Kidneys pt 1 Flashcards
Basic Renal function is to?
- Filter the blood of
- Removal of waste
- Maintain proper concentrations of electrolytes
- maintaining acid/base balance
- Regulate blood volume and pressure
- Produce EPO
What is the basic functional unit of the kidney?
Nephron - consists of glomerulus, renal tubule
Site of filtration in the kidney?
Glomerulus
Where does water and salt get reabsorbed in the kidney?
Renal tubule
The proximal convoluted tubule (PCT) reabsorbs what 65% of? 80% of? 100% of?
- 65% of Sodium, potassium, calcium
- 80% of phosphate, water, bicarbonate
- 100% of glucose and amino acids
What else does the PCT do?
Reabsorbs 60% of the glomerular filtrate
Secretes drugs/toxins that are too big (or protein bound) to be filtered
Reasborbs water passively
Makes ammonia from gluatmine (acidifies urine)
What are the 4 segements of the loop of Henle?
4 segments -
thin descending limb (DLH)
Thin ascending limb (ALH)
Medullary thick ascending limb (mTALH)
Cortical thick ascending limb (cTALH)
Overall function of the loop of henle?
Create a concentration gradient and form concentrated urine.
What does the Collecting Tubule do?
- Reabsorbs
- NaCl
- Bicarb
- H20 - urine concentration
- Excretes
- H+
- Urea
- Regulates urine volume
AKI is?
Rapidly worsening of renal function
Clinically seen with quickly rising BUN/Cr
Accumulation of nitrogenous wastes in the blood
Caused by prerenal, postrenal, intrarenal
What is the definition of AKI?
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 occured in the past 7 days)
OR
Oliguria of <0.5 ml/kg/hour for >6hours.
Clinical symptoms of AKI?
Weakness, lethargy, anorexia, N/V, General malaise, diarrhea, pruritis, drowsiness, hiccups, SOB, dizziness
Signs of AKI?
Usually point towards the underlying cause ie prerenal vs postrenal - Prerenal - tachycardic, hypotensive - Post renal - distended bladder, CVA tender, enlarged prostate
Anuria or Oliguria
Change in volume status/weight
Change in mental status
Edema
Weakness
What are the diagnostic tests you run for AKI?
BMP, Urinalysis & urine microscopy, - urine culture, measurement of urine output, renal ultrasound, may add urine spot for osmolaility, urine sodium, creatinine
What are possible life threatening complications of AKI?
Hyperkalemia
Fluid overload
Signs of uremia - pericarditis, altered mental status
Severe metabolic acidosis (pH <7.1)
Treatment for AKI? When should you dialyze?
Depends on the CAUSE
- Dialyze if
- serum creatinine is >5-10 mg/dl
- Unresponsive acidosis
- Fluid overload
- Uremic complications
What is prerenal failure? This is the ________ of AKI.
- Prerenal failure is reduced effective blood circulating to the kidney
- Absolute reduction in fluid volume (hemorrhage, dehydration) or
- Effective volume depletion - CHF, cirrhosis (hepatorenal syndrome)
this is the most common cause of AKI
Prerenal failiure is reversible? T/F
Yes, rapidly reversible if underlying cause is found and corrected - kidney themselves are okay
What are some examples of true intravascular depletion? What is this an example of?
Hemorrhage, burns, diuretics, dehydration, GI losses, vomiting, diarrhea, enteric fistula
This can lead to prerenal AKI
What are some examples of decreased circulating volume? This can lead to?
CHF, cardiac tamponade, aortic stenosis, cirrhosis with ascites, nephrotic syndrome
This can lead to prerenal AKI
What are some examples of impaired renal blood flow? What can this lead to?
ACEi - can decrease blood flow to kidneys
NSAIDs
Renal artery stenosis
Renal vein thrombosis
This can lead to prerenal AKI
What labs distinguish prerenal failure?
Serum BUN:Cr ratio > 20:1
Urine sodium <20 meg/L
Fractional excretion of sdoium (FENa) <1%
Urine specific gravity > 1.020
These occur because the kidney is responding to prerenal failure by increasing reabsorption.
Serum BUN:Cr ratio in prerenal failure would be?
Greater than 20:1
Urine sodium in prerenal failure would be?
<20 meg/L
Fractional excretion of sodium (FENa) in prerenal failure would be?
<1%
Measures the percent of sodium filtered by the kidney that is excreted into the urine.
