Acute Renal Failure

Front 1

The most widely used serum (plasma) marker for estimating GFR is ______

Describe the relationship b/w the above marker and GFR

Back 1

• creatinine
• Inverse relationship: as creatinine (in plasma) rises, GFR decreases

Front 2

Define:

azotemia
oliguria
anuria

Back 2

• azotemia: retention of nitrogenous waste products (increase in urea & creatinine) due to ⇓ GFR

• Oliguria: Urine output < 500 mL in 24 hrs

• Anuria: Complete absence of urine formation ( or < 50 mL in 24 hrs)

Front 3

List the 3 general categories of processes that cause ACUTE forms of azotemia

Back 3

Pre-renal: Affecting renal blood flow (BUN:Creatinine > 15:1)

Intrinsic: disease affecting the small vessels, glomeruli or tubules (BUN:Creatinine ≤ 15:1)

Post-renal: from obstruction to urine flow in ureters, bladder, or urethra (BUN:Creatinine > 15:1). Obstruction ⇓ GFR

Post-renal:

Front 4

Ingestion of what food(s) can ⇑ serum creatinine?

Back 4

• Cooked meat
• Creatine (not creatinine) supplements (body building)

Front 5

Symptomatic ureamia is usually not seen until GFR is < _____

Back 5

15 mL/min

Front 6

What are the 2 forumulas used to estimate GFR? Which is regarded as more accurate?

Back 6

1. MDRD (modification of diet in renal disease)
• most accurate
• includes modifier for African-American and women
• doesn't rely on estimate of body weight

2. Crockcroft-Gault
• Includes a modifier for women
• Requires an estimate of lean body weight

Front 7

What is the value of obtaining a renal ultrasound in a patient w/ azotemia?

Back 7

To evaluate the size of the kidneys, which are often smaller than normal in CKD, and to look for other anatomic clues, like ureteral obstruction.

Front 8

List the major causes of acute prerenal failure

Back 8

• ⇓renal perfusion from ⇓ circulating blood volume
--GI hemorrhage, diarrhea, diuretics
• Volume sequestration (third spacing)
---burns, pancreatitis, peritonitis, rhabdomyolysus
• ⇓effective arterial volume
---cardiogenic shock, sepsis
• ⇓ in Cardiac output from peripheral vasodilation
--- sepsis, drugs
• profound renal vaso-constriction
--- severe heart failure, hepatorenal syndrome, NSAIDs

Front 9

Explain how NSAIDs and ACE-inhibitors can cause acute renal failure

Back 9

NSAIDs
• Blockage of prostaglanding production by NSAIDs can result in SEVERE vasoconstriction of the afferent arteriole and can lead to acute renal failure
• ACE-inhibitors decrease efferent arteriolar tone and in turn decrease glomerular capillary perfusion pressure

Front 10

Once the mean arterial pressure falls below ____ mmHg, there is a steep decline in GFR

Back 10

80 mmHg

Front 11

ACE-inhibitors should not be given to patients with renal artery stenosis because:

Back 11

Patients are dependent on efferent arteriolar vasoconstriction for maintenenance of GFR pressure and are particularly susceptible to precipitous declines in GFR when given and ACE inhibitor

(Even riskier in bilateral renal artery stenosis)

Front 12

Muddy brown granular casts in the urine of a patient with azotemia is most consistent with ____

Back 12

Acute Tubular Necrosis (ATN)
• Casts occur because the tubules slough off cells
• ATN accounts for approximately 90% of acute intrinsic renal failure

Front 13

Acute intrinsic renal failure is caused by _______ 90% of the time. What is a diagnostic finding?

Back 13

Acute Tubular Necrosis (ATN)
• Muddy brown granular casts

Front 14

What is the normal GFR in a 25-year old? In a 70-year old?

Back 14

Front 15

Acute Tubular Necrosis (ATN or oliguric ARF) can be distinguished from prerenal azotemia by which lab assessments?

Back 15

• BUN: Creatinine Ratio
• Fractional excretion of sodium (FENA)