Kidneys: Part 1 (paulson) Flashcards
Basic Renal Function:
-list the 3 main functions of the kidney
- Filtration of the blood
- Regulating blood volume & blood pressure
- Producing erythropoietin
Describe how the kidneys filter blood
- -Removal of waste
- -Maintaining proper concentrations of electrolytes
- -Maintaining acid/base balance
Nephron=
The basic functional unit of the kidney
Nephron contains:
- glomerulus
- Renal tubule
Glomerulus:
-fx?
Site of blood filtration
Renal tubule:
-fx?
Where water and salts are resorbed
Proximal Convoluted Tubule (PCT) reabsorbs ___% of the glomerular filtrate
60%
Proximal Convoluted Tubule (PCT)
-describe the glomerular filtrate reabsorption breakdown (i.e. %’s of each reabsorbed electrolyte)
- Sodium, Potassium, & Calcium= 65%
- Phosphate, Water, & Bicarbonate= 80%
- Glucose & Amino acids= 100%
Proximal Convoluted Tubule (PCT): other functions?
-Secretes drugs/toxins that are too big (or protein-bound) to be filtered
- Water reabsorbed passively
- ->Driven by osmotic gradient from reabsorption of other solutes
-Makes ammonia from glutamine (acidifies urine)
100% of glucose should be reabsorbed UNDER normal glucose levels. But once glucose gets to ____ it starts spilling into the urine (glucose in urine indicates elevated glucose levels and there might be damage in the proximal convoluted tubule)
200
Loop of Henle consists of __ segments
4
List the 4 segments of the loop of henle
- Thin descending limb (DLH)
- Thin ascending limb (ALH)
- Medullary thick ascending limb (mTALH)
- Cortical thick ascending limb (cTALH)
What is the overall fx of the loop of henle?
Creates a concentration gradient and forms concentrated urine (aka concentrates the urine further)
Distal Convoluted Tubule (DCT)
-is mainly involved in ___ & ___ reabsorption
- *sodium & calcium reabsorption
- -Reabsorbs another 5-10% of sodium
- -10-15% of calcium reabsorption
what is the DCT regulated by?
Regulated by PTH and Vitamin D
Collecting Tubule:
list all functions
- NaCl reabsorption
- Bicarb reabsorption
- Potassium excretion
- H+ excretion
- Water reabsorption–>Urine concentration
- Urea excreted
- Regulates urine volume
Memorize this slide for the exam
-basically the kidney is trying to concentrate the urine and trying to excrete the things it doesn’t need, and reabsorb what the body does need
slide 8 pic
Acute Renal Failure (ARF) AKA Acute Kidney Injury (AKI)=
=Rapid worsening of renal function
AKI is indicated by quickly rising ____ OR the accumulation of _______
- -Quickly rising BUN/Cr
- -nitrogenous wastes in the blood
Acute Renal Failure (ARF) AKA Acute Kidney Injury (AKI) is caused by a variety of disorders (list 3 categories)
- Prerenal
- Postrenal
- Intrarenal
BUN=
blood urea nitrogen
If you had 1 test to order for kidney issues (what is the best test?)
BMP
Which Pt demographic gets AKI?
- No particular race or age more than others
- -Underlying etiologies for each type do have certain groups more likely to acquire
- Up to about 10% of people in the hospital
- Up to 2/3 of patients in the ICU
- About 1% of patients develop after general surgery
(think sick Pts)
AKI-Definition according to AKIN/KDIGO (memorize)
- Criteria vary widely
- **Abrupt (within 48 hours) absolute increase in the serum creatinine of ≥0.3 mg/dl above baseline –or-
- **Serum creatinine increases ≥50% (known or presumed to have occurred in the past 7 days) -or-
**Oliguria of <0.5 ml/kg/hour for >6 hours
oliguria=
one of the earliest signs of impaired renal function (just know– some urine production but NOT as much as there should be) aka decreased urinary output
Pt weighs 100 Kg:
-what is their normal urine output per 6 hours?
