The investigators will study 2 separate groups:

• Cardiology patients undergoing invasive coronary angiography +/- PCI (Percutaneous coronary intervention).
• Patients undergoing CT examination with contrast medium. All patients will receive intravenous (I.V) hydration for 8-12h before and 36 to 48 h after angiography with 0.45% saline 100ml/h.

All patients will receive oral N-acetyl cysteine 1200 mg twice daily, a day before, on the day of the angiography and for another 48 hours.

In addition, patients will be assigned to receive oral pentoxyphylline (P group) or placebo (C - control group) tablets 3 times a day one day before, on the day of the procedure and for another 48 hours.

Baseline Serum Creatinine (S.Cr) levels in will be taken before angiography and two days after angiography. Radio-contrast nephropathy is defined, in this study, as increase in serum ≥ 25 % of baseline after injection of the radio-contrast agent. Pentoxyfylline is an orally active haemorheological agent for the treatment of peripheral vascular disease, cerebrovascular disease and a number of other conditions involving a defective regional microcirculation. Pentoxyfylline acts primarily by increasing red blood cell deformability, by reducing blood viscosity and by decreasing the potential for platelet aggregation and thrombus formation (mechanism unclear). Pentoxyfylline has also proven to have a significant anti inflammatory effect as well as anti oxidant effect, mechanisms considered to be important patho-physiological causes of contrast induced nephropathy.

Impairment of renal function following exposure to intravenous radio-graphic contrast materials is the third major cause of renal hospital acquired renal dysfunction. Renal dysfunction occurs most often in patients with chronic renal failure and or patients with diabetes mellitus and contributes to the morbidity and mortality. Previous research work proved that the use volume expansion with N-acetyl cysteine (NAC) is superior to volume expiation alone to prevent renal impairment due to radio-contrast5. NAC a potent anti oxidant may prevent CIN by stopping direct oxidative tissue damage and by improving renal hemodynamics.Pentoxyfylline has also proven to have a significant anti inflammatory effect as well as anti oxidant effect.Preangiographic and the highest post-angiographic values of Creatinine and eGFR (estimated glomerular filtration rate) will be recorded. Levels of the biomarker Neutrophil - gelatinase - associated lipocalin (NGAL) will be tested randomly in 49 patients p as a biomarker for contrast induced nephropathy. Blood serology for NGAL will be drown from patients before the procedure and 2 hours after angiography.

Inclusion Criteria:

Cardiology patients:

1. Hospitalization for ACS (acute coronary syndrome) with NSTEMI or Unstable Angina
2. Diabetic patients (treated with insulin or oral hypoglycemic drugs) or patients with basal serum creatinine greater than 1.3mg/dl in females and 1.5 mg/dl in male patients.
3. Informed consent
4. Age between 18-75

Radiology patients:

1. Radiology patients should be diabetic patients (treated with insulin or oral hypoglycemic drugs) or patients with basal serum creatinine of 1.3mg/dl in females and 1.5 mg/dl in male patients.
2. Informed consent
3. Age between 18-75