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Acute renal failure (Proceedings)

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Nov 01, 2009

Renal disease overview
           1. Renal insufficiency: 75-85% loss of renal function
           2. Renal failure: 85+% loss of renal function
                    a. Acute
                    b. Chronic
                    c. Acute on chronic

Clinical signs of renal failure
          1. Anorexia
          2. Lethargy
          3. Dehydration
          4. Vomiting +/- Much less than dogs.
          5. Diarrhea +/- Uncommon

Laboratory findings of renal failure
          1. Elevated BUN and creatinine
          2. Elevated serum phosphorus
          3. Normal to decreased serum potassium
          4. Decreased TCO2 and HCO3
          5. Decreased urine specific gravity

Acute vs. chronic
          1. Best single test to differentiate: PCV
                      a. Acute renal failure: PCV is normal
                      b. Chronic renal failure: PCV < 20%
          2. Acute: disease onset is usually subacute to acute – days of illness instead of weeks of gradual decline.
          3. Once Acute is established, you need to aggressively attempt to find the cause

Primary workup
          1. To establish a diagnosis of acute renal failure
          2. History of acute onset
          3. Chem Profile: BUN, creatinine, phosphorus, potassium, TCO2-HCO3
          4. CBC: PCV, WBC
          5. Urinalysis: SG, bacteria, crystals

Secondary workup
          1. Know what diseases are likely to cause acute renal failure
          2. Divide them into Horses and Zebras
          3. Concentrate on the Horses first
          4. But, don't forget about the Zebras
          5. Differential list: 4 Horses
                      a. Ethylene glycol (antifreeze)
                      b. Lily toxicosis
                      c. Pyelonephritis
                      d. Hydronephrosis secondary to ureteral obstruction
          6. Differential list: 14 Zebras
                      a. NSAIDs
                      b. ACE inhibitors
                      c. Cholecalciferol rodenticide (Vitamin D toxicosis)
                      d. Antihypertensive drug
                      e. Renal lymphoma
                      f. Prolonged anesthesia
                      g. Aminoglycosides
                      h. Amphotericin-B
                      i. Radiographic contrast agents
                      j. Insect or snake venom
                      k. Acute pancreatitis
                      l. Heat stroke
                      m. Transfusion reaction
                      n. Melamine in tainted food (should not see again)
          7. Ethylene glycol (antifreeze)
                      a. Exposure within the last 6 hours
                      b. Hypocalcemia
                      c. Calcium oxalate crystalluria
                      d. U/S: hyperechoic cortex and medulla (due to CalOx crystals) and medullary rim sign (MRS)
                      e. Positive ethylene glycol test
                      f. Recap: history, chemistry panel, urinalysis, renal ultrasound, EG test
          8. Lily toxicosis
                      a. Within the last 4 days
                      b. Recap: history
          9. Pyelonephritis
                      a. Painful kidneys/abdomen – usually
                      b. Radiographs – enlarge kidney(s). Normal sized kidneys when acute phase.
                      c. Excretory urogram – dilated renal pelvis
                      d. Ultrasound – enlarged kidney(s) with dilated, irregular renal pelvis (unless too acute)
                      e. Urinalysis – bacteria in sediment
                      f. Urine culture – positive growth
                      g. Recap: exam, radiographs, (excretory urogram), ultrasound, UA, U culture
          10.     Hydronephrosis due to ureteral obstruction
                      a. Painful kidneys/abdomen – usually
                      b. Radiographs – enlarged kidney(s); urolith(s) in ureter
                      c. Excretory urogram – no flow
                      d. Ultrasound – enlarged kidney(s) with dilated renal pelvis – may be extremely dilated
                      e. Recap: exam, radiographs, ultrasound