100 Kg x .5ml = 50mL per hour–> so normal should be around 300 mL per 6 hrs
Criteria for acute kidney injury
-slide 12
image
AKI: clinical Sx
Weakness/lethargy Anorexia Nausea/vomiting General malaise Diarrhea Pruritis Drowsiness Hiccups SOB Dizziness
AKI: clinical features
- -> prerenal: (list Sx)
- ->postrenal (list Sx)
-list ex’s of general clinical features
- Usually point toward the underlying cause
- -Ie: Prerenal, could be tachycardic and hypotensive
- -Postrenal: distended bladder, CVA tenderness, enlarged prostate
- Anuria or oliguria
- Change in volume status/weight
- Change in mental status
- Edema
- Weakness
AKI: diagnostic tests?
-**BMP
- Urinalysis & urine microscopy:
- ->Urine culture
- Measurement of urine output
- Renal ultrasound
- May add urine spot for osmolality, urine sodium, creatinine
AKI:
-list possible Life-Threatening Complications
- Hyperkalemia
- Fluid overload
- Signs of uremia
- Severe metabolic acidosis (pH <7.1)
Ex’s of signs of uremia
Ie: pericarditis, altered mental status
AKI: tx depends on the ____
CAUSE
AKI: tx
-dialyze if:
- Serum creatinine >5-10 mg/dl
- Unresponsive acidosis
- Severe electrolyte disorders
- Fluid overload
- Uremic complications
What is the MC cause of AKI?
prerenal failure
Prerenal failure=
- Reduced effective blood circulating to kidney
- Rapidly reversible if underlying cause found and corrected–> Kidneys themselves OK
Describe the causes of reduced effective blood circulating to the kidney (in prerenal failure)
-Absolute reduction in fluid volume (ie: hemorrhage or dehydration) –or-
-Effective volume depletion
CHF, cirrhosis (hepatorenal syndrome)
True Intravascular Volume Depletion (list ex’s)
- Hemorrhage
- Burns
- Diuretics
- Dehydration
- GI losses
- Vomiting
- Diarrhea
- Enteric fistula
Decreased Effective Circulating Volume (list causes)
- CHF
- Cardiac tamponade
- Aortic stenosis
- Cirrhosis with ascites
- Nephrotic syndrome
Impaired Renal Blood Flow (list 4 causes)
ACEI
NSAIDs
Renal artery stenosis
Renal vein thrombosis
Labs that distinguish prerenal failure (memorize)
- Serum BUN:Cr ratio: ≥20:1
- Urine sodium: <20 meq/L
- Fractional Excretion of Sodium (FENa): <1%
- ->Measures the percent of sodium filtered by the kidney that is excreted into urine
-Urine specific gravity: >1.020
–>Occur because the kidney is responding to prerenal failure by increasing reabsorption
Prerenal failure: tx
Correct the underlying cause! Ie:
- CHF: Diurese the patient
- Dehydration: IVF
- Hemorrhage: Blood + fluids
Postrenal failure:
- how common?
- describe how postrenal failure occurs (hint: what is blocked?)
Least common of the 3 main types of renal failure
Postrenal= ureters, bladder, urethra (**Blockage here causes renal failure)
Postrenal failure: etiology
- Nephrolithiasis
- BPH
- Obstructing tumor within the -GU system (or adjacent ie: cervical cancer)
- Bladder outlet obstruction
- Blood clots within the urinary tract
- Medications (ie anticholinergics)
- Neurogenic bladder
Postrenal failure: clinical Sx
- May have abdominal or groin pain, bladder discomfort
- Mass at flank, suprapubic area, or abdomen
- Rectal exam
- Pelvic exam
- Anuria
anuria=
failure of the kidneys to produce urine.
Postrenal failure: diagnostic labs?
- Post-void residual >100 ml –> bladder outlet obstruction
- Ultrasound or IVP (Intravenous pyelogram)–> Dilated ureters or renal pelvis
- Abdominal CT?–> Eval for mass
Postrenal failure: tx?
-Relieve the obstruction!
