CNN EXAM- CHRONIC KIDNEY DISEASE WITH
APPROVED QUESTIONS AND ANSWERS| 2026 LATEST
UPLOAD |GRADED A+
List the limitations of the modification diet of renal disease (MDRD) and Cockgraft-Gault
equations - CORRECT ANSWER- The major limitation for both equations is that at
glomerular filtration rates above 60, their estimation is not accurate. The equation is
much more accurate for stages II to V.
Cockgraft-Gault does not take into account ethnicity or nutritional status. The MDRD is
preferred because it has been extensively studied and takes into account other
variables.
MDRD is limited in that it only accounts for 1 race (black). Other minority groups are not
accounted for and thus their GFR may not be truly representative.
***TAKE AWAY*** Both are less accurate with GFR greater than 60.
List the Cockgraft-Gault equation - CORRECT ANSWER- Calculated by the following:
(140-age) x lean body mass (kg) / serum creatinine (mg/dl) x 72. The equation is further
modified by multiplying the result by 0.85 for woman (as a way for accounting for the
lower body mass).
The Cockgraft-Gault equation is easily memorized and only requires one blood test to
calculate, the serum creatinine.
Limited by variances in the body mass (relies on serum creatinine for calculations). Can
be over or under estimated based on GFR.
It also loses accuracy in patients with amputated limbs, particularly the lower extremity
List the Modification Diet of Renal Disease equation - CORRECT ANSWER-
Calculated by using:
(Age) exp[-0.176] x (BUN [mg/dl]) exp[-0.170] x (Alb [g/dl]) exp[+0.318] x (0.762 if
female0 x (1.18 if black)
Complicated equation and shouldn't be memorized.
-Regarded as being more accurate method
-Widely studied and also accounts for nutrition and ethnicity
-Limitations include losing accuracy at GFR greater than 60 and lab errors
-Serum BUN and albumin required and if inaccurate or inconsistent, will be effected
-Limited by patients with unusual body mass as is seen with obese, malnourished and
amputees
, Describe appropriate dialysate calcium concentrations in patients on either
hemodialysis or peritoneal dialysis - CORRECT ANSWER- The dialysate concentration
is normally set to 2.5 mEq/L. At this concentration, little or no calcium is exchanged
between dialysate and the serum.
In patients with elevated calcium levels a lower dialysate concentration will be needed
to remove excess calcium. Conversely, if patients need calcium, a dialysate
concentration of 3.5 mEq/L will provide calcium to the patient. Initial therapy to raise the
serum calcium level is through both calcium and vitamin D supplementation.
Describe the kidney's role in calcium and phosphorus homeostasis - CORRECT
ANSWER- The kidney is instrumental in excreting excess phosphorous and producing
the active form of vitamin D, called calcitriol.
Calcitriol is a hormone which travels to the gut and aids in both phosphorus and calcium
absorption. Moreover, calcium phosphorus is regulated by the hormones PTH
(parathyroid hormone). PTH is released from the parathyroid gland and functions to
elevate serum calcium levels and lower phosphorus levels.
***Note that the kidneys are involved in both phosphorus excretion (under influence of
PTH) and phosphorus absorption via calcitriol.
Discuss the pathophysiology of aluminum toxicity in patients with chronic kidney
disease - CORRECT ANSWER- Aluminum is excreted by the kidneys. In patients with
renal disease, the ability to excrete aluminum is hindered. Aluminum toxicity was a
much larger problem when aluminum based phosphate binders were used. The
aluminum would be absorbed by the gut and accumulate over time.
Aluminum causes the following abnormalities:
- acute toxicity
- dementia
- osteomalacia
- anemia
- hypercalcemia (by displacing calcium in bony matrix)
Treatment of acute aluminum toxicity is via hemodialysis with low aluminum dialysate
concentration. Osteomalacia, dementia, anemia and hypercalcemia are products of
chronic exposure to aluminum. Prevention is huge with avoidance of aluminum based
phosphate binders and frequent monitoring of dialysis water system for elevated
aluminum levels.
