What is the pelvic lymph node normal size? Determination from normal MRI examinations

Area of Science:

• Radiology
• Medical Imaging
• Anatomy

Background:

• Limited data exists on maximal pelvic lymph node sizes.
• Normal size parameters for mesorectal lymph nodes are currently unknown.

Purpose of the Study:

• To estimate the normal size of pelvic lymph nodes.
• To determine the upper limits of normal size for pelvic and mesorectal lymph nodes.

Main Methods:

• Prospective pelvic MRI examinations on 36 healthy volunteers (22 female, 14 male).
• Balanced fast field echo (b-FFE) sequence with 3-mm contiguous slices.
• Measurement of short axis diameters of lymph nodes in internal iliac, external iliac, common iliac, mesorectum, and inguinal regions.

Main Results:

• 1147 lymph nodes were measured; age, gender, and side had no significant influence on size.
• Upper limits (95th percentile) for normal lymph node size (short axis): mesorectum (3.9 mm), external/common iliac (5.3 mm), internal iliac (6.3 mm), inguinal (4.4 mm).
• Note: The abstract results section has some inconsistencies in values. The text states 5.3, 4.4, 6.3, 3.9 mm for external/common iliac, internal iliac, inguinal, and mesorectum respectively. The advances in knowledge section states 6, 6, 5, 7 mm for external/common iliac, internal, iliac, and inguinal respectively. The mesorectum nodes should be considered abnormal if over 4 mm.

Conclusions:

• This study provides maximal normal size values for pelvic lymph node areas.
• Mesorectal lymph node size data is reported for the first time.
• Mesorectal nodes >4 mm short diameter and other pelvic nodes exceeding their respective upper limits should be considered abnormal.