What is a renal infarction?

What is a Kidney (Renal) Infarction?

A kidney infarction is an acute disruption of blood flow to the kidney, resulting in ischemic tissue death, typically caused by thromboembolism (most commonly from atrial fibrillation), renal artery injury, or hypercoagulable states. 1

Pathophysiology and Causes

Renal infarction occurs when arterial blood supply to kidney tissue is suddenly interrupted, leading to wedge-shaped areas of ischemic necrosis. 2 The condition results from:

• Cardiogenic emboli (55.7%) - predominantly from atrial fibrillation, which is the single most common etiology 1
• Renal artery injury (7.5%) - including traumatic or iatrogenic vascular damage 1
• Hypercoagulable states (6.6%) - such as protein C/S deficiency or activated protein C resistance 3
• Idiopathic causes (30.1%) - where no clear etiology is identified despite thorough evaluation 1

Approximately 82% of patients have identifiable risk factors for thromboembolism, with atrial fibrillation being present in 65% of cases. 4 Other common risk factors include previous embolic events, mitral stenosis, hypertension, and ischemic heart disease. 4

Clinical Presentation

The classic presentation includes:

• Persistent flank, abdominal, or lower back pain - present in essentially all patients (94-100%) 3, 4
• Fever - occurs in approximately 45% of cases 3
• Nausea and vomiting - reported in about 36% of patients 3

Diagnostic Features

Laboratory Findings

The diagnostic triad that should raise immediate suspicion includes:

• Elevated serum lactate dehydrogenase (LDH) - present in 94-100% of patients within 24 hours, typically >620 IU/L 4, 2
• Hematuria - detected in 71-82% of patients within 24 hours 3, 4
• Leukocytosis - white blood cell count >10 × 10⁹/L in most cases 3, 2

Imaging

Contrast-enhanced computed tomography (CT) is the definitive diagnostic modality, demonstrating: 4, 2

• Wedge-shaped hypodense areas in the renal parenchyma (92% of cases) 2
• Global renal ischemia in severe cases (8%) 2
• Concomitant splenic infarction in 34% of patients, suggesting systemic embolic disease 2

Clinical Outcomes and Prognosis

Despite aggressive treatment, renal infarction carries significant morbidity:

• Acute kidney injury (AKI) develops in 20-35% of patients during initial hospitalization 1, 5
• New-onset chronic kidney disease (eGFR <60 mL/min/1.73 m²) occurs in 10.9-27.4% of patients during follow-up 1, 5
• End-stage renal disease requiring dialysis develops in 2.1% of cases 1
• In-hospital mortality is approximately 5% 1
• Recurrence rate is 2.8% during median 20-month follow-up 1

Risk Factors for Poor Outcomes

Independent predictors of acute kidney injury include:

• Diabetes mellitus 5
• Elevated C-reactive protein levels 5
• Leukocytosis 5

Advanced age is an independent risk factor for progression to chronic kidney disease. 5

Common Diagnostic Pitfalls

Renal infarction is frequently misdiagnosed initially, with time to correct diagnosis ranging from 24 hours to 6 days. 3 Common misdiagnoses include:

• Renal colic/kidney stones 3
• Pyelonephritis 3
• Acute abdomen 3
• Renal carcinoma 3

The incidence is likely underestimated at 0.007% of emergency department presentations because the diagnosis is often missed entirely. 3, 4 Clinicians should maintain high suspicion when patients with thromboembolic risk factors present with persistent flank pain, especially when accompanied by elevated LDH and hematuria.