Nephro Flashcards
(37 cards)
Factors that control renal blood flow
- Systemic arterial pressure
- Circulating volume
- Renal and vascular resistance
- autoregulation
Describe the distribution of renal blood flow
- 90% RBF goes to cortex (flow 500ml/min to 100 g tissue)
- 10% RBF goes to medulla (outer zone =100ml/min per 100g tissue vs inner zone is 25ml/min)
- **CHANGES IN RBF WILL LARGELY REFLECT CHANGES IN CORTEX
Uses of kidney US
- To quantify kidney size
- To evaluate for hydronephrosis
- To evaluate the perirenal space for abscess or hematoma
- To screen for ADPKD
- To localize the kidney for invasive procedures
- To evaluate for kidney vein thrombosis (doppler US)
- To assess kidney blood flow (doppler US)
Uses of kidney IVP
- To assess renal size and contour
- To investigate recurrent urinary tract infection
- To detect and locate calculi
- To evaluate suspected urinary tract obstruction
Uses of radionuclide studies in kidney
- To quantify total kidney function and the contribution of each kidney
- To evaluate kidney parenchymal integrity
- To evaluate kidney infection or scar
- To evaluate renovascular hypertension
- Little benefit when the single kidney GFR is below 15 ml/min
- Most use 99 technetium
uses of CT in kidney
- To further evaluate a renal mass
- To display calcification pattern in a mass
- To delineate the extent of renal trauma
- To guide percutaneous needle aspiration or biopsy
- To diagnose adrenal causes for hypertension
uses of MRI in kidney imaging
- Diagnosing renovascular lesions
- To assess renal vein thrombosis
- Evaluation of potential living kidney donors and transplanted kidneys
- To evaluate suspected pheochromocytoma
- Delineating complex mass where CT is not definitive
- Staging kidney neoplasms, particularly in evaluating for renal vein or inferior venal caval extension of tumor
Angiography in kidney imaging
Suspected artery lesions: atherosclerotic or fibrodysplatic stenoic lesions of the renal arteries, aneursysms, arteriovenous fistulae.
• Large vessel vasculitis
• Unexplained hematuria
• Kidney transplantation
• Diagnoses for renal vein thrombosis
• Complex or highly unusual renal masses or trauma etc
*can be diagnostic or therapeutic
Uses of kidney biopsy
• The cause cannot be determined or adequately predicted by less invasive diagnostic procedure
• The signs and symptoms suggest parenchymal disease that can be diagnosed by pathologic evaluation
• The differential diagnosis includes diseases that have different treatments, different prognoses, or both.
(Acute renal failure; Nephrotic or nephritic syndrome; Hematuria; Systemic Disease)
• Transplant Allograft
FENa
- Fraction of filtered Na that is excreted
- Expect to be low if: kidney is Na avid, tubules are intact
- Calculate: FENa=U[Na]/P[Na] x P[Cr]/U[Cr]
- Most useful in oilguric renal failure
- FENa<1% can be seeni n causes of ARF (other than pre-renal azotemia)
What sorts of things can you detect by urinalysis?
- Blood (strip detects peroxidase): blood, myoglobin, free hemoglobin
- Neutrophils (Leukocyte alkaline esterase)
- Nitrate (azo dye)→presence suggests bacteria
- Protein
- Specific gravity approximates osmolality→high specific gravity then urine concentrating ability is intact
determining GFR with serum creatinine
• Estimate w/ serum creatinine clearance (calculated with formulas, depends on age, sex, race, weight etc)
o Hyperbolic relationship b/t GFR and Scr concentration (large changes in GFR are reflected as small changes in Scr)
o Pt must be in steady state! (conditions can change Scr w/o affecting GFR eg: hepatic cirrhosis, limb amputation, spinal cord injury, morbid obesity)
• Large muscle mass can inc. Scr
• Cimetidine, trimethoprim, probenecid all block proximal secretion and inc. Scr
• Ketones, methanol, cephalosporins, isopropanol all interfere with jaffe reaction and inc. Scr
clinical manifestations of ARF
o Elevated serum BUN and creatinine o Urine output: • Anuria (400 cc/day) o Metabolic acidosis (dec. bicarb o Hyperkalemia o Hyperphosphatemia/Hypocalcemia
complications of ARF
oMetabolic: hyperkalemia, hypocalcemia, hyperphosphatemia
oCardiovascular: pulmonary edema, arrhythmias, hypertension, pericarditis
oNeurologic: asterixis, somnolence, coma, seizures
oHematologic: anemia, coagulopathies, bleeding diathesis
oGastrointestinal: nausea, vomiting, hemorrhage, mucous membrane ulceration
oInfections: urinary tract infection, wound infection, pneumonia
supportive care management of ARF
o Intravascular volume overload (Low Salt diet, Water restriction (15
o Hyperphosphatemia, Hypermagnesemia, Hypocalcemia (Phosphate binding agents (CaAcetate, Sevelamer), avoid milk; Discontinue Mg containing antacids (Mylanta, Maalox); Ca-gluconate, Ca-carbonate)
Key points prerenal azotemia
- decrease in effective circulating blood volume
- kidney is intact
- major causes: hypovolemia, cardiac–CHF, MI, peripheral vasodilation, increased renal vascular resistance
- urine lytes: FENa20, Osm>500,
- inc. serum BUN/Creatinine
- Tx: replace fluid, tx CHF
- complete recovery if perfusion restored
Key points post-renal obstruction
- must have bilateral obstruction for symptoms
- urethral obstruction, bladder neck obstruction (tumors, BPH), intrauretal, extrauretal
- obstruction on imaging (urine lytes not helpful)
- Sx of frequency/urgency (can have anuria)
- complete recovery if obstruction removed quickly
Key points Acute tubular necrosis
-sudden death of tubular (not glomerular) cells!
-can be ischemic or caused by nephrotoxic agents
-urine sedimentation: granular casts
urine lytes: FENa>1%, Na>20
-no tx available
-pts will mild injury will recover completely, the worse the injury the less likely they are to recover
key points Acute interstitial nephritis
- allergic reaction usually to a drug (requires 1-2 wks of exposure)
- Hx: drug hypersensitivity (skin rash, urticaria, fever, athralgia)
- peripheral eosinophil >10%
- Urine WBCs with negative urine culture
- WBC casts w/o evidence of pyelonephritis
- Gold standard: Biopsy
key points acute glomerulonephritis
- inflammation of glomeruli (typically auto-immune)
- assoc w/ other autoimmune diseases
- urine sedimentation: dysmorphic RBCs, RBC casts, WBC casts, proteinuria
key points renal athero-emboli
- small atheromatous crystals flick off arterial wall and embolize to the kidney
- typically due to manipulation of arteries
- no treatment
- renal function rarely recovered
grading renal dysfunction in terms of creatinine clearance
o Cl creat 60-99 ml/min = mild impairment
o Cl creat 30-59 ml/min=moderate impairment
o Cl creat 15-29 ml/mim = severe impairment
o *renal replacement therapy usually at clearance of 5-10
stages of chronic renal failure
o Stage 1: normal GFR, but signs of kidney disease-e.g. proteinuria o Stage 2: GFR 60-99 o Stage 3: GFR 30-59 o Stage 4: GFR 15-29 o Stage 5: GFR <15 o Stage 6: On renal replacement therapy
symptoms of mild chronic renal failure
: minimal fatigue, salt and H2O retention causing edema and hypertension
