Solving the Clinico-pathologic Puzzle-Real World Biochemical Profiling

Fred L. Metzger DVM, ABVP
Metzger Animal Hospital
State College, PA


ALBUMIN:  (ALB)

Albumin is produced exclusively in the liver.  It is a serum protein that affects the osmotic pressure, binds calcium and transports fatty acids and many drugs.  

  • INCREASED ALBUMIN: Suggests dehydration  
  • DECREASED ALBUMIN: Suggests starvation, parasitism, chronic malabsorptive disease, chronic liver disease, protein losing enteropathy and glomerulonephritis.  

ALKALINE PHOSPHATASE (ALKP)      

Alkaline phosphatase has 6 isoenzymes with liver and bone being the major isoenzymes.  Elevated ALKP activity in the serum indicates increased production in the liver, bile ducts and growing bone or decreased excretion in bile and urine.  The enzyme is induced by abnormally low bile flow and corticosteroid use.  Because of this, ALKP is a less specific liver test.  

  • INCREASED ALKP:
    • Suggests liver disease caused by failure of bile flow (cholestasis)
    • Steroid use
    • Bone growth. 
    • ALKP can increase with pancreatitis and feline hyperthyroidism.  
  • DECREASED ALKP:
    • Not associated with common medical conditions  

** Felines have less ALKP than canines and slight excesses are rapidly excreted by kidneys, therefore any increase is significant!  
** Normal ALKP values in puppies and kittens are higher than in adults because of active bone growth.   

AMYLASE (AMYL)   

The pancreas, liver and small intestine serve as sources of amylase.  When healthy, the majority of amylase is derived from non-pancreatic sources.   Amylase aids in the digestion process.  

  • INCREASED AMYLASE:
    • Pancreatic inflammation, necrosis or pancreatic duct occlusions releases AMYL into the blood and abdominal cavity elevating serum levels 2-3 times normal. 
    • Amylase may increase from upper intestinal inflammation and decreased renal excretion.  
  • DECREASED AMYLASE:
    • Not clinically significant      

ALANINE TRANSFERASE (ALT)

ALT is liver specific and is released when the individual liver cells become damaged.  ALT is present in large quantities in the cytoplasm of canine and feline liver cells (HEPATOCYTES).  This enzyme enters the blood stream when liver cells are damaged or destroyed and circulates for a few days.   

  • INCREASED ALT:
    • Suggests hepatocellular leakage. 
    • THIS TEST IS VERY SENSITIVE AND SPECIFIC FOR LIVER DISEASE, but does not indicate cause or reversibility of the damage
  • DECREASED ALT:
    • Not associated with common medical conditions  

CALCIUM (CA+) 

CA2+ levels in extracellular fluid and bone are controlled mainly by the parathyroid hormone (PTH) and vitamin D and the interaction of these with the gut, bone, kidney and parathyroid glands.

  • INCREASED CALCIUM (HYPERCALCEMIA)
    • Dissolving bone lesions sometimes associated with reabsorption
    • Hyperparathyroidism
    • Increased Vitamin D levels (HYPERVITAMINOSIS D)
    • Malignant (cancerous) tumor of the lymphoid tissue (LYMPHOSARCOMA) MOST COMMON CAUSE
    • Anal gland tumors
    • ADDISON’'S DISEASE (hypoadrenocorticism)
    • Kidney Failure
  • DECREASED CALCIUM (HYPOCALCEMIA)  
    • Ethylene glycol poisoning
    • Pancreatitis
    • Low albumin levels (HYPOALBUMNEMIA)
    • Vitamin D deficiency
    • Post-thyroidectomy  

CHOLESTEROL (CHOL)

Cholesterol is not a diagnostic test when used alone but supplements other tests.  Cholesterol is primarily produced in the liver and excreted in bile.

  • INCREASED CHOLESTEROL
    • Hypothyroidism (LOW THRYOID LEVELS)
    • Obstructive biliary disease
    • Cushing’s disease
    • A condition of the kidneys marked by water retention between the tissues, excessive protein in the urine, low albumin levels and elevated cholesterol levels. (NEPHROTIC SYNDROME)

CREATININE (CREAT)

Creatinine is a nonportein nitrogenous product of muscle metabolism.  CREAT levels are kidney specific and not as affected by diet and protein catabolism then BUN levels.

