Chapter 34 - Acute Renal Injury & Chronic Kidney Disease

• renal failure is a condition in which the kidneys fail to remove metabolic end products from the blood and regulate fluid, electrolyte, and pH balance of the extracellular fluids
• AKI is abrupt in onset and is often reversible if recognized early and treated appropriately
• CKD is the end result if irreparable damage to the kidneys that develops slowly, usually over the course of a number of years
• underlying causes of renal failure:

  • renal disease
  • systemic disease
  • urologic effects of non-renal origin
• assessment measures to identify persons at risk for development of AKI includes those with preexisting renal insufficiency and diabetes and elderly persons
• aging has effects on one's renal reserve
• prerenal causes of AKI:

  • hypovolemia
  • decreased vascular filling
  • heart failure and cardiogenic shock
  • decreased renal perfusion due to vasoactive mediators, drugs, and diagnostic agents
• postrenal causes of AKI:

  • bilateral urethral obstruction
  • bladder outlet obstruction
• both prerenal and postrenal causes of AKI will result in decreased GFR due to:

  • the result of a lack of flow to the kidney (prerenal)
  • result of backpressure on the kidney (postrenal)
• acute tubular necrosis occurs due to:

  • prolonged renal ischemia
  • exposure to nephrotoxic drugs, metals, and organic solvents
  • trauma, burns, and major surgery are common precursors
  • intratubular obstruction resulting from hemoglobinuria, myoglobinuria, myeloma light chains, or uric acid casts
  • acute renal disease
• the onset or initiating phase of AKI lasts hours or days and includes the time from the onset of the precipitating event until tubular injury occurs
• the maintenance phase of AKI is characterized by a marked decrease in the GFR
• the recovery phase of AKI is a period during which repair of renal tissue takes place
• common causes of CKD:

  • hypertension
  • diabetes mellitus
  • polycystic kidney disease
  • obstructions of the urinary tract
  • glomerulonephritis
  • cancers
  • autoimmune disease
  • diseases of the heart or lungs
  • chronic use of pain medication
• CKD is slow to develop and arises from other disorders
• over time, the renal tissue is slowly damaged and lost in CKD, resulting in an insidious onset
• Stage 1 CKD is kidney damage with normal or increased GFR
• stage 2 CKD is kidney damage with mild decrease in GFR
• stage 3a CKD is mild to moderate decrease in GFR
• stage 3b CKD is moderate to severe decrease in GFR
• stage 4 CKD is severe decrease in GFR
• stage 5 CKD is kidney failure/ESRD
• progression of CKD:

  • diminished renal reserve
  • renal insufficiency
  • renal failure
  • end-stage renal disease
• clinical manifestations of CKD:

  • azotemia
  • alterations in water, electrolyte, and acid-base balance
  • mineral and skeletal disorders
  • anemia and coagulation disorders
  • hypertension and alterations in cardiovascular function
  • GI disorders
  • neurologic complications
  • disorders of skin integrity
  • immunologic disorders
• factors determining manifestations of CKD:

  • the extend of renal function that is present
  • coexisting disease conditions
  • the type of renal replacement therapy that the person is receiving
• in azotemia, urea starts to accumulate in the blood, which is an early sign of kidney failure
• with CKD disease progression, azotemia can eventually result in uremia
• azotemia is nitrogenous waste accumulation in the blood that can occur without symptoms
• uremia is symptoms associated with decreased clearance of nitrogenous wastes
• uremia occurs when approximately two-thirds of the nephrons are destroyed
• causes of uremia:

  • encephalopathy
  • periphral neuropathies
  • pruritus and serositis
• sodium and water balance helps the kidneys function in the regulation of ECF volume
• sodium and water imbalance can be an early sign of kidney damage, causing isosthenirua or polyuria with nearly isotonic urine to plasma
• in CKD, one has a reduced ability to excrete sodium which leads to fluid volume expansion, edema, and hypertension
• approximately 90% of potassium excretion is through the kidneys
• potassium excretion increases as they kidney adapts to a decrease in GFR
• hyperkalemia can happen in late stage CKD and renal failure
• the kidneys normally regulate blood pH by eliminating H+ produced in metabolic processes and regenerating bicarbonate
• breakdown in the kidneys' ability to regulate blood pH can result in metabolic acidosis
• metabolic acidosis can become stabilized with the buffering capacity of bone, but can result in skeletal disorders due to increased bone resorption