Exam 3 Flashcards
Excreted urine is normally ____% water, and ____% solutes
94% water, 6% solutes
3 solutes that are in the highest amounts in the urine
Urea, Chloride, and Sodium
3 solutes that are in the least amount in the urine
Uric acid, glucose, and albumin
What is the highest amount of solute present in the urine?
Urea
What is the lowest amount of solute present in the urine?
Albumin
Osmolality
the number of particles in a solution
Specific Gravity
The mass of solutes in solution
Urea vs NaCl affect on osmolality of urine
Urea does not dissociate, NaCl does. So 1 mole of NaCl has twice the osmolality of 1 mole of Urea
What does isosmotic mean? What is the osmolality of isosmotic urine?
The osmolality initial filtrate = osmolality of the plasma
Isosmotic urine is ~300 mOsm
What is the final osmolality of urine determined by?
The distal tubes and the collecting duct
What is the maximum urine osmolality possible? What is this limited by?
1400 mOsm/kg. This is limited by the medullary interstitium because urine can only become as hypertonic as that.
What is the normal urine osmolality range?
275-900 mOsm/kg
If ADH is present, osmolality ______ as water is ________ in the collecting ducts
increases; absorbed
ADH causes ______ of water which leads to ______ urine
reabsorption; concentrated
What secretes ADH?
Posterior pituitary gland
What is the normal urine-to-serum osmolality ratio (U/S)? What does this mean?
1.0-3.0. It means that urine osmolality should be 1-3 times greater than the serum osmolality
What does the U/S ratio evaluate?
the ability of the kidneys to properly concentrate the urine
What is normal urine specific gravity?
1.002-1.035
What affects specific gravity?
presence of large molecular weight solutes such as glucose, urea, and protein
What is the normal daily urine volume excretion?
500-1800 mL/day
Polyuria
Excretion of excessive amounts of urine (>3L a day)
Oliguria
decreased excretion of urine <400mL a day
Anuria
no urine excretion
Common feature of renal chronic diseases? What happens to SG and osmolality of the urine and why? What does this cause?
Inability to reabsorb and secrete solutes as it passes through the nephron.
SG and osmolality are the same as those of initial ultrafiltrate in Bowman’s space (1.010 and 300 mOsm/kg) They are isosmotic/isosthenuric.
This causes polyuria and nocturia.
What is the purpose of a fluid deprivation test?
It differentiates causes of water diuresis (neurogenic diabetes vs nephrogenic diabetes). It evaluates the renal concentrating ability of the kidneys.
Neurogenic diabetes
Defective ADH production or secretion
Nephrogenic diabetes
Lack of renal response to ADH
Describe the fluid deprivation test procedure.
- Patient drinks no fluids from 6pm-8am
- Urine specimen collected at 8am and osmolality determined (If urine osmolality is <800, test is continued. If urine osmolality is >800, this is normal and test is ended).
- Urine and serum specimen collected at 10am (If urine osmolality is >800 or U/S ratio is >3, normal and test is ended. If neither of these conditions are met, ADH is administered.
- ADH administered
- Urine and serum specimens collected at 2pm and 6pm
During the fluid deprivation test, what does a positive response to ADH administration indicate?
Urine osmolality is >800 or >3. The results indicate that the patient’s kidney can respond to ADH, but inadequate ADH is produced by patient (neurogenic diabetes).
During the fluid deprivation test, what does a negative response to ADH administration indicate?
Urine osmolality <800 or U/S ratio < 3.
These results indicate that the renal receptors for ADH are dysfunctional and your body is not responding to ADH (nephrogenic diabetes).
What is osmolar clearance?
It indicates the volume of water required to eliminate the solutes from the plasma
How do you calculate osmolar clearance (Cosm)?
Cosm (mL plasma per minute) = (Uosm/Sosm) x volume excreted by kidneys (mL/min)
What is the Cosm reference range?
2-3 mL/min
What is free water clearance?
The additional water that exceeds bodily needs and is eliminated in the urine
How to determine free water clearance? (Ch2o)
Ch2o (mL/min) = volume excreted by kidneys (mL/min) - Cosm (mL/min)
Total volume of urine excreted by the kidneys = _____ + _______
Cosm + Ch2o
What does it mean if Ch2o is negative?
Urine is concentrated due to dehydration; urine is hyperosmotic or hypertonic (Uosm > Sosm)
What does it mean if Ch2o is positive?
Urine is dilute because of water diuresis. Urine is hypo-osmotic or hypotonic (Uosm < Sosm)
What does it mean if Ch2o is zero?
Total urine volume = osmolar clearance volume. Urine is isosmotic (Uosm = Sosm) No excess water is being eliminated.
Normal GFR
greater than or equal to 60 mL/min
What does a GFR of <60 indicate?
kidney disease
What does a GFR of <15 mean?
Kidney failure
Briefly describe Inulin clearance test. Pro/Con?
Used to assess GFR; It readily passes glomerular filtration barriers and is not reabsorbed or secreted. It is the ideal substance for determining GFR but it is not practical for routine GFR because it must be administered IV
What is the most used clearance test for routine assessment of GFR?
