Veterinary Clinical Medicine-I (General and Systemic)

CHEMICAL EVALUATION OF URINE

Urine pH:

• Acidic urine -increased acid excretion or production (increased protein catabolism, [high protein diet, fever, starvation, nursing], metabolic or respiratory acidosis, paradoxical aciduria with alkalosis).
• Alkaline urine --increased alkali excretion or production (decreased protein catabolism [e.g., low protein diet], cystitis due to urea-splitting bacteria, prolonged storage at room temperature, metabolic or respiratory alkalosis).
• Urine pH is not an accurate indicator of systemic acid/base balance.

Protein:

• Urine protein results must be interpreted in conjunction with specific gravity.
• A small amount of protein is present in urine
• A sulfosalicylic acid precipitation test is done to confirm the presence of proteinuria.

Glucose:

• Glucose is not normally found in urine.
• Glucosuria occurs when blood glucose levels exceed the renal threshold
• Glucosuria with hyperglycemia ---  diabetes mellitus, with dextrose administration, or secondary to catecholamines or glucocorticoids.
• Glucosuria without hyperglycemia --when hyperglycemia is transient or in selective renal proximal tubule dysfunction.

Ketones:

• Ketonuria occurs when ketone production exceeds the renal tubular absorption capacity.
• Ketonuria may occur in diabetes mellitus, pregnancy, ketosis, or starvation.

Haemoprotein

• Haemoproteinuria --from increased RBCs, hemoglobinuria, or myoglobinuria.

Bilirubin:

• Dogs with concentrated urine may have trace to 1+ bilirubinuria;

Evaluation of Urine Sediment

• Voided samples also may contain squamous epithelial cells. 
• Crystals also may be found normally, depending on urine pH, species, and diet.
• Calcium oxalate crystals are found in acidic urine, whereas, triple phosphate, amorphous phosphates, and struvite crystals are found in alkaline urine.

Hematuria

• > 15 RBCs/hpf.

Pyuria

• > 10 WBCs/hpf.

Casts:

• More than 2 casts/lpf are considered significant.
• Hyaline casts are proteinaceous and may be observed normally, with proteinuria or with mild renal disease.
• Cellular casts always are abnormal.
• RBC casts -- haemorrhage, WBC casts --nephritis, and renal tubular cell casts occur with necrosis and sloughing of renal tubules.
• Granular casts --composed of degenerated cells and protein and ---renal tubular necrosis.
• Waxy casts  --desiccated granular casts and suggest advanced, chronic renal disease.

Crystals:

• Abnormal crystals include calcium oxalate monohydrate (ethylene glycol toxicity), ammonium biurate (hepatic disease), cystine (hereditary tubular disease), tyrosine (hepatic disease), leucine (hepatic disease), bilirubin (with bilirubinuria), and drug crystals (e.g., sulfas).

Cells:

• Abnormal cells include renal tubular cells, caudate epithelial cells (from the renal pelvis), increased numbers of transitional epithelial cells, neoplastic cells, and inflammatory cells.

Organisms:

• Bacteria, yeast, fungi, and parasite ova may be found in urine.