Describe the role of parathyroid hormone (PTH) on calcium and phosphorus -
CORRECT ANSWER- PTH is stimulated by 2 mechanisms: either a low serum calcium
level or elevated phosphorus
APPROVED QUESTIONS AND ANSWERS| 2026 LATEST
UPLOAD |GRADED A+
List the limitations of the modification diet of renal disease (MDRD) and Cockgraft-Gault
equations - CORRECT ANSWER- The major limitation for both equations is that at
glomerular filtration rates above 60, their estimation is not accurate. The equation is
much more accurate for stages II to V.
Cockgraft-Gault does not take into account ethnicity or nutritional status. The MDRD is
preferred because it has been extensively studied and takes into account other
variables.
MDRD is limited in that it only accounts for 1 race (black). Other minority groups are not
accounted for and thus their GFR may not be truly representative.
***TAKE AWAY*** Both are less accurate with GFR greater than 60.
List the Cockgraft-Gault equation - CORRECT ANSWER- Calculated by the following:
(140-age) x lean body mass (kg) / serum creatinine (mg/dl) x 72. The equation is further
modified by multiplying the result by 0.85 for woman (as a way for accounting for the
lower body mass).
The Cockgraft-Gault equation is easily memorized and only requires one blood test to
calculate, the serum creatinine.
Limited by variances in the body mass (relies on serum creatinine for calculations). Can
be over or under estimated based on GFR.
It also loses accuracy in patients with amputated limbs, particularly the lower extremity
List the Modification Diet of Renal Disease equation - CORRECT ANSWER-
Calculated by using:
(Age) exp[-0.176] x (BUN [mg/dl]) exp[-0.170] x (Alb [g/dl]) exp[+0.318] x (0.762 if
female0 x (1.18 if black)
Complicated equation and shouldn't be memorized.
-Regarded as being more accurate method
-Widely studied and also accounts for nutrition and ethnicity
-Limitations include losing accuracy at GFR greater than 60 and lab errors
-Serum BUN and albumin required and if inaccurate or inconsistent, will be effected
-Limited by patients with unusual body mass as is seen with obese, malnourished and
amputees
, Describe appropriate dialysate calcium concentrations in patients on either
hemodialysis or peritoneal dialysis - CORRECT ANSWER- The dialysate concentration
is normally set to 2.5 mEq/L. At this concentration, little or no calcium is exchanged
between dialysate and the serum.
In patients with elevated calcium levels a lower dialysate concentration will be needed
to remove excess calcium. Conversely, if patients need calcium, a dialysate
concentration of 3.5 mEq/L will provide calcium to the patient. Initial therapy to raise the
serum calcium level is through both calcium and vitamin D supplementation.
Describe the kidney's role in calcium and phosphorus homeostasis - CORRECT
ANSWER- The kidney is instrumental in excreting excess phosphorous and producing
the active form of vitamin D, called calcitriol.
Calcitriol is a hormone which travels to the gut and aids in both phosphorus and calcium
absorption. Moreover, calcium phosphorus is regulated by the hormones PTH
(parathyroid hormone). PTH is released from the parathyroid gland and functions to
elevate serum calcium levels and lower phosphorus levels.
***Note that the kidneys are involved in both phosphorus excretion (under influence of
PTH) and phosphorus absorption via calcitriol.
Discuss the pathophysiology of aluminum toxicity in patients with chronic kidney
disease - CORRECT ANSWER- Aluminum is excreted by the kidneys. In patients with
renal disease, the ability to excrete aluminum is hindered. Aluminum toxicity was a
much larger problem when aluminum based phosphate binders were used. The
aluminum would be absorbed by the gut and accumulate over time.
Aluminum causes the following abnormalities:
- acute toxicity
- dementia
- osteomalacia
- anemia
- hypercalcemia (by displacing calcium in bony matrix)
Treatment of acute aluminum toxicity is via hemodialysis with low aluminum dialysate
concentration. Osteomalacia, dementia, anemia and hypercalcemia are products of
chronic exposure to aluminum. Prevention is huge with avoidance of aluminum based
phosphate binders and frequent monitoring of dialysis water system for elevated
aluminum levels.
Describe the role of parathyroid hormone (PTH) on calcium and phosphorus -
CORRECT ANSWER- PTH is stimulated by 2 mechanisms: either a low serum calcium
level or elevated phosphorus
