Short answer
Burr cells, also called echinocytes, are red blood cells with many short, usually fairly uniform projections. They are one of the smear findings where artifact is common, so a fresh, well-prepared smear matters. When the finding is real, it can fit with kidney failure or uremia, pyruvate kinase deficiency, or other illness contexts that affect red-cell metabolism or survival.
What burr cells mean
| Pattern | Common next question | Why it matters |
|---|---|---|
| Burr cells on a single poorly prepared smear | Could this be artifact? | Stain, drying, or storage issues can create echinocyte-like cells. |
| Burr cells with elevated creatinine or BUN | Is uremia or kidney failure part of the picture? | Kidney disease is a classic context for echinocytes. |
| Burr cells with chronic hemolysis or childhood anemia | Could pyruvate kinase deficiency be relevant? | That enzyme defect can show echinocytes on smear. |
| Burr cells after transfusion or in serious illness | Was the blood sample old or metabolically stressed? | Stored blood and systemic illness can both distort red cells. |
Artifact vs real burr cells
The biggest practical question is whether the burr cells are real. A report that says “possible artifact” or “crenated cells” often means the lab wants a fresh sample and a careful look at the feathered edge. If burr cells are present across many fields on a good smear, the result deserves more weight.
What to check next
- Was the smear fresh and technically well prepared?
- Are creatinine, BUN, and eGFR abnormal?
- Are hemoglobin, reticulocytes, bilirubin, LDH, or haptoglobin abnormal too?
- Is there a history of kidney disease, dialysis, or a known hemolytic disorder?
- Would a repeat smear or hematology review help confirm the morphology?
Questions to ask
- Did the lab call these burr cells, echinocytes, crenated cells, or artifact?
- Were the burr cells present throughout the smear or only in one area?
- Are kidney markers, electrolyte markers, or anemia markers abnormal?
- Would a repeat CBC and smear change the interpretation?
What follow-up may include
Follow-up may include a repeat smear on a fresh sample, creatinine, BUN, eGFR, electrolytes, hemolysis labs, and hematology review when burr cells are persistent, unexplained, or paired with kidney dysfunction or anemia.
When a blood-smear reference matters more
MedlinePlus blood-smear guidance matters when a red-cell shape finding needs to be interpreted as a pattern rather than a diagnosis. It helps anchor the result in smear quality, repeat review, and the CBC or hemolysis context that decides how seriously to take one abnormal shape.
FAQ
What are burr cells on a blood smear?
Burr cells are red blood cells with many short, regular surface projections. They are also called echinocytes.
Are burr cells always a sign of disease?
No. Burr cells are often artifactual, especially if the smear was old, poorly prepared, or stained in a suboptimal way.
What conditions are associated with burr cells?
They can appear with kidney failure or uremia, pyruvate kinase deficiency, and sometimes after transfusion of older stored blood or during serious illness.
How are burr cells different from acanthocytes?
Burr cells have many small, fairly uniform projections. Acanthocytes have fewer, irregular, blunter spicules and usually point to a different set of causes.
What tests usually follow burr cells?
Common follow-up tests include repeat smear review, creatinine, BUN, eGFR, electrolytes, and anemia labs such as reticulocytes, bilirubin, LDH, and haptoglobin when hemolysis is suspected.
When are burr cells more concerning?
They matter more when they are persistent on a good smear or when they appear with kidney dysfunction, anemia, or hemolysis markers.