Body Imaging – Kidney
CEUS is a safe, versatile and reliable tool for imaging the kidney in the following clinical contexts:
- Characterization of indeterminate renal masses
- Evaluation of renal parenchyma in patient with suspected renal abscess
- Evaluation of renal transplants in patients with suspected renal vascular complications and renal infarcts
- Follow-up of non-surgical renal lesions
- Guide interventional procedures
- Follow-up interventional procedures
CEUS uses ultrasound contrast agents (UCAs) to improve the clarity and reliability of conventional ultrasound scans. UCAs are comprised of liquid suspensions of biodegradable gas-filled microspheres (sometimes called “microbubbles”). When they are injected into a patient’s arm vein during an ultrasound exam, they flow through the body’s microcirculation without impediment, and are metabolized and expelled from the body within minutes.
Dr. Richard G. Barr, Commonly asked CEUS questions
Imaging and timer begin with the start of the saline flush. Continuous recording from first arrival of a bubble in the FOV to lesion characterization, which usually less than 2- minutes. From the cine clips, still images can then be saved at the end of the study. Scanning the entire lesion particularly in indeterminate masses is required. Often scanning the kidney for additional lesions is possible.
CONTRAST AGENT DOSING: Depends on transducer and instrumentation, and body habitus. In general, for adult patients, a dose of 1.5-2.4 ml Lumason; Definity 0.2-0.4ml; Optison 1.0-1.5ml
Echogenic appearance on grey scale ultrasound and absence of color flow despite hypervascularity is typical, but not specific for angiomyolipomas (AML). CEUS can help identifying hypervascularity mixed with hypovascular components, typical for AML. Necrotic non-enhancing components are not typical for AML.
Angiomyolipoma (mixed vascularity)
Partly exophytic echogenic kidney mass is peripherally rapidly enhancing after contrast administration, while demonstrating hypovascular enhancement centrally, which persists on later contrast phases.
81-year old woman with incidental finding of two small echogenic intracortical angiomyolipomas (AML). The tumors are hypovascular and are barely enhancing after contrast administration, which is typical for small AML.
Renal Cell Carcinoma
The most common and aggressive type of renal cell carcinoma is the clear cell type. While the histologic subtypes of renal cell carcinomas cannot be distinguished on conventional ultrasound, it can often be characterized by CEUS: clear cell carcinomas are typically hypervascular and may show compartments of necrosis, while papillary and chromophobe carcinomas are usually uniformly hypovascular. With CEUS tumor thrombi within renal veins can also be more confidently detected.
Clear Cell carcinoma
Typical clear cell carcinoma with strong irregular peripheral enhancement after contrast administration comparable to renal cortex. There is central non-enhancing necrosis. Hypervascular portions demonstrate washout (hypoechoic appearance compared to renal parenchyma) on late phase, which is also typical.
Cystic Renal Cell Carcinoma
Cystic mass with irregular septations, which is a non-specific finding on greyscale ultrasound as this appearance may be seen with benign complex as well as with cystic malignancies.
CEUS demonstrates strong enhancement and reveals additional nodularities within the septations, which excludes a benign complex cyst. Mass was removed and pathology revealed cystic clear cell renal carcinoma.
Papillary Renal Cell Carcinoma
Incidental finding of a small exophytic renal tumor, which is hypoechoic on greyscale ultrasound and non-specific. A complex cyst can therefore not be distinguished from a solid tumor.
CEUS demonstrates uniform weak enhancement with washout on the late phase, which is typical for papillary carcinoma, confirmed by excision. A complex cyst as well as a more aggressive clear cell carcinoma could therefore be ruled out.
- Barr, Richard G., et al., Society of Radiologists in Ultrasound (SRU): Contrast-enhanced Ultrasound—State of the Art in North America Ultrasound Quarterly: September 2020 – Volume 36 – Issue 4S – p S1-S39 doi: 10.1097/RUQ.0000000000000515
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