Kidney Disease Patho Flashcards
Kidneys
- Paired, retroperitoneal organs just above the lower edge of ribs bilaterally
- Received 20-25% of cardiac output
- Functional units = nephrons
- Born with ~1 million/kidney, do NOT regenerate
AKI
- Acute Kidney Injury
- Abrupt/rapid decrease in kidney functional
- Possibly reversible if correct early
CKD
- Chronic Kidney Disease
- Progressive decrease in kidney function
- Often irreversible
Types of AKI
- Prerenal
- Intrinsic - focus on drug-induced causes
- Postrenal
Prerenal AKI
- Volume depletion - hemorrhage, GI losses, renal losses, skin loss, etc.
- Decrease in BV - decreased CO, pulmonary hypertension, valvular disease, liver failure, sepsis, etc.
- Functional - NSAIDs, ACEIs, ARBs, etc.
Intrinsic AKI
- Vascular damage
- Glomerular damage
- Acute tubular necrosis
- Acute interstitial nephritis
AKI Patho
- Common denominator: decreased renal blood flow
- Prerenal: compromised kidney perfusion leads to decreased GFR
- Intrinsic: glomerular/tubular injury causing release of renal afferent arteriole vasoconstrictors
- Postrenal: obstruction of urinary tract increases tubular pressure and decreases the filtration driving force
- Decreased renal blood flow leads to cell ischemia and death
Glomerularnephritis
Causes by immune diseases, infections, and drugs
-Immune diseases: lupus, IgA nephropathy
-Infections: Stept, bacterial endocarditis
-Drugs: chronic heroin abuse
Symptoms: proteinuria, hematuria, edema, increased blood pressure, RBCs = mickey mouse
Polycystic Kidney Disease
- Hereditary
- Form noncancerous fluid-filled sacs
- Disrupts kidney function
- Presentation: enlarged abdomen, flank pain, hematuria, frequent UTI, increased BP
Other Diseases Causing AKI
- Urinary tract obstruction: BPH
- Anatomic urinary tract abnormalities - reflux
- Recurrent UTI
- Kidney stones
- Unrecovered AKI
- Drug-induced kidney disease
CKD Hypothesis
- Initial kidney injury via decreased nephron mass or increased metabolic demand
- Increased workload for remaining nephrons to maintain similar level of solute excretion
- Residual nephrons compensate (renal reserve) => hypertrophy and hyperfiltration
- Typically signs/symptoms are absent early on
Adaptions = Maladaptive
- Residual nephron hyperfilter and hypertrophy to maintain GFR but also progress CKD
- Increases glomerular capillary pressure, damages capillaries, leads to glomerulosclerosis
- Signs/symptoms may not be apparent until 75% of nephrons or more are lost
Functions of Kidney (6)
- Waste Product Excretion: removal of urea, creatinine, drugs, etc.
- Bone Structure: vitamin D activation, calcium/phosphorous balance
- Blood Formation: EPO synthesis
- Blood Pressure: renin synthesis, sodium removal, water balance
- Acid-Base Regulation: H+/NH4+/HCO3- balance
- Cardiac Activity: potassium balance
AKI Definition
- Increased SCr >= 0.3 mg/dL within 48 hours
- Increased SCr >= 1.5 from baseline within 7 days
- Decreased urine volume <0.5 mL/kg/hour for 6 hours
CKD Definition
-Abnormalities in kidney structure/function preset for 3 or more months
AND
-Implications for health
-Could also be defined by structural abnormalities AND/OR eGFR decreases
Uremia
- Accumulation of nitrogenous waste products
- Tons of symptoms associated with ESRD
- Slide 18
AKI/CKD Relationships
AKI
- Increased risk of CKD/ESRD
- Possible AKI outcomes: GFR returning to baseline, decreased GFR, ESRD
CKD
- Increased risk of AKI
- *Go hand in hand**
Assessment of Kidney Function Options
- Blood urea nitrogen (BUN)
- SCr
BUN
- Concentration increases in bloodstream as kidney function decreases
