Renal Infarction

Snapshot

A 68-year-old man presents to the emergency room with a 2-day history of abdominal pain, nausea, and vomiting. He denies any urinary frequency or urgency and denies any recent changes in his diet. His temperature is 100.4°F (38°C) and pulse is 104/min. He has a past medical history significant for type II diabetes mellitus and coronary artery disease. He has had two stents in the past three years. On physical exam, there is bilateral flank tenderness upon palpation. A non-contrast computerized tomography (CT) scan without contrast is negative for urolithiasis. A CT scan with contrast reveals a wedge shaped perfusion defect in both kidneys.

Introduction

Clinical definition
- complete occlusion of main renal artery or segmental branch
Epidemiology
- incidence
  - very rare
  - 0.7-1.4% found on autopsies
- risk factors
  - cardiovascular disease
Etiology
- cardioemboli
  - cardiomyopathy
  - endocarditis
  - artificial valves thrombi
- renal artery injury and thrombosis
  - Marfan syndrome
  - trauma
  - polyarteritis nodosa
  - other vasculitidies
- hypercoagulable states
  - hereditary thrombophilia
  - antiphospholipid syndrome
Pathogenesis
- complete occlusion of main renal artery or segmental branch artery
Associated conditions
- atrial fibrillation
Prognosis
- 11-12% mortality in first month after diagnosis
  - renal infarction occurs in patient populations with significant morbidity and mortality, such as atrial fibrillation
patients are at risk for future repeat renal infarctions

Presentation

Imaging

Spiral CT without contrast
- indications
  - initial test for flank pain to evaluate for renal calculi
CT with contrast
- indications
  - if there are no calculi seen on initial imaging
  - to evaluate for renal infarction
- findings
  - wedge-shaped perfusion defect
80% sensitivity

Studies

Labs
- ↑ creatinine
  - but it can also be normal if embolus is unilateral
- ↑ lactate dehydrogenase (> 2-4x upper limit of normal)
- little or no ↑ in serum aminotransferases
Urine studies
- hematuria
- proteinuria
Electrodiagnostics
- electrocardiogram to evaluate for atrial fibrillation
Diagnostic criteria
- in the correct clinical context, the combination of elevated lactate dehydrogenase and normal serum aminotransferase is strongly suggestive of renal infarction
note, this combination is also seen in transplant rejection, late myocardial infarction, and hemolysis, but these are clinically distinct from renal infarction

Differential

Renal atheroemboli
- incomplete occlusion of distal vessels
- will likely have eosinophilia, eosinophiluria, and hypocomplementemia
Nephrolithiasis
- stones seen on imaging
lactate dehydrogenase is normal

Treatment

Medical
- anticoagulation
  - indications
    - atrial fibrillation
    - hypercoagulable state
    - delayed diagnosiss
      - anticoagulation therapy is prophylactic to prevent future events
  - drugs
    - heparin followed by warfarin
Percutaneous endovascular therapy
- thrombolysis and thrombectomy
  - indications
    - in patients who are diagnosed early
if diagnosed early, viable tissue may be saved with thrombolysis

Complications