Indian Journal of Radiology and Imaging Indian Journal of Radiology and Imaging

GENITOURINARY IMAGING
Year
: 2004  |  Volume : 14  |  Issue : 4  |  Page : 373--378

Renal vasculature evaluation using a multidetector CT scanner : A brief study of 20 cases


AR Joshi, S Nalavde, S Merchant, S Gujare 
 Professor & Head of Radiology Dept, LTMMC & LTMGH , Sion, Mumbai -400 022, India

Correspondence Address:
S Nalavde
7 Dayabhai Nivas, 52 Taikal Wadi, Mahim, Mumbai -400 016
India

Abstract

Purpose : To evaluate renal vasculature using a multidetector CT scanner (Multidetector CT Angiography). Materials & Methods : Twenty patients were evaluated using a multislice CT scanner (Siemens, Volume Zoom, Siemens Corp., Siemenstrasse, Forchheim, Germany), out of which twelve had complaints of hypertension, abdominal pain and eight were renal donors. The spiral CT acquisition was done by rapid intravenous injection of 100 cc of water-soluble iodinated contrast medium via a pressure injector at the rate of 2.5ml/sec via a 20G angiocath in the antecubital vein. Images of 1.25 mm slice thickness with 1mm slice collimation were taken from the twelfth dorsal or the first lumbar vertebral level upto the pubic symphysis. No oral contrast was given in these patients. Post processing of the reconstructed axial data was done using Maximum Intensity Projection {MIP}, Surface Shaded Display (SSD) and the Volume Rendering (VR) technique. Results : Out of the twenty subjects studied: six had renal artery stenosis (RAS), eight were donors, three had renal malignancies (RCC), one had an ectopic kidney and two were cases of aortoarteritis with renal involvement. Conclusion : CT angiography is a good, cost effective and non-invasive modality as it gives vascular, anatomic and functional depiction of the kidneys in one sitting



How to cite this article:
Joshi A R, Nalavde S, Merchant S, Gujare S. Renal vasculature evaluation using a multidetector CT scanner : A brief study of 20 cases.Indian J Radiol Imaging 2004;14:373-378


How to cite this URL:
Joshi A R, Nalavde S, Merchant S, Gujare S. Renal vasculature evaluation using a multidetector CT scanner : A brief study of 20 cases. Indian J Radiol Imaging [serial online] 2004 [cited 2019 Oct 14 ];14:373-378
Available from: http://www.ijri.org/text.asp?2004/14/4/373/28675


Full Text

 Introduction



Multidetector computed tomography is a useful imaging modality that is replacing conventional angiography in assessment of vascular anatomy and in the diagnosis of vascular disorders. Recent development of hardware permits MDCT scanner (Siemens, Volume Zoom) to provide high resolution data acquired in a significantly shorter time. The improvement of software for 3D reconstruction, allows easy image manipulation on workstations or personal computers.

 Materials and methods



Retrospective analysis comprising of twelve patients with complaints of hypertension, abdominal pain and eight renal donors was performed at our institution using multidetector CT scanner (Siemens, volume zoom, Siemens Corp., Siemenstrasse, Forchheim, Germany), under different clinical settings, between 2001 - 2003

The age distribution was between 18 - 63 yrs (14 males, 6 females,

M: F =2.3:1) mean age being 40 years.

CT Protocol:

The technique consists of image acquisition, image processing and finally image display. As regards the image acquisition the following was our protocol: 100cc of iodinated contrast was injected at 2.5 ml/sec, using automated techniques e.g.: care bolus (for beginning of acquisition). Images that were obtained were of 1.25 mm slice thickness with 1mm slice collimation. Scanning is done from the twelfth dorsal or the first lumbar vertebral level to the level of the pubic symphysis. After the arterial phase, a venous phase is followed using same image acquisition parameters (60 cc after contrast). Further which a delayed acquisition (12/15 min after contrast injection) is done with 5mm slice and 5mm collimation to image the pelvicalyceal system, ureter and bladder. No oral contrast is used. Acquired images were axially reconstructed with overlapping slices and transferred to an imaging workstation (Wizard) for image processing i.e. MIP (Maximum Intensity Projection), SSD (Surface Shaded Display), and transferred for Volume Rendering to Virtuoso

All studies were post processed in a standard format and the renal vasculature was evaluated.

Of the 20 subjects studied; 14 were males and 6 were females, with the following distribution;

 Results



In potential living renal donors CT angiography becomes a fast, noninvasive and cost effective technique for evaluation of renal vasculature as well as function preoperatively [5],[7]. In our study of eight donors, five had a normal renal vasculature and three had accessory renal arteries (a normal variant), which becomes surgically very significant. These patients subsequently underwent a conventional aortogram (DSA) and the findings were confirmed and two were declared unfit as donors.

