You are in: eMedicine Specialties > Radiology > PEDIATRICS Mesenteric AdenitisArticle Last Updated: Mar 18, 2008AUTHOR AND EDITOR INFORMATIONSection 1 of 10
  Author: Brian Burke, MD, Assistant Professor, Department of Radiology, University of New York School of Medicine; Consulting Radiologist, Department of Radiology, North Shore University Hospital Brian Burke is a member of the following medical societies: American College of Radiology, American Institute of Ultrasound in Medicine, American Roentgen Ray Society, and Radiological Society of North America Coauthor(s): Micha Ziprkowski, MD, Associate Chief, Pediatric Radiology, Associate Professor of Clinical Radiology, Department of Radiology, North Shore University Hospital Editors: Henrique M Lederman, MD, PhD, Consulting Staff, Department of Radiology, The Children's Hospital of Philadelphia; Professor of Radiology and Pediatric Radiology, Chief, Division of Diagnostic Imaging in Pediatrics, Federal University of Sao Paulo, Brazil; Bernard D Coombs, MB, ChB, PhD, Consulting Staff, Department of Specialist Rehabilitation Services, Hutt Valley District Health Board, New Zealand; David A Stringer, BSc, MBBS, FRCR, FRCPC, Professor, National University of Singapore; Head, Diagnostic Imaging, KK Women's and Children's Hospital, Singapore; Robert M Krasny, MD, Consulting Staff, Department of Radiology, The Angeles Clinic and Research Institute; John Karani, MBBS, FRCR, Consulting Staff, Department of Radiology, King's College Hospital, London Author and Editor Disclosure Synonyms and related keywords: mesenteric lymphadenitis, acute ileitis, appendicitis, lymphoma INTRODUCTIONSection 2 of 10
  BackgroundMesenteric adenitis is a self-limited inflammatory process that affects the mesenteric lymph nodes in the right lower quadrant. Its clinical presentation mimics that of acute appendicitis. Until recently, the diagnosis was most frequently made when laparotomy performed to assess presumed appendicitis yielded negative findings; now, cross-sectional imaging is routinely applied in the examination of patients. PathophysiologyMesenteric adenitis is most frequently caused by viral pathogens, but other infectious agents have been implicated, including Yersinia enterocolitica, Helicobacter jejuni, Campylobacter jejuni, and Salmonella or Shigella species.1, 2, 3 An association with streptococcal infections of the upper respiratory tract, particularly the pharynx, has been reported. In younger children and infants, concurrent ileocolitis may be present; this finding suggests that the lymph node involvement may occur in reaction to a primary enteric pathogen. FrequencyUnited StatesIn 2 recent series involving patients with clinical symptoms suggestive of acute appendicitis, mesenteric adenitis was the most frequent alternative diagnosis; it was present in 8-12% of patients. In Europe and North America, the proportion of patients with Y enterocolitica infection who undergo appendectomy is 3.0-9.0%. InternationalAs an etiologic agent of mesenteric adenitis, Y enterocolitica is less common in developing nations than in other nations. In Europe and North America, the proportion of patients with Y enterocolitica infection who undergo appendectomy is 3.0-9.0%. In 2 small studies of children who underwent appendectomy in Bangladesh, Yersinia organisms were not found. Mortality/MorbidityMost cases are self-limited, although disease lasting longer than 2 weeks is common. With Yersinia ileocolitis, small-bowel disease may be severe, and gangrene and death have been reported. Children who undergo laparotomy for presumed appendicitis are at risk for surgical complications. RaceNo racial predilection is reported. SexTwo large published series provide no information about the sex ratio. The clinical differential diagnosis in patients with right lower quadrant pain is broader in girls, especially in adolescents in whom gynecologic pathology must be considered. AgeMesenteric adenitis can occur in adults, but it is most common in children and adolescents younger than 15 years. Associated enteric disease most often occurs in those younger than 5 years.4 AnatomyMesenteric lymph nodes are present near mesenteric vessels and between bowel loops. They normally appear flattened, ovoid, or disc-shaped, and they have a characteristic fatty central hilum and a solid peripheral cortex (see Image 1). Vessels enter and exit the node at the hilum and branch within the node in a fashion similar to that of the kidney. Normal mesenteric lymph nodes vary in size, but, in general, the short-axis diameter is 4 mm or shorter. Clinical DetailsMesenteric adenitis is a self-limited condition characterized by fever, abdominal pain, nausea, and, occasionally, diarrhea. Pain and tenderness are often centered in the right lower quadrant, but they may be more diffuse than in appendicitis. The site of tenderness may shift when the patient's position changes, whereas the location of the tenderness tends to be fixed with appendicitis. Leukocytosis is common. The diagnosis of mesenteric adenitis is one of exclusion; confirmation is based on a benign clinical course, and management is conservative. Preferred ExaminationUltrasonography of the right lower quadrant with graded compression has been the mainstay of diagnosis in children.5 Recently, many centers have adopted CT as an alternate or, sometimes, the primary diagnostic modality in the setting of presumed appendicitis, especially in men and in those in whom visualization of the appendix may be compromised by their body habitus. Although the findings are frequently nonspecific, abdominal radiographs occasionally reveal findings and permit alternative diagnoses (eg, appendicoliths). Limitations