Chronic diarrhoea in an elderly woman

An 89 year old woman was admitted with a six week history of severe watery brown diarrhoea. She had not travelled recently or changed her diet, but she had lost half a stone (3 kg) in weight. She had a history of diverticulosis, recurrent urinary tract infections, and hypertension but no family history of cancer. She was a non-smoker who lived alone and was independently mobile with a frame, requiring no package of care.

On examination she was afebrile, her pulse was 95 beats/min, and her blood pressure was 150/88 mm Hg. Her abdomen was soft and non-tender. Per rectal examination and a plain abdominal film were unremarkable. Bloods on admission showed raised inflammatory markers, and within days of admission her electrolytes became deranged, with hypernatraemia (sodium 158 mmol/L) and hypokalaemia (potassium 2.5 mmol/L). Blood gas results showed a metabolic alkalosis (pH 7.52, pCO₂ 37 mm Hg, bicarbonate 31 mmol/L) and hyperchloraemia (chloride 116 mmol/L). Cloudy urine, which was positive for Escherichia coli, was collected after insertion of a urinary catheter. Stool culture and Clostridium difficile toxin were negative. Flexible sigmoidoscopy showed sigmoid diverticulosis, and a random biopsy showed a mild increase in chronic inflammatory cells.

Figures 1⇓ and 2⇓ show axial and sagittal computed tomograms of the abdomen