Urinalysis, Urine Studies and Kidney Disease Flashcards
- Describe the methods to analyze urine focusing on appearance and odor.
color: red (hematuria), bile pigments(liver failure), cloudy (infection), white/milky (chyluria), foods
turbidity: cloudy (UTI or hematuria)
odor: genetic conditions (maple syrup, phenylketonuria (musty), rancid (hypermthioniemia or tyrosinemia)); fruity (ketones)
- Explain the significance of finding protein in the urine by the dipstick.
associated with poor renal outcomes and epithelial dysfunction in the renal tubules
due to damage of capillary wall or podocytes, dipstick is qualitative and is specific for albumin only, electrophoresis may be necessary for urinary proteins other than albumin
- Explain the significance of a positive blood test by the dipstick.
dysmorphic cells (glomerular disease) caused by RBC passing through GBM an going through high tonicity of renal tubule (glomerulonephritis causing spicules, blebs, or vesicles- acanthocyte 80% hematuria is non-glomerular
may be positive if the urine contains free hemoglobin or myoglobin; RBC confirm blood not hemoglobinura or myoglobinuria
- Describe what microalbunminuria is, and explain the significance in a patient with diabetes mellitus.
in diabetics, persistent microalbuminuria can lead to diabetic nephropathy; important to check regularly
microalbuminuria is between 30 and 300 mg per 1 g of creatinine, detection requires special methods such as enzyme lined immunosobent assay with antibodies
- Identify the various cells that can be seen on microscopy of the urine sediment and explain their clinical significance.
RBC- acanthocytes of glomerulonephritis
WBC- inflammation or infection
transitional epithelial cell- infection or neoplasia
renal tubular cell- inflammation or ATN
- Identify the various casts that can be seen on microscopy of the urine sediment and explain their clinical significance.
casts: uromodulin precipitates and entraps cells (favored in dehydration or acid urine)
hyaline-in normal individuals
granular are usually pathologic (fine or coarse granular) from serum proteins or embedded cells
muddy brown casts (course granular cast in ATN)
glomerulonephritis hallmark of RBC cast
WBC: pyelonephritis, interstitial nephritis and tubulointerstitial disorders
waxy/broad: form in dilated and atrophic tubules due to chronic parenchymal disease
- Identify the various crystals that can be seen on microscopy of the urine sediment and explain their clinical significance.
calcium oxalate (double pyramids or dumbbell): ethylene glycol toxicity, kidney stones
triple phosphate (coffin-lid): with urea splitting organisms ie. Proteus
urate (rhomboid or needle)- gout
cysteine (hexagonal): kidney stones in children, tubular transport defect or stones
indinavir (starburst): protease inhibitor of HIV tx.
- Correlate urinary abnormalities with some common kidney diseases.
nephrotic syndrome: proteinuria, hyperlipidemia/lipiduria
hematuria: anti-glomerular BM and vasultidities or immune complex mediated disease and injury due to infection; in patients older than 50, important to rule out malignancy
episodes of gross hematuria: Alport’s syndrome or thin BM syndrome or IgA nephropathy
- Understand the clinical rationale four urine studies such as urine osmolality and urinary electrolytes and apply them appropriately to clinical problems.
specific gravity is a convenient and rapidly obtained indicator of osmolality
isosthernuric urine is same concentration as serum (hyperglycemia, diuretics, ATN)
hypostheuric urine is less dense than serum (over hydration, primary polydipsia or diabetes insipid us)
hypersthenuric urine implies preserved concentrating ability in the absence of proteinuria/glycosuria
SPG> 1.040 indicates extrinsic osmotic agent (contrast)
- Understand the clinical use and limitation of urine collections for GFR and protein.
24hr urine collection is inconvenient for the patient but may be useful in detecting nephrotic syndrome through analysis for protein (quantification of protein)
getting a creatinine can also tell you the quality of the collection, ratio of 3.5 is getting into the nephrotic range
notice also that the quantitative measurements on dipstick can be altered based on the amount of water a patient is drinking
Define urinalysis.
the physical, chemical and microscopic examination of urine
List important aspects of urine collection and processing that are important to remember.
clean catch, midstream of the first or second urine of the day (not doing menses)
urine should not sit for long periods of time (avoid lysis) and refrigeration can precipitate phosphates or uric acid
- Describe the methods to analyze urine: dipstick for protein, blood and other substances. (pH, hemoglobin/blood, glucose, protein)
pH: high (infection, diuretics, vomitting); low (academia, high protein diet or meds)
blood (peroxidase reaction): if dipstick is positive but micro is negative means cells have lysed (hemoglobin/myoglobin), false negative vitamin C
glucose (oxidase reaction): highly specific
protein: highly sensitive to albumin, but not at low levels (false positive with quat. ammonium); alt tests include acid precipitation, SPEP/UPEP - light chains, 24h urine collection, spot urine protein
bile pigments: very little clinical use
ketones: does not detect B-hydroxybutyrate (often 80%)
leukocyte esterase (WBC) false (-) high protein, glucose, tetracycline and cephalexin, excess oxalate
nitrate (bacteria that reduce nitrates): does not reduce Pseudomonas, N gonorrhoeae, Strep faecalis, Enterococcus or M. tb
- Describe the methods to analyze urine: microscopic evaluation of urine sediment.
mount filtrate of urine collection
cellular elements: RBC, WBC, epithelial cells (squamous, transitional)
casts
cystals
urine fat/lipids- nephrotic syndrome (Maltese Crosses)
microorganisms (bacteria, fungi, Trichomonas, Schistosoma haematobium)
Describe the correlation between urine protein and creatinine.
direct correlation between the two; 1:1
