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[upbeat intro music][Dr. Handy] Hi, welcome to Harrison's PodClass, where we discuss important concepts in internal medicine.

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I'm Cathy Handy. [Dr. Wiener] And I'm Charlie Wiener, and we're coming to you from the Johns Hopkins School of Medicine.

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[Dr. Handy] Welcome, everyone, episode 94, today we'll be talking about a 15-year-old with right lower quadrant pain.

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[Dr. Wiener] Okay, Cathy, today you're caring for a 15-year-old student who presented to the emergency department with right lower quadrant pain that started yesterday.

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Given his presentation, he was taken emergently to the operating room for an appendectomy.

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However, on exploratory laparotomy, his appendix appeared quite normal and the surgeon visualized striking mesenteric adenitis and terminal ileitis.

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The operation was aborted without further intervention and he was admitted to the medical intensive care unit.

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On further questioning, the patient endorsed eating chitterlings at a family gathering a week prior.

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You suspect his infection is due to which of the following?

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A. Clostridium difficile; B. E. Coli; C. Staph aureus; D. Trichinella spiralis; or E. Yersinia enterocolitica.

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[Dr. Handy] Can we first discuss what are chitterlings?

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Are those the same as chitlins popular in the south?

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[Dr. Wiener] Yes, well, chitterlings are common dish prepared from pig intestines.

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Essentially, every culture that consumes pork has a version of this dish.

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They can be grilled, stuffed, stewed, or fried.

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I can honestly say that I'm not a huge fan, but that has little bearing on this question.

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[Dr. Handy chuckles] All right, so let's go back to the patient presentation here.

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So he had an emergent exploratory laparotomy for presumed appendicitis, but he was found instead to have ileitis and mesenteric adenitis.

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[Dr. Wiener] Right, and presumably this is acute, we're not given any non-infectious causes, such as Crohn's disease in the options.

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So which of the infections are you thinking of?

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[Dr. Handy] All right, well, the answer choices are all infections, and what we have here is an example of pseudo appendicitis.

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So of the choices listed, this is typically associated with Yersinia enterocolitica infection, so the answer would be E.

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[Dr. Wiener] All right, well, you're going to have to tell me more about that.

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[Dr. Handy chuckles] Yersinia enterocolitica infection typically causes terminal ileitis and adenitis as was presented in this patient.

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It's transmitted from inadequately cooked pork or contaminated meats, milk, or even vegetables.

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A high percentage of pigs carry pathogenic Yersinia enterocolitica and their feces can contaminate other animals because the organism can colonize many species.

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The organism also can live in water, so ingestion of contaminated water may cause disease.

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Symptoms are typically diarrhea, which may be bloody and also fever.

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It's typically self-limited, and if endoscopy is performed, you see thickening and ulcerations of the terminal ileum and cecum, with elevated round or oval lesions that can overlay the Peyer patches.

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Radiographically, mesenteric lymph nodes are enlarged.

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[Dr. Wiener] Does this infection cause sepsis or other complications?

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[Dr. Handy] Septicemia is more likely in patients with preexisting conditions, such as diabetes mellitus, liver disease, advanced age, malignancy, or HIV/AIDS.

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Interestingly, Yersinia are among the iron loving bacteria, so patients with any condition involving iron overload, such as hemochromatosis and thalassemia are also at higher risk of severe disease.

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As in enteritis of other bacterial etiologies, post infective complications, such as reactive arthritis occur mainly in individuals who are HLA-B27 positive.

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[Dr. Wiener] You mentioned that the Yersinia infection is typically self-limited.

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Does it require any treatment?

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[Dr. Handy] Data from clinical trials do not support antimicrobial treatment for adults or children with Yersinia enterocolitica diarrhea.

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Systemic infections with bacteremia or focal infections outside the gastrointestinal tract generally do require antimicrobial therapy.

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Yersinia enterocolitica strains nearly always express beta-lactamases, and because of the relative rarity of systemic infections, there are no clinical trial data to guide antimicrobial choice or to suggest the optimal dose and duration of therapy, but on the basis of retrospective case studies and in vitro sensitivity data, fluoroquinolone therapy is effective for bacteremia in adults.

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A third-generation cephalosporin is also a reasonable alternative.

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Amoxicillin and amoxicillin / clavulanic have shown poor efficacy in case series, so I wouldn't recommend those.

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Trimethoprim / sulfamethoxazole, gentamycin, and imipenem are all also active in vitro.

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[Dr. Wiener] Great, so what about the other choices? Any comments on those?

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[Dr. Handy] Sure. Trichinella is classically associated with consuming undercooked pork products, but is associated with neuromuscular damage and inflammation as opposed to terminal ileitis or pseudo appendicitis.

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In fact, trichinosis is remarkably uncommon in the U. S. from commercial pork.

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You're more likely to get it from undercooked wilds or game meat.

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Clostridium difficile causes a colitis and E. coli can cause enteritis, although not classically associated with terminal ileitis and adenitis.

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And I'll just add, not listed here, but Campylobacter jejuni is the other infection that is associated with pseudo appendicitis.

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[Dr. Wiener] Okay, thanks. So the teaching points in this case are that Yersinia enterocolitica infection is the cause of pseudo appendicitis in adolescents and adults and it may arise from contaminated food.

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It typically causes diarrhea with ileitis and mesenteric adenitis.

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The infection typically does not require antibiotic therapy except for in susceptible or bacteremic individuals.

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[Dr. Handy] And you can read more about this in Harrison's chapter on the plague and other Yersenia infections.

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[upbeat outro music][Mr. Shanahan] This is Jim Shanahan, publisher at McGraw Hill.

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