Observations on the sodium and potassium content of mucus from the large intestine.

Potassium is sometimes depleted in diseases of the intestine in which diarrhoea is a prominent symptom, such as idiopathic steatorrhoea (Lubran and McAllen, 1951) and ulcerative colitis (Posey and Bargen, 1950). Occasionally abnormal quantities of mucus are present in the stools in these conditions. It may occur in patients with villous tumours of the large bowel and is then almost always associated with chronic watery diarrhoea and excessive loss of mucus (Southwood, 1962). In most reports of this complication, sodium depletion and dehydration accompany the hypokalaemia. The stools and watery mucus, in some cases exceeding several litres daily, contain 103 to 158 mEq. of sodium and 15 to 80 mEq. of potassium per litre (Shnitka, Friedman, Kidd, and MacKenzie, 1961). Southwood (1962) and Duthie and Atwell (1963) drew attention to wide variations in the concentrations of potassium encountered in rectal discharges containing mucus, in contrast to a narrower range for sodium. Roy and Ellis (1959) and Cooling and Marrack (1957) considered that the villous tumours actively secrete potassium, but Shnitka et al. (1961) and Rowe (1964) regarded the excessive loss from the surface of the tumours of mucus, rich in both sodium and potassium, sufficient to account for the electrolyte depletion. The study of mucus from the large bowel is hampered in many instances by difficulties in freeing samples from faeces or blood, while owing to dilution, the electrolyte concentrations found in material recovered from the rectal discharges of patients with villous tumours may not represent those present at the time of secretion. A report by Little (1964) that mucoid fluid obtained from a colostomy above an annular carcinoma of the colon contained 140 mEq. of potassium per litre, indicated that fresh mucus from the large bowel might contain amounts of potassium in excess of those previously reported. A potassium content of 93 mEq. per litre in a sample of mucus obtained at operation in this hospital from the surface of a small carcinoma in the rectum of an elderly male patient lent some support to this view. An opportunity to make a more thorough study of colonic mucus free of faeces and blood arose during the investigation of a patient with a partial volvulus of the sigmoid colon. The results of these observations are reported here and a comparison made with data obtained from material recovered from the watery stools of a patient with a villous papilloma of the rectum.