CHAPTER 26

ACUTE RENAL FAILURE AND CHRONIC KIDNEY DISEASE

CHAPTER 26

ACUTE RENAL FAILURE AND CHRONIC KIDNEY DISEASE

WHEN KIDNEYS FAIL

Less waste is removed More waste remains in the blood Nitrogenous compounds build up in the blood

BUN: Blood urea nitrogen Creatinine

Renal function approximated by: initial creatinine level/current creatinine level

ACUTE RENAL FAILURE Prerenal

Decreased blood supply Shock, dehydration, vasoconstriction

Postrenal Urine flow is blocked

Stones, tumors, enlarged prostate Intrinsic

Kidney tubule function is decreased Ischemia, toxins, intratubular

obstruction

QUESTION

Which type of acute renal failure (ARF) would be most likely to accompany benign prostatic hypertrophy?

a. Prerenalb. Postrenalc. Intrinsicd. Extrinsic

ANSWER

b. Postrenal Postrenal ARF occurs when the flow of

urine is blocked by kidney stones, tumors, or an enlarged prostate gland. Because the male utethra passes through the prostate, if it is enlarged the urethra may become blocked.

RADIOCONTRAST AGENTS CAN CAUSE ARF

Giving N-acetylcysteine reduces the risk of ARF by 50% in a meta-analysis

Recommended for clients at risk of renal failure who are receiving radiographic contrast media

Diabetics, clients with sepsis Underlying vascular, renal, or hepatic

disease Receiving other nephrotoxic drugs

(Kellum, J.A. [2003]. A drug to prevent renal failure? Lancet 362,589-590.)

SCENARIO

A man developed acute renal failure after emergency surgery for a severed left leg…

He came in with a serum creatinine of 1.2 mg/dL, but now it is 5.6 mg/dL

His BUN is 86 mg/dLQuestion: Why would leg damage cause renal failure? What is his remaining kidney function?

URINE CONTAINING TUBULAR CELL CASTS Casts are formed

when cells are packed together in the tubule lumen

They block the tubule

When the mass of cells washes loose, it appears in the urine

SCENARIO

Mr. J is an alcoholic with kidney problems… He is severely dehydrated with an infected leg

ulcer, benign prostatic hypertrophy, and anemia

His urine is dark and contains myoglobin and tubular cell casts

His creatinine and BUN are both elevated Question: What may have caused his acute tubular

necrosis?

CHRONIC RENAL FAILURE

Fewer nephrons are functioning Remaining nephrons must filter

more Hyperperfusion Hypertrophy

DEVELOPMENT OF CRF

Diminished renal reserve Nephrons are working as hard as they can

Renal insufficiency Nephrons can no longer regulate urine density

Renal failure Nephrons can no longer keep blood

composition normal End-stage renal disease

UREMIA

Uremia = “Urine in the Blood” Renal filtering function decreases

Altered fluid and electrolyte balanceo Acidosis, hyperkalemia, salt wasting,

hypertension Wastes build up in blood

Increased creatinine and BUNo Toxic to CNS, RBCs, platelets

Kidney metabolic functions decrease Decreased erythropoietin Decreased Vitamin D activation

QUESTION

Which of the following renal disorders is characterized by increased BUN and creatinine levels?

a. ARFb. CRFc. Uremiad. All of the abovee. b and c

ANSWER

d. All of the aboveIn each disorder listed, the ability to

remove nitrogenous waste is diminished. This causes nitrogenous compounds (BUN and creatinine) to accumulate in the blood.

SCENARIO

A man has chronic renal failure… He has high creatinine and BUN,

hyperkalemia, acidosis with normal pCO2, and severe anemia

His blood glucose has reached 340 mg/dL one hour after a hospital meal

He complains of having broken two toes in the last few weeks, even though he eats a lot of dairy products for calcium

SCENARIO (CONT.)

Question: What is the most likely cause of

his chronic renal failure? What caused his anemia? Why are his bones brittle even

though he eats dairy products?

CARDIOVASCULAR CONSEQUENCES OF CRF

Decreased blood viscosity

+ Increased blood

pressure +

Decreased oxygen supply

less erythropoietin

anemia

lower blood viscosity

blood flows through vessels more swiftly

heart rate increases

left ventricle dilation and hypertrophy

not enough oxygen to support LV contraction

anginaischemia

LHF

increased workload on left heart

QUESTION

Tell whether the following statement is true or false:

CRF leads to decreased cardiac output (CO).

ANSWER

TrueThe increased blood pressure (HTN) and

hypoxemia that accompany CRF leads to increased myocardial work (the heart has to work harder to meet the metabolic demands of body tissues). Eventually the heart becomes unable to meet these metabolic demands, and CO will decrease.

MANIFESTATIONS OF KIDNEY FAILURE

TYPES OF DIALYSIS