Mesenteric Abnormalities

Mesenteric Abnormalities
17
Ramesh S. Iyer, MD
Learning Objectives
1.List diagnostic considerations for diffuse and multifocal mesenteric abnormalities.
2.Identify mesenteric adenitis on US and CT.
3.Generate a differential diagnosis for mesenteric cysts.
Introduction
Mesenteric Adenitis
The mesentery is a dual layer of peritoneum that suspends the
small and large bowel from the posterior abdominal wall. It is fanor cone-shaped, originating from the superior–­central abdomen
and radiating inferiorly and peripherally. Mesenteric abnormalities
may be divided into focal, multifocal, and diffuse processes. Focal
mesenteric lesions are described in the sections below. Diffuse
mesenteric pathologies include edema, inflammation, and hemorrhage. These processes typically replace the normal mesenteric fat
with soft tissue attenuation on CT, creating a “misty mesentery”
appearance, and cause increased echogenicity on US (Fig. 17.1).
They also may displace bowel peripherally or encase the superior
mesenteric vessels. Multifocal mesenteric masses most often represent lymphadenopathy. Primary diagnostic considerations for mesenteric lymphadenopathy are non-Hodgkin lymphoma, metastatic
disease, and infection (Fig. 17.2).1
Mesenteric adenitis represents benign nodal enlargement from
an underlying viral or bacterial infection. Common bacterial
agents include Yersinia enterocolitica and Streptococcus.2,3 In most
cases, the terminal ileum is the likely site of infection.4 Presenting
signs and symptoms include fever, emesis, leukocytosis, and right
lower abdominal pain. Clinically distinguishing mesenteric adenitis from acute appendicitis is challenging, allowing imaging to
play an important role in the diagnostic workup.4–7
US and CT are the most common modalities for imaging mesenteric adenitis (Figs. 17.3 and 17.4). CT offers a more sensitive
and specific evaluation of mesenteric processes, but involves ionizing radiation. There is no clear consensus regarding the normal
size of mesenteric lymph nodes in children. Most authors report
that a cluster of 3 or more mesenteric lymph nodes with short-axis
diameters exceeding 5 mm is required to make this diagnosis
FIG. 17.1 ● Mesenteric panniculitis in a 12-year-old male. Axial (A), coronal (B), and sagittal (C) images
from a contrast-enhanced CT show diffuse inflammatory edema of the mesentery (arrows in A, B, and C).
Normal mesenteric fat has been replaced by soft tissue attenuation.
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194 Pediatric Imaging: The Essentials
FIG. 17.2 ● Mesenteric lymphadenopathy in an 18-year-old female with
non-Hodgkin lymphoma. Coronal (A)
and sagittal (B) reformatted images
from a contrast-enhanced CT demonstrate lymphadenopathy within the mesentery (yellow arrows in both A and B),
bilateral axilla (blue arrows in A), and
the left neck (orange arrow in A).
on US (Fig. 17.3).2–4,8–10 However, others believe that enlarged
mesenteric lymph nodes in a child with abdominal pain are a relatively nonspecific finding and that these criteria allow for significant overlap between mesenteric adenitis and normal nodes.9,10
For example, Karmazyn et al.10 reported that using a cluster of 3
or more lymph nodes, each with 8-mm diameters, would be more
appropriate to diagnose mesenteric adenitis by CT. The enlarged
nodes are most often located in the right abdomen anterior to the
psoas muscle.1,4 Associated mild ileal or colonic wall thickening
may be seen in up to one-third of cases, particularly in children
less than 5 years old.3,11 Before arriving at a diagnosis of mesenteric adenitis, it is critical to exclude acute appendicitis as a cause
for abdominal pain.
Treatment of mesenteric adenitis is typically supportive care
only, as the clinical course is benign and self-limited. Antibiotics
are considered for moderately or severely ill children with
suspected bacterial enterocolitis.
FIG. 17.3 ● Mesenteric adenitis by ultrasound in a 2-year-old
female with right lower quadrant abdominal pain. Focused abdominal sonography reveals a cluster of three round hypoechoic mesenteric lymph nodes with short axes of 6 to 7 mm.
