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Renal

Links

• local: Critical Care and Blood Gas/Lytes,  Urology, Vasculitides

Acute Renal Failure

• Cr, BUN, lytes, U/A and FENa
• FENa: fractional excretion of sodium
  • < 1.0%: prerenal, which for ARF means hypovolemia
  • > 1.0%: suspect interstitial nephritis (see U/A)

Hemolytic-Uremic Syndrome (HUS)

• Hemolytic-Uremic Syndrome (eMedicine)
• see also: Diagnostic Dilemmas and D/Dx
• One of the "thrombotic microangiopathies" along with thrombocytopenic purpura (TTP), childhood HUS, and adult HUS. Most common cause of ARF in children, occurs in elderly as well. Children tend to do well, with many recovering spontaneously.
• endothelial damage seems to be primary lesion, causing capilary and arteriolar thromosis, microangiopathic hemolytic anemia, thrombocytopenia, and acute renal failure in children 1-4 yo and the elderly.
• associated with bloody diarrhea from EHEC, esp 0157:H7, esp when fever and leukocytosis
• Bactrim may increase risk of HUS in pts with EHEC

Hypoparathyroidism and Hypocalcemia

• Hypocalcemia with
  • hyperphosphatemia
    • normal renal function -> hypoparathyroidism (HPT) (or acute phosphate load?)
    • renal failure
  • low or normal phosphate: vitamin D deficiency, malabsorption, acute pancreatitis, osteoblastic tumor metastasis.
• malabsorption/Vit D deficiency: normal and low serum PO4
• HPT: low Ca due to reduced ca efflux from bone, reduced renal ca reabsorption and reduced intestinal absorption

Kidney Stones

Initial evaluation and management

• U/A: not always heme positive, may show crystals
• abdominal film: 80% show stones (not in my experience!)
• lytes: BUN/Cr, Ca, PO4, uric acid
• pain control: IM, then oral percocet + ibuprofen 600 mg q6h
• hydration: IV, oral fluids (4 liters PLUS/day, beware water intox in elderly)
• strain urine
• IVP if not passing by day 1-2 (vs. helical CT?)
• U/S or helical CT after stone is passed to screen for staghorn calculus or Polycystic Kidney?

Prevention: Ca-Oxalate Stones

See Prevention of Recurrent Nephrolithiasis - Nov 15, 1999 - AFP

meds

• thiazide, citrate, PO4

diet

(Anything to do with diet and kidney stones seems to have very weak evidence.)

• fluid: 2.5-3.0 liters/day (transparent urine)
• avoid: grapefruit juice
• encourage: red wine, possibly tea (beer?)
• restrict sodium?
• probably irrelevant: normal calcium intake, mineral water. Dietary calcium restriction may increase the risk of stone formation as well as favoring bone calcium depletion.

References

• Outlines in Clinical Medicine: Kidney Stones
• PubMed Search: Diet and Kidney Stones

Polycystic Kidney (autosomal dominant PSKD)

• Polycystic Kidney Disease from eMedicine
• generally followed by nephrologist.
• screen family members with ultrasound, genetic screens may be shortly available. Defect in 1/1000 euro-americans.
• 90% cystic kidneys are autosomal dominant, all have cysts by age 30. Cysts also occur in liver, pancreas and spleen -- due to gene defect in "polycystin". May see colonic diverticula. Presents with pain, hematuria, nocturia (decreased ability to concentrate urine). Develop UTI, hypertension, Kidney Stones, ESRD.
• intracranial aneurysms present in 5-10% of asymptomatic patients (screening value unclear)
• cardiac valvular abnormalities (mostly MVP) may occur (screen with cardiac ultrasound?)

Potassium

• total body K: 30 mEq/kg
• K < 3.3: deficit 200 mEq
• usual intake: 40-80 mEq/day
• max IV rate: 20-30 mEq/hour. Over 30 needs monitor, over 40 needs central line.
• chg pH 0.1 --> -chg K 0.6 mEq/L
• kidney clears K load quickly, but has obligatory K loss (@ 5-10 mEq/L urine).
• potassium aliquots: add 1-3ml of 1% lidocaine to each aliquot.

hyperkalemia therapy (K > 7.5 or EKG changes)

• Ca Gluconate: 5-10 ml of 10% soln IV over 2 minutes. Rept. x 1. (Beware: dig + Ca --> dig toxicity). Lasts 1 hour, works stat.
• D10 + NaHCO3 90 mEq 1L over 3h (1/3 in first 30 minutes) with Humulin R 25 S/Q. (OR Humulin R 10 units IV with 1 amp D50).
• NaHCO3 1 amp. IV over 5 min, repeat in 10 min.
• Kayexalate: 20-50 gm in 100-200 ml 20% sorbitol PO q 3-4 hours up to 5x daily. Decr. 1 mEq K per gm Kayex, gain 1.5 mEq Na.