Overview
Renal Vein Thrombosis (RVT)
1. Clinical Overview
Summary
Renal Vein Thrombosis (RVT) is the Formation of a Thrombus (Blood Clot) within One or Both Renal Veins, leading to impaired venous drainage of the kidney. RVT can be Acute (Sudden onset with severe symptoms) or Chronic (Gradual onset, Often asymptomatic or with subtle findings). The most important association in adults is Nephrotic Syndrome, particularly Membranous Nephropathy, which creates a profound Hypercoagulable State. Other causes include Malignancy (Renal Cell Carcinoma), Trauma, Dehydration, and Hypercoagulable Disorders. In Neonates, RVT is often associated with Dehydration, Polycythaemia, Sepsis, or Perinatal asphyxia. Clinical presentation varies: Acute RVT may present with Sudden Flank Pain, Haematuria, Renal Enlargement, and Acute Kidney Injury; Chronic RVT may be asymptomatic or present with declining renal function and Pulmonary Embolism (PE). Diagnosis is by Doppler Ultrasound or CT/MR Venography. Treatment involves Anticoagulation (Typically for ≥6 months), With Thrombolysis or Thrombectomy reserved for severe acute cases. [1,2,3]
Clinical Pearls
"Nephrotic Syndrome = RVT Risk": Especially Membranous Nephropathy. Screen if symptomatic or consider prophylactic anticoagulation if severely nephrotic.
"Acute RVT = Flank Pain + Haematuria + AKI": Classic triad, But often incomplete.
"Renal Cell Carcinoma": Can invade renal vein and IVC. Always consider in unilateral RVT.
"Chronic RVT May Present as PE": Clot can propagate or embolise.
2. Epidemiology
Demographics
| Factor | Notes |
|---|---|
| Incidence | Rare overall. More common in specific risk groups. |
| Age | Adults: Any age. Peak with nephrotic syndrome. Neonates: A distinct population. |
| Sex | Variable by underlying cause. |
Aetiology
| Category | Causes |
|---|---|
| Nephrotic Syndrome | Major Cause in Adults. Membranous Nephropathy (~20-40% risk of RVT). Other causes: Minimal Change, FSGS, Amyloidosis. |
| Malignancy | Renal Cell Carcinoma (Direct invasion of renal vein ± IVC). Other malignancies causing hypercoagulability. |
| Hypercoagulable States | Antiphospholipid Syndrome. Protein C/S deficiency. Antithrombin deficiency. Factor V Leiden. |
| Trauma | Direct renal injury. |
| Extrinsic Compression | Retroperitoneal mass. Lymphadenopathy. |
| Dehydration | Especially in Neonates, Infants. |
| Neonatal Causes | Dehydration, Birth asphyxia, Maternal DM, Sepsis, Polycythaemia, Umbilical vein catheterisation. |
| Others | Oral Contraceptive Pill. Pregnancy/Postpartum. |
3. Pathophysiology
Mechanism
- Thrombus Formation: In renal vein due to hypercoagulability, Stasis, Or endothelial injury (Virchow's Triad).
- Venous Outflow Obstruction: Impaired drainage from kidney.
- Renal Congestion: Oedema. Haemorrhage. Infarction (If acute and complete).
- Consequences:
- Acute RVT: Renal swelling, Haematuria, AKI (If bilateral or solitary kidney).
- Chronic RVT: Collateral vein development. May be asymptomatic or lead to renal atrophy.
- Thrombus Propagation: Can extend into IVC.
- Embolisation: Can cause Pulmonary Embolism.
Nephrotic Syndrome and Thrombosis
- Urinary Loss of Anticoagulant Proteins: Antithrombin III, Protein C, Protein S.
- Increased Hepatic Synthesis of Procoagulants: Fibrinogen, Factor V, Factor VIII.
- Hyperlipidaemia: Increased platelet aggregation.
- Haemoconcentration: Hypovolaemia.
4. Clinical Presentation
Acute RVT
| Feature | Notes |
|---|---|
| Sudden Flank Pain | Acute onset. Severe. Unilateral (Or bilateral). |
| Costovertebral Angle Tenderness | |
| Haematuria | Gross or Microscopic. |
| Oliguria / AKI | If bilateral, Solitary kidney, Or pre-existing renal impairment. |
| Nausea / Vomiting | |
| Fever | Possible. |
| Renal Enlargement | On imaging. |
| Left Varicocele (Males) | If left renal vein thrombosis (Left gonadal vein drains into left renal vein). |
Chronic RVT
| Feature | Notes |
|---|---|
| Often Asymptomatic | Collaterals develop. |
| Proteinuria Worsening | If nephrotic (Venous congestion worsens proteinuria). |
| Declining Renal Function | Gradual. |
| Pulmonary Embolism | May be first presentation. |
| Lower Limb Oedema | If IVC extension. |
Neonatal RVT
| Feature | Notes |
|---|---|
| Palpable Flank Mass | Enlarged kidney. |
| Haematuria | |
| Thrombocytopenia | Consumption. |
| Hypertension | |
| AKI |
5. Investigations
Laboratory
| Test | Findings |
|---|---|
| Urinalysis | Haematuria (Macro or Micro). Proteinuria (May worsen). |
| U&Es / Creatinine | Elevated if AKI. |
| FBC | Thrombocytopenia (Consumption, Neonates). |
| Coagulation | Usually normal. DIC rarely. |
| LDH | May be elevated (Tissue infarction). |
| 24h Urine Protein | Quantify nephrotic-range proteinuria. |
| Serum Albumin | Low in nephrotic syndrome. |
| Thrombophilia Screen | Antithrombin III, Protein C/S, Factor V Leiden, Antiphospholipid antibodies. |
Imaging
| Modality | Findings / Notes |
|---|---|
| Doppler Ultrasound (Renal) | First-Line. Absent or reduced flow in renal vein. Echogenic thrombus. Renal enlargement. May miss small or chronic thrombi. |
| CT Venography (CT Angiography) | Gold Standard. Filling defect in renal vein. Renal enlargement. Perinephric stranding. Assess IVC extension. |
| MR Venography (MRV) | Alternative if CT contraindicated. Good visualisation. |
| Renal Scintigraphy (MAG3 / DTPA) | May show reduced function on affected side. |
| Renal Biopsy | May show features of nephrotic syndrome cause. Congestion. Usually not needed for RVT diagnosis. |
6. Management
Management Algorithm
SUSPECTED RENAL VEIN THROMBOSIS
(Flank pain, Haematuria, AKI, Nephrotic syndrome, PE)
↓
CONFIRM DIAGNOSIS
- Doppler Ultrasound (First) OR
- CT Venography (Gold Standard)
↓
ASSESS FOR UNDERLYING CAUSE
- Is Nephrotic Syndrome present? (Membranous?)
- Is there Renal Cell Carcinoma? (CT shows mass + vein invasion)
- Screen for Thrombophilia
↓
ASSESS SEVERITY
┌────────────────┴────────────────┐
ACUTE SEVERE RVT CHRONIC / LESS SEVERE RVT
(Bilateral, Severe AKI, (Unilateral, Asymptomatic,
Haemodynamic compromise) Stable renal function)
↓ ↓
Consider: **ANTICOAGULATION**
- **Catheter-Directed
Thrombolysis**
- **Thrombectomy**
(Case-by-case, Specialist)
↓
ANTICOAGULATION (MAINSTAY)
┌──────────────────────────────────────────────────────────┐
│ **HEPARIN (Initial)** │
│ - LMWH (Enoxaparin) OR Unfractionated Heparin │
│ │
│ **TRANSITION TO ORAL** │
│ - Warfarin (Target INR 2-3) OR │
│ - DOAC (Rivaroxaban, Apixaban, Edoxaban) │
│ │
│ **DURATION** │
│ - Provoked (e.g., Nephrotic, Transient risk): ≥3-6 months│
│ - Unprovoked / Ongoing risk: Longer / Indefinite │
│ - Nephrotic Syndrome: Often continue while nephrotic │
│ (Risk persists) │
└──────────────────────────────────────────────────────────┘
↓
TREAT UNDERLYING CAUSE
- Nephrotic Syndrome: Immunosuppression as indicated
(e.g., Membranous)
- Renal Cell Carcinoma: Surgical resection (Radical
nephrectomy ± IVC thrombectomy)
- Dehydration (Neonates): Rehydration
↓
PROPHYLACTIC ANTICOAGULATION IN NEPHROTIC SYNDROME
┌──────────────────────────────────────────────────────────┐
│ - Consider in high-risk patients: │
│ - Serum Albumin less than 20-25 g/L │
│ - Membranous Nephropathy │
│ - Other thrombotic risk factors │
│ - No universal consensus. Individualised decision. │
