Can a renal infarct (kidney infarction) cause hematuria (blood in urine)?

Renal Infarction and Hematuria

Yes, renal infarction can cause hematuria, with approximately 38-71% of patients with renal infarction presenting with hematuria. 1, 2

Pathophysiology of Hematuria in Renal Infarction

Renal infarction occurs when blood flow to a portion of the kidney is disrupted, leading to ischemic damage of renal tissue. This damage can cause:

1. Direct vascular injury - Disruption of small blood vessels in the affected area
2. Tissue necrosis - Death of renal parenchyma leading to bleeding into the collecting system
3. Inflammatory response - Local inflammation that can damage the filtration barrier

Clinical Presentation of Renal Infarction

Renal infarction typically presents with:

• Pain - Persistent flank, abdominal, or lower back pain (present in 71-100% of cases) 1, 2
• Hematuria - Present in 38-71% of patients within 24 hours 1, 3, 2
• Laboratory findings:
  • Elevated serum lactate dehydrogenase (LDH) in 86-94% of cases 1, 2
  • Leukocytosis in 67-100% of cases 3, 2
  • Elevated C-reactive protein in 54.5% of cases 2

Diagnostic Considerations

It's important to note that:

1. Hematuria is not universal - A recent study of 52 patients with confirmed renal infarction found hematuria in only 38.5% of cases on admission 2
2. Hematuria may develop over time - The percentage of patients with hematuria increases to 71-82% within 24 hours after pain onset 1
3. Severity correlation - Higher serum LDH levels (indicating more severe infarction) correlate with the presence of hematuria 2

Risk Factors for Renal Infarction

The most common causes of renal infarction include:

• Cardiogenic factors (55.7% of cases) 4:
  • Atrial fibrillation (most common, present in 44.2% of cases) 2
  • Mitral stenosis
  • Ischemic heart disease
• Renal artery injury (7.5% of cases) 4:
  • High-velocity deceleration injuries (motor vehicle accidents, falls)
  • Penetrating trauma
• Hypercoagulable states (6.6% of cases) 4
• Idiopathic causes (30.1% of cases) 4

Diagnostic Approach

For patients presenting with persistent flank/abdominal pain and hematuria:

1. Consider renal infarction in patients with risk factors for thromboembolism
2. Order contrast-enhanced CT as the preferred diagnostic modality 5, 1
3. Look for the triad of:
   • Risk factors for thromboembolism
   • Persistent pain
   • Elevated LDH and/or hematuria 1

Clinical Pitfalls

1. Delayed diagnosis - Median time from presentation to diagnosis is 41.5 hours (range: 2-552 hours) 2
2. Misdiagnosis - Often initially misdiagnosed as renal colic, pyelonephritis, or acute abdomen 3
3. Absence of hematuria - The absence of hematuria does not rule out renal infarction, especially early in presentation 2
4. Anticoagulation status - Patients can develop renal infarction even while on anticoagulation therapy if INR is subtherapeutic 3

Outcomes

Renal infarction can lead to:

• Acute kidney injury in 20.1% of patients
• New-onset reduced kidney function (eGFR <60 mL/min/1.73m²) in 10.9% of patients
• End-stage renal disease in 2.1% of patients 4

In conclusion, while hematuria is a common finding in renal infarction, its absence should not exclude the diagnosis, especially in patients with risk factors for thromboembolism who present with persistent pain and elevated LDH.