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Flashcards in Chronic Renal Disease Deck (40):

What is the definition of chronic kidney disease?

A permanent reduction in glomerular filtration rate (GFR).

If an acute kidney injury lasts longer than 3 months it's considered chronic.


Explain the CKD Stages

CKD Stage 1: GFR is greater than or equal to 90 and there is evidence of kidney damage

CKD Stage 2: GFR is 60-89 and there is evidence of kidney damage

CKD Stage 3 "Mild CKD": GFR is 30-59

CKD Stage 4 "Moderate CKD": GFR is 15-29

CKD Stage 5 "Severe CKD": GFR is less than 15 or patient is on dialysis


What is the most common cause of CKD?

Diabetes nephropathy


What are the most common causes of CKD? (6)

  1. Diabetic nephropathy (most common)
  2. Hypertensive nephrosclerosis & renal vascular disease
  3. Glomerulonephritis
  4. Polycystic kidney disease
  5. Interstitial nephritis
  6. Obstruction


What are the 3 theories that explain why CKD is silent? Explain them.

  • Intact nephron hypothesis
    • the concept that each nephron is either a fully functional unit or does not function. Surviving nephrons can increasetheir functional capacity by undergoing hypertrophy. As further nephrons are destroyed in progressive renal diseasethe kidney's capacity to accommodate to emergencies diminishes and renal insufficiency begins to develop.
  • The magnification phenomenon
    • They magnify their excretion of a given solute
  • Individual Solute Control Systems
    • Each solute has a specific control system that is geared to maintain external balance in CKD. Each solute system has individual tubular handling and hormonal influences.


True or False: In CKD, you're always in a steady state of creatinine balance

True. As GFR decreases, serum creatinine increases until you reach a steady state (amount of creatinine created is equal to the amount of creatinine excreted)


Explain normal water handling for eliminating waste (concentration and dilution)

On average, a person makes about 600 mosm of waste in a day.

A normal kidney can concentrate urine up to 1200 mosm/L and dilute down to 50 mosm/L.

Therefore, a normal kidney could excrete 600 mosm of waste in 0.5 liters (maximum concentration) or 12 liters (maximum dilution)


Explain water handling in a failing kidney.

On average, a person makes about 600 mosm of waste a day.

Failing kidneys cannot properly dilute and concentrate so the maximum concentration is only about 300 mosm/L while the most dilute is about 200 mosm/L.

So, this person could excrete 600 mosm in 2 liters (obligate water excretion) or the 600 mosm in 3 liters (maximum water excretion).


Explain sodium handling in CKD vs normal

In normal patients, kidneys excrete and retain sodium based to stay in balance. However, patients with CKD has lost the ability to rapidly respond to changes in sodium intake or extrarenal losses so if there are large increases in sodium intake (diet), the patients get edema and if there are major decreases in sodium (e.g. diarrhea), the patients easily get volume depletion.


Sodium Imbalance in CKD patients is very common and causes adaptations. What are they? (5)

  • Volume expansion (about 90% of CKD patients are volume expanded)
  • Increased tubular fluid flow rate (because there is increased volume)
  • Hyperfiltration in remaining nephrons (there are damaged nephrons and the remaining ones are being overworked. This is one of the reasons why CKD is progressive)
  • Natriuretic peptides
  • Local vasoactive substances


True or False: In severe CKD (GFR under 20%), the kidneys can't get rid of enough potassium so the GI helps. The GI helps to excrete up to 50% of the potassium load.



What are the 4 adaptive processes that help with potassium excretion? What happens to these processes in CKD?

  1. Increased tubular flow (to excrete more)
  2. Increased solute load per nephron (each nephron takes more load and excretes more K)
  3. Increased Na delivery (more Na causes increase of K exchange at distal nephron)
  4. Increased aldosterone (to excrete potassium) 

In CKD, when GFR falls under about 20%, there starts to be issues with potassium secretion as these adaptive processes can't keep up. As CKD progresses, you lose more and more nephrons.


True or False: All patients with CKD become hyperkalemic


Patients with CKD can become hyperkalemic with large intakes of potassium because they have trouble excreting it.


Acid is excreted in what 3 forms?

  1. NaH2PO4+
  2. H+
  3. NH4+


In CKD, out of the 3 forms of excreted acid, NaH2PO4+, H+, and NH4+, which acid does not change in terms of excretion? 



What happens to acid balance in CKD?

When nephrons are lost, there is less ammonia being created so less ammonium being excreted. When kidney function falls below about 25% of normal, patients start to get metabolic acidosis.


