Clinical Chemistry 1 - Past Paper PDF

Epithelial Cells Three types of epithelial cells can be found in urine: 1. Renal tubular: originate from the tubules of the nephrons in the kidney 2. Transitional: originate from the renal pelvis, ureters, bladder, and proximal two-thirds of the urethra 3. Squamous: originate from the terminal end o...

Epithelial Cells Three types of epithelial cells can be found in urine: 1. Renal tubular: originate from the tubules of the nephrons in the kidney 2. Transitional: originate from the renal pelvis, ureters, bladder, and proximal two-thirds of the urethra 3. Squamous: originate from the terminal end of the urethra, and from the vagina. CHEM 110 - Clinical Chemistry 1 – LO3 Page 59 Renal Tubular Epithelial Cells Occur singly or in pairs Often round by may have a flat side or cuboidal or columnar shape Transitional Epithelial Cells Slightly larger than RTE’s; may have a teardrop, pear or round shape Squamous Epithelial Cells Large, flat cells; may be rolled up to give a cigar shape or folded Abundant cytoplasm In normal urine, very few renal tubular epithelial cells and transitional epithelial cells may be found due to sloughing of aged cells. Increased numbers of these cells indicate inflammation within the kidney or lower urinary tract. An increased number of renal tubular epithelial cells suggest tubular damage. This damage can occur due to nephrotoxic agents such as heavy metals, organic solvents, or ethylene glycol, or renal infections such as pyelonephritis, or diminished blood supply to the kidney. Any condition that is causing the RTEs to die, acute tubular necrosis. An increased number of transitional epithelial cells can be due to renal calculi (stones), a bladder infection, or trauma due to catheterization. Squamous epithelial cells are not generally considered to be significant. A large number in female urine is most often indicative of vaginal contamination due to improper specimen collection. In summary: Increased RTEs Page 60 Acute tubular necrosis Pyelonephritis Kidney Transplant rejection Increased Transitional Cystitis Renal Calculi Catheterization Increased Squamous Insignificant (usually means vaginal contamination) CHEM 110 – Clinical Chemistry 1 – LO3 Crystals Crystals are found in urine when chemicals are present in excess of their solubility. They frequently occur in normal urine, especially if the specimen has been refrigerated. Most crystals are diagnostically insignificant, and some laboratories do not bother reporting normal crystals. Only a few crystals are abnormal and must be reported. A good atlas of urine sediment is the best aid in identifying crystals to determine if they are normal or abnormal. The chart on the following pages shows some of the more common normal crystals. Normal Crystals Crystal Uric Acid Amorphous Urates Urine pH acid acid Description These crystals come in a variety of shapes: diamonds, hexagons, prisms. They are often yellow to red-brown in colour. Although considered normal, a large number may indicate gout. These appear microscopically as granular sediment. In large numbers they may obscure other elements in the sediment. Macroscopically they appear as pink precipitate which is sometimes referred to as “brick dust”. pink precipitate They can be dissolved with hot tap water. CHEM 110 - Clinical Chemistry 1 – LO3 Page 61 Calcium Oxalate acid (may also be found in neutral or alkaline) Sodium Urates acid Hippuric Acid acid Triple Phosphate Page 62 alkaline These crystals are 3 dimensional and are described as colourless, refractile envelopes; occasionally they appear as dumbbells. Although they are considered normal, they are found in cases of ethylene glycol (antifreeze) poisoning where they can cause considerable obstruction in the kidney. These appear as colourless or yellow needles or prisms occurring in sheaves or clusters These crystals are 2 dimensional and appear microscopically as colourless “picket fences” with both ends pointed. These 3-dimensional crystals are described as “coffin lids”. Sometimes they appear as feathery fern leaves. They may be associated with chronic urinary tract infections. CHEM 110 – Clinical Chemistry 1 – LO3 Amorphous Phosphates alkaline These appear microscopically as granular sediment which looks like amorphous urates. They may also obscure other urine sediment elements. Macroscopically they appear as white precipitate when present in large numbers. They cannot be dissolved with warm tap water. white precipitate Calcium Carbonate alkaline Colourless dumbbells or colourless granules. Calcium Phosphate alkaline These appear as colourless prisms which may form a rosette. They can also appear as a thin irregular shaped plate/sheet. Ammonium Biurate alkaline These appear microscopically as yellowbrown spheres with striations on the surface. Irregular projections may appear on the crystal giving it a “thorny apple” look. Care must be taken not to confuse with leucine crystals. Solubility tests may be required. CHEM 110 - Clinical Chemistry 1 – LO3 Page 63 Abnormal Crystals Abnormal crystals are rare and clinically significant. The chart below shows some of the abnormal crystals that can be found in urine sediment. All are found at an acid pH. Type Description Cystine Colourless hexagonal plates These crystals Leucine Yellow, oily looking spheres with radial striations. Tyrosine Fine needles or sheaves Cholesterol Colourless transparent plates with notched corners. These crystals are found in the urine of patients with maple syrup disease which is an error in leucine metabolism. The urine excreted has a characteristic maple syrup odour. Leucine crystals can also be found in severe liver disease. Leucine crystals should be confirmed by chemical solubility testing. These crystals are seen in tyrosinosis, a disease of tyrosine metabolism. They can be found together with leucine crystals in patients with severe liver disease such as terminal cirrhosis or severe viral hepatitis. Tyrosine crystals should be confirmed by chemical solubility testing. Found in patients with the nephrotic syndrome or severe urinary tract infection. Cholesterol is normally too large to pass through the glomerular barrier. Therefore, they should be accompanied by proteinuria and lipiduria. Bilirubin Delicate needles: Found in patients with liver disease where red brown in bilirubin is present in the urine. colour, may form balls Page 64 are diagnostic of cystinuria. It is an inherited metabolic disorder where cystine is not reabsorbed by the renal tubules. Formation of renal calculi composed of cystine may also occur. Cystine crystals should be confirmed by chemical solubility testing. CHEM 110 – Clinical Chemistry 1 – LO3