Divisions
The paraaortic lymph node group is divided into three subgroups: preaortic, retroaortic, and right and left lateral aortic.

The preaortic group drains the abdominal part of the gastrointestinal tract above the mid-rectum.
The retroaortic group drains from the lateral and preaortic glands.
The lateral group drains the iliac lymph nodes, the ovaries, and other pelvic organs. The lateral group nodes are located adjacent to the aorta, anterior to the spine, extending laterally to the edge of the psoas major muscles, and superiorly to the crura of the diaphragm.
Dissection
When a paraaortic lymph node dissection or sampling is done as a part of the treatment of cancer, the lateral aortic lymph node group is the most important group. There are typically 15 to 20 lymph nodes on each side.

When dissected, the dissection usually includes the region from the bifurcation of the aorta to the superior mesenteric artery or the renal veins

As part of laparoscopic surgery for many types of gynecologic cancers such as endometrial cancer, laparoscopic bilateral para aortic lymphnode dissection is performed .
Imaging of Para-aortic Lymph Nodes
Imaging for para-aortic lymph nodes with either standard computed tomography (CT) or magnetic resonance imaging (MRI) is indeed limited, with sensitivities of 55.5% and 57.5%, respectively. Positron-emission tomography (PET) or PET-CT does appear to have increased sensitivity.
A review of patients who underwent PET followed by histologic evaluation of the para-aortic lymph nodes found an overall sensitivity of 78%, but the false-negative rate for detecting para-aortic lymph node metastases was 12%. This increased to 22% for patients with PET uptake in the pelvis. Gouy and colleagues report a false-negative rate for PET-CT that is consistent with the published literature at 12% (29/237 patients), with slightly less than half of these being micrometastases ≤ 5 mm (13/29) and the rest > 5 mm.
Even though the sensitivity of PET appears superior to CT and MRI, detection of para-aortic lymph nodes remains problematic. It should be noted that the work by Gouy and colleagues provides useful estimates for false-negative rates for PET-CT in both pelvic PET-CT–positive and PET-CT–negative populations, which is, in and of itself, an important contribution to the literature.



References:https://en.wikipedia.org/wiki/Paraao...r-too-few.aspx