What Are Enlarged Retroperitoneal Lymph Nodes?

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

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. Lymph nodes function like little immune system outposts, scattered along a system of canals that drain fluids from tissues in particular territories of the body.

When lymph nodes that become enlarged are in a specific part of the body known anatomically as the retroperitoneum, there are many potential causes, including the following:

  • Infections, such as tuberculosis
  • Inflammation from any number of causes, including diseases such as sarcoidosis
  • Cancer from a distant site in the body that metastasizes to the lymph nodes
  • Blood cancers that develop in the lymph nodes or spread to the lymph nodes
  • Other rare causes

There are always many different potential reasons for any lymph node to swell, and not all of them are cancerous. In fact, when a person sees a doctor for swollen lymph nodes, cancer is not usually the cause. Rather, viral infection is more likely to blame—especially if the swollen lymph nodes are along the neck. However, there are some types of lymph node swellings that are less suggestive of benign conditions, such as a massive conglomeration of enlarged lymph nodes that appear stuck together in imaging studies.

Retroperitoneal Lymph Nodes May Enlarge in Various Diseases

Retroperitoneal lymph nodes located in a place where they cannot generally be felt or noticed when they begin to swell, and so doctors may come to learn of their enlargement by way of an imaging study such as a CT scan of the abdomen and pelvis.

Sometimes retroperitoneal lymph nodes do become sufficiently involved with a disease to produce symptoms, as nearby structures may be affected; in some cases, symptoms might lead to an imaging study that detects the retroperitoneal lymph node enlargement. However, the cause of the swelling may not be readily apparent from the imaging scans, and a biopsy of the involved lymph nodes is often required.

In the case of people who have weakened immune systems, some of the possibilities for enlarged retroperitoneal lymph nodes are: infection with a kind of bacteria called mycobacterium; lymphoma, a blood cancer that usually begins in the lymph nodes; and kaposi’s sarcoma, a cancer that develops from the cells that line lymph or blood vessels. The enlarged nodes might be the beginning phase of a disease that will eventually have lymph nodes enlarged in different sites of the body, or progressive generalized lymphadenopathy syndrome.

When there are multiple sets of lymph nodes involved in the retroperitoneum and the scan also shows an enlarged liver and spleen, this can be more suggestive of lymphoma, however there are other possibilities. Castleman disease is a rare disease that involves the lymph nodes. Other names include: Castleman’s disease, giant lymph node hyperplasia, and angiofollicular lymph node hyperplasia. Dr. Benjamin Castleman first described it in the 1950s.

Castleman disease is considered a lymphoproliferative disorder, meaning there is overgrowth of cells of the lymph system.

Though it is not a cancer, it can be very similar to lymphoma and some forms can develop into a lymphoma.

Where is the Retroperitoneum and Why Does it Matter?

Gross anatomy determines the name of these 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.

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 of the body or for a specific organ. For example, there is a particular lymph node in the thorax that is near the aorta. That lymph node might generally be called a thoracic lymph node. Becoming more specific, if it is in the compartment near the heart, it would also be considered 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 intraperitoneal, or within the peritoneum, while others are behind it, or retroperitoneal.

Retroperitoneal Organs

The reason for lymph node enlargement may sometimes relate to the organs that are near the enlarged nodes. Several organs are within the peritoneum and some are actually partially within and partially outside the peritoneum. Students may use the following memory device to learn which organs are retroperitoneal:

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, and vice versa. For instance, the ureters carry urine from the kidney to the bladder, and masses in this area can block a ureter, causing urinary symptoms. Retroperitoneal lymphadenopathy often does not produce any symptoms, but extensive disease can lead to abdominal discomfort or blocked urine flow.

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.

Retroperitoneal Lymph Nodes in Other Cancers

Other cancers can also metastasize to retroperitoneal lymph nodes. One such cancer is testicular cancer. Testicular cancer usually spreads in a predictable fashion through the retroperitoneal lymph nodes (RPLN), and in some instances, an operation called a retroperitoneal lymph node dissection (RPLND) is done. One possible complication of this surgery is retrograde ejaculation. If the surgeon cuts a nerve during the surgery, ejaculation still can occur, but the the sperm end up in the bladder, and so infertility is a problem.

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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