acute leaks from the uretral anastomosis and is characterized as encapsulated fluid collection without internal septations adjacent to the ureterovesical junction in the early postoperative period.
Large urinomas can rupture intraperitoneally and cause free peritoneal fluid.
-LYMPHOCELES
Lymphocele form as a result of the disruption of perivascular or hilar lymphatics and usually occur 4-8 weeks after surgery.They appear as round and hypoattenuating collections on MDCT.
Lymphocele requires treatment only if the patient is symptomatic,
if the lymphocele is compressing the ureter,
or if it is infected.
Fig. 10: Lymphocele-the left common iliac vessels are displaced laterally and superiorly, because of unilocular thin-walled, fluid-filled structure
Nefrogenic complications:
1.ACUTE TUBULAR NECROSIS usually occurs in the immediate postransplant period,
it is multifactorial and represents one of the main causes of the delayed graft and it has no impact on patients and graft survival.
2.REJECTION:
* Hyperacute rejection: is a rare and is often manifested during surgery.
It is mediated by preformed antibodies that can usually be excluded before transplantation
* Accelerated acute rejection: similar to hyperacute rejection only delayed until two or three days after surgery.
*Acute rejection: It is clinically defined as an elevation in the level of serum creatinine and is diagnosed by kidney biopsy .
*Chronic rejection: may appear months to years after surgery and is and is most often due to sclerosing vasculitis, progression of atherosclerosis (vascular calcification) Fig. 11 and extensive interstitial fibrosis.
Fig. 11: Renal graft rejection, 15 months after renal transplantation in right iliac fossa, in 57-yr-old man with end-stage renal disease releted to polycystic kidney disease and bilateral renal arterial calcification . Aorta, transplant renal artery and both internal iliac artery presents with massive calcifications.