Renal vein thrombosis (plural: renal vein thromboses) can be either from "bland" thrombus or tumor thrombus (extension of tumor into the vein). There are numerous etiologies for bland thrombus, but it most commonly occurs in the hypercoagulable nephrotic syndrome. Renal vein thrombus is commoner on the left side, presumably due to the left renal vein being considerably longer than the right.
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Pathology
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in children, renal vein thrombosis is the most common vascular condition in the neonatal kidney 1
dehydration and sepsis are common underlying factors for renal vein thrombosis
maternal diabetes
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in adults, renal vein thrombosis can result from a variety of disorders, including:
renal sepsis (thrombophlebitis)
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tumor thrombus, e.g.
lymphoma 5
in rare cases, adrenal carcinoma
urinary obstruction (rare) 6
trauma is another potential cause of renal vein thrombosis
Complications include pulmonary embolism, renal atrophy, and papillary necrosis. Bland thrombus can coexist with tumor thrombus.
Radiographic features
Ultrasound
Grayscale ultrasound findings include:
renal enlargement with hypoechoic cortex from edema (early phase)
decreasing size and increased echogenicity (late)
Doppler findings include:
reversal of arterial diastolic flow
absent venous flow
visualization of thrombus within the lumen
high resistance in the renal artery with elevated resistive index
CT
as with venous thrombosis elsewhere, the thrombosis is observed as a filling defect during venous phase imaging following intravenous contrast
enlarged kidney
persistent cortical enhancement and lack of parenchymal enhancement
calyceal opacification is often delayed, diminished, or absent in the affected kidney
changes in attenuation, either focal or diffuse, may be present due to perfusion abnormalities 3
stranding of the perinephric fat owing to edema and thickening of the renal fascia may occur
perinephric hemorrhage may occur
in the chronic phase of renal vein thrombosis, the affected renal vein becomes attenuated because of retraction of the clot
collateral vessels may appear around the kidney in chronic cases
MRI
Renal vein thrombus may be shown on T1-weighted spin echo pulse sequences when the signal void of flowing blood in the renal vein is replaced by high signal because of thrombus.
Gradient echo technique shows thrombus as a filling defect of intermediate signal intensity that replaces the high signal of flowing blood.
Coronal MRI helps determine the extent of vena caval involvement.
MRI in patients with acute renal vein thrombosis may also show loss of corticomedullary differentiation on T1-weighted spin echo images, increased signal in the affected kidney on T2-weighted images, renal fascial thickening, and renal enlargement.
MR renal venography may be performed, especially if the patient has renal impairment which does not permit the use of intravenous contrast medium 4.
Treatment and prognosis
treatment of nephrotic syndrome: steroids and immune-suppression therapy
treatment of underlying renal cell cancer includes surgery for early-stage disease
anticoagulation therapy
Complications
Recognized complications of renal vein thrombosis include: