Causes of Renal Hemorrhage
Renal hemorrhage is most commonly caused by trauma (both blunt and penetrating), vascular malformations, and iatrogenic injuries during procedures, with the management approach determined by hemodynamic status and the specific underlying cause. 1
Traumatic Causes
Blunt Trauma
- High-velocity deceleration injuries (90% of cases)
- Motor vehicle accidents
- Falls from height
- Sports injuries (skiing, snowboarding, horse riding)
- Mechanism: Rapid deceleration causes kidney movement against fixed points at the renal pelvis and vascular pedicle 1
- Severity classification follows the American Association for Surgery of Trauma (AAST) scale from grade I-V
Penetrating Trauma
- Gunshot wounds and stab wounds (1.4-3.3% of renal injuries)
- More likely to cause renal vascular injuries compared to blunt trauma 1
- Often associated with other intra-abdominal injuries
Vascular Causes
Arteriovenous Malformations (AVMs)
- Can cause massive hematuria and retroperitoneal hemorrhage
- May present with symptoms mimicking urinary tract infection 2
- Classified as traumatic or non-traumatic
- Can lead to high-output heart failure if severe 3
Renal Artery Aneurysms
- Risk of rupture increases with:
- Size >2 cm in diameter
- Non-calcified aneurysms
- Pregnancy (especially in premenopausal women) 1
Vascular Diseases
- Arteritis (e.g., Takayasu's arteritis)
- Atheroemboli
- Thromboemboli
- Spontaneous renal artery dissection 1
Iatrogenic Causes
Percutaneous Procedures
- Percutaneous nephrostomy (PCN)
- Percutaneous nephrolithotomy
- Renal biopsy
Complication rates:
- Clinically significant bleeding occurs in approximately 4% of PCN procedures
- Mild hematuria occurs in about 50% of patients after PCN
- Risk factors for bleeding include thrombocytopenia 1
- Vascular injuries requiring embolization or nephrectomy occur in about 1% of cases 1
Dialysis-Related
- Increased risk in patients with renal failure, particularly during surgical procedures
- Pathogenesis involves platelet biochemical abnormalities and altered platelet-vessel wall interactions 4
- Heparinization during hemodialysis may increase bleeding risk
Other Causes
Neoplastic
- Renal tumors (benign and malignant)
- Vascular tumors (hemangiomas)
- Angiomyolipomas (risk of spontaneous hemorrhage)
Congenital
- Fibromuscular dysplasia (FMD)
- Second most common cause of renal artery stenosis
- Most commonly affects middle and distal two-thirds of renal artery
- Can lead to aneurysm formation and rupture 1
Miscellaneous
- Arteriovenous fistulas
- Retroperitoneal fibrosis
- Prior abdominal radiation therapy
- Lithotripsy complications 1
Management Approach
Hemodynamically Unstable Patients
- Require immediate operative management
- Resuscitative Endovascular Balloon Occlusion of the Aorta (REBOA) may be used as a bridge to definitive treatment 1
Hemodynamically Stable Patients
- CT angiography is the preferred diagnostic modality
- Management options include:
Special Considerations
- Persistent bleeding should prompt consideration of arteriographic evaluation for renal artery abnormalities such as pseudoaneurysms or fistulas 1
- In patients with renal insufficiency, Council balloon catheters may be used to control hemorrhage without open exploration 5
Pitfalls and Caveats
- Hematuria may not correlate with injury severity, particularly in high-grade injuries and ureteropelvic junction injuries (absent in 10-25% of cases) 1
- Penetrating injuries require imaging regardless of hematuria degree due to high association with other intra-abdominal injuries 1
- Renal vein injuries can cause massive hemorrhage that may be underdiagnosed 5
- Blind angioembolization is not recommended when angiography is negative for active bleeding 1