Sickle Cell Nephropathy

Snapshot

An 18-year-old African American man with a history of sickle cell trait presents with 1 week of painless gross hematuria. On review of systems, he endorses a 10 pound weight loss within the past 2 months. Physical exam reveals a left-sided abdominal mass. His serum creatinine is found to be elevated. He is sent to the emergency room for urgent CT imaging. (Renal medullary carcinoma secondary to sickle cell trait).

Introduction

Clinical definition
- nephropathy associated with sickle cell disease or trait
  - vaso-occlusion
  - renal medullary carcinoma
Epidemiology
- incidence
  - proteinuria
    - 20-25% in sickle cell disease
  - renal insufficiency
    - 5-30% in sickle cell disease
- risk factors
  - vaso-occlusion
    - sickle cell disease > trait
  - renal medullary carcinoma
    - sickle cell trait > disease
    - patients of African ancestry
Pathogenesis
- normal ↓ O₂ tension in the renal medulla is low enough to induce RBC sickling
- sickling of red blood cells in medulla capillaries cause increased viscosity
- increased viscosity causes ischemia and infarction in renal medulla
- this can lead to renal infarcts and papillary necrosis
Prognosis
- prognostic variable
  - negative
    - renal failure
- increased mortality risk for those with renal failure, regardless of treatment
- prognosis is < 1 year for renal medullary carcinoma
commonly very aggressive and metastasizes early

Presentation

Imaging

Ultrasound
- indications
  - to exclude other abnormalities such as nephrolithiasis
- recommend views
  - renal
- findings
  - can detect renal papillary necrosis
CT
- indications
  - if renal medullary carcinoma is suspected (young patient with sickle cell trait and gross hematuria)
- findings
mass in kidney

Studies

Labs
- electrolyte abnormalities
  - impaired distal H+ and K+ secretion can cause a renal tubular acidosis
    - hyperkalemia
    - metabolic acidosis
- ↑ creatinine
Urinalysis
- proteinuria
- low specific gravity and osmolarity
  - indicates loss of urine concentrating ability
Hemoglobin electrophoresis
- presence of HbS
Diagnostic criteria
generally, this is a diagnosis of exclusion

Differential

Treatment

Conservative
- hydration and blood transfusions as needed
  - indications
    - isolated hematuria
    - hydration can dislodge blood clots
Medical
- dialysis
  - indications
    - end-stage renal disease
Operative
- renal transplant
  - indications
end-stage renal disease not responsive to dialysis

Complications