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Author: Alan Koay
Editor: Dr Suneet Sood
Narrators: Thong Yi Kun, Alan Koay

Transcript

Ryan had just finished with his rounds and stood in front of the elevator, on the way to the operating theatre. He was looking forward to operating on a challenging stomach cancer. The elevator had just pinged when he heard a voice.

“Doctor, may I ask you about a case?”

Ryan turned around. In front stood a zealous medical student hoping to get his logbook signed. Ryan didn’t really have the time, but, hey, as the chief resident in surgery he had some teaching responsibilities also. “What’s your name,” he asked.

“Jon.”

“Okay, Jon, make it quick.”

Jon began rattling off the full patient history,

“This patient is a 46 year old Chinese policeman. He presents with pain in the right upper abdomen. I thought he probably has gallstones, but he also has a long background of Crohn’s disease. The symptoms don’t fit with Crohn’s disease, but I don’t like to make a second diagnosis.”

“Maybe he does have gallstones? Does he have any risk factors?” Asked Ryan briskly.

Jon was taken aback for a second, trying hard to remain calm. Right-o, the 5 Fs: Female, fat, fertile, fair, forty. Jon was about to blurt out the magical F words when he realised the male policeman had almost none of those risk factors. He panicked, sweat is rolling down his cheeks as his silence became longer and longer.

Ryan asked, a little more kindly, “Maybe Crohn’s can lead to gallstone formation?”

Jon hung his head.

“Crohn’s disease is a form of inflammatory bowel disease that can affect any part of your GI tract, from the mouth to the anus. Crohn’s can cause a severe ileitis there. What’s absorbed in the ileum?”

“Vitamin B12?” asked Jon, knowing fully well that that wasn’t the correct answer.

“Well, of course, B12 is absorbed in the terminal ileum, but B12 has nothing to do with gallstones,” said Ryan, a little curtly. When Jon looked blank, Ryan continued, “Have you thought of bile salts?”

Bile salts! Jon didn’t know where bile salts fit in, but he did know about them. “You mean like sodium taurocholate and sodium cholate and so on?”

“Yes,” said Ryan, “any others?”

“Er, I can’t think of any” said  Jon

“Well,” said Ryan, “What will happen if the bile salts are not absorbed?”

“I know this!” exclaimed Jon, seeing the light.

“Go on then.” Dr Ryan replied

“Bile salts are expelled into the duodenum in the bile, and are reabsorbed in the ileum,” Jon explained

“And when there is extensive Crohn’s ileitis?” prompted Ryan

“Because of the ileal inflammation, bile salts are not reabsorbed effectively. The bile acid pool decreases,” said Jon, and “the bile acid to Cholesterol ratio in your biliary system decreases, leading to the precipitation of cholesterol stones.”

“Similarly, the ileum is responsible for absorption of fat. Thus, patients with Crohn’s tend to be deficient in vitamins A, D, E, and K.” added Ryan, turning away.

“Er, can I get my logbook signed” asked Jon, hopefully?

“I think you need to read up the names of the other bile salts, don’t you?” asked Ryan

“Ah yes, of course” said Jon, faking a smile as Ryan walked off.

To summarise: Diseases of the terminal ileum such as in Crohn’s disease, can cause not only malabsorption of nutrients, but also disrupt the enterohepatic circulation, resulting in gallstones.

References
Heaton K, Read A. Gall stones in patients with disorders of the terminal ileum and disturbed bile salt metabolism. Br Med J. 1969;3(5669):494-6.