During the period from March 2014 to March 2016, a prospective study included 30 potential live kidney donors (20 men and 10 women) were evaluated with MDCT angiography at Nasr City insurance hospital, Cairo in preparation for kidney donation.
Mean donor age at time of evaluation was 37 years (range 24 to 55 years).
In our hospital, kidney donation couldn’t be performed except after passing through meticulous steps
Ministry of health and Health Insurance organization have strict regulations including patient consents and other legal requirements for approval of kidney donation
The approval of local ethical committee was obtained as well as medico-legal procedures for kidney donation for both related and non-related donors.
Inclusion and exclusion criteria
As the CT angiography was the last step in pre-operative evaluation of transplant donor, we had no exclusion criteria as the donors were screened clinically and with laboratory investigations in transplantation clinic to rule out any medical contraindications for kidney donation such as mental illness, history of tuberculosis, urological diseases or cancer.
We excluded only donors who didn’t proceed to transplantation (only one case due to left hydronephrosis secondary to ureteric stone which was missed in pre-CTA ultrasound).
All donors were subjected to
I. Clinical examination
II. Laboratory investigations including Hepatitis markers, liver functions, coagulation profile, renal functions (serum creatitnine and blood urea).
III. U/S and Doppler U/S to rule out major anomalies which could exclude donor from the program
IV. Renal CTA
In addition, renal ultrasound was routinely performed before CT angiography to rule out major anomalies which could exclude donors from the program. So, the CT angiography was performed to healthy donors.
19 subjects were evaluated pre-operatively by 4 sections MDCT and 11 subjects were evaluated by 16-section MDCT
Donors were referred to CT unit from transplantation clinic; they were scheduled to perform the examination.
Serum creatinine and blood urea levels were mandatory before the scan, all donors were below the accepted limit for IV contrast injection (serum creatinine limit was 1.4 mg/dl and blood urea limit was 40 mg/dl)
Each candidate was instructed to fast at least 8 hours before scan and ingest 1 litre of water 60 minutes before examination. No oral contrast material was administered.
Each donor attended in the scheduled day, his/her laboratory investigations were re-checked, and the nurse inserted a canula and he/she waited in the CT lobby.
After the study was performed, the attending radiologist rapidly revised the examination to insure that it was satisfactory and informative.
Each donor had to wait about 30 minutes after examination in CT lobby in case that any contrast allergy or adverse effects occurred. The donor was instructed to ingest one liter of plain water in the lobby to quicken contrast clearance.
Multidetector CT Protocol
As mentioned above, the study was performed by two machines (Asteion 4, Toshiba medical systems) and (Aquilion 16, Toshiba Medical Systems).
CT Scan was performed in cranio-caudal direction. Unenhanced CT of abdomen and pelvis was performed from the vertebral body of T12 to the sacro-iliac joint by 5-mm sections thickness and table speed of 5 mm per-rotation, collimation = 4×1 & rotation time = 0.5 second.
Subsequently, all donors received 70-80 ml intravenous non-ionic iodinated contrast material containing 300 mg/ml iodine (Optiray™ 300 [Ioversol Injection 64%])
Contrast enhanced CT was initiated, the arterial phase was adjusted according to bolus tracking method (refer to physics chapter), then cortico-medullary and excretory phases were adjusted at 55 seconds and 10 minutes after injection respectively.
Post CTA procedure workup
One- and 5-mm axial images and 5-mm coronal images routinely were reviewed by two the specialist and consultant for all phases. Images were transferred to a workstation (VITREA, Toshiba medical systems) and the following reconstructions were obtained for all cases:
• Sagittal reformation of each kidney to measure kidney length (figure 4.1);
• Axial thin-section maximum intensity projection (MIP) images of the renal arteries and veins (figure 4.2 A)
• Curved coronal reformation across the renal arteries and veins (drawn through axial images, figure 4.2 B )
• Thin-section coronal MIP : VR images obtained on the basis of previous curved coronal reformations (figure 4.2 C)
• Three-dimensional (3D) volume-rendered images for evaluation of arteries and veins (figure 4.3).