FIG. 17.4 ● Mesenteric adenitis by CT in an 11-year-old female
with right lower abdominal pain. Axial (A) and coronal (B) images
from a contrast-enhanced CT illustrate several enlarged mesenteric
lymph nodes in the right lower abdomen (yellow arrows in both
A and B). Note the normal appendix (blue arrow in A).
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Mesenteric Abnormalities 195
Table 17.1 Differential Diagnosis for
Mesenteric Cyst
• Mesenteric cyst
• Enteric duplication cyst
• Ovarian cyst
• Pancreatic pseudocyst
• Meckel diverticulum
FIG. 17.5 ● Mesenteric cyst in a 16-year-old female. Longitudinal
(left) and transverse US images of the pelvis depict an ovoid cyst
posterior and to the right of the cervix. The structure is distinct from
the right ovary (not shown). The cyst is primarily anechoic with scattered hypoechoic septations.
Mesenteric Cysts and Masses
Mesenteric cysts are rare intra-abdominal lesions typically seen
in neonates and young children less than 5 years old. They are
most common within the small bowel mesentery though they
may be situated anywhere along the gastrointestinal tract.12–14
Histologically, they are benign cystic proliferations of lymphatic
tissue.12 Presenting symptoms include abdominal pain or palpable
mass. Mesenteric lymphatic malformations are more frequently
invasive and multilocular compared to simple cysts, though both
are derived from dysplastic lymphatic channels.13 Mesenteric
FIG. 17.6 ● Posttransplant lymphoproliferative disorder (PTLD)
of the mesentery in a 6-year-old male. Axial (A) and coronal (B)
contrast-enhanced CT images show a lobular, homogeneously hypo­
dense mass (arrowheads in A) encasing the superior mesenteric vessels (arrow in A and B).
cysts have a nonspecific appearance on all modalities and may
have septations, internal debris, or blood products (Fig. 17.5).14,15
Differential diagnostic considerations for a mesenteric cyst
include enteric duplication cyst, ovarian cyst, pancreatic pseudocyst, and Meckel diverticulum (Table 17.1).3 Cystic malignancies
are also possible but less likely.16 Mesenteric cysts are surgically
resected, occasionally with segmental resection of adjacent small
bowel, with an excellent long-term prognosis.12,13
Solid tumors arising from the pediatric mesentery are also
rare. They range from benign entities such as lipomas, mature
teratomas, and hamartomas to malignancies including immature germ cell tumors and sarcomas (Fig. 17.6).17 Lesions may
be asymptomatic or cause vague abdominal pain and ­distension.
Painful presentations may result from tumoral hemorrhage, torsion, or metastatic disease (Fig. 17.7).18 Treatment of primary
mesenteric tumors usually involves surgical resection along with
chemotherapy and radiation for malignant lesions.
FIG. 17.7 ● Torsion of a mesenteric lipoma in a 14-year-old male
presenting with acute lower abdominal pain. A: Right pelvic US image
illustrates a lobular echogenic mass where the patient was exquisitely tender. B: Axial contrast-enhanced CT image demonstrates a well-defined,
septated, fat-containing mass with surrounding edema (white arrows).
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196 Pediatric Imaging: The Essentials
Take Home Points: Mesenteric Adenitis
Mesenteric adenitis
•Benign nodal enlargement from
viral or bacterial infection, often
of terminal ileum
•May mimic appendicitis clinically
•US or CT: cluster of 3 or more
mesenteric nodes each with
short axes >5 mm by US or >8
mm by CT
•Usually in right lower abdomen
•Treatment—benign, self-limited
References
1. Donnelly LF. Gastrointestinal. In: Pediatric Imaging: The Fundamentals.
2nd ed. Philadelphia, PA: Saunders Elsevier; 2009:110–112.
2. Lucey BC, Stuhlfaut JW, Soto JA. Mesenteric lymph nodes seen
at imaging: causes and significance. Radiographics. 2005;25:
351–365.
3. Anton CG, Podberesky DJ. Pediatric mesenteric abnormalities. In:
Donnelly LF, ed. Diagnostic Imaging: Pediatrics. 2nd ed. Salt Lake
City, UT: Amirsys; 2012:4-154–4-161.