of TechniquesThe normal appendix is sonographically occult in a significant subset of patients. When lymph node enlargement is detected on sonographic examination in these patients, excluding appendicitis as a cause of reactive adenopathy is difficult.6, 7 In some centers, CT is performed for the evaluation of appendicitis without intravenous and/or oral contrast enhancement. This approach reduces the sensitivity of CT for bowel wall thickening and mesenteric adenopathy, especially in small children with a paucity of intraperitoneal fat. With any imaging modality, the finding of lymph node enlargement as an isolated finding is nonspecific; it can be observed in association with several inflammatory processes. Occasionally, nodes exceeding the normal size threshold are observed in children who have no demonstrable disease. DIFFERENTIALSSection 3 of 10
Appendicitis Crohn Disease Sprue Other Problems To Be ConsideredInfectious gastroenteritis
RADIOGRAPHSection 4 of 10
FindingsFindings on supine and upright abdominal radiographs are often normal. Nonspecific findings include a regional ileus or evidence of bowel wall thickening in the right lower quadrant (see Image 2). Degree of ConfidencePlain radiographic findings can never indicate a specific diagnosis in mesenteric adenitis, but they can occasionally confirm an alternative diagnosis. Cross-sectional imaging may be indicated regardless of the plain radiographic findings. CT SCANSection 5 of 10
FindingsDiagnostic features include enlarged mesenteric lymph nodes, with or without associated ileal or ileocecal wall thickening, in the setting of a normal appendix.8 Rao et al specified the criterion of 3 or more nodes with a short-axis diameter of at least 5 clustered in the right lower quadrant (see Images 3-4).9 Lymph nodes are generally larger, more numerous, and more widely distributed in mesenteric adenitis than in appendicitis. Ileal thickening is diagnosed when the wall is thicker than 3 mm over at least 5 cm of the bowel despite bowel lumen opacification and distention (see Image 5). Degree of ConfidenceIn the prospective study by Rao et al, none of the 18 patients with the aforementioned CT criteria had surgical or clinical evidence of appendicitis, whereas appendicitis was correctly diagnosed in 56.9 Further imaging is generally not indicated, although a definitive diagnosis might not be made in a case with equivocal findings until laparotomy performed for the evaluation of appendicitis reveals negative findings. False Positives/NegativesNonopacified bowel may be mistaken for enlarged lymph nodes, especially in thin patients or small children. Bowel wall thickness is difficult to determine in this setting. ULTRASOUNDSection 6 of 10
FindingsIn patients with fever, abdominal tenderness, and a normal appendix, adenopathy that predominantly involves but is not limited to the right lower quadrant suggests the diagnosis (see Images 6-7). Usually, 5 or more nodes are present and are often clustered (see Image 8). Nodal tenderness in response to transducer pressure is typical. Nodes are more rounded and hypoechoic than normal. Abnormal nodes have a short-axis diameter of at least 5 mm, and the diameter can exceed 1 cm. The nodes are typically larger and more numerous with mesenteric adenitis than with appendicitis (see Images 9-10).10 The demonstration of hyperemia within the node and surrounding mesentery with Doppler imaging is variably reported (see Images 11-12). Other findings include intestinal hyperperistalsis, which is seldom observed in appendicitis; nodular or circumferential thickening of the bowel wall; mesenteric thickening; fluid-filled loops; cecal involvement; and free fluid (see Image 13).11 Occasionally, a fluid-filled appendix is seen, but the lumen is readily compressible.12 Degree of ConfidenceAlthough nodal size and number are generally greater in mesenteric adenitis than in appendicitis, overlap does occur. In Simonovsky's large series of 609 patients, 426 had appendicitis, and 81 had mesenteric adenitis.13 The inflamed appendix was missed in 2 of the latter cases. Puylaert stated that in adult patients with right lower quadrant pain in whom the sole findings are enlarged mesenteric lymph nodes, the risk of appendicitis is 64%.14 Therefore, the diagnosis of mesenteric adenitis is hazardous when the appendix is not visualized; correlative CT may be beneficial in this setting. In mesenteric adenitis and lymphoma, the size, shape, distribution, and Doppler imaging characteristics of the lymph nodes overlap considerably, although the clinical context is useful in narrowing the differential diagnosis.15 False Positives/NegativesMesenteric lymph nodes that exceed the normal size threshold may be visualized in the absence of disease, although these are usually nontender. NUCLEAR MEDICINESection 7 of 10
FindingsNuclear scintigraphy is seldom useful in this setting. A single case report describes abnormal white-cell localization in the nasopharynx, cervical lymph nodes, and right lower quadrant during imaging with indium-111–labeled white blood cells in a 4-year-old boy with fever, pharyngitis, and abdominal pain.16 INTERVENTIONSection 8 of 10
Mesenteric adenitis is usually a self-limited disease, and management is conservative. Radiologic intervention is generally not indicated. Rotavirus and other viral vectors are the presumed cause in most cases. Although cultures are seldom obtained, most cases resolve without antibiotic treatment. Medical/Legal Pitfalls
See also the Medscape topic Medical Malpractice and Legal Issues. Special Concerns
MULTIMEDIASection 9 of 10
REFERENCESSection 10 of 10
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