Urine specific gravity in prerenal failure would be?
Greater than 1.020
What is the treatment for prerenal AKI? CHF, Dehydration, Hemorrhage
Correct the underlying cause
CHF - Diurese the patient
Dehydration - IVF
Hemorrhage: Blood and fluids.
What is postrenal failure? What are some of the causes?
This is damage to the kidneys, AKI, due to something after the kidneys - in the ureters, bladder, urethra. Blockage at those spots cause renal failure
Nephrolithiasis, BPH, obstructring tumor in the GU stystem, bladder outlet obstruction, blood clots within the urinary tract, medications, neurogenic bladder
What are clinical symptoms of postrenal failure?
May have abdominal or groin pain, bladder discomfort
Mass at flank, suprapubic area, or abdomen
Rectal exam
Pelvic exam
Anuria
What is the diagnostic testing you should do with postrenal failure?
Post void residual - >100 ml –> Bladder outlet obstruction.
Ultrasound or IVP (intravenous pyelogram) - dilated ureters or renal pelvis
Abdominal CT - to evaluate for mass.
What is the treatment for postrenal failure?
Relieve the obstruction
May - catheterize patient, nephrostomy tube, stenting, lithotripsy, perform surgery to remove a mass
What is intrinsic renal failure?
One or both kidneys have been damaged and don’t work properly
some causes happen quickly, others develop over time.
What are causes of Intrinsic renal failure?
Acute tubular necrosis (ATN) - most common cause of intrinsic AKI
Nephrotoxins - NSAIDS, contrast agents, aminoglycosides, cyclosporine A, cisplatin, heme pigments
Interstitial diseases - acute interstitial nephritis, SLE, infectino
Glomerulonephritis
Vascular disease - polyarteritis nodosa, vasculitis
What labs define intrinsic renal failure?
Serum BUN:Cr ratio of 10-15:1
Urine sodium: >40 meq/l
FENa: >2%
Urine specific gravity of 1.010-1.020
Serum BUN:Cr ratio in intrinsic renal failure would be?
10-15:1
Urine sodium in intrinsic renal failure would be?
>40 meq/l
FENa in intrinsic renal failure would be?
>2%
Urine specific gravity in intrinsic renal failure would be?
1.010-1.020
What is the most common cause of intrinsic AKI?
Acute tubular necrosis
What are the three major causes of acute tubular necrosis?
Renal ischemia - all causes of severe prerenal disease can cause postischemic ATN
Nephrotoxins - aminoglycosides, heme pigments, cisplatin, radiocontrast media, pentamide, mannitol, synthetic cannabinoides
Sepsis
How do you diagnose acute tubular necrosis?
Classic UA description - 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
How do you treat acute tubular necrosis?
Hold nephrotoxins
Treat underlying cause - supportive management
Some will give diuretics for fluid overload - don’t use if oliguric
Most patients spontaneously recover renal function - better if non oliguric
Prognosis of ATN?
May not return to baseline renal function - worse with each episode
ATN during hospitalization associated with higher in hospital and long term mortality.
What is Acute interstitial nephritis?
Immune mediated process of tubulointerstitial injury - inflammatory infiltrate in the interstitium
What medications most commonly cause acute interstitial nephritis (AIN)
Cephalosporins, penicllins, allopurinol, diuretics, NSAIDs, sulfonamides
What triad (classic) is associated with AIN.
Fever, maculopapular rash, eosinophilia
What are the UA findings of AIN?
WBCs, white cell casts, may have eosinophils, protein
What is the treatment for AIN?
Stop offending med/treat underlying cause - Glucocorticoids
Usually good prognosis after treatment
What is glomerulonephritis?
Renal glomeruli are damgaed by deposition of inflammatory proteins in the glomerular membrane
What causes glomerulonephritis?
Focal: Henoch-Schonleinpurpura, postinfectious, IgA nephropathy, Hereditary nephritis, SLE
Diffuse: Postinfectious, membranoproliferative, SLE, vasculitis, rapidly progressive GN
What are the clinical features of glomerulonephritis?
Hematuria, edema of face/eyes in the morning, feet/ankles in the evening, HTN common
How do you diagnose Glomerulonephritis?
HEmaturia, urine might be tea or cola colored.
RBCs, and RBC casts on UA, misshapen RBCs, proteinuria
Renal biopsy
What’s the treatment for Glomerulonephritis?
Steroids, immunosuprressants/chemo medications.