4. Macari M, Hines J, Balthazar E, et al. Mesenteric adenitis: CT
diagnosis of primary versus secondary causes, incidence, and clinical
significance in pediatric and adult populations. AJR Am J Roentgenol.
2002;178:853–858.
5. Toorenvliet B, Vellekoop A, Bakker R, et al. Clinical differentiation
between acute appendicitis and acute mesenteric lymphadenitis in
children. Eur J Pediatr Surg. 2011;21:120–123.
6. Gilmore OJ, Browett JP, Griffin PH, et al. Appendicitis and mimicking
conditions: a prospective study. Lancet. 1975;2(7932):421–424.
7. Patlas MN, Alabousi A, Scaglione M, et al. Cross-sectional imaging
of nontraumatic peritoneal and mesenteric emergencies. Can Assoc
Radiol J. 2013;64(2):148–153.
8. Rao PM, Rhea JT, Novelline RA. CT diagnosis of mesenteric adenitis.
Radiology. 1997;202(1):145–149.
9. Sivit CJ, Newman KD, Chandra RS. Visualization of enlarged mesenteric lymph nodes at US examination: clinical significance. Pediatr
Radiol. 1993;23(6):471–475.
10. Karmazyn B, Werner EA, Rejaie B, et al. Mesenteric lymph nodes in
children: what is normal? Pediatr Radiol. 2005;35:774–777.
11. Sung T, Callahan MJ, Taylor GA. Clinical and imaging mimickers of
acute appendicitis in the pediatric population. AJR Am J Roentgenol.
2006;186:67–74.
12. Chang TS, Ricketts R, Abramowsky CR, et al. Mesenteric cystic
masses: a series of 21 pediatric cases and review of the literature. Fetal
Pediatr Pathol. 2011;30(1):40–44.
13. Weeda VB, Booij KA, Aronson DC. Mesenteric cystic lymphangioma: a congenital and an acquired anomaly? Two cases and a review
of the literature. J Pediatr Surg. 2008;43(6):1206–1208.
14. Chung MA, Brandt ML, St-Vil D, et al. Mesenteric cysts in children.
J Pediatr Surg. 1991;26(11):1306–1308.
15. Sato M, Ishida H, Konno K, et al. Mesenteric cysts: sonographic findings. Abdom Imaging. 2000;25(3):306–310.
16. Ranganath SH, Lee EY, Eisenberg RL. Focal cystic abdominal masses
in pediatric patients. AJR Am J Roentgenol. 2012;199(1):W1–W16.
17. Gonzalez-Crussi F, Sotelo-Avila C, deMello DE. Primary peritoneal,
omental and mesenteric tumors of childhood. Semin Diagn Pathol.
1986;3(2):122–137.
18. Haller JO, Schneider M, Kassner G, et al. Sonographic evaluation of
mesenteric and omental masses in children. AJR Am J Roentgenol.
1978;130:269–274.
Chapter Self-Assessment Questions
1. Which of the following conditions is the most common clinical
differential consideration for mesenteric adenitis?
A. Malrotation
B. Necrotizing enterocolitis
C. Inflammatory bowel disease
D. Appendicitis
2. Which of the following imaging features would be most suggestive of a mesenteric tumor?
A. Fat attenuation
B. No discernible organ of origin
C. Claw sign
D. Aortic encasement
Answers to Chapter Self-Assessment Questions
1. D Acute appendicitis is the most important differential consideration for mesenteric adenitis. The clinical presentations are
often indistinguishable, including fever, leukocytosis, and right
lower abdominal pain. Appendicitis should be excluded by imaging before a diagnosis of mesenteric adenitis is made.
2. B When an abdominal mass shows no clear organ of origin,
a primary mesenteric tumor should be suspected. Fat attenuation
and aortic encasement may be seen with mesenteric tumors but
are nonspecific findings. The “claw sign” refers to tissue extending along the margins of a mass, suggesting that the mass arises
from this parenchymal organ. For example, Wilms tumor often
exhibits a renal claw sign.
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