Renal Vein Tumor Extension 腎靜脈瘤栓

醫學詞匯注釋與簡要講解

Key factsSynonym:extension of tumor into renal vein.Definition:extension of tumor from a renal neoplasm into the renal vein,and possibly the inferior vena cava (IVC),occasionally right atrium.

Classic imaging appearance:renal vein distended by tumor with visible tumor vessels on color Doppler and tumor enhancement on contrast-enhanced CT or MRI.

Other key facts:(1)renal vein extension occurs with renal cell carcinoma(RCC),Wilms tumor,transitional cell carcinoma,lymphoma;(2)reported incidence of RCC extension to renal vein 21%-35%,IVC 5%-10%.

Wilms tumor 腎母細胞瘤

Imaging findings

Best imaging clue

Enhancement of renal vein tumor differentiates tumor and thrombus (non-enhancing).

CT findings

Renal vein may be distended.

Renal vein tumor probably not visible on non-contrast scans.

CTA:hypodense filling defect in renal vein,or absence of flow(with occlusion).Possible “tram-track” sign of blood flow around tumor.

Enhancement of renal vein tumor during arterial and venous phases.

Tumor may be invisible in equilibrium phase (blood and tumor=density).

Renal primary readily seen,enhances in arterial phase.

tram-track 電車軌道

equilibrium phase 平衡期

MR findings

Renal vein may be distended.

Low or intermediate signal in renal vein tumor on non-contrast T1and T2weighted images.

Low signal filling defect in renal vein,well seen on TOF or phase contrast MRA.Gd-enhanced MRA does not clearly improve renal vein or IVC tumor visualization.

Renal vein tumor enhancement visible on T1weighted images follow Gd enhancement.

Renal primary readily seen,variable enhancement with Gd.

Ultrasound findings

Renal vein may be distended.

Fig 1 Renal vein tumor extension from RCC in inferior pole of right kidney.a)Axial enhanced CT and b)coronal reconstruction showed the left renal vein was distended by strongly enhancing tumor (arrow).Tumor is seen to extend into the IVC(arrow).c)Axial T2WI showed high signal tumor in the left renal vein (arrow),and d)enhanced MRI showed low signal filling defect in left renal vein (arrow).

Tumor in RV hypoechoic or intermediate echogenicity.

Renal vein flow void on color Doppler (absent flow with occlusion).

Tumor vessels in renal vein shown with color Doppler (low PRF,high sensitivity required).

Low resistance Doppler waveforms in tumor vessels.

Renal primary readily seen,including tumor vessels,on color Doppler.

Imaging recommendations

CTA or MRA are best modalities for determining the presence and extent of renal vein tumor.MRA is superior to CT for IVC tumor extent (CT compromised by flow artifact,especially from renal veins).Cardiac motion may interfere with MRI visualization of tumor high in IVC or right atrium.Color Doppler US can visualize superior extent of IVC tumor through liver“window”.

Overall accuracy of color Doppler US is excellent in small children,poor in adults (renal vein visualization problems).

CTA 和MRA 是推薦用于腎靜脈瘤栓的檢查，MRA 對下腔靜脈內瘤栓顯示更好，不受血流偽影影響，但心臟搏動會影響下腔靜脈或右心房內瘤栓的顯示。

彩超對低齡兒童顯示效果佳。

Differential diagnosis

Renal vein thrombosis

Considerable overlap in CT/MR and US findings,but no enhancement of thrombus on CT/MR,no tumor vessels on US.

Renal primary readily seen in cases of renal vein tumor extension.

Sluggish renal vein flow

Due to extrinsic renal vein or IVC compression,or IVC obstruction.

Potential false positive for renal vein occlusion on US and non-contrast MRA.

Pathology

General

RCC is most common tumor,by far,to extend to the renal vein or IVC.In cases of renal vein extension,RCC primary is at least 4.5 cm.IVC extension most often from the right kidney (vein shorter than left).

Gross pathologic or surgical features

Venous RCC is poorly attached and can be removed surgically with clear margins.Both tumor and bland thrombus are present in most specimens.

Staging or grading criteria

RCC extension to renal vein and IVC graded as Robson stage Ⅲa.

Clinical issues

Presentation

Renal vein tumor extension is usually asymptomatic.Presentation usually is that of the renal primary tumor (e.g.,hematuria,mass,constitutional symptoms).Secondary renal vein thrombosis can produce acute renal vein occlusion symptoms.

Treatment

Surgical resection of kidney and venous tumor.

It is important to know extent of venous tumor,as this dictates surgical approach.

Prognosis

Not substantially different from stage I and II disease,much better than stage III (lymph node mets).

5-year survival is more than 60% in most series.

影像學的目的是確定瘤栓范圍，以利于手術方式的確定。