The kidneys have several functions in the body. They help maintain overall fluid balance within the body, regulate and filter electrolytes and minerals in the blood, and remove wasteful minerals and electrolytes from the body through urine. Sickle cell disease can affect the kidneys by causing damage to the blood vessels and the filtration system within the kidneys.

How do we measure kidney health?

• Creatinine Clearance (CrCl): A blood or urine test that measures how well a chemical compound called creatinine is removed from the body by the kidneys.


• Blood Urea Nitrogen (BUN): A blood test that measures how much of a compound called urea nitrogen is left in the body as a way to evaluate how well the kidneys are working.


• Cystatin C: A blood test that measures the amount of protein called Cystatin C is in the body to evaluate how the kidney’s filtering system is working.


• Albumin: A urine test that measures the amount of a protein called albumin to evaluate how well the kidneys filtering system is working.


• Glomerular Filtration Rate (GFR): A formula that estimates the rate of blood flow through the kidneys using creatinine and other measurements to evaluate the overall health of the kidney.

How does sickle cell disease affect the kidneys?

Kidney disease generally occurs over time, and chronic kidney disease is common in adults and a risk factor for early death. The sickled cells can block blood flow within the kidney and lead to changes in the way the blood vessels work. Thus, oxygen is not able to get to the kidney as well causing death of the kidney cells. Those with sickle cell disease have about a 2-3-fold increased risk of developing chronic kidney disease (1). Approximately 12% of adults have stage 3 or worse kidney disease (2).

Kidney disease can start to develop as early as in infancy, and it can often go undetected until it has already progressed to advanced stages (3). Early signs of kidney disease related to sickle cell disease include hyperfiltration (designated by a high GFR) and protein in the urine. Hyperfiltration can be seen in up to about 75% of children (4). Some of these patients will eventually go on to develop more serious kidney disease.

We would like to understand more about how curative therapy impacts kidney function. The COALESCE study will help us gather more information by collecting GFR values on patients before and after curative therapy.

References

1. Yeruva SL, Paul Y, Oneal P, Nouraie M. Renal Failure in Sickle Cell Disease: Prevalence, Predictors of Disease, Mortality and Effect on Length of Hospital Stay. Hemoglobin. Sep 2016;40(5):295-299. https://doi.org/10.1080/03630269.2016.1224766


2. Saraf SL, Zhang X, Kanias T, et al. Haemoglobinuria is associated with chronic kidney disease and its progression in patients with sickle cell anaemia. Br J Haematol. Mar 2014;164(5):729-39. https://doi.org/10.1111/bjh.12690


3. Olaniran KO, Eneanya ND, Nigwekar SU, et al. Sickle Cell Nephropathy in the Pediatric Population. Blood Purif. 2019;47(1-3):205-213. https://doi.org/10.1159/000494581


4. Aygun B, Mortier NA, Smeltzer MP, Hankins JS, Ware RE. Glomerular hyperfiltration and albuminuria in children with sickle cell anemia. Pediatr Nephrol. Aug 2011;26(8):1285-90. https://doi.org/10.1007/s00467-011-1857-2