Synopsis
The role of radiologist and imaging is evolving
from traditional role of identifying renal lesion and detecting enhancement, to
predicting aggressiveness and biology of the renal tumor as well as providing operative
guidance. MR imaging can play a very important role not only as a problem
solving tool but also as a ‘first-line’ examination for assessment of renal
tumors. Additional information garnered from MRI has a potential to
significantly impact management by guiding therapeutic decisions.Abstract
Update
on Body MRI Protocols & Applications
Genitourinary
MRI
Small
renal masses are increasingly diagnosed incidentally. This results in
management dilemma because at histopathology significant numbers of small renal
masses are either benign tumors such as angiomyolipoma (AML) or oncocytoma, or
are neoplasms with relatively indolent behavior [1]. Surgical treatments such
as partial and total nephrectomy although provide excellent oncologic control
is associated with development and worsening of renal insufficiency and
associated cardiovascular morbidity [2]. Therefore, ability to non-invasively
investigate renal tumor histopathology and aggressiveness can guide treatment
decision and lower treatment cost.
Within
this paradigm, the role of radiologist and imaging is evolving from traditional
role of identifying renal lesion and detecting enhancement, to predicting
aggressiveness and biology of the tumor as well as providing operative
guidance. MR imaging can play a very important role not only as a problem
solving tool in traditional sense by detecting subtle enhancement and
macroscopic and microscopic fat, but can provide deeper insight into tumor
biology.
Number
of key observations highlighting the role of MR in evaluation of renal masses
is as listed below:
1. Differentiating benign renal masses
from malignant tumors.
- There is some controversy
regarding the role of signal loss on opposed phase chemical shift imaging in
discriminating AML from RCC [3,4].
- Lipid poor AML tend to have
uniform low T2 signal and uniform enhancement without evidence for necrosis [5,6].
- There is overlap in the
morphologic features of Oncocytoma and RCC on conventional imaging [7].
Furthermore segmental enhancement inversion is noted in oncocytoma as well as
other renal neoplasms [8].
2. Histologic subtyping RCC
- Papillary subtype of RCC usually
have low T2 signal and are hypovascular when compared to clear cell RCC.
Furthermore, clear cell subtype have heterogeneous T2 signal and demonstrate
heterogeneous hypervascularity [9].
- Chromophobe subtype is difficult
to differentiate from clear cell RCC on the basis of enhancement. However,
advance diffusion and perfusion MR techniques have shown some promise [10].
3. Predicting tumor
aggressiveness/outcome
-
Cystic
RCC with less than 25% solid enhancing component tend to be less aggressive
than solid RCC [11].
-
High
stage clear cell RCC tend to me more heterogeneous with different texture
compared to low stage RCC on Apparent diffusion coefficient (ADC) map [12].
-
High
grade clear cell RCC tend to have lower ADC compared to low grade clear cell
RCC [13].
4. Preoperative
planning for minimally invasive surgery
Acknowledgements
No acknowledgement found.References
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