Year : 2002 | Volume
: 19 | Issue : 1 | Page : 50--53
Comparison of spiral CT angiography vs digital subtraction angiography in the evaluation of living kidney donors
Santosh Kumar, Manoj Tharakan, Ninan Chacko, Lionel Gnanaraj
Department of Urology and Radiodiagnosis, Christian Medical College and Hospital, Vellore, India
Department of Urology, Christian Medical College and Hospital, Vellore - 632 004
Recent reports suggest that spiral computed tomographic (CT) angiography could replace conventional angiography and intravenous urography (IVU) for the assessment of potential live kidney donors. The purpose of this study was to assess the accuracy of spiral CT in kidney donor workup. 10 consecutive renal donors had IVU, percutaneous transfemoral selective renal angiography and spiral CT angiography between January and March 2001. The spiral CT and renal angiograms were assessed independently by two radiologists. The number of renal arteries, presence or absence of renal artery stenoses and associated parenchymal abnormalities were assessed. A total of 27 renal arteries were detected. Transverse scans viewed in a tine loop format with maximum intensity projection and shaded surface display detected all 27 vessels. All 27 vessels were detected by conventional catheter angiography. A simple renal cyst was noted in both spiral CT and conventional angiogram. Venous anatomy including a retroaortic renal vein was visualized in spiral CT angiogram but not visualized by conventional angiography. Spiral CT angiography performed as an outpatient procedure is less invasive, less expensive, and provides good images of the arterial and venous anatomy in addition to the visualization of the other abdominal viscera. A plain X-ray of the abdomen was taken 15 rains after injection of contrast to acquire an IVU like image. Spiral CT angiography has the potential to replace conventional catheter angiography and IVU in the assessment of renal donors.
|How to cite this article:|
Kumar S, Tharakan M, Chacko N, Gnanaraj L. Comparison of spiral CT angiography vs digital subtraction angiography in the evaluation of living kidney donors.Indian J Urol 2002;19:50-53
|How to cite this URL:|
Kumar S, Tharakan M, Chacko N, Gnanaraj L. Comparison of spiral CT angiography vs digital subtraction angiography in the evaluation of living kidney donors. Indian J Urol [serial online] 2002 [cited 2021 Jun 14 ];19:50-53
Available from: https://www.indianjurol.com/text.asp?2002/19/1/50/20291
Live kidney donors undergo extensive preoperative evaluation, which includes medical history, laboratory testing and radiological imaging. Assessment of a potential live kidney donor requires intravenous urography (IVU) in order to determine the renal size, function of both the kidneys, evaluation of the calyces, pelvis and ureteric anatomy, as well as to detect renal or ureteral calculi.  Potential donors with normal IVU undergo renal angiography for anatomic definition of the renal arteries and the detection of accessory renal arteries. Recently, spiral computed tomographic (CT) angiography has been used to delineate the renal vascular and collecting systems.  Spiral CT angiography has the potential to achieve the diagnostic accuracy of conventional angiography without the risks of catheter angiography. The purpose of this study was to assess the accuracy of spiral CT compared with catheter angiography for the assessment of potential renal donors.
Material and Methods
A total of 10 kidney donors were evaluated between January to March 2001. A thorough history, clinical examination and laboratory assessment was performed to exclude from donation candidates with renal dysfunction. Donors had documented histocompatibility with recipients. Potential donors received an intravenous bolus of 100 ml (2 ml/kg) of contrast at the rate of 3 ml per second through a peripheral vein. During the arterial phase, 14 to 20 seconds after the start of injection, helical scanning was begun above the kidney and continued to 3 cm below the aortic bifurcation using 2 mm collimation and a pitch varying from 1.5 to 1.8 depending on the required length of coverage. Continuous anatomic information was obtained from the data acquired by the spiral CT, which couples a continuously rotating tube and table feed. Images are obtained during a single breath hold (usually 30 seconds), thus eliminating respiratory artifacts. Approximate patient examination time is 5-10 mins and image reconstruction and data analysis are complete in 20 mins. Image analysis includes not only visualization of the axial images in a cine mode, but also interactive multiplanar reformatting with thin maximum intensity projection (thin MIP) and shaded surface display (SSD). Thin MIP and SSD displays provide angiographic-like images and can discriminate calcification from the contrast material. A plain X-ray of the abdomen was taken 15 mins after injection of contrast to acquire an IVU like image.
Radiological investigations included IVU followed by conventional angiography and spiral CT angiography. All spiral CT angiograms were done and interpreted before digital subtraction angiography by a radiologist who had no knowledge of the conventional angiography results. Digital subtraction angiograms were done as day care procedure with hospital admission whereas spiral CT angiograms were done as an out patient procedure. All the potential donors underwent open donor nephrectomy.
