Kidney

Front 1

Describe theprimary functions of the glomerulus

Back 1

workingunit of filtration in the kidneys. Blood enters the afferent arteriole andleaves the efferent arteriole. Hydrostatic pressure fights against oncoticpressure to allow filtration. Because of the filtration barrier, molecules greaterthan 6500 Daltons (including proteins) are not filtered

Front 2

proximal tubule

Back 2

Reabsorptionoccurs in the proximal tubule. Fluid in the filtrate entering the proximaltubule is reabsorbed, driven by sodium transport from the lumen into the bloodby the Sodium/Potassium ATPase (3Na out, 2 K in) in the Basolateral membrane ofthe epithelial cells. This generates an electrochemical and concentrationgradient that drives absorption.

Front 3

loop of Henle

Back 3

Inthe loop of Henle there is continued reabsorption of sodium, water, andchloride. This occurs predominantly in the thick ascending limb. This isdependent on Na-K-Cl cotransporter. The main function of the loop of Henle isto create a concentration gradient in the medulla of the kidney. The remainingfluid is then sent to the distal tubule.

Front 4

Describe the function of the kidney as itrelates to sodium

Back 4

predominantlyreabsorbed in the thick ascending limb and is dependent on a Na-K-Clcotransporter.

Front 5

Describe the function of the kidney as itrelates to water

Back 5

varythe dilution of urine from 50 to 1200 mOsm/L. Plasma osmolality controlssecretion of antidiuretic hormone (ADH) which it turn controls the permeabilityof the collecting tubule to water

Front 6

Describe the function of the kidney as itrelates to potassium

Back 6

65%is filtered and reabsorbed in the proximal tubule, 20-25% is filtered in theloop of Henle (TAC) via Na-K-2Cl symporter. It is secreted by the corticalcollecting duct, which depends on delivery of sodium and presence or absence ofaldosterone. Increased distal sodium delivery, increased urine flow, loop orthiazide diuretics, and non-reabsorbable anions increase excretion. Aldosteronecauses hyperkalemia and volume depletion (but decreased sodium counteractsthis).

Front 7

Describe the function of the kidney as itrelates to magnesium

Back 7

only1% is present in extracellular fluid. It is an important cofactor for enzymaticreactions requiring ATP and is regulated by intestinal and kidney excretion,however, the mechanism is unclear. Two grams are filtered a day, and 100 mg areexcreted via urine. Most of the reabsorption (70%) occurs in the TAL of theloop of Henle. In the kidney, reabsorption of magnesium is affected bydiuresis, hormones, drug toxicity, and recovery from kidney failuretransplantation and is dependent upon a voltage gradient.

Front 8

Describe the function of the kidney as itrelates to acid base homeostasis

Back 8

hydrogen(acid) and sodium are closely linked, anything that increases sodium absorptionwill also increase urinary hydrogen excretion. Bicarbonate (base) is filteredeveryday (4520 mmol), most of the absorption occurs in the proximal tubule (75-90%), but it requires sodium and ATP. The other10-25% is reabsorbed in the distal tubule. No bicarbonate is usually present inthe urine. Acid base balance is affected by increased dietary acid load, volumecontraction, hypokalemia, increased aldosterone secretion, and ventilatorfailure (increased carbon dioxide pressure).

Front 9

Describe the function of the kidney as itrelates to calcium

Back 9

most(99%) is stored in bones. Most (60-70%) of reabsorption occurs in the proximaltubule via passive diffusion. 20% of reabsorption occurs in the corticalcollecting tubule. Reabsorption is affected by PTH, and 1,25-OH D3. Thiazidediuretics, PTH, and 1,25 OH D3 affect the remainder of calcium reabsorption,which travels to the distal tubule.

Front 10

Describe the function of the kidney as itrelates to phosphate

Back 10

Mostis stored in bone (80-85%). Daily the kidneys filter 6-7 grams of phosphate,where 80-90% of reabsorption occurs in the proximal tubule. This is sodiumdependent (Na-PO4 cotransporter), and expression of this cotransporter isregulated by dietary intake, FGF23 (a member of the fibroblast GF family,produced by osteocytes in response to increased serum phosphorus) and PTH.

Front 11

Whatare the endocrine functions of the kidney?

Back 11

Four major
renin secretion, Synthesis of Erythropoietin, 1-hydroxylation of 25-OH Vitamin D, Catabolism of Insuli.

Front 12

What's renin?

Back 12

secretedby the juxtaglomerular cells of the kidney in response to hypotension,sympathetic stimulation, and decreased sodium delivery to the distal tubule.Renin is an enzyme that participates in the body’s renin-angiotensinaldosterone system that mediates extracellular volume and arterialvasoconstriction.

Front 13

what's erythropoietin?

Back 13

produced by the peritubular cellsin the kidney and stimulated by hypoxia (anemia and hypoxemia) and controls redblood cell production. In kidney failure, decreased production leads to anemia.

Front 14

1-hydroxylation of 25-OH Vitamin ?

Back 14

Thisproduces the hormonally active form of vitamin D and increases the level ofcalcium in the blood by increasing the uptake of calcium from the gut into theblood. Stimulating factors include hypocalcaemia, hypophosphatemia, increasedPTH, and increased GH, where inhibitors include kidney failure and increasedFGF23.

Front 15

Catabolism of Insulin?

Back 15

thekidney clears insulin via two routes, 1) glomerular filtration and subsequentluminal reabsorption in the proximal tube by endocytosis, 2) diffusion ofinsulin from peritubular capillaries where it is bound in the distal tubule.This binding stimulates the reabsorption of sodium, phosphate and glucose.Kidney failure leads to prolongation of insulin’s actions.

