Kidney Pathophysiology Flashcards
Acute renal failure
Kidneys abruptly stop working with rapid decline in GFR.
Causes rapidly developing BUN, creatinine, and electrolyte imbalance.
Chronic renal failure
Progressive loss of kidney function.
Causes same effects as acute renal failure but developing over time.
What are the three general categories which kidney disease is initiated in?
- Large blood vessels supplying the kidney or vessels of the body overall
- Glomeruli, tubules, renal interstitium
- Parts of the urinary tracts outside the kidneys.
Prerenal Renal failure
Decreased blood supply to the kidney
Due to a cause external to kidneys, such as heart failure, severe hemorrhage, severe decrease in blood pressure, renal artery stenosis
Occurs when renal blood flow is reduced to <20% of normal –> this is the point at which cells become hypoxic due to low oxygen.
Intrarenal Renal failure
Abnormality in the kidney itself.
Due to damage to blood vessels of the kidney, to the tubular epithelial cells, or to the renal interstitium
Postrenal renal failure
Obstruction of the urinary collecting system.
If BOTH kidneys have distal obstruction, then backup of urine into the kidneys can lead to kidney damage.
If it is just to one kidney then the other can increase urine output to compensate.
Oliguria
Diminished urine output below level of intake of water and solutes leading to accumulation of water and solutes in the body fluids.
Possible etiologies of prerenal acute renal failure
- ECF volume decrease (hemorrhage, vomiting, diarrhea, large burns)
- Cardiac failure
- Hypotension (shock, anesthesia, renal artery stenosis)
Possible etiologies of intrarenal acute renal failure
- Conditions that injure the glomerular capillaries (malignant HTN, vasculitis, acute glomerulonephritis)
- Conditions that damage the renal tubular epithelium (renal tubular necrosis due to ischemia or toxins)
- Conditions that cause damage to the renal interstitium.
Possible etiologies of postrenal acute renal failure
- Bilateral obstruction of the ureters or renal pelvis by large kidney stones or blood clot
- Bladder obstruction
- Obstruction of the urethra
What is the biggest acute threat of acute renal failure?
Hyperkalemia – Injury to the tubule and deposition of casts makes secretion of electrolytes difficult.
Increase of even 4 mEq/L can be fatal.
Physiologic effects of acute renal failure
- Retention of water and electrolyes
- Hyperkalemia
- High concentration of non-protein nitrogens in ECF (uremia, azotemia)
- Metabolic acidosis
- Death within 8-14 days if no treatment.
Vicious cycle of chronic renal failure
Progressive injury of functional nephrons –> Leads to sclerosis of the glomerulus which further decreases kidney function.
What are the most common etiologies of CKD in developed nations?
- DM
- HTN
- Glomerulonephritis
Common etiologies of pre-renal CKD
Atherosclerosis of large vessels
Common etiologies of intrarenal CKD
Diabetes mellitus/obesity/metabolic syndrome
Hypertension; nephrosclerosis
Glomerulonephritis – e.g. local or systemic (polyarteritis nodosa, SLE) causes
Nephrotic syndrome disorders
Infections
Nephrotoxins
Polycystic kidney disease (genetic)
Common etiologies of postrenal CKD
Urinary tract obstructions -calculi, BPH, urethral constriction
What happens to the function nephrons in a person with CKD?
Increased blood flow, increased reabsoprtion, and hypertrophy
Additional effects of CKD
Anemia – due to decreased erythropoietin secretion by kidneys
Neuropathy – cognitive and neuromuscular due to uremia
Osteomalacia – bones are partially absorbed
due to less active vitamin D formation . Vitamin D is activated by 2 steps: liver then kidney
Accumulation of phosphate due to decreased GFR
Phosphate binds with Ca2+ leaving less ionized Ca2+ in the serum, stimulating PTH secretion, causing bone resorption
Heart failure, pulmonary edema
Increased half-life of insulin
What are the two main categories of renal vascular disease?
- Renal artery stenosis
2. Nephrosclerosis