Sickle cell disease can hit each organ in the body hard that organ damage may be irreversible: the kidney is no exception. Renal complications of sickle cell disease are vast. Understanding their occurrence is key to preventing kidney failure, which affects 4 to 18% of people living with sickle cell disease.
Today, we shall have a look at how sickle cell disease leads to various renal complications. It will enable us to partly acknowledge the ‘Nnywa Ku Mazzi’ campaign which was held in Kampala early this year. Let’s get this started.
The ability to understand, and identify the renal complications among this population is key to their kidneys’ survival because of the following observations.
People living with sickle cell disease hyper-secrete creatinine via the proximal tubules, and since the main parameters used to assess kidney function include creatinine. It implies masking significant renal impairment among people with sickle cell disease before serum creatinine rises.
Renal complications of sickle cell disease are;
-impaired urinary potassium excretion and acidification,
-tubular and glomerular dysfunction,
-medullary carcinoma, and
-acute necrosis and renal failure.
42% of children aged 6 to 8 and 9% of adults aged 18 to 20 have enuresis. It is due to hyposthenuria. Hyposthenuria is the inability to concentrate urine, and this complication is progressive with age. The inability to concentrate urine is due to the loss of the deep juxtamedullary nephrons (functional unit of the kidney).
Hyposthenuria leads to frequent urination which puts these people at a higher risk for the depletion of the intravascular volume, leading to dehydration. They cannot respond to decreased oral fluid intake by concentrating the urine. It is where the organisers based the ‘Nnywa Ku Mazzi’ campaign – now you can relate.
In other instances, the sickle red cells can occlude the vessels supplying blood to the Vasa recta, leading to infarction of the kidney medulla resulting in renal papillary necrosis which manifests as hematuria. Proteinuria is quite common due to occasional injury to the glomerulus.
Microalbuminuria is an early indicator of renal injury. Unfortunately, it is asymptomatic, making urinalysis a viable test in the sickle cell clinic visits.
Gout due to the accumulation of uric acid can easily be mistaken for an acute vaso-occlusive crisis when it presents with joint pains. However, gout and hypertension are early indicators of renal damage and should prompt further investigation when finding among people living with sickle cell disease.
Find more information about chronic kidney disease here. For now, let’s focus on the recommendations for managing renal complications in sickle cell disease as put forth by the expert panel on evidence-based management of sickle cell disease.
1. If you identify microalbuminuria or macroalbuminuria, order 24-hour urine to test for protein.
2. Refer people with proteinuria (>300 mg/24 hours) to a nephrologist for further evaluation.
3. For adults with microalbuminuria without other apparent cause, initiate ACE inhibitor therapy.
4. For adults with proteinuria without another apparent aetiology, begin ACE inhibitor therapy.
5. For children with microalbuminuria or proteinuria, consult a nephrologist.
6. Consider patients with SCD with modest elevations of serum creatinine (>0.7 mg/dL in children, >1.0 mg/dL in adults) to have renal impairment and refer to a nephrologist for further evaluation.
7. Give ACE inhibitor therapy for renal complications when indicated even in the presence of normal blood pressure.
8. Renal replacement therapy (e.g. hemodialysis, peritoneal dialysis, and renal transplantation) should be used in people with SCD if needed.
Related article: Acute Renal Failure in Sickle Cell Disease: Recommendations.