In the four young hypertensive patients, Renal Artery Stenosis (RAS) was detected; RAS was evaluated in its extent, severity, location and distal vasculature. Additionally the function of the kidneys was also studied on delayed CT images. All four patients underwent a DSA. Out of these our findings were confirmed in three patients, who further underwent angioplasties. One patient had no stenosis on MDCT but was diagnosed to have approximately 30% stenosis on Colour Doppler which was confirmed on DSA.

The third case was a 55 years old male with complaints of pain in the epigastrium with hypertension and anorexia. Incidental RAS was picked up in the arterial phase of the triple phase study and a pancreatic head mass was clearly visualized on the venous phase. This patient was lost for follow-up as he refused any further investigation and treatment for the pancreatic tumor.

Three patients aged 49yrs, 83yrs and 67 yrs were diagnosed as having renal malignancies (RCC's) on USG. The first patient had complaints of pain in the left lumbar region with a palpable left lumbar mass. The second patient had come for hernia surgery and was diagnosed on USG as having a left renal malignant mass. Third patient had history of right sided flank pain with hematuria.

In the first case, neovascularity of the left renal mass was very well demonstrated, with details of the mass and surrounding structures. An additional finding of accessory right renal artery was detected. CT thus helped in vascularity assessment and staging, and also provided assessment of function of the residual unaffected renal parenchyma and also of the contralateral kidney. These findings were confirmed operatively.

In the second case the left upper pole mass showed relatively less enhancement with no neovascularity and also had cortical cysts.

In the third case, a right renal mass was seen arising from the mid region of the right kidney and showed a central area of necrosis along with a calcific focus. Neovascularity was seen in the form of enlarged capsular vessels from the right renal artery and also from an enlarged right lumbar artery supplying the mass. An enlarged branch from the right testicular vessel was seen In the third case, a right renal mass was seen arising from the mid region of the right kidney and showed a central area of necrosis along with a calcific focus. Neovascularity was seen in the form of enlarged capsular vessels from the right renal artery and also from an enlarged right lumbar artery supplying the mass. An enlarged branch from the right testicular vessel was seen to bifurcate and supply the mass inferiorly. Additionally thrombosis of the IVC and right renal vein was also noted (indicating tumor thrombus extending into the IVC via the left renal vein).

Two patients who were known cases of aortoarteritis with complaints of intractable HT, underwent CT angiography. In the first patient, the study revealed a complete block of the aorta at the infrarenal level; with involvement of the left renal artery origin and resultant left renal atrophy. The right kidney revealed compensatory hypertrophy. In the second patient there was moderate narrowing of the descending thoracic aorta with bypass aortic grafting with right sided nephrectomy.

In another 35 year male diagnosed as right sided ectopic kidney on USG, CT renal angiography showed the right kidney placed in the right iliac fossa with malrotation i.e. renal pelvis located anteriorly. It had three arterial supplies, two branches arising from the aorta and one from the right common iliac artery. Both the kidneys showed good function. Delayed scans showed the complete course of the right ureter. These findings were confirmed on DSA.

 Discussion



So far conventional arteriography or DSA has been the gold standard for the evaluation of renal vasculature. But owing to its invasive nature with associated complications, as well as the time and effort involved, catheter angiography is not suited as a screening modality [1].

A wide variety of diagnostic modalities such as duplex and color Doppler sonography, MR angiography, intravenous DSA and of late multidetector CT angiography are available for this purpose.

This study aims to evaluate the role of spiral CT (MDCT) in the diagnosis of renal vasculature pathologies.

In this study multidetector spiral CT proved to be an excellent modality for the detection, localization and quantification of renal arterial stenosis, neovascularity and feeding vessels of renal malignancies, as well as accessory vessels in donors. As opposed to angiography, multidetector CT offers information not only regarding the vessel lumen but also of the vessel wall and the surrounding structures. The ability to view the data set in all three dimensions constitutes an added advantage. It provides a better idea of the location and nature of stenosis, as well as of plaques [6],[8].

Laparoscopic nephrectomy is now becoming the surgery of choice for living renal donors. It was introduced in living renal donors in 1995, offering advantages such as less time in hospital, less post-operative pain, few cosmetic concerns and less convalescence time. Thus, preoperative evaluation of these donors using Multislice computed tomography , combines a minimally invasive surgery with minimally invasive imaging giving arterial and venous anatomy with functional capacity of the kidney. Along with arterial anatomy, renal venous anatomy has gained significance; as venous bleeding is a potentially serious complication of laparoscopic surgery . The number of arteries , their sizes and the locations of their origins on the aorta determine whether the kidney is suitable for donation. The lengths of arteries from their origins to the first bifurcation are measured . A stump of 2 centimeters of the artery is required for the transplantation [3] .