- May:
- -Catheterize patient
- -Nephrostomy tube
- -Stenting
- -Lithotripsy
- -Perform surgery to remove a mass
Intrinsic Renal Failure=
- One or both kidneys have been damaged and don’t work properly
- Some causes happen quickly, whereas others develop over time
Intrinsic Renal Failure: Causes (list 5)
- Acute tubular necrosis (ATN)= MC cause of intrinsic AKI
- Nephrotoxins
- Interstitial diseases
- Glomerulonephritis
- Vascular diseases
List Ex’s of interstitial disease that can cause intrinsic renal failure
Acute interstitial nephritis, SLE, infection
List Ex’s of Nephrotoxins that can cause Intrinsic renal railure
NSAIDs, contrast agents, aminoglycosides, cyclosporine A, cisplatin, heme pigments
List Ex’s of vascualar diseases that can cause intrinsic renal failure
Polyarteritis nodosa, vasculitis
Labs that Define Intrinsic Renal Failure (list 4) memorize for exam
- Serum BUN:Cr ratio: 10-15:1
- Urine Sodium: ≥40 meq/l
- FENa: >2%
- Urine specific gravity: 1.010-1.020
Acute Tubular Necrosis (ATN) is the MC cause of ____
intrinsic AKI
Acute Tubular Necrosis (ATN):
-list 3 major causes
-Renal ischemia–> All causes of severe prerenal disease can cause postischemic ATN
-Nephrotoxins:
Aminoglycosides, heme pigments, cisplatin, radiocontrast media, pentamidine, mannitol, synthetic cannabinoids (K2/spice), tenofovir, IVIG
-Sepsis
ATN- Diagnosis? (**key finding on UA)
- Classic UA–> “Muddy brown granular epithelial cell casts and free renal tubular epithelial cells”
- FENa, BUN:Cr ratio, urine specific gravity, urine osmolality consistent with intrinsic AKI
- May also have hyperkalemia and have metabolic acidosis
ATN- Treatment?
- Hold nephrotoxins
- Treat underlying cause, supportive management
- Some will give diuretics for fluid overload–> **Don’t use for those who are oliguric
ATN- Prognosis?
-which Pts do better?
- Most patients spontaneously recover renal function
- **Do better if they are nonoliguric
- May not return to baseline renal function
- ATN during hospitalization associated with higher in-hospital and long-term mortality
Acute Interstitial Nephritis (AIN) is an immune-mediated process of _______
tubulointerstitial injury–> Inflammatory infiltrate in the interstitium
What is the MC cause of Acute Interstitial Nephritis (AIN)?
MC caused by medications:
Cephalosporins, penicillins, allopurinol, diuretics, NSAIDs, sulfonamides
AIN:
-other causes?
Also caused by illness:
Legionella, CMV, Streptococcus, Mycobacterium, EBV, candida, SLE, sarcoidosis, Sjögren syndrome
AIN can be associated with fever, _______, & _______ (**classic symptoms?
maculopapular rash, and eosinophilia (classic)
KNOW
Acute Interstitial Nephritis (AIN):
- UA findings
- Gold standard for diagnosis?
**WBCs, white cell casts, may have eosinophils, protein
-GOLD STANDARD= kidney biopsy
AIN: tx?
- Stop offending med/treat underlying cause.
- *-Glucocorticoids
Prognosis: Usually good
Glomerulonephritis= renal glomeruli are damaged by ______
deposition of inflammatory proteins in the glomerular membrane
Glomerulonephritis: causes
-focal?
Focal: Henoch-Schönleinpurpura, postinfectious, IgA nephropathy, hereditary nephritis, SLE
Glomerulonephritis: causes
-diffuse?
Diffuse: Postinfectious, Membranoproliferative, SLE, vasculitis, rapidly progressive GN
Glomerulonephritis:
-clinical features?
Hematuria, edema of face/eyes in morning, feet/ankles in evening, HTN common
Glomerulonephritis: diagnostic labs?
- Hematuria. Urine might be tea or cola colored.
- **RBCs and RBC casts on UA, misshapen RBCs, proteinuria
- Renal biopsy
Glomerulonephritis: tx
Tx: Steroids, immunosuppressants/chemo medications
