What Are Enlarged Retroperitoneal Lymph Nodes?

Retroperitoneal lymph nodes are in the abdomen, but at the back, behind the intestines.

Lymph Nodes

Lymph nodes are small bean-shaped structures located all over the body—they are part of the lymph system, a sort-of parallel network to the blood vessels of the circulatory system. They function like little immune system outposts that check out fluids draining from tissues. They help fight bacteria, and also may become involved with cancer cells, when they are downstream from the site of a tumor.

There are many different reasons for lymph nodes to swell or come to medical attention, however. And most of the time, when a patient comes to a doctor with swollen lymph nodes, cancer is not the reason.

Retroperitoneal Lymph Nodes

Retroperitoneal lymph nodes are lymph nodes located a specific compartment of the body, called the retroperitoneum. The retroperitoneum describes a part of the abdominal cavity—the part of the abdomen that is generally closer to your backbone than to your belly button, back behind the intestines.

The precise definition for this compartment is based in anatomy, for instance: “the part of the abdominal cavity that lies between the posterior parietal peritoneum and anterior to the transversalis fascia.” However, thinking of the retroperitoneum as an area of the abdomen near the back is just fine here. Retroperitoneal lymph nodes are one of many lymph node groups found around the body, as shown in the following list:

  • Retroperitoneal lymph nodes - found in the retroperitoneum
  • Inguinal lymph nodes - found in the groin region
  • Axillary lymph nodes - found in the armpits
  • Mediastinal lymph nodes - found in the chest, near the heart

Lymph nodes can be named for any region, or for a specific organ, or any combination—kind of like nesting Russian dolls, or umbrella terms that get more and more specific as the need arises.

For example, let’s take a particular lymph node in the thorax that is near the aorta. That lymph node might generally be called a thoracic lymph node, or getting more specific, if it is in the compartment near the heart, it would be a mediastinal lymph node, or even more specifically, if it is located beside the aorta, a periaortic lymph node—all of which would be correct naming, but periaortic would be the most specific.

The peritoneum is a membrane that lines the cavity of the abdomen and also covers abdominal organs. Imagine it as a 'double bubble of plastic wrap' that gets all twisted up in itself during development. Some organs are intra -- or within – the peritoneum, while others are behind it, or retroperitoneal.

Retroperitoneal Organs

Some organs are actually even partially within and partially outside the peritoneum. A memory device students use to learn which organs are retroperitoneal is SAD PUCKER:

S: suprarenal or adrenal gland
A: aorta/inferior vena cava
D: duodenum (second and third part)

P: pancreas (except the tail of the pancreas)
U: ureters
C: colon (ascending and descending)
K: kidneys
E: esophagus
R: rectum

The organs followed by parentheses are only partially retroperitoneal. Sometimes a disease process that affects one of these organs will also affect the associated lymph nodes. The ureters carry urine from the kidney to the bladder, and masses in this area can block a ureter, causing urinary symptoms.

Retroperitoneal Lymph Nodes in Various Diseases

While removal of retroperitoneal lymph nodes may be associated with testicular cancer, swollen retroperitoneal nodes may arise for any number of reasons, and the cause of the swelling may not be apparent from the imaging scans. Potential causes include infections such as tuberculosis, inflammation from diseases such as sarcoidosis, and cancers such as lymphoma or metastasis from another site.

Retroperitoneal Lymph Nodes in Lymphoma

Lymphomas are a group of cancers of the lymph system. Lymphomas usually start in the lymph nodes, and retroperitoneal lymph nodes are affected in many lymphomas.

There are two main categories of lymphoma:
1) Hodgkin’s lymphoma, or HL-- and here is the link out to Hodgkin’s.
2) Non-Hodgkin’s lymphoma, or NHL which accounts for nearly 90 percent of all lymphomas, is comprised of far more types than Hodgkin's lymphoma.

Both HL and NHL may result in retroperitoneal lymph node involvement. While HL is more likely to spread in a defined pattern, from one lymph node group to the next, NHL may arise and come to involve different groups of lymph nodes, including retroperitoneal lymph nodes, at the time of presentation. Other cancers can also metastasize to these lymph nodes. Retroperitoneal lymphadenopathy often does not produce any symptoms, but extensive disease can lead to abdominal discomfort or blocked urine flow.

Sources:

Lymph Nodes. Lawrence M. Weiss. Cambridge University Press, Apr 28, 2008

Radiopaedia.org. Retroperitoneal organs (mnemonic).

Non-Hodgkin Lymphomas. James Armitage et al. Lippincott Williams & Wilkins, Aug 8, 2013.

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