└──────────────────────────────────────────────────────────┘
Thrombolysis / Thrombectomy
| Notes |
|---|
| Reserved for Severe Acute Bilateral RVT with Significant AKI or Massive IVC Thrombus. |
| Catheter-directed thrombolysis. Surgical/Endovascular thrombectomy. |
| High bleeding risk. Case-by-case basis. |
7. Complications
| Complication | Notes |
|---|---|
| Pulmonary Embolism | Major risk. Thrombus propagates or embolises. |
| Acute Kidney Injury | Especially bilateral RVT, Solitary kidney. |
| Chronic Kidney Disease | Renal atrophy if chronic. |
| IVC Thrombosis | Extension of thrombus. |
| Adrenal Haemorrhage | Left adrenal vein drains into left renal vein. Rare. |
| Anticoagulation Bleeding | From treatment. |
8. Prognosis and Outcomes
| Factor | Notes |
|---|---|
| Renal Function Recovery | Good if unilateral, Acute, Promptly treated. Chronic or bilateral may have residual impairment. |
| Recurrence | Possible if underlying hypercoagulable state persists (e.g., Ongoing nephrotic syndrome). |
| PE Risk | High if untreated. |
| Mortality | Low with treatment. Depends on underlying cause (Higher in malignancy). |
9. Evidence and Guidelines
Key Guidelines
| Guideline | Notes |
|---|---|
| No specific formal guidelines for RVT | Management based on case series, Expert opinion, Extrapolation from VTE guidelines. |
| Nephrotic Syndrome | KDIGO. Anticoagulation if RVT confirmed. Consider prophylaxis if high risk. |
10. Patient and Layperson Explanation
What is Renal Vein Thrombosis?
RVT is a blood clot in one of the veins that drains blood from the kidneys. It can affect one or both kidneys.
What causes it?
Common causes include:
- Nephrotic Syndrome: A kidney condition that makes the blood more likely to clot.
- Kidney Cancer: The tumour can grow into the vein.
- Dehydration: Especially in babies.
- Blood clotting disorders.
What are the symptoms?
- Sudden pain in the side or back.
- Blood in the urine.
- Reduced urine output.
- Leg swelling (If the clot extends).
- Sometimes no symptoms at all.
How is it diagnosed?
An ultrasound or CT scan of the kidneys and veins.
How is it treated?
- Blood-Thinning Medication (Anticoagulants): To prevent the clot from getting bigger and to allow the body to break it down.
- Treating the Underlying Cause: Such as treating kidney disease or removing a kidney tumour.
- Rarely, Other Procedures: Clot-busting drugs or surgery for very severe cases.
11. References
Primary Sources
- Asghar M, et al. Renal Vein Thrombosis. Clin Kidney J. 2015;8(3):287-290. PMID: 26034590.
- Llach F. Hypercoagulability, renal vein thrombosis, and other thrombotic complications of nephrotic syndrome. Kidney Int. 1985;28(3):429-439. PMID: 3908797.
- KDIGO. Clinical Practice Guideline for Glomerulonephritis. Kidney Int Suppl. 2012;2(2):139-274.
12. Examination Focus
Common Exam Questions
- Major Association: "What is the most common underlying cause of RVT in adults?"
- Answer: Nephrotic Syndrome (Especially Membranous Nephropathy).
- Classic Presentation (Acute): "What is the classic triad of acute RVT?"
- Answer: Flank Pain, Haematuria, Acute Kidney Injury (Though often incomplete).
- Imaging: "What is the gold-standard investigation for RVT?"
- Answer: CT Venography (CT Angiography).
- Treatment: "What is the mainstay of treatment for RVT?"
- Answer: Anticoagulation (Heparin initially, Then Warfarin or DOAC for ≥3-6 months).
Viva Points
- Membranous Nephropathy = ~20-40% RVT Risk: Screen if symptomatic.
- Renal Cell Carcinoma: Can invade renal vein and IVC. Surgical treatment.
- Left Varicocele (Sudden Onset): Think Left RVT (Gonadal vein drains into LRV).
- Neonatal RVT: Think Dehydration, Asphyxia, Sepsis. Often unilateral.
Medical Disclaimer: MedVellum content is for educational purposes and clinical reference. Clinical decisions should account for individual patient circumstances. Always consult appropriate specialists.