Renal Vein Thrombosis

Pathophysiology

Virchow’s triad of endothelial disruption, stasis, and hypercoagulability is applicable to renal vein thrombosis. In the neonatal-pediatric population, venous stasis secondary to hemoconcentration and low renal perfusion pressure predispose to thrombus formation within the renal venous system. The underlying cause of adult renal vein thrombosis can be divided into two categories: systemic disease states including nephrotic syndrome, malignancy, and other hypercoagulable conditions; and local factors including instrumentation, suprarenal inferior vena cava (IVC) filters, or extrinsic compression from cysts, aneurysms, or adjacent malignancies.

The nephrotic syndrome secondary to membranous glomerulonephritis is associated with the highest risk of renal vein thrombosis. The nephrotic condition imposes a hypercoagulable state with changes in glomerular permeability leading to urinary loss of small-molecular-weight plasma proteins, including antithrombin III, producing a relative antithrombin III deficiency. In addition, thrombocytosis; increases in the levels of fibrinogen and factors V, VIII, and X; accelerated fibroblast degeneration; and increased activation of Hageman factor occur in the nephrotic state and contribute to this thrombotic tendency. Last, patients with the nephrotic syndrome often have a contracted intravascular volume secondary to a low oncotic pressure and diuretic use, causing hemoconcentration and renal venous stasis.

Other systemic conditions associated with adult renal vein thrombosis include pregnancy, use of oral contraceptives, renal cell carcinoma, other malignancies, trauma, retroperitoneal adenopathy or fibrosis, and defined or inherited conditions causing or associated with hypercoagulability.

In most instances, the thrombotic process is initiated in arcuate and intralobular venules, with subsequent propagation into larger venous outflow vessels, proceeding centripetally to involve the renal vein. In contrast, with trauma, extrinsic compression, intrinsic instrumentation (suprarenal IVC filters), or direct invasion of the vein by renal cell carcinoma, the thrombotic process typically begins in the major venous tributaries or within the renal vein.

Clinical Presentation

In neonates, renal vein thrombosis most often occurs in association with hypoxia, sepsis, hypotension, dehydration, diarrhea, hypoglycemia, seizure disorders, or toxemia. Other predisposing conditions include maternal diabetes, congenital heart disease, polycythemia vera, sickle cell disease, congenital hypercoagulable conditions, and adrenal hemorrhage. The clinical presentation is usually that of sudden onset of abdominal distention, a flank mass, hematuria, oliguria or anuria, proteinuria, or hypertension in a newborn less than 72 hours old. Bilateral renal vein involvement is heralded by the onset of progressive renal insufficiency. The condition can remain asymptomatic only to be detected later in life by the presence of an atrophic kidney. Infants and neonates are more likely than adults to have hematologic evidence of intravascular consumptive coagulation, including thrombocytopenia, decreased fibrinogen concentration, and an increase in fibrin split products. Renal vein thrombosis can manifest itself by thrombus propagation into the inferior vena cava with pulmonary artery embolization.

The clinical presentation in the adult can be divided into acute symptoms and chronic symptoms. Acute renal vein thrombosis typically manifests with the sudden onset of flank pain, hematuria, proteinuria, or deterioration in kidney function. The obstruction of renal venous outflow causes congestion, edema, and later hemorrhagic infarction of the kidney. If venous outflow cannot be established through venous collaterals, the kidney is susceptible to rupture and potentially fatal retroperitoneal hemorrhage. Bilateral renal vein thrombosis can lead to acute oliguria and kidney failure. Additional sequelae of acute renal vein thrombosis include hypertension, pulmonary embolus, and adrenal hemorrhage. Chronic renal vein thrombosis can remain asymptomatic, demonstrate an extrarenal manifestation such as pulmonary embolus or remote thrombosis, or manifest with gradual decline in kidney function, new onset of renal tubular dysfunction, or progressive proteinuria.

For unilateral renal vein thrombosis, the outcome for the involved kidney depends on the acuteness of the thrombotic process, the collateral venous circulation, the rapidity and extent of recanalization, and the cause of the underlying disease process. The involved kidney can proceed to one of three outcomes: adequate collateral venous circulation leading to recovery of normal function; circulatory compromise leading to increased renin production and hypertension; circulatory compromise progressing to an atrophic nonfunctioning kidney without hypertension.