  • INCREASED CREATININE LEVELS
    • Accumulation of constituents in the blood that are normally excreted in the urine. 
    • Can result in a severely toxic condition and can occur in severe kidney disease (UREMIA)  

GLUCOSE (GLU)

  • INCREASED BLOOD GLUCOSE
    • Persistent elevated levels indicate diabetes mellitus.
    • Release of epinephrine due to stress can cause transient elevated levels.
    • Sample collection after blood meal may alter results
  • DECREASED BLOOD GLUCOSE:
    • Insulinoma,
    • Starvation,
    • Addison’s disease,
    • Hypopituitaryism,
    • Shock,
    • Severe exertion  

INORGANIC PHOSPHATE (PHOS)

Control of phosphorus is complex and is influenced by the actions of PTH and vitamin D and the interaction of these hormones with the gut, bones, kidneys and parathyroid glands.

  • INCREASED PHOS
    • Hemolysis (Red Blood Cells contain significant amounts of PHOS, hemolysis of blood samples or delayed removal of the serum from the clot can falsely elevate PHOS values.
    • RENAL DISEASE (because of the decreased amounts of PHOS being excreted in urine)
    • Hypoparathyroidism Growth Hyperthyroidism in felines
    • Uremia is the most common cause of hyperphosphaternia.
  • DECREASED PHOS
    • Hypoparathyroidism
    • An increased alkalinity (HIGH PH) of the blood and tissues (ALKALOSIS)
    • Neoplasia    

TOTAL BILIRUBIN (TBIL)   Bilirubin is derived from the break down of hemoglobin and circulates in conjugated and unconjugated forms.  TBIL measurements are the combination of both forms.  

  • INCREASED TBILI  
    • Liver Disease
    • Hemolytic disease (destruction of red blood cells)

UREA NITROGEN (BUN)

Urea is the primary solid component of urine and the end product of protein decomposition.

  • INCREASED BUN
    • Increased levels of nitrogenous waste products (AZOTEMIA)
    • Gastrointestinal hemorrhage
    • Renal Disease (pre, renal or post)
    • Heart disease
    • Hypoadrenocorticism (ADDISON’S DISEASE)
    • Dehydration
    • Shock  
  • DECREASED BUN
    • Portosystemic Shunt
    • Severe Liver Failure  

TOTAL PROTEIN (TP)

Total protein is the sum of the albumin and globulin in the blood.  When measured on serum it usually consists of albumin, globulins and fibrinogen.  It is often used as an indicator of hydration status.  

  • ELEVATED TP:
    • Dehydration
    • Anything increasing Albumin or Globulin
  • DECREASED TP
    • Anything decreasing Albumin or Globulin  

GLOBULIN

Globulin is primarily produced in the liver.  It helps with nutritive functions and helps maintain colloidal osmotic pressure it helps to form enzymes, antibodies, coagulation factors, transport substances.

  • INCREASED GLOBULIN:
    • Chronic inflammatory disease
    • Parasitism
    • Neoplasia
    • Immune-mediated disease  
  • DECREASED GLOBULIN: Not a medical condition  

** GLOBULIN VALUE IS CALCULATED FROM TOTAL PROTEIN – ALBUMIN**
Not clinically significant    

GAMMA GLUTAMYL TRANSPEPTIDASE (GGT)

GGT is involved in the metabolism of a peptide called glutathione and is mainly associated with the membranes of liver cell surfaces, bile duct epithelium and renal convoluted tubular epithelial cells.

  • INCREASED GGT:
    • Cholestatic liver disease
    • Cushing’s disease
    • Disease of the portal biliary system
  • DECREASED GGT: Not clinically significant
**IN FELINES, INCREASED GGT TENDS TO INCREASE MORE THAN ALKP WITH CHOLESTASIS**

LIPASE (LIPA)

Lipase is the primary enzyme responsible for the decomposition of fat.  

  • INCREASED LIPASE:  
    • Pancreatitis (acute and chronic)
    • Renal failure Intestinal inflammation
    • Small intestinal obstruction
    • Following the administration of steroids
    • GI perforation  
  • DECREASED LIPASE:  
    • Not clinically significant

AMMONIA (NH3)

Ammonia is a waste product eliminated from the body by the liver and kidneys. When the body is unable to eliminate this waste, toxic levels build and cause hepatic encephalopathy.  

  • INCREASED NH3
  • Hepatic insufficiency
  • Congenital  and acquired hepatic shunts
  • Bile duct obstructions
  • Inflammation of the biliary system    

MAGNESIUM (MG2+)

Magnesium is second only to potassium as the most abundant cellular positively charged ion.  Magnesium balance is primarily controlled by renal function  

  • INCREASED MAGNESIUM (small animal):
    • Renal Failure
    • Endocrine disorders  
  • DECREASED MAGNESIUM (small animal):  
    • Associated with diabetes (25% of human diabetics have low magnesium)
    • Chronic diarrhea Loop diuretics