Renal failure associated with colonoscopy—what is the link?

In January 2006, a 75-year-old woman presented to her primary care physician with severe arterial hypertension and acute renal failure (ARF). She had been hypertensive for 25 years associated with stage 3 chronic kidney disease (serum creatinine 75 μmol/l and estimated GFR 45 ml/ mn/1.73 m2 in October 2005). Her medical history was remarkable for a colic cancer treated by partial colectomy in 2002. A control colonoscopy was done in November 2005; the preparation was done with a sodium phosphate bowel purgative. Her medications included enalapril, hydrochlorothiazide, amlodipine, atenolol and aspirin. The serum creatinine was 340 μmol/l. All immunological exams were negative, and hormonal assays failed to reveal any hormonal cause for hypertension. A bilateral renal arterial stenosis was excluded by a renal angiography. In April 2006, the renal function was still impaired (serum creatinine 410 μmol/l) and the patient was referred to the nephrology unit. Clinical examination was normal, there was no proteinuria and urine sediment analysis was negative. A kidney biopsy was performed (Figure 1). What is the cause of her renal failure? The diagnosis: Acute phosphate nephropathy complicated of chronic renal failure. The kidney biopsy showed, besides mild vascular lesions related to hypertension (Figure 1A), numerous intratubular crystal deposits in the kidney parenchyma (Figure 1A–C). They were stained by Von Kossa (Figure 2), confirming the calcium phosphate nature of the deposits. So ARF was related to nephrocalcinosis, which was related to the ingestion of sodium phosphate purgative. In December 2007, the renal function was still severely impaired with an estimated GFR of 11 ml/min/1.73 m2.