Cross-sectional Imaging Evaluationof Renal Masses Most renal masses are neoplastic in nature.. Primary renal tumors in adults are classified, based on histogenesis and histopathology, in
Trang 1laparoscopic approach to donor nephrectomy is
possible or whether an open approach should be
adopted[3] In view of this, the presence of a tiny
single calculus (<5 mm diameter) or a cyst of
same size in one of the donor kidneys is not a
con-traindication for its retrieval for a recipient,
irre-spective of the complexities in its vascular
variants If both donor kidneys are normal, then
the kidney with the less complex vascular anatomy
is preferred, making a less invasive laparoscopic
ap-proach for nephrectomy feasible The left kidney is
usually preferred for a recipient because it provides
a longer segment of the renal vein, which joins the
inferior vena cava (IVC), and thus provides more
maneuverability to the surgeon to suture the donor
vessel patch to the recipient’s iliac vein
In addition to defining the vascular anatomy and
variants, imaging should clearly depict pathologic
conditions like renal artery atherosclerosis,
fibro-muscular dysplasia, aneurysm, and thrombosis
Ac-cessory renal arteries are seen in up to 30% of cases,
and they usually originate from the aorta
Occa-sionally, these arteries may arise from the iliac
ar-teries and rarely, from the mesenteric and lumbar
arteries [4] Delineation and clear outlining of
small accessory arteries, which can be as small as
1 to 2mm in diameter, are important imaging
pre-requisites from a surgical standpoint Furthermore,
a clear differentiation between two separate
acces-sory arteries from prehilar branching (renal artery
branching within 20 mm of renal artery origin) is
extremely helpful and can sometimes help avoid
torrential bleeding complications[5]
Similarly, multiple renal veins are seen in up to
30% of patients An important presurgical imaging
communication is confirmation of the presence or
absence of venous variants such as the circumaortic
renal vein (a single renal vein that is split or two renal
veins encircling the aorta before joining the IVC),
an isolated retroaortic left renal vein, and
abnorma-lities such as venous thrombosis and varices[4]
Recently, the assessing of kidney volume before
transplant has also gained importance, because
transplant of the larger donor kidney has a more
fa-vorable posttransplant outcome rate
Imaging in donors
With the advent of MDCT and advances in the MR
scanner, current donor evaluation protocols are
im-proving rapidly Both these imaging modalities
have proven promising in detecting vascular and
collecting system variants with an established
in-crease in readers’ confidence[6] With this
develop-ment, the use of catheter angiography for mapping
renal vasculature has virtually faded Furthermore,
the value of image postprocessing has added to
in-creased acceptability of the CT and MR images to
referring physicians because postprocessed images provide a close simulation to the operative findings during surgery[7] The high–resolution, thin-slice acquisitions provided by the newer CT and MR im-aging scanners make it now possible to detect thin accessory renal arteries (Fig 1)[8] CT and MR ur-ography also provide a clear delineation of the pye-loureteral anatomy, with added benefits provided
by three-dimensional (3D) postprocessing Multidetector CT versus MR imaging for evaluation of renal donors The better spatial resolution, faster speed, and greater cost effectiveness of CT have led to a wide ac-ceptance of CT over MR imaging in most centers Al-though CT and MR angiography have demonstrated substantial agreement in the preoperative evalua-tion of renal donors [9], more published research data on the integrity of CT technique, contrast vol-ume, and injection rates, and various revolutionary
CT protocol techniques, have definitely tilted the balance toward MDCT, leading to its widespread ac-ceptance for imaging renal donors The interob-server disagreement in the interpretation of CT and MR angiography is related to overreading and underreading of small vessels (1–2 mm in diame-ter) (Fig 2)[10,11] With the similarity of CT and
MR imaging accuracies, the potential advantages and disadvantages associated with each modality have been widely discussed recently
MR angiography is a safe and noninvasive tech-nique for comprehensive evaluation of renal donors It is radiation free and particularly advanta-geous in patients who are prone to allergic reaction from iodinated contrast media The limitations of
Fig 1 A console-generated coronal maximum inten-sity projection in a 56-year-old female donor showing three arteries (thin arrows) supplying the right kid-ney, branching of the right main renal artery (thick arrow), and two renal veins (asterisks).
Singh & Sahani
80
Trang 2Cross-sectional Imaging Evaluation
of Renal Masses
Most renal masses are neoplastic in nature
In-fectious, inflammatory, and nonneoplastic masses
constitute a small subset of renal masses Many
re-nal neoplasms demonstrate characteristic cell of
or-igin, histology, and clinicobiologic behavior Renal
neoplasms may be primary or metastatic in origin
Primary renal tumors in adults are classified, based
on histogenesis and histopathology, into renal cell,
metanephric, mesenchymal, mixed epithelial and
mesenchymal, and neuroendocrine neoplasms
[1] They are further categorized, based on tumor
biology and histopathology, into benign and
malig-nant neoplasms The imaging characteristics of
renal masses are protean; accurate distinction of
benign and malignant neoplasms may not be
pos-sible because of overlap of imaging findings A
re-cent trend is toward percutaneous biopsy of renal
masses in an attempt to characterize renal masses
for the purpose of making treatment decisions
The number of biopsies in patients who have advanced or multicentric renal neoplasms has in-creased, when a benign renal tumor is suspected,
or in the presence of a known nonrenal primary
or systemic malignancy[2] Based on imaging findings, renal masses may be broadly classified into predominant soft tissue, ad-ipose tissue, or cystic masses Renal cell carcinoma (RCC) is by far the most common soft tissue mass
in the kidney (Fig 1) However, RCCs may demon-strate significant tumor heterogeneity and may appear entirely cystic or show a small proportion
of macroscopic fat (Fig 2)[3,4] Other uncommon soft tissue renal masses in adults include onco-cytomas, metanephric adenomas, benign and malignant mesenchymal neoplasms, and neuroen-docrine neoplasms Cystic renal lesions include kidney cysts (including hemorrhagic cysts), ab-scesses, and cystic neoplasms (multilocular cystic
R A D I O L O G I C
C L I N I C S
O F N O R T H A M E R I C A
Radiol Clin N Am 46 (2008) 95–111
Department of Radiology, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX 78229, USA
* Corresponding author.
E-mail address: prasads@uthscsa.edu (S.R Prasad).
- Cross-sectional imaging techniques
Multidetector-row CT technique
MR imaging technique
MR imaging versus multidetector-row CT
- Pattern-based approach to renal mass
characterization: tumor morphology
Renal mass with predominant soft tissue
component
Renal mass with predominant macroscopic
fat
Renal mass with predominant (or
exclusive) cystic component
- Pattern-based approach to renal mass characterization: tumor topography
- Percutaneous biopsy of renal masses
- Staging of renal cell carcinomas
- Management of renal masses: knife, needle, or pills?
- Follow-up imaging after surgery and ablative treatment
- Summary
- References
95
0033-8389/08/$ – see front matter ª 2008 Elsevier Inc All rights reserved doi:10.1016/j.rcl.2008.01.008
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