Creatinine clearance
Most accurate creatinine clearance is obtained using a _____ urine specimen.
24-hour
What is the external body surface area of an average individual?
1.73 meters squared
Creatinine clearance depends directly on ________.
Muscle mass
Creatinine clearance calculation
C (mL/min) = U x V 1.73 m^2
_____ x _______
P SA
What do creatinine clearance results tell us?
Measure of GFR to help us determine/evaluate renal function
What is the purpose of an eGFR? When would we use it? What is the calculation based on?
Assists in detecting chronic kidney disease. We would use it whenever a serum creatinine test is performed on patients > 18 y.o.
The calculation is based on serum creatinine level, age, gender, and ethnicity
What are substances that can be used for clearance tests? Which are more sensitive and specific?
Creatinine, Inulin, Cystatin C, and B2-Microglobulin
Cystatin C and B2-microglobulin are more sensitive and specific biomarkers than creatinine
What is the purpose of screening for microalbuminuria?
It monitors diabetes mellitus patients for detection and treatment of early nephropathy
What is the most important factor leading to proteinuria?
Hyperglycemia
What is the most common test used to measure RPF?
P-aminohippurate clearance test
What is renal tubular acidosis? What test is used to measure this?
Patients excrete alkaline urine despite a systemic acidosis. Oral Ammonium Chloride Test is used.
Normal serum osmolality
275-300 mOsm/kg
List the 4 types of renal disease
- glomerular
- tubular
- interstitial
- vascular
Primary glomerular disorders:
Called glomerulonephritides; consist of several different types of glomerulonephritis. Affect glomerulus directly
Secondary glomerular diseases
Initially and principally involve other organs
What is the primary mode of glomerular injury? What does glomerular damage result from?
Immune-mediated processes (antigen and antibody complexes)
Glomerular damage results from chemical mediators and toxic substances
Features that characterize glomerular damage (NEPHRITIC syndrome)
Hematuria, proteinuria, oliguria, azotemia, edema, hypertension
Features that characterize NEPHROTIC syndrome
Heavy, LARGE amounts or proteinuria (>3.5g/day), hypoproteinemia, hyperlipidemia, lipiduria, generalized edema
Describe the glomerulonephritide acute glomerulonephritis (AGN)
Main cause is streptococcal infection - occurs 1-2 weeks after a strep infection and mostly seen in children
Describe the glomerulonephritide Rapidly Progressive Glomerulonephritis (RPGN)
AKA Crescentic glomerulonephritis because there is cellular proliferation in Bowman’s capsule that forms crescents - leukocyte infiltration and fibrin deposition in crescents
Describe the glomerulonephritide Membranous Glomerulonephritis (MGN)
Basement membrane thickening leading to LOSS OF THE FOOT PROCESSES
COMPLEMENT ACTIVATION is responsible for the glomerular damage
This is the MAJOR CAUSE of the NEPHROTIC syndrome in adults
What is the major cause of nephrotic syndrome in adults?
Membranous Glomerulonephritis
Describe the glomerulonephritide Minimal Change Disease (MCD)
Dysfunction of T-cell immunity
MOST COMMON CAUSE OF NEPHROTIC SYNDROME IN CHILDREN
What is the most common cause of nephrotic syndrome in children?
Minimal Change Disease (MCD)
Describe the glomerulonephritide Focal Segmented Glomerulosclerosis (FSGS)
Sclerosis of glomeruli characterized most by diffuse damage to the glomerular epithelium (podocytes)
*CAN RECUR AFTER RENAL TRANSPLANTATION
What glomerulonephritide can recur after renal transplantation?
FSGS
Describe the glomerulonephritide MPGN
Most cases are immune mediated caused by cellular prolifeation, leukocyte infiltration, and thickening of basement membrane
4 distinct morphological changes of glomerulus in glomerular diseases
- cellular proliferation
- leukocytic infiltration
- basement membrane thickening
- hyalinization with sclerosis
Describe the glomerulonephritide IgA nephropathy
Deposition of IgA in the glomerular mesangium
*ONE OF THE MOST PREVALENT TYPES OF GLOMERULONEPHRITIDES WORLDWIDE
What is the most prevalent types of glomerulonephritides worldwide?
IgA nephropathy
What is ATN? What are the two types? What do 50% of all cases of ATN result from?
Acute Tubular Necrosis - Characterized by the destruction of renal tubular epithelial cells
2 Types: Ischemic ATN and Toxic ATN
50% of all cases result from surgical procedures
Differentiate between Ischemic ATN and Toxic ATN
Ischemic: follows a hypotensive event that results in decreased perfusion of the kidneys followed by renal tissue ischemia
Toxic ATN: results from exposure to nephrotoxic agents
Tubular damage caused by either form of ATN is _________.
reversible
What is Fanconi’s syndrome?