Typically, ammoniagenesis can increase to accomodate excess acid. However, in CKD, ammoniagenesis increase is limited to about 4 fold.


Is serum calcium tightly regulated?

Yes, very


Is serum phosphate tightly regulated?

Yes, it's tightly regulated but not as much as Ca


PTH regulates and is regulated by serum _____



What regulates gut absorption of calcium and phosphorus?

Active vitamin D (1,25 dihydroxyvitamin D)


Does Active Vitamin D modulate PTH production?

Yes, along w/ serum calcium


What is the classic trade off hypothesis that relates decreasing GFR with increasing PTH?

It was believed that when GFR fell, calcium levels would fall and phosphate would go up. In order to bring the calcium back to normal, the PTH would go up. PTH's job is to restore the serum calcium. It activates vitamin D to increase GI calcium absorption and also takes calcium from bone to deposit into serum.


This hypothesis was an oversimplification as we now know that there are other players involved.


What is the new understanding of the relationship between GFR and PTH in CKD?

In CKD, phosphate balance is abnormal.

High phosphate levels don't occur until severe CKD because before then, FGF-23 and PTH levels rise to maintain phosphate balance. FGF-23 suppresses 1,25 vitamin D production which in turn suppresses serum calcium from decreased gut absorption.


Why is bone disease caused by CKD?

In CKD, phosphate drops which increases FGF-23 which decreases 1-25 vitamin D which causes a drop in serum calcium. The drop in serum calcium causes an increase in PTH. PTH takes calcium from the bone to put into the serum to try to bring calcium levels back to normal. This causes bones to demineralize causing osteopenia/osteoporosis/bone pain/fragility fractures.


What is uremia? (3)

  1. Systemic intoxication from retained metabolic products (urea or other solutes that accumulate in CKD)
  2. Overproduction of counter-regulatory hormones (PTH)
  3. Underproduction of kidney hormones (erythropoietin, 1,25 vitamin D)


 What are clinical features of uremia? (10)

  1. Neurologic disorders (encephalopathy)
  2. Hematologic disorders (anemia)
  3. Cardiovascular disorders (pericarditis, CHF)
  4. Pulmonary disorders (pulmonary edema)
  5. GI disorders (anorexia, N/V)
  6. Metabolic-Endocrine disorders
  7. Bone, calcium, phosphorus disorders
  8. Skin disorders (pruritus)
  9. Psychological disorders (depression)
  10. Fluid and electrolyte disorders


Basically everything..


Why do CKD patients get anemia?

Erythropoiesis is decreased due to low renal mass. RBC survival is shorter due to uremia. Uremia also decreases ability to absorb iron.

Dialysis patients have even more reasons for anemia:

Blood loss

Marrow space fibrosis due to secondary hyperparathyroidism.


True or False: Anemia and HTN occur in more than 90% of patients with CKD



How does CKD cause HTN?

  • Expansion in ECF volume because of decreased salt excretion. 
  • Increased activity of the renin-angiotensin system
  • Dysfunction of autonomic nervous system


What is the number one cause of secondary hypertension?



Why is renal disease progressive?

The intact nephron hypothesis.

As nephrons lose function, others take on more work load. This causes changes in the functioning nephrons:

  • glomerular hypertrophy
  • increased blood flow per nephron
  • increased intra-glomerular pressure
  • increased solute flow per tubule


Stare at this chart


True or False: CKD patients are more likely to die than to progress to needing dialysis.

True. They typically develop cardiovascular disease and die.


True or False: Patients with CKD are in the highest risk group for cardiovascular disease



What are the most important management principals for CKD? (4)

  1. Delay CKD progression
  2. Treat complications of CKD
  3. Screen and treat cardiovascular risk factors
  4. Prepare for dialysis


What is the most important way to decrease CKD progression?

Blood pressure control. It is not easy to control BP in CKD patients. Typically need a combination of 3 or more drugs to manage.

BP goal is under 130/80 mmHg in all CKD patients.


What is the main drug of choice for BP control in CKD patients?



True or False: no therapy can completely stop the progression of CKD



True or False: It is important for CKD patients to see a nephrologist before going on dialysis

True. But about 1/3 of patients with CKD do not see a nephrologist before starting dialysis and about 80% of those start dialysis with a catheter which increases risk of infection. Infection is the number 2 cause of death of CKD patients.


What stage of CKD do you start management for slowing the progression with ACEi or ARBs, cholesterol control, smoking cessation, weight loss, etc?

Stage 1