CNN Exam- Chronic Kidney Disease questions and answers well illustrated.

CNN Exam- Chronic Kidney Disease questions and answers well illustrated. List the limitations of the modification diet of renal disease (MDRD) and Cockgraft-Gault equations - correct answers.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 answers.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 answers.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 answers.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 answers.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 answers.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 answers.PTH is stimulated by 2 mechanisms: either a low serum calcium level or elevated phosphorus PTH acts to increase serum calcium and lower phosphorus. It increases calcium by 2 methods: - Stimulates the release of calcium from bone (body's reserve of calcium stores) - Stimulates the kidney to release calcitriol (active form of Vitamin D). Calcitriol will raise the serum calcium level by increasing calcium absorption in the gut. PTH also acts to decrease serum phosphorus. Accomplishes this by acting on the kidneys to excrete phosphorus in the urine. In patients with CKD, PTH is elevated because the kidneys do not respond appropriately. Kidneys can neither produce calcitriol or excrete phosphorus. Thus, PTH levels rise (also known as secondary hyperparathyroidism) and a viscous cycle ensues. Define adynamic bone disease - correct answers.Adynamic bone disease occurs when bone turnover is absent. The pathophysiology is as follows: Parathyroid hormone levels are increased in response to low serum calcium and renal failure. Therapy is begun with calcium containing phosphate binders and calcitriol. The resulting increase in calcium and lowering of phosphorus causes PTH levels to decrease to near normal levels. This causes bone to be essentially dormant. The physiology of a patient with chronic kidney disease dictates that PTH levels at 1.5-2 times normal are needed in order to maintain healthy bone turnover. Otherwise, bone becomes dormant and essentially inactive/ When treating patients for hyperphosphatemia and vitamin D deficiency, care must be taken not TOO overzealous so as not to reduce PTH levels to normal. Define metastatic calcification - correct answers.Local or wide deposition of predominately calcium salts in otherwise normal tissue in the setting of hypercalcemia This occurs when the calcium and phosphorus levels are high. High is defined by a calcium-phosphorus product of greater than 70. Accomplished with diet restricted for phosphorus and judicious use of phosphate binders. Describe the importance of calcium phosphorus product - correct answers.When calcium and phosphorus levels reach a certain point, they can combine in the bloodstream and precipitate out. The form mineral deposits in organs as well as blood vessels which is injurious to their function. Nephrologists must keep track of the calcium phosphorus product or simply multiply the serum calcium with the serum phosphorus. If the product exceeds 70, the patient is at increased risk of calcium phosphorus deposition. It is imperative to monitor the calcium phosphorus product in all patients with CKD with interventions to lower that product is necessary. Describe the role of vitamin D on calcium and phosphorus - correct answers.The activate form of vitamin D, calcitriol is produced by the kidneys. Calcitriol is released in response to low serum calcium levels and under the influence of parathyroid hormone. Calcitriol acts on the gut to increase absorption of both phosphorus and calcium. In patients with CKD, calcitriol is not produced adequately. Patients with CKD and low calcium levels are frequently given supplemental calcitriol.