Appendiceal lymphoid hyperplasia is a benign condition characterized by reactive enlargement of lymphoid follicles in the appendiceal wall. Most commonly seen in children and young adults, it develops secondary to viral infections, gastroenteritis, or systemic immune activation. Lymphoid hyperplasia can narrow the appendiceal lumen, mimicking acute appendicitis or triggering true appendicitis. On imaging, it appears as appendiceal wall thickening and luminal narrowing; however, inflammatory changes are generally limited.
Age Range
5-30
Peak Age
15
Gender
Equal
Prevalence
Common
The appendix contains abundant lymphoid tissue (GALT — gut-associated lymphoid tissue) that plays a role in immune response to antigens in the bowel lumen. During viral infections (EBV, CMV, adenovirus), bacterial gastroenteritis, or systemic immune activation, these lymphoid follicles enlarge reactively — characterized by B-cell proliferation and germinal center expansion. Hyperplastic follicles thicken the appendiceal wall and protrude into the lumen at the submucosal level, narrowing the luminal diameter. This narrowing facilitates accumulation of mucin and fecal material, potentially increasing intraluminal pressure and triggering secondary acute appendicitis. On imaging, this pathophysiology is reflected as diffuse or focal wall thickening, submucosal edema, and mild periappendiceal inflammatory changes. The increased cellularity of lymphoid tissue appears as homogeneous soft tissue density and enhancement on CT, while appearing as hypoechoic wall thickening on US.
Diffuse, symmetric, homogeneous thickening of the appendiceal wall with absence or minimality of periappendiceal fat stranding — a critical combination in differential diagnosis from acute appendicitis. While appendicitis is accompanied by asymmetric wall thickening, prominent periappendiceal stranding, and fecalith, lymphoid hyperplasia findings are more homogeneous and symmetric with limited surrounding inflammation.
Diffuse, symmetric thickening of the appendiceal wall (wall thickness >3 mm). Thickening is homogeneous with preserved wall layers. Appendiceal outer diameter is increased (>6 mm) but periappendiceal inflammatory changes are limited.
Report Sentence
Diffuse, symmetric wall thickening (__ mm) of the appendix is observed, which may be compatible with lymphoid hyperplasia.
Thickened appendiceal wall shows homogeneous enhancement. Stratified (layered) enhancement pattern — low-density submucosal edema between inner mucosal and outer muscular enhancement — appears more homogeneous compared to acute appendicitis.
Report Sentence
The thickened appendiceal wall shows homogeneous enhancement without significant periappendiceal inflammatory changes.
Reactive lymphadenopathy in the mesenteric area — multiple, small (<10 mm short axis), oval lymph nodes. May show clustering in the ileocecal region. No necrosis or calcification.
Report Sentence
Multiple small, reactive-appearing mesenteric lymph nodes are observed in the ileocecal region.
Target sign on short axis section of the appendix on ultrasonography — hypoechoic thickened wall and central echogenic lumen. Wall thickening is symmetric and diffuse without significant inflammatory changes in surrounding fat.
Report Sentence
Target sign with symmetric wall thickening is observed in the appendix without significant inflammatory changes in the surrounding fat.
Increased vascularity in the thickened appendiceal wall on color Doppler. Vascular flow is diffusely increased along the wall. Diffuse vascularity increase rather than focal hyperemia (seen in appendicitis) supports lymphoid hyperplasia.
Report Sentence
Diffuse increased vascularity is observed in the thickened appendiceal wall on Doppler examination.
Criteria
Widespread lymphoid follicle enlargement throughout the appendiceal wall. All wall segments are symmetrically affected.
Distinct Features
Diffuse symmetric wall thickening on CT and US, homogeneous appearance. Most common form after viral infection in children.
Criteria
Localized lymphoid follicle enlargement in the appendiceal wall. Generally focal thickening at the appendiceal tip or base.
Distinct Features
Focal wall thickening may raise suspicion of neoplasm — homogeneous enhancement on CT and absence of surrounding inflammatory changes support benign nature.
Distinguishing Feature
LAMN shows cystic dilatation and low-density mucinous content. Lymphoid hyperplasia shows solid wall thickening and homogeneous enhancement without cystic component.
Distinguishing Feature
Intussusception shows invagination of the appendix into the cecal lumen — target sign or sausage-shaped mass. Lymphoid hyperplasia shows in situ appendiceal thickening without invagination.
Distinguishing Feature
Appendicolith is an intraluminal calcified structure that does not cause wall thickening by itself. Lymphoid hyperplasia shows diffuse wall thickening without intraluminal calcified structure.
Urgency
routineManagement
conservativeBiopsy
Not NeededFollow-up
no-follow-upAppendiceal lymphoid hyperplasia is a benign, self-limiting condition that does not require treatment in most patients. Lymphoid hyperplasia spontaneously regresses with resolution of the underlying viral infection or gastroenteritis. It may be incidentally detected in appendectomy specimens performed for suspected acute appendicitis. Follow-up or biopsy may rarely be needed for focal lymphoid hyperplasia to exclude neoplasm. Conservative management is sufficient in uncomplicated form (no secondary appendicitis). If secondary acute appendicitis has developed (periappendiceal stranding, fever, leukocytosis), surgical treatment is performed.
Lymphoid hyperplasia is generally self-limited and occurs during viral infections. It can lead to secondary acute appendicitis by causing luminal obstruction. It accounts for a significant proportion of appendicitis cases in children. Conservative management is sufficient in uncomplicated cases; appendectomy is required if appendicitis develops.