Exam 5 Study Guide Flashcards
What is nephrolithiasis?
Also known as kidney stones or renal calculi. This is the presence of renal stones in the renal pelvis and are made of calcium, struvite, uric acid, or cystine.
What are calcium stones? Explain.
They are the most common type of kidney stones. They typically occur from idiopathic hypercalciuria or in the setting of hyperparathyroidism because this causes an increase in osteoclast activity which are the bone cells that break down bone and release calcium into the blood.
What are struvite stones? Explain.
They are the second most common type of kidney stones and are made of magnesium, ammonium, and phosphate salts.
They result from chronic UTIs with urease-producing bacteria which break down the urea in the urine to salts that compose the struvite stones.
They cause intractable UTIs, pain, bleeding, and abscesses.
What are uric acid stones? Explain.
They are the third most common type of kidney stones and result from a breakdown of purine. These types of stones tend to form in those with excess purine intake or those with gout.
What are cystine stones? Explain.
They are the least common type and occur more in children.
What is the pathogenesis of nephrolithiasis?
This occurs due to an oversaturation of the urine with ions. The cations and anions bond with one another and form salts which turn into crystals. These crystals then form the stones that pass the ureter and cause excruciating flank pain and obstruction. This obstruction causes the urine to back up into the kidneys causing hydronephrosis and renal failure.
What are the risk factors for nephrolithiasis?
- gout which causes the accumulation of uric acid
- high protein diets resulting in increased purine intake
- high sodium diet resulting in increased calcium excretion and therefore calcium stone formation
What are the clinical manifestations of nephrolithiasis?
- flank pain that radiates to the groin (renal colic)
- anuria and hematuria
What are the 3 stages of AKI?
Stage 1: Creatinine of 1.5-1.9x higher than the baseline
Stage 2: Creatinine of 2-2.9x higher than the baseline
Stage 3: Creatinine of 3x higher than baseline or in those <18 years of age, a decrease in GFR to <35 ml/min
What is a normal GFR level?
90-120 ml/min
What is pre-renal AKI?
Caused by impaired blood flow to the kidney or decreased renal perfusion resulting in a decreased GFR.
What are the causes of pre-renal AKI?
1.vasoconstriction/hypotension/hypovolemia
2. renal artery stenosis
3. heart failure due to inadequate cardiac output
What is the main cause of intra-renal AKI?
Acute tubular necrosis because it is impairing renal function at the cellular level of the kidneys
What is acute tubular necrosis?
A severe necrosis of tubular epithelial cells. The cells slough off and collect in the tubule, causing obstruction which leads to increasing tubular pressure and decreased GFR. This causes the arteriole to vasoconstrict and leads to backflow of fluid into the renal interstitial tissue. This will all lead to rising BUN and creatinine which will peak and then come back down. As it comes back down, patients will diurese and become severely dehydrated.
What can you see in a UA with those with acute tubular necrosis?
muddy brown cast cells
What occurs in post-renal AKI?
Caused by any obstruction such as bladder outlet obstruction which can occur as a result of prostatic hyperplasia or uretral obstruction from a kidney stone.
What are the clinical manifestations of AKI?
- oliguria, anuria
- electrolyte imbalances including hyperkalemia and hyponatremia
- metabolic acidosiss
- BUN: Creatinine ratio will be >20 in a pre-renal AKI and normal in intra-renal AKI
- FeNa will be <1% in pre-renal AKI and >2% in an intra renal AKI
What is FeNa?
Fractional excretion of sodium that is used to evaluate AKI and to differentiate between pre-renal and acute tubular necrosis.
What does FeNa <1% indicate?
Indicates pre-renal AKI and that the kidneys are conserving sodium
What does FeNa >2% indicate?
Kidneys are wasting sodium which indicates acute tubular necrosis
What does a BUN: Creatinine ratio indicate?
BUN: creatinine ratio >20 is consistent with pre-renal AKI
What are the stages of CKD?
Stage 1: GFR >90: Patients are asymptomatic
Stage 2: GFR 60-80: Patients experience an increase in PTH, early bone disease, and increasing creatinine and urea.
Stage 3: GFR 30-59. They will have erythropoietin deficiency, anemia, and an increase in creatinine and urea. They will have mild HTN.
Stage 4: GFR of 15-29. These patients will have increased triglycerides, metabolic acidosis, hyperkalemia, and elevated BUN/creatinine.
Stage 5: GFR <15 or need for dialysis. This results in uremia, severe HTN, anemia, and hyperphosphatemia.
What are the most common causes of CKD?
diabetes, HTN, and glomerulonephritis
What is pathogenesis of CKD?
chronic injury to kidneys which causes irreversible loss of nephrons and causes an increase in glomerular filtration pressure in the remaining nephrons. this causes more nephrons to fibrose and scar.