I am sure you were aware of this, but, yes, NAC has been shown to be beneficial to kidney function. Questionable if it protects against infection but you can use NAC for kidney protection to if you feel inclined to do so!
The effect of N-acetylcysteine on renal function, nitric oxide, and oxidative stress after angiography
http://www.nature.com/ki/journal/v64.../4494143a.html
The effect of N-acetylcysteine on renal function, nitric oxide, and oxidative stress after angiography.
Treatment with NAC significantly improved the effect of contrast media on creatinine clearance, and maximal beneficial effect was observed 24 hours after angiography. Creatinine clearance (mL/min) was 59.5 plusminus 4.4, 64.7 plusminus 5.8, and 58.7 + 3.9 at baseline, 24, and 96 hours after angiography in the NAC group, respectively, and 65.2 plusminus 3.2, 51.5 plusminus 3.7, and 53.6 plusminus 3.9 in the placebo group, respectively (P < 0.0001). NAC treatment prevented the reduction in urinary nitric oxide after angiography. The urinary nitric oxide/creatinine ratio (mumol/mg) was 0.0058 plusminus 0.0004, 0.0057 plusminus 0.0004, and 0.0052 plusminus 0.0004 at baseline, 24, and 96 hours after angiography in NAC group, respectively, and 0.0057 plusminus 0.0007, 0.0031 plusminus 0.0005, and 0.0039 plusminus 0.0005 in the placebo group, respectively (P = 0.013). NAC had no significant effect on urinary F2-isoprostanes.
Conclusion
NAC treatment has renoprotective effect in patients with mild chronic renal failure undergoing coronary angiography that may be mediated in part by an increase in nitric oxide production.
N-acetylcysteine as a preventive measure for acute renal failure: A plea for more accurate detection of renal function in critically ill patients
http://www.ncbi.nlm.nih.gov/pubmed/17522549extract not available on this one