When tissue resembling the uterine lining grows outside the uterus, it is diagnosed as endometriosis [1]. These benign growths can establish themselves in various locations within the body, leading to considerable discomfort. They are most commonly found in the pelvic region, yet endometriosis can manifest in unexpected places, such as the intestines, brain, and lungs. A sporadic form of endometriosis affecting approximately 1% of patients is ureteral endometriosis [2]. In this variant, the ureters are impacted. In the article below, I will delve into the symptoms these nodules can elicit in this context and explore available treatment options.

What is Ureteral Endometriosis?

Ureteral endometriosis is a specific form of endometriosis that affects the ureters, which are the tubes that carry urine from the kidneys to the bladder. There are two primary forms of ureteral endometriosis:

• Extrinsic Ureteral Endometriosis: In this type, endometrial tissue surrounds the ureter and infiltrates it from the outside. This is the more common form encountered in medical practice when dealing with ureteral endometriosis [2].
• Intrinsic Ureteral Endometriosis: In this rare form, endometrial tissue directly penetrates through either the muscle layer or the top cell layer of the ureter [2].
  

It is worth noting that ureteral endometriosis usually affects only one ureter. Interestingly, it is more commonly found in the left ureter than in the right [3]. Furthermore, research has pinpointed the specific location where endometriosis most frequently occurs. The endometriosis lesions can mainly be found in the lower third of the ureter, which is quite close to the urinary bladder, within the pelvic area. Patients with ureteral endometriosis often have endometriosis lesions in other parts of their bodies [3, 4, 5].

 Good to Know!

Generally, individuals possess two kidneys, and the ureters serve the crucial function of directing urine from these kidneys to the bladder. [6]. Although endometriosis lesions on the ureter are relatively uncommon, they are notably more prevalent among women diagnosed with deep infiltrating endometriosis [4, 7, 3, 8].

Ureteral Endometriosis: Symptoms

You might be curious about how to recognize endometriosis on the ureter. Endometriosis, as you may already know, can manifest with many symptoms. Key indicators include pain during menstrual periods, prolonged menstrual bleeding, a shortened menstrual cycle, and issues with bowel movements. Pain during urination or sexual intercourse is also possible. Additionally, some women may experience infertility due to endometriosis [9]. However, when endometriosis tissue is situated on the ureter, it may not necessarily cause immediate symptoms. In such cases, asymptomatic urinary retention in the kidney often occurs, which can eventually lead to a decline in kidney function [8, 4].

“Asymptomatic” means that there are no noticeable symptoms to indicate the complication. Urinary retention in the kidney can result from the backward flow of urine into the kidney from the urinary tract or an obstruction in urine outflow [10]. Endometriosis can alter the ureter in a way that hampers urine drainage. Most frequently, endometriosis exerts pressure on the ureter from the outside, impeding the smooth flow of urine. This creates a blockage akin to a dam, causing urine to accumulate in the kidney and preventing elimination. If you have a congested kidney, you may experience pain in your back or the side of your abdomen [10].

Notably, a doctor can detect kidney urinary retention via ultrasound from the flank.

What Causes Ureteral Endometriosis?

The exact causes of ureteral endometriosis remain a mystery, but experts have proposed various mechanisms for its development. One theory suggests that endometriosis cells may spread like metastasis, utilizing lymphatic channels or blood vessels to attach themselves to urological structures, including the ureter. This mechanism could also be relevant in cases of endometriosis affecting the bladder. Another theory posits that stem cells transform into endometriosis cells, giving rise to the characteristic endometriosis lesions [2].

Several risk factors have been identified:

• Diagnosis of deep infiltrating endometriosis [3, 4, 7, 8].
• Presence of an endometriosis node on the septum rectovaginale (the partition wall between the vagina and the rectum) larger than 3 cm [4, 7].
• Existence of “kissing ovaries,” where the ovaries come into contact with each other in the midline [11].

Ureteral Endometriosis: Diagnosis

Detecting endometriosis tissue on the ureter can be challenging, as it often goes unnoticed for an extended period. Therefore, a comprehensive diagnosis is of utmost importance. It is crucial to consider relevant risk factors in this context. For instance, if there is a palpable endometriosis node on the partition between the vagina and the rectum (detectable through the rectum), it is prudent to explore the possibility of ureteral endometriosis. The same consideration applies if endometriosis is present on the pelvic wall or an ultrasound reveals “kissing ovaries.” Even without kidney-related symptoms, a kidney ultrasound is recommended in such cases. This examination helps assess kidney function and can prove valuable for routine check-ups. Before and following surgery, a renal ultrasound is highly beneficial. It allows for pre-operative assessment, especially to identify any congestion, and enables the involvement of urologists in surgical preparations. If there are concerns about ureteral distress, a urologist should thoroughly examine it. In specific situations, such as when there is congestion in the renal pelvis or cases of intrinsic ureteral endometriosis, kidney scintigraphy or MRI (magnetic resonance imaging) may be warranted [2]

Good to Know!

Physicians utilize various classifications to categorize the severity of endometriosis. While the rASRM classification provides insights into the extent of endometriosis spread, the ENZIAN classification describes deep infiltrating endometriosis. If you have received a diagnosis of ureteral endometriosis, including the ENZIAN classification in the operative report and physician’s notes can be extremely helpful for accurate documentation and treatment planning.

Treatment of Ureteral Endometriosis

The key to treating ureteral endometriosis is addressing endometriosis comprehensively. Treating deep infiltrating endometriosis in the pelvis and endometriosis lesions on the ovaries is essential to prevent further damage to the ureters and minimize the risk of recurrences [12]. Surgery is typically the preferred approach, conducted through three to four tiny abdominal incisions using laparoscopic techniques, commonly employed for endometriosis procedures. This method allows for the precise exposure of the ureter, separating it from surrounding tissues (ureterolysis). Depending on the situation, the placement of a catheter or ureteral splints may be considered before surgery, with thorough discussions beforehand [4, 5, 13]. 

Often, external removal of endometriosis tissue from the ureter allows the ureter to recover from the narrowing caused by the endometriosis.

However, in certain situations, surgery may reveal that a portion of the ureter needs to be removed [13]. Rarely, reimplantation of the ureter into the bladder (ureterocystoneostomy) may be necessary, typically in severe cases of intrinsic ureteral endometriosis [14]. The general approach is to attempt to restore the ureter’s function by removing unwanted tissue and then observe its recovery post-procedure. The removal or reimplantation of parts of the ureter is considered only if initial efforts fail [2].

Following surgery for endometriosis near the ureter or involving the ureter itself, conducting a renal ultrasound before discharge is crucial. This assessment helps monitor improvements in pre-existing urinary retention and the potential development of new urinary issues or worsening conditions, including complications from surgery.

In a Nutshell

Endometriosis of the ureter is relatively rare, making it particularly challenging because patients with this condition may not necessarily experience symptoms. When symptoms manifest, they typically appear late and may include lower back or flank pain. The precise mechanisms underlying the development of ureteral endometriosis are still debated among experts. Some believe that endometriosis tissue may spread through the bloodstream or lymphatic system, while others posit the theory of stem cell transformation into endometriosis cells. Several risk factors have been identified, including women with touching ovaries, deep infiltrating endometriosis, or endometriosis nodes on the partition between the vagina and rectum, who may be at a higher risk of developing ureteral endometriosis. Diagnostic tools such as ultrasound, MRI, and scintigraphy can be valuable in identifying this condition. Treatment typically involves surgical intervention to free the ureter from surrounding tissue. In severe cases, reimplantation of the ureter or partial removal may be necessary to manage the condition effectively.