Renal vein thrombosis
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# Overview
Renal vein thrombosis (RVT) is the formation of a clot or thrombus obstructing the renal vein. Rayer was the first to describe thrombosis of renal vein in nephrotic patients during postpartum. Based on the onset of symptoms renal vein thrombosis can be classified into acute and chronic.

# Historical perspectives
- In 1837, thrombosis of the renal vein was first described in nephrotic patients by Rayer in postmortem evaluations.
- In 1843, Robinson induced renal vein thrombosis in rats.
- In 1876, Buchwald and Litten observed renal vein thrombosis in dogs.
- In 1939, Derow, Schlesinger, and Savitz presented a case of renal vein thrombosis in nephrotic syndrome.

# Classification
- Renal vein thrombosis is classified based on the onset of the symptoms   
- Based on the location RVT may be unilateral or bilateral.
Left renal vein involvement is more common than right renal vein.
- Left renal vein involvement is more common than right renal vein.

# Pathophysiology
Mechanisms which are responsible for developing renal vein thrombosis are classified into three categories: Vascular damage, venous stasis, and hypercoagulable state.
- Vascular endothelial damage: Vascular injury leads to exposure of tissue factor, collagen, and endothelium to the blood, causing activation of the extrinsic pathway of coagulation  .
- Stasis: Normal endothelium has anticoagulation activity driven by thrombomodulin, endothelial protein C receptor ( EPCR), tissue factor pathway inhibitor and heparin-like proteoglycans. The major determinant of anticoagulation activity in the blood is the ratio of endothelial cell surface to blood volume . Stasis of blood in greater vessels means decreased exposure of anticoagulants of the endothelial surface to the blood which results in promoting thrombi formation.
- Hypercoagulable state: As a definition, any laboratory abnormalities or clinical conditions which can be associated with an increased risk of thrombosis or clinical presentation of recurrent thrombosis without predisposing factors is considered hypercoagulability. Hypercoagulability (thrombophilia) includes hereditary and acquired conditions which enhance a tendency for developing thrombi in the veins, arteries, or both. Renal vein thrombosis can also be secondary to nephrotic syndrome, particularly membranous nephropathy due to loss of proteins in urine like antithrombins.

# Causes

## Causes

# Differentiating Renal vein thrombosis

# Epidemiology and Demographics
Malignancy especially renal cell carcinoma is the most common etiology consists of
Prevalence of renal vein thrombosis in nephrotic syndrome is 5 to 60%  .Membranous nephropathy is responsible for 20 to 60 % of the cases which makes it the most common cause of renal vain thrombosis among nephrotic syndromes. Other etiologies like minimal change disease, membranoproliferative glomerulonephritis, and focal segmental glomerulosclerosis cause 10 to 50 % of the cases  .

# Risk Factors

# Screening
- Screening should be done for patients
Who present with signs of renal infarct
Who has chronic bilateral RVT with worsening creatinine and proteinuria to see whether anticoagulation is necessary
- Who present with signs of renal infarct
- Who has chronic bilateral RVT with worsening creatinine and proteinuria to see whether anticoagulation is necessary
- There is no beneficial evidence regarding screening in patients with nephrotic syndrome and overt embolism.

# Natural History, Complications, and Prognosis
Complications:
- Acute renal failure
- End stage renal failure
- Pulmonary embolism
- DVT
- Portal vein occlusion (portal hypertension)
- Sepsis
- Ipsilateral adrenal gland hemorrahge
Factors that determine prognosis in renal vein thrombosis:
- Baseline renal function
- Renal function of the contralateral kidney
- Adequacy of treatment
- Speed of the developed thrombose
- Severity and progression of underlying causes

# Diagnosis

## Signs and Symptoms

## Imaging
- Doppler ultrasonography: Diagnostic screening
- Renal venography: Gold standard test for RVT diagnosis
- CT angiography: 100% sensitive for diagnosis
- Spiral computed tomography (CT) with contrast
- Magnetic resonance imaging (MRI)

# Treatment
Therapy in RVT        :
 ATRIA risk score = Anticoagulation and Risk Factors in Atrial Fibrillation
ATRIA score for predicting bleeding associated with warfarin:
low-risk = (0 to 3 points) patients have hemorrhage rates of 1% per year
Intermediate risk = patients have hemorrhage rates of less than 5% per year
High-risk = (5 to 10 points) patients have hemorrhage rates of more than 5% per year

# Related Chapters
- Nephrotic syndrome

# Renal vein thrombosis in pediatrics
Renal vein thrombosis  as one of the venous thromboebolic event, is more common in pediatric population due to lower renal perfusion pressure, anticoagulant deficiency, and renal venous anatomy               .