- Less useful than SCr since it can be affects by outside factors
Factors that Raise BUN
- High protein diets
- Corticosteoids and tetracyclines (catabolic effects)
- Upper GI bleed
- Dehydration
Factors that Lower BUN
- Malnourished
- Liver disease
Cockcroft Gault Equation Information
- Estimates kidney function in adults for medication dosing
- Use IBW for normal weight patients, ABW for obese patients, and TBW for underweight patients for BW in equation
- CrCl: mL/min
- BW: kg
- SCr: mg/dL
Cockcroft Gault Equation
CrCl = [(140-age) * BW/72 * SCr] * (0.85 if female)
MDRD Equation
- Estimates GFR normalized to 1.73 m^2
- Used to stage CKD and for drug dosing
CKD-EPI Equation
- eGFR standardized
- K = 0.7 for females and 0.9 for males
- alpha = -0.329 for females and -0.411 for males
Urinalysis
- Tested for physical and chemical characteristics, microscopic exam of voided urine
- Helps with diagnosis of renal disease and could contain early warning signs
Macroscopic Analysis of Urine
- Color
- Clarity
- Smell
Color
- Can change dramatically based on hydration and urine concentration
- Color varies from colorless to dark yellow normally
Red => Orange Urine Causes
- Myoglobin: crush injuries, seizures, cocaine-induced muscle damage
- Hgb/RBC: hemolysis (drugs, strenuous exercise), menstruation contamination, kidney stones
- Food: carrots, beets, rhubarb
- Drugs: rifampin, azo
Brown => Black Urine Causes
- Myoglobin: crush injuries, seizures, cocaine-induced muscle damage
- Bile pigments: hemolysis, bleed into tissues, liver disease
- Drugs: metronidazole, nitrofuratoin
Blue => Green Urine Causes
-Drugs: Propofol and Amitriptyline
Clarity
- Normal = clear
- Turbidity: sign of excessive cellular material from crystals or infection
- Foam: proteinuria
Formed Elements in Urine
- Cells, casts, or crystals
- Microorganisms: contamination, UTI
- Reference: 0 to trace
Cells in Urine
RBCs: reference = 0-3/hpf
-glomerulonephritis, infection, stones, polycystic disease
WBCs: reference = 0-2/hpf
-UTI, pyelonephritis, eosinophilurea
Tubular epithelial: reference = 0-1/hpt
-Tubular damage => acute tubular necrosis
Squamous cells
-Lower genital tract or skin contamination
Casts
- Cylindrical mass of proteins and/or cells
- Few clear casts = normal
- RBCs always pathological: renal hematuria, glomerulonephritis
- WBCs - pyelonephritis or acute interstitial nephritis
- Granular: pathogenic, acute tubular necrosis
Crystals
- Stores: calcium oxalate, uric acid, cystine
- Drugs: acyclovir, sulfonamides
Urine Chemistry Elements
- pH
- Specific Gravity
- Protein
- Glucose
- Ketone
- Nitrite
- Leukocyte estrase
pH + Urine
- Reference = 5-8
- Changes from acid-base disorders, various diseases, and drugs
Specific Gravity + Urine
- Reference = 1.003-1.030
- Measures urine concentrating capability of kidneys
- Low specific gravity occurs with diabetes insipidus
- High specific gravity with syndrome of inappropriate antidiuretic hormone
Protein + Urine
- Reference = negative
- Marker of kidney damage
- Mild: 0 to +1 (10-30 mg/dL)
- Moderate: +2 to +3 (100-300 mg/dL)
- Overt: +4 (>2000 mg/dL
Glucose + Urine
- Reference = negative
- Once blood glucose exceeds 180 mg/dL, more will appear in urine than normal
- Due to uncontrolled DM
Ketone + Urine
- Reference = negative
- Diabetic ketoacidosis
- Fasting starvation
- High ketone diets
Nitrite + Urine
- Reference = negative
- Nitrate converted to nitrite by bacteria
- Usually a marker of UTIs or other bacterial infections
Leukocyte Estrase + Urine
- Reference = negative
- Enzyme released from white blood cells
- Suggestive of UTI or other infection
