Y. enterocolitica is serotyped into around 60 serogroups by their O lipopolysaccharide surface antigens. Most subtypes are nonpathologic to humans. Serogroups that are harmful to humans are O:3 and O:9, which are most common in Europe, and serogroup O:8 which is most prominent in the United States. Animals and humans who are infected with this bacteria and who never develop symptoms or convalesce from a symptomatic episode may become carriers and will harbor the Y. enterocolitica bacteria in their GI tract. [8]

Most patients who contract Y. enterocolitica never develop symptoms. Often mild symptoms of diarrhea and abdominal pain may occur during yersiniosis. More advanced signs of this infection include watery or bloody diarrhea, fever, chills, and increased abdominal pain. If mesenteric adenitis is also present patients will have moderate to severe right lower quadrant abdominal pain. This is easily mistaken for acute appendicitis. They may exhibit abdominal guarding and rebound tenderness with McBurney's sign (point tenderness one-third of the way between the umbilicus and the anterior superior iliac crest). Localized adenitis causes this at the terminal ileum where most of the bacteria are concentrated. Extreme watery or bloody diarrhea is often misdiagnosed as salmonellosis, shigellosis, or Giardia enteritis. Patients with advanced infections especially those left untreated will present with signs of sepsis, dehydration, and shock. [9]

Lab and radiologic tests are done more for excluding other etiologies such as appendicitis, Meckel's diverticulitis, or inflammatory bowel diseases. Stool cultures should be done to make the diagnosis of Y. enterocolitica. If this particular bacteria is suspected, the microbiology department should be notified because isolation of this organism from stool requires the use of a special Cefsulodin-Irgasan-Novobiocin (CIN) agar. In severe progressive cases, especially in immunocompromised patients, CT imaging may be needed to confirm or rule out intrahepatic or splenic abscesses. [4][10]

Most Y. enterocolitica infections are self-limiting and require no treatment. Patients with more pronounced symptoms of diarrhea and dehydration should first be treated symptomatically. They will need to be resuscitated with intervenous fluids and stabilized. Appropriated lab tests and x-rays should be ordered to rule out other possible surgical etiologies of their symptoms. As this is often a self-limiting condition, antibiotics are usually not required, but in more advanced cases, cases that do not respond to symptomatic therapy or cases of immunocompromised patients, antibiotics should be initiated. Because this is a beta-lactamase producing bacteria, penicillins, and first and second generation cephalosporins are ineffective and should not be used. The recommended antibiotic therapy for Y. enterocolitica is a combination of doxycycline and an aminoglycoside. Other antibiotics that have been proven effective in treating this condition are trimethoprim-sulfamethoxazole, fluoroquinolones, chloramphenicol, and third-generation cephalosporins. Immunocompromised patients with splenic or hepatic abscesses may respond to percutaneous drainage of these abscesses. Long-term intervenous antibiotics should also be administered. [4][11]

Appendicitis is probably the most well-known misdiagnosis of patients with Y. enterocolitica infections thus the term pseudoappendicitis. Other differential diagnoses to rule out would be inflammatory bowel disease, Meckel's diverticulitis, mesenteric lymphadenitis, ischemic colitis and sigmoid diverticulitis. There are many infective causes of similar symptoms that must be ruled out. These include various parasitic infections, Giardiasis, salmonellosis, shigellosis, and Clostridium difficile colitis. [12][3]

This disease is most often self-limiting. Treating the symptoms with fluids, rest, and fever control is usually sufficient, and patients recover fully after 24 to 48 hours. Immunocompromised patients or patients with the more systemic disease will have a poorer prognosis. [13]

There are no identifiable long-term sequelae of this disease. Some studies speculated that patients with prolonged courses of this condition might develop autoimmune thyroid disease or other auto-immune pathology; however, this has not been proven. [13]

Y. enterocolitica is mainly a disease of the GI tract. It results from direct contact and ingestion of contaminated material, water, and food.This highlights the importance of handling food and maintaining a hygenic environment to avoid contracting the bacteria. 

Often patients are misdiagnosed with appendicitis and undergo an appendectomy. The diagnosis of Y. enterocolitica is never made because their symptoms subside without treatment and they feel better just by receiving intravenous antibiotics during the perioperative period. This condition is undoubtedly underdiagnosed. [7]

Collecting an accurate history usually leads to the correct diagnosis of pseudoappendicitis. Knowledge of the epidemiology and treatment of this condition could spare the ill patient an unnecessary surgery. The clinician must also be patient, as the appropriate treatment of this condition is supportive care. Awareness of the self-limiting nature of this disease is mandatory for the treating staff and patient.(Level V)