All the patients were accepted for donor nephrectomy. 27 arteries were reported by spiral CT as well as by the conventional angiography (100% accuracy). Review of the axial images, thin MIP and SSD showed all the 27 arteries. Maximum intensity projection and SSD images should be always viewed in conjunction with axial images to avoid missing small arteries. Multiple arteries were reported on spiral CT angiography and digital subtraction angiography in 5 donors (two patients had bilateral double vessels). Early prehilar branching of renal artery was seen in two renal units of the same patient by both spiral CT angiography and DSA. The arteries were assessed for the presence of calcification and stenosis. The details of the venous anatomy were clear in spiral CT angiograms. Details of the adrenal, gonadal and the lumbar vein joining the left renal vein is seen clearly by viewing reformatted images of the spiral CT at the workstation which is very useful to the surgeon planning a laparoscopic donor nephrectomy. Vascular images of the donor kidneys seen on both the conventional and spiral CT angiography were confirmed for the side that underwent donor nephrectomy.
A simple renal cyst was noted on both spiral CT and conventional angiogram in one donor. There were no complications encountered with the conventional as well as the spiral CT angiograms in this series.
Anatomic imaging of potential living renal donors has been performed with IVU followed by conventional arteriography. Preoperative conventional arteriography has four recognized objectives: (a) renal artery number, (b) renal artery length, (c) renal arterial aneurysmal and occlusive disease, and (d) unsuspected renal parenchymal abnormalities.  The purpose of this study was to assess the accuracy of spiral CT angiography compared with catheter angiography for the assessment of potential. renal donors.
5 of the potential donors had multiple arteries (50%) diagnosed both by the conventional and the spiral CT angiograms. 1 patient had bilateral early (prehilar) branching of renal artery. The generation of three-dimensional renderings of the arterial tree has been an important factor in the acceptance of CT for the evaluation of potential living donors by transplant surgeons.  There were 7 accessory polar arteries identified in the 20 renal units studied. Attention has been given to detection of these small (less than 2 mm) accessory vessels to help surgeons avoid additional blood loss and possibly a focal renal infarct. However, some of these small vessels especially at the upper pole are sacrificed at surgery, as they are too small to transplant and do not affect patient outcome, since renal volume loss is negligible. 
Spiral CT angiogram delineates venous normal and anomalous anatomy in greater detail. Venous anomalies can be identified preoperatively, and unexpected injury can be prevented during its removal. This additional information is very useful to the laparoscopic removal of the kidney.  1 case of retroaortic renal vein was seen in our study that was confirmed at surgery. Circumaortic and retroaortic left renal veins are important anomalies that occur in 17% and 3% of healthy subjects, respectively. 
1 donor was found to have a solitary renal cyst on spiral CT and conventional angiography. The spiral CT characterizes parenchymal lesions in greater detail. This could lead to the diagnosis of incidental tumefactions. In the long run whether this will decrease the donor pool or not is an issue that is still not addressed. An additional advantage of pre-transplant screening with CT is the evaluation of other abdominal organs for unsuspected abnormality.
Spiral CT angiography is performed as an outpatient procedure and is less invasive compared with the conventional angiography. The morbidity from arterial puncture may be devastating and occurs in 1.73% of cases, including thromboembolism in 0.14%, pseudoaneurysm in 0.05%, bleeding in 0.26%, arteriovenous fistula formation in 0.01 %.  Intravenous administration of the contrast eliminates the thromboembolic complication that may result from the arterial catheter.
The other advantage of using spiral CT is its cost (Rs.5,500 vs Rs. 11,700). It provides excellent details of the venous anatomy as well as replacing 2 procedures (conventional angiogram and IVU) with 1. Spiral CT angiogram is safe, reliable, cost effective, accurate and acceptable. The use of conventional angiogram can be reserved in the workup of potential kidney donors when there is doubt regarding vascular anatomy.
Helical CT arteriography is accurate and highly specific for arterial and venous anatomy. It provides vital information needed for the surgical team before open or laparoscopic live donor nephrectomy. At our institution this imaging modality has replaced conventional angiogram and IVU in evaluation for live donor nephrectomy. Helical CT arteriography can become the primary imaging modality for preoperative assessment of potential renal donors. Conventional renal angiography is still the gold standard for identification of arterial multiplicity and fibromuscular dysplasia, and should be used adjunctively if there is an ambiguity. Live donation should be made less painful and more comfortable, and spiral CT angiography meets this objective.
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