Endoscopic surveillance for colorectal cancer has been reported to decrease its mortality. The guidelines recommend that colon examinations including colonoscopy be done at regular intervals in individuals over 50 years of age (1). Colonoscopy requires an adequate level of cleansing for effective evaluation of the colonic mucosa (2). The main types of laxatives used for bowel cleansing are oral sodium phosphate (OSP) and polyethylene glycol (PEG). Safety is also very important, as in the case of sodium phosphate, which was rejected by the United States Food and Drug Administration despite its convenience because it gives an increased risk of phosphate nephropathy. Because of such safety concerns, current guidelines suggest use of PEG over OSP (2, 3). PEG is a biologically inactive substance that does not bear an electrical charge and therefore cannot influence the movement of other solutes (4). It is a water-soluble, nontoxic polymer that is minimally absorbed in the gastrointestinal tract (5).
Although PEG is generally considered to be safe for colonic cleansing, it can occasionally induce adverse events such as renal failure, hyponatremia, upper gastrointestinal bleeding or aspiration caused by vomiting, and even death (2, 3, 6). Here, we report a case of hyponatremia in the syndrome of inappropriate secretion of antidiuretic hormone (SIADH) resulting in generalized tonic–clonic seizures after PEG precolonoscopic cleansing. As far as we know, there have been no prior reports describing an association between SIADH and PEG use for colonic cleansing.
A 69-year-old woman visited our gastrointestinal clinic for routine colonoscopic checkup. She had a history of diabetes and dyslipidemia, for which she had been taking glimepride, sitagliptin, metformin and atorvastatin. She had taken the medicines up to the day before colonoscopy but not on the procedure day. For precolonoscopic bowel preparation, the patient ingested 4 L of a standard bowel preparation solution containing an isosmotic solution of PEG. While the patient was waiting for colonoscopic examination, she began complaining of generalized weakness and sweating. She developed a stuporous mentality and generalized tonic–clonic seizures. Her vital signs showed a blood pressure of 143/74 mmHg and a pulse of 76 beats per minute. A physical examination did not show any signs of distended jugular veins, pedal edema, ascites, decreased skin turgor or dry mucous membrane, indicating an euvolemic state. No specific neurologic signs were evident.
Her laboratory results (Tables 1, 2) showed a serum sodium level of 113 mEq/L, a decreased effective serum osmolality of 233 mOsm/kg (<275 mOsm/kg) and an increased urine osmolality of 344 mOsm/kg (>100 mOsm/kg). Her serum creatinine level was 0.51 mg/dL, blood urea nitrogen 6.2 mg/dL (<10 mg/dL), plasma uric acid 3.1 mg/dL (<4 mg/dL), and she had a normal acid/base and potassium balance. Thyroid function tests and basal cortisol tests failed to...