Mesenteric Adenitis

I. What every physician needs to know.

Right lower quadrant (RLQ) pain is a common initial presenting complaint with acute appendicitis as the most frequent cause. Mesenteric adenitis, also known as mesenteric lymphadenitis, is caused by inflamed mesenteric lymph nodes and is the second most common cause of acute RLQ abdominal pain. Mesenteric adenitis can be classified as primary or secondary.

Primary mesenteric adenitis is defined as three or more RLQ lymph nodes measuring 5mm or larger with or without mild terminal ileal wall thickening of <5mm. Primary mesenteric adenitis is usually a self-limited disease, caused by both viruses and bacteria. The average age of patients presenting with mesenteric adenitis is approximately 25 years with an age range of 5-44 years. Classically, most cases were diagnosed after surgery for suspected appendicitis. In the era of imaging, approximately 2-16% of patients presenting with symptoms of acute appendicitis are found to have mesenteric adenitis.

Secondary mesenteric adenitis is defined as lymphadenitis associated with an underlying inflammatory process such as Crohn’s disease, systemic lupus erythematosous, and diverticulitis.

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If these patients have an acute onset, are relatively young and lack worrisome symptoms such as weight loss, then a presumptive diagnosis of mesenteric adenitis may be reasonable. Observation in the hospital may be prudent and close outpatient follow-up will detect most misdiagnoses in a timely manner.

Older patients, patients with multiple comorbidities, patients with worrisome symptoms such as weight loss or patients with a subacute course may have diseases that mimic mesenteric adenitis such as malignancy, Crohn’s disease or ruptured cecal diverticulitis. In these cases, operative or non-operative biopsies may be needed to make a diagnosis.

II. Diagnostic Confirmation: Are you sure your patient has Mesenteric Adenitis?

Primary mesenteric adenitis classically presents with fever, RLQ abdominal pain, and leukocytosis mimicking acute appendicitis. A recent study in the pediatric population suggests that it is not clinically possibly to accurately distinguish between mesenteric adenitis and acute appendicitis. Therefore, imaging is required to make a diagnosis. If the diagnosis remains uncertain, then laparoscopic appendectomy sometimes with mesenteric lymph node biopsy may be needed for confirmation. Primary mesenteric adenitis has various causes with a large number of cases due to Yersina enterocolitica or Yersina pseudotuberculosis. However, cases have been reported due to Mycobacterium tuberculosis, Staphlococcus aureus, beta hemolytic Streptococcus, Parvovirus B19, HIV, and rarely, Cryptococcus.

A. History Part I: Pattern Recognition:

The typical patient is an adolescent or young adult with the acute onset of RLQ pain often with mild diarrhea. The pain may start in the upper abdomen or periumbilical region but will localize in the RLQ. Diarrhea has been reported in over one-third and fever in over a half of confirmed cases of mesenteric adenitis caused by Y. enterocolitica. There is a paucity of data on the illness caused by other pathogens. The tenderness to palpation may be less localized than in appendicitis. Some patients may have signs or symptoms of infection elsewhere such as pharyngitis or lymphadenopathy.

B. History Part 2: Prevalence:


C. History Part 3: Competing diagnoses that can mimic Mesenteric Adenitis.

The differential diagnosis is that of acute abdominal pain, particularly in the RLQ quadrant. Several percent of patients undergoing appendectomy will be given a pathologic diagnosis of mesenteric adenitis. In patients with diarrhea, the disease may be confused with Crohn’s disease. Other causes of painful mesenteric lymphadenopathy include malignancy and, especially in immunocompromised hosts, less common infections such as Mycobacterium avium complex. Almost any infectious or inflammatory disorder of the abdomen can do this as well including acute diverticulitis, cholecystitis, pancreatitis and perforated viscus.

D. Physical Examination Findings.

Right lower quadrant abdominal tenderness to palpation is the hallmark of the disease. Low-grade fever, guarding, rebound and rectal tenderness may also occur. This makes the disease difficult to distinguish from acute appendicitis. Lymphadenopathy elsewhere on exam may help distinguish this condition.

E. What diagnostic tests should be performed?

1. What laboratory studies (if any) should be ordered to help establish the diagnosis? How should the results be interpreted?

