Overview of Enlarged Retroperitoneal Lymph Nodes

Lymph nodes are small, bean-shaped structures located all over the body. They are part of the lymph system, a network to the vessels that function like immune outposts, filtering fluids from tissues to help neutralize infection and minimize toxic exposure.

When lymph nodes of the abdominal cavity (known as the retroperitoneum) become enlarged, there are many potential reasons for this, and not all of them are cancerous. In fact, in most cases, cancer is the last concern on the list.

Still, there are certain patterns of enlargement that are concerning and require more extensive evaluation, including imaging studies and biopsies.

Retroperitoneal lymph nodes are located in a specific part of the abdominal cavity immediately behind the intestine that is closer to your backbone than your belly button. The swelling of the nodes themselves is referred to as lymphadenopathy.

Unlike other types of lymph nodes, retroperitoneal lymph nodes generally cannot be felt or seen when enlarged. Because of this, doctors will often only discover an enlargement after conducting an imaging study such as a computed tomography (CT) scan of the abdomen and pelvis.

Oftentimes, the swelling will be the result of an infection, manifesting with either a diffuse pattern if the underlying infection is systemic (involving the whole body) or a constrained pattern if the infection is localized.

Among some of the more common causes of swollen retroperitoneal lymph nodes:

• Infections such as tuberculosis
• Inflammatory conditions such as sarcoidosis
• Cancers that spread (metastasize) to the lymph nodes
• Blood cancers that develop in the lymph nodes or spread to the lymph nodes
• Rare, non-cancerous conditions like Castleman disease which cause the overgrowth of lymph nodes

Although swollen lymph nodes in and of themselves can tell us little about the underlying illness, there are some red flags doctors will look for.

In instances like these, the doctor may recommend a biopsy to obtain a tissue sample for evaluation or an imaging study known as positron emission tomography (PET), which is able to detect a metastatic malignancy better than other imaging technologies.

More often than not, the cause of swollen retroperitoneal lymph nodes will be secondary, meaning that they are collaterally affected by a disease or disorder affecting an organ within or near the retroperitoneum. These include such as organs as:

• Adrenal glands
• Ascending or descending colon and duodenum
• Esophagus
• Kidneys and ureters
• Pancreas

Sometimes a disease 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. Masses in this area can block a ureter, causing urinary tract symptoms that trigger the inflammation and the production of inflammatory cytokines. When this happens, retroperitoneal lymphadenopathy will almost invariably occur.

Cancer is clearly the most concerning cause of retroperitoneal lymphadenopathy. Two of the most common malignancies associated with this are lymphoma and testicular cancer.

Lymphomas are a group of cancers of which are considered lymphoproliferative (meaning that it causes the excessive production of white blood cells called lymphocytes). Lymphomas usually start in the lymph nodes; retroperitoneal lymph nodes are typically affected. There are two main categories of lymphoma:

• Hodgkin’s lymphoma (HL), which is primarily nodal (affect the lymph nodes)
• Non-Hodgkin’s lymphoma (NHL), which is nodal and extranodal (affecting other organs)

Moreover, with lymphoma, a CT scan will typically reveal that both the liver and spleen are enlarged along with the retroperitoneal lymph nodes.

Cancers can often metastasize from a primary tumor to retroperitoneal lymph nodes. One such cancer is testicular cancer.

In some instances, an operation called a retroperitoneal lymph node dissection may be used to help manage the advanced disease.

When enlarged lymph nodes in the retroperitoneum are identified, the significance of this finding depends on all of the other information, including the medical history of the individual with the enlarged nodes.

One important aspect of enlarged nodes in this particular location is that they are quite isolated from the rest of the body and are not as easily detected as lymph nodes in the neck, armpits or groin, for instance.

Sometimes lymph nodes are "borderline-enlarged" on imaging, meaning they are slightly larger than usual, but not necessarily a cause for concern. In these cases, there may be follow-up imaging performed and comparison to past studies to see if there has been enlargement in the interim.

Always talk to your health care team if you have questions about findings such as enlarged retroperitoneal lymph nodes or questions about the significance of these findings.