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Schistocytes



DEFINITION


Red cell fragments that are considered to be the hallmark of microangiopathic hemolysis



SYNONYM


Schizocyte



PHYSIOLOGY


Schistocytes result from shredding of red cells as they pass through microvasculature containing fibrin thrombi or altered endothelium. Any traumatic or physical injury to red cells can lead to schistocyte formation.


CAUSES OF ABNORMALLY HIGH LEVELS: Disseminated intravascular coagulation (DIC), vasculitis, hemangiosarcoma, dirofilariasis, intravenous catheters, burns, heart valve disease, myelofibrosis, glomerulonephritis. May be seen in severe iron-deficiency anemia (increased red blood cell fragility causes fragmentation).



CLINICAL APPLICATIONS


NEXT DIAGNOSTIC STEP TO CONSIDER IF LEVELS HIGH: Evaluate patient’s clinical history and physical exam, heartworm status, coagulation profile, tick titers.


IMPORTANT INTERSPECIES DIFFERENCES: Schistocytes are not typically seen in cats with DIC, possibly because their smaller red blood cells are less likely to be damaged by fibrin in vascular spaces.



SPECIMEN AND PROCESSING CONSIDERATIONS


SPECIMEN: EDTA whole blood (lavender-top tube) for CBC and blood smear evaluation


RELATIVE COST: $$ (reported as part of CBC)



PEARLS


Even small numbers of schistocytes are significant, indicating underlying microangiopathy; unlikely to be induced artifactually by smear preparation technique.


Absence of schistocytes does not rule out DIC (correlate with coagulation profile). A CBC report of poikilocytosis (a broad term that refers to circulating presence of any abnormally shaped RBCs) warrants pathologist review of blood smear to better define the shape change and identify any schistocytes.


AUTHOR: FIDELIA R. FERNANDEZ



Semen Analysis



DEFINITION


Assessment of male ejaculate for volume, sperm number and morphology, percent of live sperm, presence of other cells, bacteria, and, occasionally, alkaline phosphatase and carnitine concentration; used as part of assessment of male fertility



TYPICAL NORMAL RANGE


Normal total sperm count is 400 × 10 6/ejaculate (varying depending on volume of ejaculate), with 52%-90% classified as live and normal in most dogs. Motility, which is often considered an indicator of viability, should be =80%; motility patterns are random. Sperm should have single heads of uniform shape and size; free heads should be rare; tails are normally straight to slightly curved; hooked, kinked, or multiple tails are considered abnormal. It is common to see few urethral, prostatic, or squamous epithelial cells; low numbers of bacteria are also common. Alkaline phosphatase >10,000 U/L.



PHYSIOLOGY


Ejaculate is divided into three fractions. First and third fractions are mostly prostatic secretion; the second sperm-rich fraction should be used for evaluation.



CLINICAL APPLICATIONS


CAUSES OF ABNORMALLY LOW LEVELS: Decreased numbers of normal viable sperm suggest testicular injury, neoplasia, or atrophy. Decreased concentration of seminal alkaline phosphatase and/or carnitine indicates obstruction of genital tubular structures.


NEXT DIAGNOSTIC STEP TO CONSIDER IF LEVELS LOW: Examination of testicle and epididymis on physical examination and using ultrasound; measurement of resting plasma testosterone.



SPECIMEN AND PROCESSING CONSIDERATIONS


LAB ARTIFACTS THAT MAY INTERFERE: Aged sample or exposure to temperature extremes invalidates physical and biochemical analysis


SPECIMEN: Motility must be evaluated immediately; it cannot be assessed in specimens transported to a reference laboratory. Physical analysis (color, morphology, sperm count): 1 mL semen in sterile container. Alkaline phosphatase: 1 mL semen in sterile container. Store at room temperature. Specimens <2 hours old are considered best.


RELATIVE COST: $$ (physical analysis); $ (alkaline phosphate)



PEARLS


History is an important aspect of fertility assessment. Do not rely on a single test.


AUTHOR: LOIS ROTH-JOHNSON



Sodium



DEFINITION


Electrolyte and the major extracellular cation. Concentration is relative to hydration status and extracellular fluid (ECF) volume but does not indicate total body Na content. Serum Na concentration essentially equals ECF Na concentration.



SYNONYMS


Na, Na+



TYPICAL NORMAL RANGE


Dogs: 140-150 mEq/L. Cats: 150-160 mEq/L. Conversion: mEq/L = mmol/L.

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Jul 24, 2016 | Posted by in SMALL ANIMAL | Comments Off on S

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