Front 16

what's nephritis?

Back 16

inflammationof the kidneys, where the hallmark is an inflammatory response in theglomerular capillary. Infections, toxins, and autoimmune diseases can causethis. Nutritional recommendations include volume retension (via diuretics),salt restriction (2 g/day), and possibly supplementation with omega-3 FAs.

Front 17

what's nephrosis

Back 17

non-inflammatory nephrotic syndrome, which is a degenertativedisease of the renal tubules. It can be caused by kidney disease or besecondary to another disorder. Often, hypertension and kidney insufficiency orfailure can develop. Also, severe hypoproteinemia can develop of albumin levelsfall below 1.5 g/dL. Edema can develop secondary to low oncotic pressure.Sodium restriction may help this, but be aware that hypernatremia may developif patients drink excessive solute free water. If hyperlipidemia develops,treatment consists of conventional lipid lowering therapy of stains andfibrates. Also used may be fish outs and plant sterols/stanols. For adiagnosis, at least three of the following must be present:· >3.5 g proteinuria/m2/day· Hypertension· Hyperlipidemia· Edema· Hypoalbuminemia

Front 18

What is the definition of acute kidney injury?

Back 18

deteriorationof kidney function that occurs over hours to days and results in accumulationof nitrogenous wastes

Front 19

What is acute tubular necrosis?

Back 19

mostcommon form of acute kidney injury. This requires more than one insult to thekidney (like volume depletion plus a toxin, or sepsis plus hypotension).Recovery make may take weeks or months un the underlying disease is treated.However, at the time of diagnosis, most patients are extremely ill.

Front 20

What are the primary nutritional issues of acute kidney injury and tubular necrosis?

Back 20

Most patients with tubular necrosis are hypercatabolic and requireincreased energy. Protein restriction delays recovery. Excessive caloric intakeleads to increased CO2 generation and can worsen acidosis. And fluid should bemonitored. Potassium should be restricted to 1170-1950 mg/day.

Front 21

What are kidney stones? What is the most commontype of kidney stone? Who is more likely to get them? How should they be treated?

Back 21

A kidney stone is a hard, crystalline mineral material formedwithin the kidney or urinary tract. 1/20 people suffer from kidney stones.Prevalence increases from 40-70 years of age. White males are most at risk fordeveloping them. The most common type of kidney stone is calcium oxalate (60% ofcases). Uric acid stones can be treated by dissolutiontherapy, all others need to be removed or broken down by lithotripsy beforeexcretion.

Front 22

how can kidney stones be prevented?

Back 22

Nutritionalcounseling and metabolic monitoring reduced stone reoccurance from 7-23%. Themost important factor in prevention is maintaining urine volume at 2-2.5 L/day.250 mL of fluid (at least 50% of which is water) should be taken at each meal,between meals, and at bedtime and arising to void at night. This is becauseurine tends to be most concentrated in the morning. Being aware of calciumconcentrations is also a good marker. However, low calcium diets should not beprescribed. Calcium intake should be 1200 mg/day, however, this should not comefrom supplements, because that has been associated with increased risk.Consuming oxalate may also reduce risk. Foods rich in oxalate include beets,chocolate, coffee and nuts. But be aware, only 10-20% of dietary oxalate isabsorbed (unless you have gastric bypass). Consuming high amounts of red meatmay also increase risk of stone formation. Citrate is a known stone inhibitor,it complexes with calcium. Lemon juice or potassium citrate is often used inclinical practice. Excessive vitamin C intake should be restricted to less than2 grams per day.

Front 23

What does hemodialysis do?What are the different forms of hemodialysis

Back 23

Hemodialysisis the most common way to treat advanced kidney failure. In hemodialysis, apatient is hooked up to a dialysis machine, a specialized filter called anartificial kidney, and it is used to clean the blood. Blood is circulatedthrough this permeable hollow fiber membrane. The membrane allows for diffusionand ultrafiltration across a gradient. A blood pump is applied to create ahydrostatic force that pushes the ultrafiltrate though the membrane to removefluid. Dialysis prescription can vary by time and size and type of dialyzer.One can be hooked up to the dialysis machine by a fistula (arm), PTFE graft(wrist) or catheter (double lumen, in the chest). There is also another form ofhemodialysis called peritoneal dialysis that involves the ingestion of anosmotically active solution 4-5 times a day. In children, hemodialysis can beperformed via a continuous cyclic peritoneal dialysis.

Front 24

what types of nutritional concerns come up with hemodialysis?

Back 24

Nutritionalconcerns include worsening control of glucose, strict sodium and fluidrestriction (2 g/day, 1 L/day), potassium restriction (2 gram/day), possibleprotein loss, and energy requirements not exceeding 25-40 kcal/kg. Patientswho make no urine must have strict fluid and salt restrictions.

Front 25

Discuss the nutrition considerations seen in thedrugs used for renal transplant

Back 25

Renal transplant drugs increase glucose intolerance, increaseprotein catabolism, retain sodium, and inhibit Ca, PO4, and Vit. D metabolism(leading to increased risk of osteoporosis), increase risk ofhypertriglyceridemia, hyperkalemia, hypermagnesemia, hypercholesterolemiam andcan worsen already existing diabetes.

Front 26

What are the dietary recommendations for kidney transplant recipients?

Back 26

Transplant recipients should consume moderate amounts of protein(1 g/kg), restrict sodium to 2g/day if hypertensive, restrict potassium to2g/day if hyperkalemic, receive 1200-1500 mg of calcium a day, receive 400-800mg of magnesium oxide or chelate a day, and limit cholesterol and saturated fatintake