Interstitial Cystitis and Endometriosis

Interstitial Cystitis and Endometriosis: Unraveling the Evil Twins Syndrome of Chronic Pelvic Pain


Chronic pelvic pain (CPP) is a health condition that burdens millions of women worldwide. The complexity of diagnosing and treating CPP is often overwhelming due to the multitude of potential underlying causes and associated conditions. Two such conditions, often called the “Evil Twins” syndrome, are Interstitial Cystitis (IC) and Endometriosis, both commonly found in patients suffering from CPP. This article will explore these conditions’ prevalence, diagnosis, and treatment in patients with CPP.

Understanding Chronic Pelvic Pain

Chronic Pelvic Pain (CPP) is a prevalent health condition affecting an estimated 9 million women in the United States alone. It accounts for up to 40% of laparoscopies and 10% to 12% of all hysterectomies, indicating its significant impact on women’s health. The annual expenditure on diagnosing and treating CPP is nearly $3 billion.

The “Evil Twins”: Interstitial Cystitis and Endometriosis

Two conditions frequently associated with CPP are Interstitial Cystitis (IC) and Endometriosis. These conditions can present similar symptoms and coexist in patients, making the diagnosis and management of CPP even more challenging.

Interstitial Cystitis (IC)

Interstitial Cystitis, or bladder-originated pelvic pain, is a significant disorder related to CPP. The etiology of IC is multifactorial and progressive, involving bladder epithelial dysfunction, mast cell activation, and bladder sensory nerve upregulation. The exact prevalence of IC in the United States varies, with estimates ranging from 10 to 510 per 100,000 normal population. However, current research suggests that IC might be more prevalent than previously estimated.


Endometriosis is another common condition among women with CPP, affecting more than half of the patients diagnosed with CPP. Symptoms include pain during sexual intercourse (dyspareunia), cyclical perimenstrual lower abdominal pelvic pain, symptom flares after sexual intimacy, and irritative voiding in case of urinary tract involvement. A definitive diagnosis of endometriosis requires visual confirmation of the lesion during laparoscopy and histologic confirmation of the presence of both ectopic endometrial glands and stroma.

The Overlap Between Interstitial Cystitis and Endometriosis

Research has demonstrated a high rate of overlap between IC and endometriosis in patients with CPP. This overlap poses challenges in diagnosis and treatment, as the presence of one condition does not preclude the existence of the other. Therefore, it is crucial to consider both conditions in the evaluation of patients with CPP.

Diagnosis of Interstitial Cystitis

The diagnosis of IC and endometriosis involves various tests and procedures, including the Potassium Sensitivity Test (PST), cystoscopy with hydrodistention, and laparoscopy.


Laparoscopy for direct visualization of endometriosis lesions and taking a biopsy is the gold standard for endometriosis diagnosis.

Read more: The Different Tests Used to Diagnose Endometriosis 

Potassium Sensitivity Test (PST)

The PST is a diagnostic test developed to detect abnormal permeability of the bladder epithelium, a key factor in the pathophysiology of IC. Previous studies have validated the use of the PST in diagnosing IC, particularly at the early stages of the disease.

Cystoscopy with Hydrodistention

Cystoscopy with hydrodistention is a diagnostic procedure often used to confirm the presence of IC. The bladder is filled with sterile water under passive hydrostatic pressure, then slowly drained. The presence of submucosal petechial hemorrhages, or glomerulations, confirms the diagnosis of IC.


During cystoscopy under anesthesia, your provider may remove a sample of tissue (biopsy) from the bladder and the urethra for examination under a microscope. This is to check for bladder cancer and other rare causes of bladder pain.

Urine cytology

Your provider collects a urine sample and examines the cells to help rule out cancer.


This article highlights the complex interplay between IC and endometriosis in the context of CPP. It underscores the need for careful evaluation and simultaneous consideration of these conditions in patients with CPP. A multidisciplinary approach, including the use of PST and concurrent cystoscopy and laparoscopy, is crucial for accurate diagnosis and effective treatment of concurrent interstitial cystitis and endometriosis.

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