Role of contrast-enhanced ultrasound in assessing indeterminate renal lesions and Bosniak ≥2F complex renal cysts found incidentally on CT or MRI

Abstract

Objectives: To investigate the impact of Contrast-enhanced ultrasound (CEUS) in reclassifying incidental renal findings categorized as indeterminate lesions (IL) or Bosniak ≥ 2F complex renal cysts (CRC) on Computed tomography (CT) or Magnetic resonance imaging (MRI). Methods: We retrospectively included forty-four subjects who underwent CEUS between 2016–2019 to assess 48 IL (n = 12) and CRC (n = 36) incidentally found on CT or MRI. CEUS was performed by one radiologist with 10 year of experience with a sulfur hexafluoride-filled microbubble contrast agent. The same radiologist, blinded to clinical information and previous CT/MRIs, retrospectively reviewed CEUS images/videos, categorizing renal findings with Bosniak-derived imaging categories ranging from 0 (indeterminate) to 5 (solid lesion). CEUS-related reclassification rate was calculated (proportion of IL reclassified with an imaging category >0, or CRC reclassified below or above imaging category >2F). Using histological examination or a ≥ 24 months follow-up as the standard of reference, we also estimated per-lesion sensitivity/specificity for malignancy. Results: CEUS reclassified 24/48 findings (50.0%; 95% C.I. 35.2–64.7), including 12/12 IL (100%; 95% CI 73.5–100) and 12/36 CRC (33.3%; 95% C.I. 18.5–50.9), mostly above category >2F (66.7%). CEUS and CT/MRI showed 96.0% (95%CI 79.7–99.9) versus 44.0% (95%CI 24.4–65.1) sensitivity, and 82.6% (95%CI 61.2–95.1) versus 60.9% (95%CI 38.5–80.3%) specificity. Conclusions: CEUS provided substantial and accurate reclassification of CT/MRI incidental findings. Advances in knowledge: Previous studies included Bosniak two incidental findings, thus possibly underestimating CEUS-induced reclassification rates. Using a more meaningful cut-off (Bosniak ≥2F), problem-solving CEUS was effective as well, with higher reclassification rates for CRC than in literature.

CEUS utility in the diagnosis of a stage I renal cancer developed on polycystic kidney. A case report.

“…In these cases CEUS can bring supplementary data due to its capacity of the detection of blood flows in small lesions, hypovascular tumors and in thin septa [4,9] being more sensitive than CT [10]. In our patient the CEUS examination demonstrated the presence of vascularization in the arterial phase, followed by a wash-out earlier than the rest of the organ in venous phase, which was the sign of a malignant tumor.…”

Additional value of microvascular flow imaging in the assessment of cystic and solid renal lesions

“…The superior temporal and (in case of optimal patient body habitus) spatial resolution gives this technique distinct advantage in evaluating subtle differences in contrast enhancement, coupled with the fact that the most widely used CEUS contrast agent (SonoVue/Lumason) remains intravascular. It has been demonstrated that CEUS has distinct advantage over CT in the depiction of internal septation, intracystic solid component, and their vascularization, thereby being capable of upgrading or reclassifying renal cystic lesions on the Bosniak scale [11][12][13][14]. It has also been shown recently that CEUS is an excellent choice for follow-up of equivocal (Bosniak 2F) lesions [15].…”

The Predictive Power of Bosniak 3 and 4 Cystic Renal Lesion Categorization Using Contrast‐Enhanced Ultrasound

“…1,[9][10][11] It has been also shown that CEUS Bosniak classification generally assigns a higher grade than CT or MRI. [12][13][14][15] Thus there was recently a move toward the surveillance of Bosniak 3 cystic lesions as $50% of surgically removed lesions in this category are benign. This is of particular importance for patients with chronic kidney disease, and significant comorbidities raising the risk of intervention.…”

“…While a Bosniak 4 diagnosis has been shown to be very specific for malignancy, a substantial number of Bosniak 3 lesions are either benign tumors or non‐neoplastic lesions with actual prevalence of malignancy showing great variations in the reported data 1,9–11 . It has been also shown that CEUS Bosniak classification generally assigns a higher grade than CT or MRI 12–15 . Thus there was recently a move toward the surveillance of Bosniak 3 cystic lesions as ~50% of surgically removed lesions in this category are benign.…”