Pre-renal ARF

Pre-Renal ARF

Etiology:

Decreased blood supply to kidneys:

• Blood loss, severe dehydration
• Hypotension
• CHF (decreased effective circulating vol.)
• Renal artery stenosis (bilateral)

When to Suspect Pre-Renal ARF:

1. See the whole situation (blood loss, dehydration)
2. Suspect pre-renal failure in patients with high creatinine who have the following:
   • Low BP, fast pulse (indicates fluid loss)
   • Orthostasis (when a supine pt. sits or stands, systolic BP falls more than 20, & pulse rises more than 10. This is abnormal & is called orthostasis. Indicates severe fluid loss + DKA; Give IV. Fluids )ZZ

Investigations in Pre-Renal ARF:

1. Blood:

   • High BUN
   • High creatinine BUN: creatinine ratio high (> 20)

2. Urine: (just imagine that kidneys are absorbing all the water & salt)

   • Decreased amount (oliguria)
   • Increased osmolality/specific gravity (very concentrated urine)
   • Decreased amount of Na in urine. This is called “fractional excretion” of Na (FeNa) & is expressed as a % In pre-renal failure, FeNa is less than 1%Z

Pre-Renal ARF Treatment:

• I.V. fluids, blood (according to the situation)
• Treat the cause (CHF etc); With correct Rx, renal perfusion improves & so urine output improves.
• If it is not treated soon, renal hypoperfusion can damage the tubules