Lactulose Works in the Large Bowel: But How Does It Improve Hepatic Encephalopathy in a Patient Without a Large Bowel?

ABSTRACT

Introduction: Lactulose is a non-absorbable disaccharide which acts in the large bowel, and is commonly used in the treatment of hepatic encephalopathy. We present an interesting case of altered mental status due to hepatic encephalopathy successfully managed with lactulose in a patient with history of total colectomy. Case Description/Methods: A 67-year-old male with non-alcoholic cirrhosis and inflammatory bowel disease (IBD) post total proctocolectomy with a continent ileostomy known as a Kock-pouch (K-pouch) presented to the hospital with flu like symptoms and altered mental status. He was subsequently found to be positive for COVID-19. At the time of initial evaluation, the patient was obtunded with an elevated ammonia level of 91 umol/L. Colorectal surgery was consulted as the patient was not able to empty his K-pouch. Recently, he complained of inability to catheterize and with bleeding from the stoma. Initial catheterization with a Water's tube yielded 400 cc of effluent. Nasogastric tube was placed through which he was receiving lactulose 30 mg q8 hours. The patient's mental status improved within 24 hours. The patient ultimately underwent flexible pouchoscopy with endoscopic dilation and placement of a 22 French mushroom catheter for decompression of the K-pouch. Discussion(s) Lactulose is a non-absorbable disaccharide composed of galactose and fructose. The small intestine does not have the enzymes required to breakdown lactulose so it reaches the large bowel in its original form. In the large bowel, it is metabolized by colonic bacteria into monosaccharides and then to volatile fatty acids, hydrogen and methane. Lactulose decreases both the production and absorption of ammonia mainly through the presence of gut bacteria. The question arises as to how lactulose decreased ammonia levels in this patient without a large bowel. One proposed mechanism is the translocation of bacteria normally found in the large bowel to the small intestine. Small Intestinal Bacterial Overgrowth (SIBO), is a condition causing an increased number of bacteria in the small intestine. Patients with IBD and structural abnormalities are at increased risk of developing SIBO. Lactulose is commonly used in the diagnosis through the administration of lactulose and subsequent measurements of hydrogen and methane gas in expired air. This condition, in our patient with history of ulcerative colitis and colectomy, is a proposed mechanism of the efficacy of lactulose in the treatment of hepatic encephalopathy.