What is Urinary Tract and Bladder Endometriosis?

The lining of the uterus is made up of endometrial tissue which sheds with each menstrual cycle.  When tissue which is similar to this endometrial tissue grows outside the uterus, this condition is called endometriosis.  Unlike the endometrial tissue inside the uterus, endometriosis does not shed during a menstrual cycle. Therefore, this tissue is trapped inside the pelvic cavity and can produce inflammation, pain and a myriad of other debilitating symptoms. 

While endometriosis is mostly associated with the reproductive organs, it can affect any location in the body including the urinary tract system.  When this happens it’s characterized as urinary tract endometriosis.  Within the urinary system (bladder, ureter, kidney, and urethra), the bladder is the most frequently affected organ with 85% of urinary tract endometriosis being located on the bladder.

Bladder endometriosis involves endometriotic implants which can be located on different parts of the bladder. Bladder endometriosis can either be superficial (on the surface of the outer lining and relatively shallow) or it can penetrate into the muscle wall and reach the inner lining of the urinary bladder. Most frequently, bladder endometriosis is found at the bladder dome, which is the top part of the bladder.  

If the endometriotic implants are on at the base, or trigone, of the bladder where the ureters insert and involves the ureters themselves, this can also cause kidney or renal damage.

The other common location for urinary tract endometriosis is ureteral endometriosis. The ureter is the tube which carries the urine from the kidney down to the bladder and runs on the pelvic sidewall (the left ureter carries the urine from the left kidney down to the bladder and the right ureter does the same thing on the right side). The pelvic sidewall is where the majority of endometriosis is located. If the endometriosis lesions are deeply invasive, oftentimes called “deeply infiltrating endometriosis,” it can also affect the ureters. If left untreated, the ureters can become obstructed or compressed because of the endometriosis lesions and may cause loss of renal or kidney damage, sometimes even permanently.

How Serious is Urinary Tract and Bladder Endometriosis?

Although endometriosis frequently occurs in women of reproductive age, urinary tract and bladder endometriosis is beginning to become more diagnosed and occurs in up to 12% of all endometriosis cases.  If left unrecognized and/or untreated, urinary tract and bladder endometriosis can increase the risk of urinary tract obstruction and loss of renal function.  Renal function reflects the health of the kidneys and their vital role in the removal of metabolic waste products and maintenance of water–electrolyte balance and blood pressure.  This is all essential for keeping the body’s internal systems functioning in balance or what is known as ‘homeostasis’.  Therefore, early diagnosis and treatment of urinary tract and bladder endometriosis is necessary to avoid loss of kidney function.  If a urinary tract obstruction develops slowly (over the years), it may destroy the kidney without any clinical symptoms, which is called “silent kidney loss.”

What Causes Urinary Tract and Bladder Endometriosis?

There are many different theories of what causes urinary tract and bladder endometriosis, all of which are unproven. However, the most widely accepted theory of retrograde menstruation as a cause for endometriosis has been set aside.

A few other theories have been postulated, a few of which we will briefly touch on:

Mullerianosis theory: This is the theory that endometriosis is a genetically-based disease and that a patient is essentially “born with it.” The theory is that during fetal development in-utero, there are disruptions in the embryonic cells, which may develop into endometriotic lesions that respond to estrogen (which is why most patients become symptomatic with their first period). This, of course is an extremely oversimplified explanation of the complexities behind the theory, but the Mullerianosis theory does seem to be the most plausible.  

Transplantation theory: This theory claims that endometriosis is the result of direct lymphatic (clear fluid of white blood cells, fats & proteins) or blood vessel transplantation of endometriosis to other organs. 

Iatrogenic theory:  This theory suggests that endometriosis emerges after surgery on the uterus, particularly after a cesarean section or fibroid removal, with the idea that the endometrial tissue from the inside of the uterus, is then directly spread to the extrauterine organ.

What Are the Symptoms of Urinary Tract and Bladder Endometriosis?

