On the differential diagnosis of acute renal failure

摘要: D istinguishing between vasomotor nephropathy (acute tubular necrosis, acute renal failure) and functional insufficiency (prerenal is perhaps the most common diagnostic exercise encountered in dealing with patients azotemia. In principal, it not difficult to separate these two entities on basis of history, physical examination, clinical course very different urinary characteristics which they present. practice, however, hoth conditions may occur same setting present comparable findings. Thus, differences have proved valuable as aids differential diagnosis (Table I) long subject under influence diuretics or experiencing an osmotic diuresis. Unfortunately, features separating failure from become blurred elderly younger who hypertensive diabetic nephrosclerosis other chronic parenchymal diseases. my experience, moreover, this population seems prone development unusually severe response a hemodynamic challenge, their serum creatinine concentration at times reaching preuremic levels if ‘underlying problem remains unrecognized. such patients, Inability concentrate urine normally despite marked volume depletion well documented [ 11; urine:plasma (U/P) ratio (U/P,,) apt be significantly lower than usual for failure, sodium (Na) far exceed that considered typical failure. Furthermore, had serious some time do necessarily respond promptly administration fluid [2]. Even after full restoration circulating assured by normal high pulmonary capillary wedge pressure, remain oliguric up 24 hours 21. After has been restored, often will large dose loop diuretic mannitol, again ‘signaling origin sustained insufficiency. although distinguish those nephropathy, happy circumstance does always prevail. With existence “grey zone” Na concentration, osmolality U/P,, absolutely either more definitive tests sought recent years. Most notable among index (RFI) Handa Morrin [3] fractional excretion (FE&. former, (UNa) divided simultaneous quotient multiplied 100. RFI = UNa 4 X The FEN, minor modification U/P (U/P&) substituted value, so U/P& + degree variation generally encountered, indexes give results are little significance. A below 1 percent suggested rule out possibility 451. Values 3 indeterminate Miller et al. 51 indicative Espinel Gregory 41. Both groups researchers declared superior classically employed indices marker. Indeed, one reports 41, 11 40 diagnosed having 7 20 meq/liter, 16 ratios 15 40, 13 osmolalities 350-500 mOs/kg HzO. Such values would distinctly unusual traditional criteria. all was greater percent, but 22 fell percent. Of 55 cases nonoliguric attributed 51, reportedly