In 85 % people, there is a single right renal vein. In 86 % people, there is a single left para-aortic renal branch often combined with several extra renal branches. The location and number of gonadal, adrenal and lumber veins must be delineated. Venous variants include multiple veins , right sided gonadal and adrenal veins and left retro-aortic , circumaortic and partially duplicated veins . The relationships among the renal, lumbar and gonadal veins may be varied. Because laparoscopic surgery is performed with a more limited view than open surgery , the surgeon needs to be forewarned about any anomalies. This forewarning reduces the risk of accidental venous injuries and bleeding. The renal veins and the tributaries that drain into them must be shown. Any veins that drain into proximal 2 centimeters of the gonadal vein must also be reported because they may be included in the dissection.[3]

After acquisition of raw data, in each of our patient, multiplanar reformatting; MIP (Maximum Intensity Projection), SSD (Surface Shaded Display) and VR (Volume Rendering) was performed.

MIP reconstruction is the technique of choice for image presentation because it is able to produce angiography like images, which are easily acceptable to the clinicians. It can discriminate between vessel lumen, wall and calcification. Even small vessel are well depicted as long as they have a higher CT number than the surrounding tissue. MIP images were superior to axial and semicoronal reformatted images, particularly in the diagnosis of ostial stenosis. MIP images give a compound image of the kidney that allows analysis of differential renal cortical enhancement.

Although not seen in this study, certain limitations can be expected of spiral CT. Most important of them being the is ionizing radiation especially due to increased exposure of the patient due to multiple acquisitions i.e. plain, arterial, venous and delayed phases.

Visualization of small intrarenal vessels may be difficult with spiral CT angiography. Another limitation with spiral CT angiography is that mural calcification may interfere with evaluation of renal artery stenosis [2].A potential disadvantage of spiral CT angiography is that a relatively large volume of contrast material is needed for adequate opacification of the renal arteries, which may increase the risk of inducing nephrotoxicity too, though there was no clinical evidence of nephrotoxicity in any of our patients. However with multidetector spiral CT scanner the contrast volume has decreased.

In addition, preexisting renal dysfunction, cardiac insufficiency, intolerance to contrast medium, patients with altered circulatory status and inability to cooperate are also the limiting factors in multislice CT angiography.

Inspite of these limitations CT angiography is an excellent imaging modality.

 Summary



Spiral CT angiography, performed as an outpatient procedure is a less expensive relatively non-invasive procedure that provides good images of the arterial and the venous anatomy. It has the potential to replace conventional catheter angiography and intra venous urography in the assessment of potential renal donors. It is a good adjuvant to color Doppler for renal artery stenosis and one complete investigation for renal tumors and donors; with CT angiography, CT urography and conventional CT images all obtained in one study. The software program provides superior and interactive imaging at a substantially lower cost with minimal patient time consumed and a significantly lower morbidity. Greater consumed and a significantly lower morbidity. Greater awareness about its applications, especially in renal angiography will go a long way in it replacing conventional (DSA) angiography in the assessment of renal vessels.

References

1Micheal Galanski, Mathias Prokop, Ajay Chavan, Cornelia M. Schaefer, Karin Jandeleit, et al.: Renal artery stenosis: Spiral CT angiography; Radiology 1993; 189: 185-192.
2Robert Katee, Frederik J. A. Beek, Eduard E. de Lange, Maarten S. van Leeuwen, Henk F.M.Smits, et al.: Renal artery stenosis: Detection and quantification with spiral CT angiography versus optimized DSA; Radiology 1997; 205:121-127.
3Jonas Rydberg. MD, Kenyon K. Kopecky .MD, Mark Tann. MD, Scott A. Persohn . RT , Stephen B. Leapman .MD , et al : Evaluation of prospective living renal donors for laparoscopic for laparoscopic nephrectomy with multisection CT : The marriage of minimally invasion imaging with minimally invasive surgery . Radiographics 2001.
4Dillon EH, van Leeuwen JA, Fernandez MA, Mali WPT. Spiral CT angiography. AJR 1993;160:1273-1278.
5Rubin GD, Alfrey EJ, Dake MD, et al. Assessment of living donors with spiral CT. Radiology 1995; 195:457-462.
6Helical CT scan Angiography Compared with Arteriography in the Detection of Renal Artery Stenosis. Jean-Paul Beregi, Maram Elkohen, Ghislaine Deklunder, Dominique Artaud, Jean Michel Coullet, Lionel Wattinne. AJR August 1996; 167:495-501.
7Helical computed tomography angiography in the evaluation of Chinese living renal donors. Tang S, Chan J, Tso WK, Ho KK, Chan TM, Lai KN.
8CT scan Angiography Versus Intra-arterial Digital Subtraction Angiography for Assessment of Aortoiliac Occlusive Disease. Olaf Rieker, Christoph Duber, Achim Neufang, Michael Pitton, Franz Schweden, Manfred Thelen. AJR 1997; 169:1133-1138