smitha
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CASE: A 27 yo man with AIDS is hospitalized with cough, fever, and apulmonary infiltrate on CXR.Tx is initiated with TMP-SMX.On admission, the serum creatinine is 1.6 mg/dl and BUN 21mg/dl.On reexamination 3 days later,the serum creatinine is 2.2mg/dl and BUN is 23 mg/dl.Results of U/A both on admission and 3 days later are normal.Urine output on day3 is 1350ml.The most likely cause of the increased creatinine is.....
a.AIDS glomerulonephropathy
b.Intratubular obstruction secondary to sulfonamide Tx.
c.Allergic interstsitial nephritis caused by TMP-SMX Tx.
d.TMP- mediated decrease in creatinine secretion
e.Acute tubular necrosis secondary to sepsis
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I GUESS THE ANSWER IS.....
B) INTRATUBULAR OBSTRUCTION DUE TO SULPHONAMIDES
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| shirish_sss
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i think the guest is correct.........
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| smitha
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GOOD TRY GUYS....... 
So, now, in this pt. look at the creatinine and urine analysis and urine output.............they r normal............just increasing BUN from 21 to 23 doesn't make it abnormal or high :wink: (we tend to carry away with that)............(BUN upto 25mg/dl is normal---------washington manual!!!!!!).......
So, ruling out one by one from the options........
a......AIDS glomerulopathy presents with proteinuria,and can progress to renal failure ,often with a lesion resembling FOCAL GLOMERULOSCLEROSIS.
b........Intratubular precipitation of sulfonamides can produce ARF which is accompanied by distinct crystals in the urine but is rarely seen with SULFAMETHOXAZOLE.
c........Allergic interstitial nephritis usually takes 10 days or more to develop and is usually accompanied by pyuria and eosinophiluria.
e.........ATN secondary to sepsis causes mild protenuria and granular casts in the urinary sediment.
So, we r left with only one option............d.......TMP-mediated decrease in tubular creatinine secretion,rather than actual decline in glomerular filtration rate ...........
CIMETIDINE therapy also increase serum creatinine by a similar mechanism ........."decreased tubular secretion"!!!!!!!!!! :wink:
Presence of substances like acetoacetate and cefoxitin interfere with the chemical determination of creatinine and hence elevate serum creatinine too...................
Hope iam clear...................
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| shirish_sss
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Posts: 134
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ABSOLUTELY SMITHA..............
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