Doppler findings in renal vein thrombosis

Clinical History

A 67 years old diabetic male patient presented to the emergency room with left flank pain, fever, hematuria, pedal edema, and right pleural effusion.

Imaging Findings

A 67 years old diabetic male patient presented to the emergency room with left flank pain, fever, hematuria, pedal edema, and right pleural effusion. Laboratory data showed thrombocytopenia, rising blood urea nitrogen and creatinine. An ultrasound study showed an enlarged left kidney with prominent echo-poor medullary pyramids and loss of corticomedullary differentiation. Doppler evaluation showed normal intrarenal arterial and venous signals. However, there was no venous flow at the renal hilum and at the left renal vein. Transverse scan through the upper abdominal aorta showed no colour Doppler signal within the left renal vein located anteriorly and laterally to the aorta. Contrast-enhanced helical CT scan obtained during the generalized nephrographic phase showed a thrombus in a thick-walled left renalvein extending to the IVC. The laboratory work up revealed a nephrotic syndrome and the patient was treated accordingly.

Discussion

Thrombosis of the renal vein is usually caused by an underlying abnormality of the clotting system or of the kidney itself or, in infants, dehydration. Renal veinthrombosis (RVT) is more common on the left side, presumably because of the longer left renal vein. A classic acute presentation includes gross hematuria, flank pain, and loss of renal function. Although RVT has numerous etiologies, it occurs most commonly in patients with nephrotic syndrome (ie, >3 g/d protein loss in the urine, hypoalbuminemia, hypercholesterolemia, edema). The syndrome is responsible for a hypercoagulable state. The excessive urinary protein loss is associated with decreased antithrombin III, a relative excess of fibrinogen, and changes in other clotting factors; all lead to a propensity to clot. In RVT, an intravenous pyelogram (IVP) with an abdominal plain film may reveal an enlarged kidney. If the renal pelvis is observed, it usually is distorted. An infrequent but characteristic finding of RVT is notching of the ureter, which occurs when collateral veins near the ureters become tortuous. IVP seldom is used to help make the diagnosis. Renal ultrasound is a safe noninvasive technique. With underlying RVT, the kidneys swell and become echogenic, with prominent echo-poor medullary pyramids and loss of corticomedullary differentiation. In the more severe forms areas of increased echogenicity scattered through the kidney can be seen. The arterial and venous signals on Doppler and colour flow Doppler may remain normal or become reduced due to swelling of the kidney. Sometimes, the arterial waveform shows reversed, plateauing diastolic flow. The thrombus may be demonstrated as a filling defect within the renal vein, even extending into the inferior vena cava. The condition may be unilateral or bilateral and of differing degrees on each side. The condition may resolve completely with a return to normal renal function but more commonly function is impaired and may be completely destroyed. The appearances on ultrasound show resolution of the highly echogenic areas with time and development of renal atrophy with continuing loss of the cortical medullary differentiation. CT scan currently is the procedure of choice for diagnosing RVT noninvasively. Intravenous infusion of contrast material assists in visualizing the renal veins. Contrast-enhanced CT shows thrombus in a thick-walled renalvein with or without extension into the IVC. CT scan also demonstrates the presence of renal cell cancer. The presence of inhomogeneous enhancement in the thrombus is indicative of tumour involvement. Accurate demonstration of extension of tumour thrombus into the IVC may be problematic because the IVC above the renal veins frequently appears inhomogeneous on early-phase contrast-enhanced helical scans due to mixing of enhanced blood flow from the renal veins and nonenhanced blood flow from the IVC. Multiplanar reconstruction images may be useful in demonstrating extension of tumour thrombus. Delayed scans may also improve visualization of the IVC.

Differential Diagnosis List

Final Diagnosis

Nephrotic syndrome with renal vein thrombosis

URL:	https://eurorad.org/case/5819
DOI:	10.1594/EURORAD/CASE.5819
ISSN:	1563-4086