Figure 4.1. Measurement of kidney length. Sagittal reformatted CT image shows the length of a kidney, which was measured from the top of the upper pole to the bottom of the lower pole, a method that was used to confidently measure real orthogonal kidney length
(A) (B)
( C )
Figure 4.2. Reconstruction protocol. (A) Axial MIP CT image shows a curved line drawn at the level of the LRA. This line is used to create the curved plane. (B) Curved coronal reformatted image shows a left accessory renal artery. (c) Curved thin-section MIP image better depicts the renal artery branches.
(A) (B)
Figure 4.3. Coronal VR CT images show the renal arteries (a) and the renal vein (b).
CT reporting (image interpretation)
After post-processing workup is finished, CT study is reported. The report includes
A) Non-vascular findings :
• Site, shape and diameter of each kidney
• Parenchymal thickness and pattern of enhancement.
• Presence or absence of cysts, stones, masses or hydronephrosis
• Pattern of calyceal opacification, presence or absence of filling defects.
• Presence or absence of congenital renal anomalies
• Excretory function.
• Ureter: caliber, presence or absence of dilatation, obstruction, stones
• Amount of peri-renal fat
B) CT angiographic findings
• Renal artery caliber (in MIP images) and pattern of opacification
• Presence or absence of stenotic segments.
• Distance between right first arterial segmentary bifurcation and right margin of aorta and right margin of IVC
• Distance between left first arterial segmentary bifurcation and left margin of aorta
• Renal artery diameter at bifurcation
• Presence or absence of accessory arteries.
• Origin, diameter, course and type of accessory arteries (if present)
• Presence or absence of arterial disease.
• Renal veins number, diameter at confluence.
• Distance between confluence of RRV and right margin of IVC
• Distance between confluence of LRV, left margin of aorta and left margin of IVC
• Pattern of contrast opacification of renal veins
• Presence or absence of intra-luminal venous thrombi.
• Presence or absence of renal vein tributaries.
• Diameter of venous tributaries (if present) and their distance from aorta
Statistical analysis
done using SPSS (statistical package for social sciences, version 21 IBM software)
Gold standard:
After surgery and in case of discrepancy between intra-operative data and CT findings, a second review of images was done by both surgical team and radiologist.
Donor nephrectomy was performed in all subjects through an open approach. Surgery was performed after two or three months (median two months) after CT examination. The findings on CTA were used to guide the selection of the donor kidney.
Intra-operatively, the urology surgeon recorded the surgical findings, including number of arteries, the branching distance, the number of renal veins, the presence of late venous confluence and presence venous anomalies.
Strategies for reduction of the radiation dose
1- Reduction in the number of acquired series or phases
We omitted the non-contrast series in some donors. In other donors, we omitted the venous phase MDCT acquisition as the arterial phase provided information about the presence of renal masses, renal stones and renal vein anomalies and helped in identification of small left renal veins.
2- Lowering the tube potential
Lower kVp values (120 kVp in arterial and cortico-medullary phases and 100 kVp in precontrast and excretory phases) were used in the evaluation of renal donors undergoing renal CT angiography in our study.
When the tube potential was decreased to reduce radiation dose, it was necessary to increase the tube current to obtain acceptable image quality. However, with increased tube current, images became more noisy but still acceptable for diagnostic evaluation.
3- Using short scan lengths as much as possible
Larger scan length delivers radiation dose to larger areas of the body, thus increases radiation dose to the patients. We reduced the radiation dose by restricting the scan length to the region of interest as followed:
• Scanning from the top of the kidneys instead of the top of the liver in case of evaluation of renal stones or in the case of precontrast series.
• Scanning only the upper abdomen (till bifurcation of common iliac arteries) in the cortico-medullary and nephrographic phases
• Scanning the region from the kidneys to the bladder for the excretory phase.
• Appropriate triggering of CT following contrast injection (refer to physics chapter).
• In case of non-opacification of a portion of the ureter or remaining collecting system, we obtained conventional radiography images instead of transverse CT images.
If repetition of transverse CT images was “inevitable” or “necessary”, we reduced radiation dose by using substantially smaller scanning lengths.