A complete blood count and, for women of childbearing age with a uterus, a pregnancy test, are essential laboratory studies. A mild leukocytosis is common but not specific. Blood cultures should be obtained in those who are febrile and stool cultures in those with diarrhea. Those who are older, ill-appearing, have multiple comorbidities or atypical presentations may benefit from a chemistry profile, liver function tests and perhaps an amylase or lipase. These tests are more useful in ruling out alternative diagnoses and determining the severity of illness than in confirming a diagnosis of mesenteric adenitis.

2. What imaging studies (if any) should be ordered to help establish the diagnosis? How should the results be interpreted?

If there is a high probability of appendicitis then surgical intervention may be reasonable without any imaging. If there is a desire to avoid radiation then ultrasonography can sometimes identify enlarged mesenteric nodes as well as rule out adnexal pathology in women and, if identified, appendicitis. Computed tomography (CT) scans can easily see the mesenteric lymph nodes and are useful for ruling out a wide variety of diseases that may mimic mesenteric adenitis.

If the appendix is not well-visualized, acute appendicitis cannot be excluded. Early surgical consultation is often prudent. Additionally, imaging cannot determine the cause of the adenopathy unless other clear pathologies are found. Thus, even if acute appendicitis is ruled out, careful inpatient observation and outpatient follow-up is crucial to exclude secondary causes of mesenteric adenitis.

III. Default Management.

The primary objective is to distinguish patients with a definite or probable surgical abdomen from those in whom observation, empiric treatment or CT-guided biopsy are reasonable options. If this is not clear then early surgical consultation is needed.

A. Immediate management.

Although mesenteric adenitis is usually a mild, self-limited disease, initial management should be geared to stabilizing the patient and correcting electrolyte depletion and dehydration. In severe cases, antibiotics with activity against Yersinia that overlap with those that cover enteric pathogens, such as second- and third- generation cephalosporins, piperacillin, quinolones and imipenem may be used. There is no evidence to support treatment of mild to moderate cases of Yersinia enterocolitis with associated mesenteric adenitis. In cases with severe systemic illness, bacteremia and immunocompromised patients, antibiotic treatment is indicated. Since many of these patients may go to surgery, any preoperative studies that might be indicated should be done and attention given to any active comorbidities that might affect the outcome. Most patients should be held NPO (nothing by mouth) until a decision about surgery is made.

B. Physical Examination Tips to Guide Management.

If the decision has not been made to go to the operating room, then the patient’s symptoms, vital signs and abdominal exam should be followed every few hours for the first day as one would for possible appendicitis. If the diagnosis has been confirmed pathologically, these same signs should be followed at a lesser frequency.

C. Laboratory Tests to Monitor Response To, and Adjustments in, Management.

Periodic CBC and chemistry profiles may be useful to follow the severity of illness and monitor fluid replacement.

D. Long-term management.

Mesenteric adenitis is usually a self-limited disease with no long-term management needs. However, if surgery is not performed, periodic outpatient follow-up will be needed to ensure a complete recovery is made and that the diagnosis of secondary mesenteric adenitis is eliminated. Furthermore, primary mesenteric adenitis has occasionally had a relapsing-remitting course. If the patient continues to be ill, then re-imaging and possible biopsy of any persistently enlarged mesenteric lymph nodes may be indicated. Since lymphadenopathy may be present elsewhere in the many neoplastic and inflammatory conditions that initially mimic mesenteric adenitis, a good exam with attention to palpable lymph nodes could spare a patient the added risk of a CT-guided biopsy.

E. Common Pitfalls and Side-Effects of Management.

The major pitfall of management is to fail to consult a general surgeon early in the course of illness. Appendicitis may lead to enlarged mesenteric lymph nodes. If the clinical impression suggests appendicitis, then early surgery is the safest course unless imaging clearly identifies a normal appendix. Even so, other surgical conditions such as a perforated cecal diverticulitis may also lead to painfully enlarged mesenteric lymph nodes. In cases where observation is undertaken, the patient must have regular follow-up as discussed above to ensure complete resolution of symptoms. Should this illness become subacute and no pathologic diagnosis was made in the hospital then a prompt search for an alternative diagnosis must be undertaken.

IV. Management with Co-Morbidities.

Comorbid conditions will largely affect the risk of surgery and post-operative management. However, immunocompromised patients are more likely to have opportunistic infections that mimic mesenteric adenitis. HIV, lymphoma, Mycobacterium avium complex, tuberculosis, cryptococcosis, and even Kaposi’s sarcoma may initially mimic mesenteric adenitis. These illnesses are more likely to present in a subacute manner and will not spontaneously resolve. If the patient does not appear to have a surgical abdomen, this population will often benefit from imaging guided biopsy.

