Allow me to present a common clinical scenario. The patient presents with right lower quadrant abdominal pain. Appendicitis is in the differential diagnosis. After an appropriately thorough H&P you have ascertained that it is not gastro/UTI/strep/pneumonia/constipation/porphyria/pregnancy etc., etc,. and obtain an ultrasound which shows a normal appendix but reveals the presence on enlarged mesenteric lymph nodes.



With the negative ultrasound you have ruled out appendicitis. But, mom is still adamant that she wants to know why her child is having abdominal pain. Thus, can mesenteric lymphadenitis in a child with right lower quadrant abdominal tenderness be the sole reason for the pain?

This is the question that I wanted to answer. Teleologically it makes sense that swollen lymph nodes hurt. We see them cause pain in the neck, groin, armpit et cetera. It turns out that this is a pretty common finding, though the true incidence is not specifically known because not every patient with belly pain gets imaging or laparoscopy. In some adult studies up to 20% of patients had swollen mesenteric nodes upon laparoscopy for appendicitis. It is thought that mesenteric LAN is more common in children and adolescents overall, and can be precipitated by a number of causes including gastroenteritis, inflammatory bowel disease and appendicitis. It also appears to have an association with Yersinia, so find out if your patient has been eating raw pork. Associated history and symptoms (as you’d expect) are varied and sundry and include:

  • Abdominal pain – right lower quadrant or diffuse
  • Fever
  • Antecedent UTI or URI – cervical LAN is also seen in 20% of cases. It is hypothesized that swallowed sputum travels to the gut and induces an immune response
  • Nausea and vomiting
  • Diarrhea
  • Anorexia

So, yes mesenteric nodes can be enlarged, and can be presumed to be the cause of pain in a patient with right lower quadrant tenderness in which you’ve ruled out another cause. Interestingly the nausea and vomiting often precedes abdominal pain as opposed to coming after the onset of pain as seen in appendicitis. The list of specific etiologies is long, including beta-hemolytic streptococcus, Staphylococcus species,Escherichia coli, Streptococcus viridans, Yersinia species (responsible for most cases currently), Mycobacterium tuberculosis, Giardia lamblia, and non– Salmonella typhoid (Medline – Mesenteric Lymphadenitis). In my experience it is often discovered in an effort to rule out appy on imaging (ultrasound and CT). Other diagnoses I have ruled out during the discovery of mesenteric LAN include:

  • Appendicitis
  • UTI/pyelo
  • Ectopic pregnancy
  • Cholecystitis
  • PID
  • Ovarian torsion
  • Intussusception

Interestingly Frisch et al, in a large Swedish cohort study found that the presence of mesenteric LAN in childhood was associated with a significantly decreased risk of ulcerative colitis later in life.

Patients that are not septic do not need antibiotics, provided that you have not identified a proximate bacterial cause (like UTI). In the patient with peritonitis you should still get surgery involved even if you’ve ruled out appendicitis. Likewise, labs (like a CBC) are also not necessary unless you the patient is ill appearing. If the patient is well hydrated and the pain is manageable with oral meds then they can be safely discharged home. Return precautions include worsening pain, vomiting and dehydration or ill appearance. Repeat imaging is not necessary to confirm resolution, especially since most cases self resolve within 1-2 weeks (many sooner).