Tropical Sprue

00:01 Welcome.

00:02 In this talk, we're going to cover Tropical Sprue.

00:06 What is that? Well, it's a malabsorption syndrome that's classically associated with certain infections.

00:12 And what's been shown on the left hand side is a normal villous structure within the small bowel, so you have a lot of surface area.

00:19 And when you have tropical sprue, you lose a lot of that villous surface area, so you have functionally a malabsorption.

00:26 And that will lead to a variety of syndromes to become pretty straightforward once you realize that's the problem.

00:32 In terms of the epidemiology, it is classically associated with tropical regions.

00:37 However, tropical sprue is found all over the world.

00:43 It infects indigenous populations, as well as travelers, and typically the travelers who spend more than a month in a particular location.

00:51 So, so called travelers diarrhea may be a form of tropical sprue.

00:57 Men and women have a similar incidence overall.

01:00 What's going on with this? Well in fact, the exact mechanisms are a little bit up in the air.

01:07 And the exact causative agent is not known.

01:09 If we only knew what likely bacteria was the cause, we might be able to treat it or prevent it.

01:16 In various locales, it may be due to Escherichia coli, E. coli or Klebsiella or Enterobacter.

01:22 And those are the most commonly cultured entities, but just because we can culture them also doesn't necessarily mean that they're causal.

01:30 The intestinal damage that whatever organism is responsible for the intestinal damage is attributed to exotoxins made by these bacteria and the associated secondary inflammation.

01:43 So this is going to be a schematic.

01:45 This is again, a little bit of a completely incomplete blackbox in terms of the mechanism, you have luminal bacteria of various forms, that are elaborating various exotoxins here in "toxins".

02:03 Those can be translocated and even the direct bacterial injury will elicit an inflammatory response.

02:11 The exotoxins are processed and presented through antigen presenting cells, and can then stimulate CD4+ T cells to become th1 or th2 T cells that will elaborate certain cytokines.

02:28 Those cytokines will elicit secondary inflammatory mediators and recruit additional cells, such as macrophages.

02:36 A combination of the exotoxins directly, the bacterial infection, and the secondary immune response will lead to apoptosis of the epithelial cells, or just a degeneration so that we lose that nice villous architecture.

02:53 And we will also have intraepithelial lymphocytosis.

02:56 We are recruiting a lot of inflammatory cells as a result of the immune response.

03:01 Fundamentally, we're losing surface area.

03:04 So what happens when that occurs is that we don't have good absorption.

03:09 The classic traveler's diarrhea is watery and foul smelling diarrhea, everything that we're eating is not being absorbed.

03:16 And when it's not being absorbed, the bacteria further down in the GI tract, has a field day and is able to metabolize and ferment all of that.

03:26 There's frequently steatorrhea, which means there's a lot of fat in the stool.

03:29 And again, it's because we are not absorbing all those various nutrients.

03:35 Bloating occurs and crampy abdominal pain occurs because there's fermentation.

03:39 And the bacteria that are having a field day with everything that's not being absorbed are making methane gas.

03:44 They're making hydrogen gas, they're making carbon dioxide and we're getting a massive expansion of the bowel that hurts.

03:51 And that's the crampy abdominal pain and that sensation of bloating.

03:55 Because we're having increased transit due to the hygroscopic effect of having all that unabsorbed material within the bowel, it's sucking water into the bowel.

04:07 There's very rapid movement throughout the bowel, and that may be manifested as very loud borborygmi.

04:16 If you've not heard the term before, that just a really loud bowel sounds.

04:19 It's very, very impressive when you hear it.

04:22 Fever is not very common.

04:24 So most of the manifestations are going to be restricted to the lumen.

04:28 You may feel very terrible but you're not getting a lot of systemic inflammation.

04:33 Because you're not absorbing, you will have weight loss and you probably don't feel very much like eating so you have anorexia.

04:40 If it is chronic in nature, you're not going to be absorbing appropriate things like iron and vitamin B12.

04:47 So you may become anemic and there will be clearly malnutrition because you're not absorbing the normal nutrition that is present.

04:56 How do we diagnose this? So it's the appropriate travel history? Yes, I was spending some time in a very exotic locale.

05:04 And I came back and I've got this chronic diarrhea.

05:06 I wonder if you have tropical sprue.

05:09 You do want to exclude other conditions and celiac disease and a whole variety of malabsorption syndromes can be have the same sort of manifestations.

05:20 You would want to do a blood test to make sure that there is not a megaloblastic anemia due to low vitamin B12 or folate levels because you're malabsorption.

05:28 But you would also want to check for a microcytic anemia because you're not absorbing iron appropriately, either.

05:34 The stool analysis rules out parasitic infections, so you would look for ova and parasites.

05:38 And the main reason that you want to do that is that you're going to treat that a little bit differently than a bacterial infection that is causing our tropical sprue.

05:48 You can also check for fecal fat.

05:50 But just having the appropriate history with kind of foul smelling and fatty stool is probably sufficient and you don't need to do have your poor patient while they're also feeling terrible.

06:02 Collect their feces for days and then to measure fecal fat.

06:06 A small bowel biopsy usually not required but can be done.

06:10 On the left hand side, you're seeing beautiful villous architecture, nice tall villi and kind of moderate size crypts.

06:18 On the right hand side, you're seeing that we've lost a lot of that villous architecture.

06:22 The villi are much shortened and abbreviated, the crypts are much deeper.

06:27 This has to do with injury to the villous architecture.

06:30 Fortunately, if we clear the infection, we treat it with antibiotics etc, we will restore the normal villous architecture and absorption will be restored to normal.

06:41 So how do we manage this? So basically, it's antibiotics.

06:44 And in most cases, tetracycline seems to be the antibiotic of choice.

06:49 If there is clear cut evidence of a vitamin deficiency, you'll get supplementation, usually B12 and folate but you may also supplement with iron.

06:57 And clearly if there is evidence of dehydration or malnutrition, you may want to give fluid and electrolyte resuscitation.

07:06 For refractory patients or for people who live in endemic areas, you may have to continue this antibiotic treatment and supplementation for up to a year.

07:16 And with that we finished with tropical sprue.

07:19 There is an old pop song that was called "You don't mess around with runaround Sue." Same thing here you don't mess around with tropical sprue.

07:32 Thanks.