As above, a good physical exam and a careful review of all imaging with the radiologist will determine if there are alternative locations for a biopsy that have a lower risk of complications. In patients with primary inflammatory disorders such as Crohn’s disease or systemic lupus, the primary illness may be the cause of the mesenteric adenopathy. In those with known cancer, malignant adenopathy is common. In these cases, multiple other sites of adenopathy may be apparent.

A. Renal Insufficiency.


B. Liver Insufficiency.


C. Systolic and Diastolic Heart Failure.


D. Coronary Artery Disease or Peripheral Vascular Disease.


E. Diabetes or other Endocrine issues.


F. Malignancy.


G. Immunosuppression (HIV, chronic steroids, etc).


H. Primary Lung Disease (COPD, Asthma, ILD).


I. Gastrointestinal or Nutrition Issues.


J. Hematologic or Coagulation Issues.


K. Dementia or Psychiatric Illness/Treatment.


V. Transitions of Care.

A. Sign-out considerations While Hospitalized.

When the diagnosis has not been confirmed surgically, serial abdominal examinations may be needed. Sign-out should ensure this occurs as well as information on the status of any surgical consultation. This reduces the possibility of a missed surgical abdomen.

B. Anticipated Length of Stay.

Though there is little data available for adults in the modern era, most patients with pathologically-confirmed mesenteric adenitis are young and healthy. Hospital stays for those who undergo surgery should be approximately 3-4 days.

C. When is the Patient Ready for Discharge.

Those who undergo surgery are ready for discharge when their nutritional intake meets adequate daily caloric requirements, when they are passing flatus on a regular basis, and when they can ambulate safely. Additionally, their pain should be controlled with oral medications.

D. Arranging for Clinic Follow-up.

1. When should clinic follow up be arranged and with whom?

If the patient underwent surgery, then follow-up should be with their surgeon within one week of discharge. If the patient did not undergo surgery and they are significantly improved, then follow-up can be with their primary care doctor within 1-2 weeks. If the patient did not undergo surgery but is being discharged without dramatic improvement or with ongoing diagnostic uncertainty, then follow-up should be with the surgeon within 1-2 days and the primary care doctor within one week.

2. What tests should be conducted prior to discharge to enable best clinic first visit?

No additional tests are needed but the discharge instructions and discharge summary should both clearly state what tests if any (i.e., cultures or pathology) are still pending. The patient and or family should be informed about who will provide them with any outstanding test results.

3. What tests should be ordered as an outpatient prior to, or on the day of, the clinic visit?

No tests are needed prior to a follow-up appointment unless indicated by the specific clinical situation.

E. Placement Considerations.

Complete recovery is the norm and nearly all patients should return to their prior residence.

F. Prognosis and Patient Counseling.

Full recovery is expected for those with a confirmed diagnosis as well as those who did not undergo surgery but have a high likelihood of mesenteric adenitis. For those discharged without a clear diagnosis who may have another cause for their painful mesenteric lymph nodes, the importance of early and regular follow-up should be emphasized.

VI. Patient Safety and Quality Measures.

A. Core Indicator Standards and Documentation.


VII. What's the evidence?

Ian, Aird. “Acute Non-Specific Mesenteric Lymphadenitis”. British Medical Journal. 1945. pp. 680-682. (This is a typical paper of the time period in which mesenteric adenitis became an accepted entity. The paper is descriptive and gives details of the history and exam that may allow the clinician to distinguish this entity from acute appendicitis.)

Macari, M, Hines, J, Balthazar, E, Megibow, A. “Mesenteric adenitis: CT diagnosis of primary versus secondary causes, incidence, and clinical significance in pediatric and adult patients”. American J of Roentgenology. vol. 178. 2002. pp. 853-858. (Most of the modern articles on mesenteric adenitis are in the radiologic literature. These studies are useful as most of our patients with acute RLQ abdominal pain and fever will have imaging performed in the ER before the Hospitalist is asked to see them. These articles help us understand the benefits and pitfalls of these imaging studies and emphasize the need to talk to the radiologist directly, if there is any diagnostic uncertainty.)

Toorenvliet, B, Vellekoop, A. “Clinical differentiation between acute appendicitis and cute mesenteric lymphadenitis in children”. European Journal of Pediatric Surgery. vol. 21. 2011. pp. 120-123. (Modern article demonstrating the difficulty in clinically differentiating between acute appendicitis and mesenteric adenitis.)

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