Miscellaneous Urine Testing and Fecal Testing Flashcards
Phsyiologic process that leads to eventual hemosiderin in the blood
- RBCs break in the lumen of the vessel
- Haptoglobin picks up the free hemoglobin
- Haptoglobin-hemoglobin complex goes to the liver for further catabolism
- Any unbound hemoglobin is filtered by the glomerulus and enters the urine
- PCT reabsorbs hemoglobin and will catabolize to form biliverdin (degrades into bilirubin) and ferritin
- Ferritin denatures into hemosiderin
Ferritin
- Water solubility
Water soluble
Ferritin
- Visibility w/ a light microscope
Not visible w/ a light microscope
Ferritin
- Visibility w/ an iron stain
Prussian blue negative
Hemosiderin
- Water solubility
Insoluble in water
Hemosiderin
- Visiblity w/ a light microscope
Visible w/ a light microscope
Hemosiderin
- Visibility w/ iron stain
Prussian blue positive
Causes of hemosiderinuria
- Intravascular hemolysis
- Ineffective erythropoietin
- Diseases requiring multiple blood txns
- Primary hemochromatosis
What does hemosiderin look like in a urine analysis?
- Will be found either free, w/in renal tubular cells, or in casts
- Yellow-brownish in color
What is the time delay b/w the hemolytic episode and the formation of hemosiderin granules?
Hemosiderinuria is positive 2-3 days after an acute hemolytic episode and may persist for weeks for patients w/ or w/o a healthy liver
____ is uncommon in patients w/ a healthy liver
Bilirubinuria
Causes of myoglobinuria
- Rhabdomylosis
- Trauma (crushing injury to muscle, extensive muscular activity, myocardial infarction, contact sports)
- Infections (sometimes w/ EBV and influenza)
- Toxins (Alcohol, CO, angel dust = PCP)
- Primary muscle diseases (polymyositis, dermatomyositis)
- Hereditary (Familial Paroxysmal Myoglobinuria)
____ is extremely toxic to the kidneys
Myoglobin
If myoglobin is positive in the urine, physicians may induce diuresis w/ ____ or perform ____ ____ in order to prevent renal damage
Mannitol; renal dialysis
What does myoglobin look like in the urine?
- Urine is red if fresh; light brown or black upon standing
- RBCs may be in sediment
- Reduced urine volume
- Positive reagent strip for hemoglobin/blood
Two confirmatory methods for myoglobinuria
- Chromatography
- Ammonium Sulfate Method
Describe the ammonium sulfate confirmatory test
- Causes hemoglobin to precipitate out of solution
- Positive strip testing following the addition of ammonium sulfate and centrifugation will confirm
Three types of diarrhea
- Secretory
- Osmotic
- Hypermobility
Secretory diarrhea
- “Definition”
- What causes it?
- Def: increased secretion of water into the lumen
- Caused by enterotoxin-producing organisms
Osmotic diarrhea
- “Definition”
- What causes it?
- Def: injection of osmotically active solutes preventing water absorption
- Caused by maldigestion and/or malabsorption
What causes maldigestion leading to osmotic diarrhea?
- Def: pancreatic or hepatic disorder preventing the conversion of foodstuffs into readily absorbable substances
- Caused by lactose intolerance, fructose intolerance
What causes malabsorption leading to osmotic diarrhe?
- Def: normal digestive ability but inability to properly absorb foodstuffs
- Caused by celiac disease, tropical sprue, ulcerative colitis, surgical procedures
Hypermobility diarrhea
- “Definition”
- What acuases it?
- Def: decreases fecal matter’s transit time
- Caused by laxatives, fibers, nerves, hormones, emotions, gasterectomy, gastric bypass
Why is stool brown?
Urobilinogen → stercobilinogen → urobilin
Appearance
- Pale stool = ?
Blockage of bile duct preventing conjugated bilirubin from entering the small intestine
Appearance
- Black tarry stool = ?
Blood from eosphagus, stomach, duodenum
- Blood from colon usually appears bright red
Appearance
- Small-hard stools = ?
Constipation
Appearance
- Slender ribbon-like stools = ?
Obstruction
Appearance
- Mucus-coated stool = ?
Intestinal inflammation or irritation (Crohns and colitis)
This occurs when fecal fat exceeds 7g/day
Steatorrhea
What causes malabsorption leading to steatorrhea?
- Celiac disease
- Lymphoma
- Whipple’s disease
What causes maldigestion leading to steatorrhea?
- ↓ pancreatic enzymes → pancreatitis, cystic fibrosis, pancreatic cancer
- ↓ bile acid enzymes → hepatocellualr disease, bile duct obstruction
Steatorrhea
- Physical characteristics
Pale, greasy, spongy, pasty, extremely foul smelling
Steatorrhea
- Stains
Sudan III, Sudan IV, Oil Red O stains (neutral fats stain an orange-red color)
How many fat globules of neutral fat/hpf will normal feces contain?
< 60 globules/hpf; patients w/ steatorrhea will have more
Steatorrhea
- Polarized microscopy
?
Two methods of occult blood testing
- Guaiac-based fecal occult blood (hemoccult)
- Immunochemical fecal occult blood (hemosure)
Guaiac-based fecal occult blood
- Principle
Based on the pseudoperoxidase properties of hemoglobin, other peroxidasess will interfere
Guaiac-based fecal occult blood
- Sensitivity
Not very sensitive so it won’t detect the normal amounts of blood found in stool
Guaiac-based fecal occult blood
- Specificity
?
Immunochemical fecal occult blood
- Principle
Uses polyclonal Abs directed aginst the globin portion of UNDEGRADED human hemoglobin (blood from LARGE intestine)
Immunochemical fecal occult blood
- Sensitivity
Since hemoglobin will degrade in the GI system, these tests are most sensitive to hemoglobin originating in the large intestine
Immunochemical fecal occult blood
- Specificity
?
Guaiac-based fecal occultl blood
- False positives
- Rare red meats
- Certain vegetables and fruits
- Salicylates and NSAIDS (w/in prior to 7 days)
Guaiac-based fecal occult blood
- False negatives
Ascorbic acid
Apt test
- Principle
- Used to test fetal feces for the presence of maternal blood
- Based on relative resistance of fetal hemoglobin to alkali denaturation compared to adult hemoglobin A
- Adult hemoglobin denatures to yellow-brown hematin in alkali solutions