Loss of proximal tubular function - amino acids, glucose, water, phosphorous, potassium, calcium are NOT reabsorbed. They are excreted in urine
Renal glucosuria
Excretion of glucose in the urine despite normal blood glucose levels
Renal phosphaturia
Inability of distal tubules to reabsorb inorganic phosphorous
Renal tubular acidosis
Will not produce an acid urine
Tubulointerstitial disease
Diseases involving the renal interstitium and tubules; closely involved with UTIs
Lower UTI involves:
urethra, bladder, or both
Infection of the renal pelvis
Pyelitis
Infection of the renal pelvis and interstitium
Pyelonephritis
Upper UTI involves:
renal pelvis alone or with interstitium
Most common UTI pathogen
E. coli
What differentiates lower UTIs from upper UTIs?
No pathological casts in lower UTI; in upper UTI there is presence of casts
Chronic pyelonephritis
persistent inflammation causes permanent scarring that involves the renal calyces and pelvis
Acute Interstitial Nephritis (AIN) most common cause? What will be seen in routine UA results with AIN?
acute allograft rejection of a transplanted kidney.
*Increased eosinophils!
What can vascular disease lead to?
Disorders that alter blood vessels or the blood supply to the kidney can lead to renal disease
What is a frequent finding in many kidney disorders?
Hypertension
What is acute renal failure? What are the three types of acute renal failure?
Characterized by sudden decrease in GFR, azotemia, and oliguria
1. prerenal ARF
2. Renal ARF
3. Postrenal ARF
What is prerenal acute renal failure a result from? How does it affect sodium in the urine?
A decrease in renal blood flow. Low urine sodium
What is renal acute renal failure characterized by? How does it affect sodium levels in the urine?
Renal damage; increased urine sodium
What is postrenal acute renal failure?
Obstructions in urine flow
Describe chronic renal failure. How is this different from ARF?
Progressive loss of renal function leading to irreversible and intrinsic renal disease that eventually progresses to end-stage renal disease.
This is more serious than ARF and the GFR slowly decreases instead of sudden decrease like in ARF.
What are calculi made of?
75% Calcium
4 factors influencing calculus formation
- Increased concentration of chemical salts in urine
- Optimal urinary pH (isohydruria: constant/unchanging urinary pH)
- Urinary stasis (not peeing often)
- Nucleation or initial crystal formation
What type of UTI are staghorn stones associated with? What is another name for these stones?
Upper UTIs caused by urea-splitting organisms. They are called struvite stones
What is renal colic?
Pain while passing a kidney stone
Name and describe the 3 different types of aminoacidurias
- Overflow (increase in plasma levels of the amino acid due to renal threshold being exceeded)
- No-threshold (amino acids are not reabsorbed by the tubules, so any increase in the blood = increased quantity in the urine)
- Renal (amino acids are not reabsorbed due to a tubular defect)
Cystinosis
Lysosomal storage disease that results in intracellular deposit of cystine in the lysosomes
Differentiate between Nephropathic cystinosis, Intermediate cystinosis, and Ocular cystinosis.
Nephropathic: most common and severe form, deposition of cystine crystals in proximal tubular cells can cause Fanconi’s syndrome
Intermediate cystinosis: slower rate of progression
Ocular cystinosis: manifest only ocular impairment
Cystinuria
Cystine crystals in the urine
What is excreted in the urine from a patient with Maple Syrup Urine Disease?
What is responsible for the smell of maple syrup?
Leucine, Isoleucine, Valine.
Ketoacids are responsible
What is excreted in the urine with Phenylketonuria? Why is this? What is the smell of urine of someone with this disease?
Phenylpyruvic acid (a ketone) and its metabolites. This is due to the enzyme phenylalanine hydroxylase being deficient or defective. This causes a mousy/barny smell.
Alkaptonuria - what is excreted in the urine? Why? What does this cause the color of urine?
Homogentistic acid due to decreased levels of the enzyme homogentistic acid oxidase. This causes black urine.
What is ochronosis?
Pigmentation in the ears associated with Alkaptonuria
What is diabetes mellitus characterized by?
Hyperglycemia and glucosuria
Type I vs Type II diabetes
Type I: insulin-dependent (requires insulin injections due to no production of insulin) symptoms include polyuria and polydipsia
Type II: non-insulin dependent (associated with obesity, body cannot use insulin properly)
Diabetes is the leading cause of:
Blindness
End-stage renal disease
Nontraumatic limb amputations
Type I galactosemia: deficiency of ____ enzyme
GALT; THE MOST COMMON FORM!
Type II galactosemia - deficiency of _____ enzyme? Predominant clinical feature?
GALK enzyme. Cataracts
Type III galactosemia: deficiency of ______ enzyme?
GALE
Neurogenic diabetes insipidus
Synthesis and release of ADH are reduced
Nephrogenic diabetes
Normal synthesis and release of ADH, but defective renal tubular response to ADH
What is different about diabetes insipidus when compared to diabetes mellitus? similar?
DI patients have a low SG with no glucose in urine
DM patients have a high SG with glucose in urine
Both DI and DM have polyuria and polydipsia
Porphyrias
Accumulation of porphyrins in the urine; turns urine port-wine color
Clinical presentation of porphyria
Accumulation of neurotoxic porphyrin precursors, and cutaneous lesions or a burning sensation
Port-wine color urine
