Always insert Foley catheter with unknown volume status or ?decreased U/O: further work up may include U/A ( for casts [RBC], protein, sp. gravity, eosinophils, spot urine Na, spot urine creatinine...), and renal ultrasound (rule out obstruction)

   Prerenal (UOSM > 500, UNa < 10-20 mEq/l, FE Na+ < 1, BUN:Cr > 20, Usp gr > 1.015)

1. Volume Depletion: post op, third spacing, sepsis, vomiting, diarrhea, NG suction, hemorrhage, pancreatitis, SBO, increased insensible losses: Rx -hydrate with NS; Check Iytes - BUN -creatinine; strict I/O's
2. CHF (Rx- Morphine, NTG, Lasix, Digoxin with tachyarrhythmias and/or S3, consider renal dose Dopamine 2-4 ug/kg/min), low output states

    Renal (UOSM < 350, UNa > 20-40, FE Na+ > 1-2, BUN:Cr < 10, Usp gr < 1.015)

1. Intrinsic renal disease (DM, HTN, SLE, vasculitis, uric acid...)
2. ATN (aminoglycosides, penicillinase-r antibiotics, post op, hypotension, low output state, sepsis, IV contrast (esp. with DM, dehydration, azotemia, recent aminoglycoside use), heavy metals, myoglobin, rhabdomyolysis, crush injuries, extremity ischemia, transfusion reactions, Ampho. B, Pentamidine, Cyclosporine, chemotherapy, NSAIDs, Allopurinol, tumor lysis syndrome [uric acid deposition])
3. Others - Glomerulonephritis, Intersititial Nephritis, Vascular PathoIogy, Myeloma

    Post Renal/Obstruction - clogged Foley (irrigate Foley catheter!), stones, blood clots, sloughed papillary tissue, BPH, urethral -ureteral strictures, bladder/prostate CA, ligation, neurogenic bladder

    Rhabdomyolysis - Etiology - Trauma -crush -?compartment syn., burns/frostbite, electrocution, compression, significant overexertion, convulsions; Infectious - Clostridia, Strep, TSS, viral...: Toxins -ETOH, cocaine, heroin, PCP, narcotics, snakebites, ...: Meds -TCAs, neuroleptics, antibiotics...: Endo. - DKA, thyrotoxicosis, hypothyroidism, myxedema; Others - hyperthermia, malignant hyperthermia, hypothermia, myositis (dermato- poly-), extremity ischemia; Labs CPK (>4-5x), LDH, SGOT, K, Phos,Na, + urine myoglobin;
Complications - ATN , K,Phos, DIC, compartment syn.; Rx - 1. Fluid Resuscitation (NS, RL), titrate to U/O > 200 mls/hr; 2. ?NaHC03; 3. ?IV Mannitol (1g/kg); 4. Fasciotomy prn

   Indications for Acute Dialysis: "AEIOU" -"A" -intractable acidosis; "E" - electrolyte disarray (K, Na, Ca); "I" -intoxicants (methanol, ethylene glycol, Li, ASA); "O" - intractable fluid overload: "U" -uremic symptoms (nausea, seizures, pericarditis, bleeding). Dialyze early. Keep BUN < 100 mg/dl, Creatinine < 10 mg/dl.