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Your next patient has had abdominal pain for a week. The patient’s parents think it could be related to a recent incident at summer camp. Could they be correct or are they serving up a red herring?

It has been an up and down day in the Pediatric ED. Right now, the place is quiet and you’re beginning to catch up from your last surge of patients. The resident is politely waiting to present her next case to you. It is a 12 year-old boy with abdominal pain. You settle back to hear the story.

The child has had one week of abdominal pain. It comes and goes but the cramping is severe at its peak. He has also had diarrhea. The stools have mucous, but no blood. He has not had any vomiting. He has not run a fever. His appetite is poor and he isn’t taking in very much. No one else around him has been ill. He has been to see his regular physician twice for this. The first time, he had a rapid strep test and a urine done, both of which were negative. The family was told this was likely a viral illness. He went back yesterday because his symptoms were getting worse. This time, his doctor prescribed zantac and hyoscyamine. He has been taking these but has not gotten any relief of his symptoms. In fact, he is here today because the pain is worse.

He has been a healthy boy up until his current illness. He is not on any regular medications. The family history is negative for any gastrointestinal disorders. He does report that he was attending a camp two days prior to the onset of his symptoms. The focus of the camp was on canoeing and he spent hours paddling on lakes and rivers. He only drank bottled water but does say that occasionally he swallowed some lake water when he was paddling. The family wants to know if swallowing lake water could be causing his symptoms.

On exam, he seems uncomfortable and mildly dehydrated. He has no fever but has mild tachycardia. His belly is soft with hyperactive bowel sounds. He has diffuse tenderness but particularly in the right lower quadrant. There is no guarding, no rebound, no psoas or obdurator sign. The rest of his exam is unremarkable.

OK, so you have a patient with one week of intermittent abdominal pain and diarrhea. That sounds like some sort of infectious enteritis. However, there does seem to be more pain in the right lower quadrant. Could this be appendicitis?

You decide to give this child something for pain and some IV fluids for hydration. You order labs and urine and an ultrasound get a look at his appendix.

The labs are not very exciting. Nothing is abnormal. The white count is 12.5 with an ANC of 10.1. He is feeling better from the fluids. He has a diarrheal stool in the ED so you send it for studies. You await the ultrasound results.

The ultrasound shows trace free fluid and multiple mildly prominent mesenteric nodes. He does have a 6 mm tubular structure that could be the appendix. The Radiologist concludes his dictation with “clinical correlation is advised”.

Time to re-examine the patient. He still has a soft belly but the pain remains present. He hurts all over but still a bit more in the right lower quadrant than you would like. You order a CT scan.

The CT doesn’t tie things up for you any more than the ultrasound did. The Radiologist reports a 7 mm tubular structure that is fluid filled and could represent early appendicitis. However, there is no adjacent stranding. Like the ultrasonographer, he notes multiple enlarged mesenteric nodes and suggests that the appearance of the appendix could be due to a viral process with the pain coming from the nodes rather than appendiceal inflammation.

So now what? His hydration has improved and his tachycardia has resolved. However his abdominal exam is right where you left off several hours ago. You consult the Surgeon.

Surgery sees the patient and agrees. After one week of symptoms, if this were appendicitis you would expect a more classic exam, a fever and a more elevated white count. The family is offered admission for serial abdominal exams but they opt to go home and follow-up with for a repeat examination in the morning. You are not on call the next day and the child got his follow-up exam at his own physician’s office so you don’t hear about the results until checking the stool culture a day or so later, you find the answer.

The stool culture is growing Plesiomonas shigelloides. What is that? Can it cause abdominal pain and diarrhea? Where did he get it from?

Plesiomonas shigelloides used to be known as Aeromonas shigelloides. It is a gram negative rod that can be found in soil and fresh water. It is isolated more frequently in the warmer months of the year. It typically causes outbreaks of diarrhea. Risk factors for acquiring infection with Plesiomonas shigelloides include travel to the tropics,  consumption of undercooked shellfish, drinking contaminated water, and exposure to reptiles and tropical fish. The incubation period for illness is about 24-48 hours. Infected patients most frequently develop diarrhea. They can also have severe abdominal pain and cramping, as with our patient, as well as vomiting and fever. Diarrhea can last 14 days or longer in some cases. Extraintestinal infections can occur in immunocompromised patients. In general, the illness is mild and self-limited. Patients with more severe symptoms may benefit from antibiotics. Antibiotics that are active against  Plesiomonas shigelloides include cephalosporins, fluoroquinolones, trimethoprim-sulfamethoxasole and chloramphenicol. Patients are treated based on the time it takes them to respond, generally 3-5 days.

You call the family and the patient is finally feeling better so they chose not to start treatment. They are interested to know that yes, swallowing lake water did in fact cause his problems. And you now have another item in your differential of abdominal pain.


Amy Levine, MD, is an associate professor of pediatric emergency medicine at UNC Chapel Hill.

 

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