Urinary Tract and bladder endometriosis often causes difficulties around urination, such as urinary frequency, urgency, or difficulty emptying.  Lesions found on the dome and body of the bladder can reduce the bladder’s ability to expand, which can also increase the frequency and urgency to urinate.   Lesions near the urethra at the bottom of the bladder can grow, swell and inhibit urine outflow.  This can result in retained urine in the bladder, which can promote bacterial growth and an increased risk of recurrent urinary tract infections (UTIs).

In bladder endometriosis, the diagnosis is frequently delayed because the symptoms resemble those of other conditions such as UTIs, an overactive bladder, or presumed interstitial cystitis (an inflamed or irritated bladder wall with Hunner’s lesions, which is extremely rare). Patients with bladder endometriosis may also have urinary frequency, recurrent urinary tract infections, blood in their urine, and urinary incontinence (leaking. Even if endometriosis is not directly on the bladder, symptoms of bladder endometriosis may be mimicked if there is endometriosis on the nerves that govern the bladder. It also should be noted that up to half of patients with bladder endometriosis are asymptomatic, showing no symptoms and only incidentally diagnosed at the time of surgery, either laparoscopically or cystoscopically.

Patients may notice that the following symptoms may worsen cyclically with the menstrual cycle and in the days leading up to menstruation: 

• an urgent or frequent need to urinate
• pain when your bladder is full
• burning or pain when you urinate
• feeling of incomplete bladder emptying
• blood in your urine
• pain radiating to the front of leg 
• pain in your pelvis
• lower back or flank pain
• reduced bladder capacity (leading to emptying the bladder frequently)
• feeling like you have a UTI, but the test is always negative

How is Urinary Tract and Bladder Endometriosis Diagnosed?

Urinary Tract and bladder endometriosis is a histologic diagnosis involving examining tissues and/or cells under a microscope, which requires a surgery.  Ultrasound or MRI may be utilized as imaging methods for looking to see if there are any big endometriosis nodules in the bladder. However, imaging is not perfect and will oftentimes produces false negatives.  It is not unusual for imaging to be completely negative for bladder endometriosis, despite being present. A cystoscopy (camera is inserted inside the bladder), combined with a laparoscopy, with a biopsy taken of the lesion, is the gold standard for diagnosing bladder endometriosis.

The workup for suspected bladder endometriosis can be extensive and often inconclusive, but may consist of: 

• Ultrasound uses high-frequency sound waves to obtain images from inside your body. With a transabdominal ultrasound, a device called a transducer is placed on your abdomen. In the case of a transvaginal ultrasound, the transducer is placed inside the vaginal canal, which generally is preferred when looking for pelvic endometriosis.   An ultrasound can sometimes identify the presence of large endometriosis nodules.  
• MRI scans  use powerful radio waves and magnets to help identify large endometriosis nodules in your bladder, however it will not pick up on smaller lesions.  
• Medical history and pelvic physical examination can help raise the suspicion of bladder endometriosis, however this is impossible to definitively diagnose because of its non-specific symptoms.
• Cystoscopy (bladder examination) involves inserting a scope through the urethra to view the bladder lining and inspect for endometriosis. 
• Laparoscopy (pelvic/abdomen examination) with excision of the endometriosis lesions allows samples to be removed and sent for histopathological analysis.  The presence of endometrial-like glands and/or stroma establishes a definitive diagnosis.

 Urinary Tract and Bladder Endometriosis Treatment

Urinary tract and bladder endometriosis is a progressive disease that can worsen if left untreated and dramatically interfere with a patient’s daily activities and quality of life.  Moreover, if left untreated, there can be permanent damage to other urinary tract organs, such as the ureters and/or kidneys. 

Complete excision of all urinary tract endometriosis lesions is the gold standard and the only way to diagnosis and treat endometriosis. However medical management, such as pain medications and hormonal treatments that aim to reduce inflammation and suppression of the menstrual cycle, may help reduce symptoms.