A 72-year old woman with a past history of diabetic
nephropathy and a baseline creatinine of 1.6 mg/dL was admitted with a (R) foot
ulcer. She was initially treated with ceftazidime and metronidazole IV.
Cultures showed pseudomonas aeroginosa and gentamicin was added. Blood levels of gentamicin remained in
the therapeutic range. 10 days after admission, her ulcer did not show evidence
of healing. After non-invasive arterial testing an arteriogram was recommended
and performed. Seven days following the arteriogram, the serum creatinine
bumped to 2.6 mg/dL but the patient remained non-oliguric. Physical examination
showed a blood pressure of 160/80 mmHg, heart rate 80 bpm, afebrile. She had a
non-healing right foot ulcer and 1+ peripheral edema. The rest of the
examination was normal. Her urinalysis showed a SG 1010, pH 5.0, trace glucose,
rest negative. The sediment showed many renal tubular epithelial cells and
granular casts. Urine eosinophils were negative. Electrolytes: Na 140 mEq/L, K
3.4 mEq/L, Cl 104 mEq/L, C02 26 mg/dL, BUN 40 mg/dL, Cr 2.6 mg/dL. A diagnosis
of gentamicin nephrotoxicity was made.
Risk factors for gentamicin nephrotoxicity include all of
the following except:
A.) Combination therapy with cephalosporins
B.) The length of the treatment
C.) Hyperkalemia
D.) Volume depletion
E.) Pre-existing renal disease
______________Answer to AKI Quiz Nov 3, 2011 was A, Uric acid/creatinine ratio >1
A 16-year-old boy was admitted with bilaterally enlarged kidneys and severe renal impairment. CT scan showed bilateral renal enlargement with features suggestive of an infiltrative lesion. A bone marrow examination was performed, and a diagnosis of ALL was made. The patient developed acute kidney injury after initiation of chemotherapy. What would support the diagnosis of acute uric acid nephropathy
A.) Uric acid/creatinine ratio >1
B.) Uric acid level of 8
C.) Fractional excretion (FENA) <1%
D.) Urine osmolality >500 mOsm/Kg
E.) U/P creatinine >40
Explanation
This patient has acute uric acid nephropathy. Acute uric acid nephropathy is defined as
acute oligoanuric renal failure caused by renal tubular obstruction by urate
and uric acid crystals. Acute uric acid nephropathy is observed almost
exclusively in the setting of malignancy, especially leukemia and lymphoma, in
which rapid cell turnover or cell lysis occurs from chemotherapeutic agents or
radiation therapy. The key features of acute uric acid nephropathy are shown in Fig. 1. Diagnostic clues to the type of AKI are shown in Fig. 2.
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| Fig.1 |
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| Fig. 2 |
