Introduction In general, oral bowel cleansing preparations are safe and well tolerated. The National Patient Safety Agency (NPSA) issued a Rapid Response Report in February 2009, alerting to the potential risk of harm associated with the use of oral bowel cleansing preparations. These risks included harm as a result of renal failure due to phosphate nephropathy; complications of hypovolaemia; and electrolyte disturbances. The risk of complications depends on the choice of bowel preparation and on risk factors present in the individual patient.

Methods It is a prospective study on 159 individuals, who underwent colonoscopy as a day case at the Gastroenterology Day Unit, Norfolk and Norwich University Hospital in September 2009. They all had two sachets of Picolax bowel cleansing preparation. The data collected included sex; age; history of chronic kidney disease (CKD); whether patients were on ACEi, Diuretics, and NSAIDs. We also looked at their renal function and estimated Glomerular Filtration Rate (eGFR) before and on the day of their colonoscopy. Serum Magnesium level was checked on the day of the procedure.

Results 140 out of 159 patients had no abnormality in their renal function. Six patients had a slight hyponatraemia with sodium of 131–133 mmol/l, while three other patients had significant hyponatraemia: 130 mmol/l, who was on bendrofluazide; 128 mmol/l, who was on spironolactone and furosemide; and126 mmol/l, who was not on diuretics. One had hypernatraemia (150 mmol/l). Significant hypokalaemia (3.0 mmol/l) was identified in one patient. 157/159 patients had elevation in serum Magnesium, highest level was 1.4 mmol/l. Two patients maintained normal Magnesium. Two patients with normal background renal function had only a mild rise in serum urea with normal creatinine and eGFR. Six patients were identified with CKD, three stage 3, and three stage 4/5. Only one patient of the six who was on Ramipril had mild rise in the creatinine level and eGFR dropped from 61 to 52. There was no alteration in the eGFR of other five patients. While 2/6 patients showed improvement in their renal function after taking bowel preparation. 28 patients were on one or a combination of ACEi, Diuretics and NSAIDs, only three of those patients had mildly abnormal biochemistry.

Conclusion Only a small number of patients (9%) suffered minor deterioration of their renal function or electrolyte disturbances. All but two patients had minimally raised Magnesium level of no clinical significance. None of these patients required admission to hospital as a result of these abnormalities. Patients who had CKD had no deterioration in their biochemical profile. Over all there was no clinically significant biochemical abnormality following Picolax administration.