Endometriosis is a condition where tissue similar to the lining of the uterus grows outside the uterine cavity. Kidney stones are hard deposits that form in the urinary tract from the crystallization of minerals and salts. Endometriosis does not directly cause the metabolic imbalances leading to common kidney stones. However, it can indirectly cause severe kidney complications, including obstruction, which increases the risk of secondary stone formation. This occurs when deep infiltrating endometriosis affects the ureters, the tubes connecting the kidneys to the bladder.
The Mechanism of Urinary Tract Endometriosis
This indirect pathway begins with Urinary Tract Endometriosis (UTE), where endometrial-like tissue grows on or near the ureters. Most cases involve the distal portion of the ureter, located in the pelvis. This tissue is hormone-sensitive, swelling and bleeding during monthly cycles.
This cyclical inflammation leads to dense scar tissue (fibrosis) around the ureter. This scarring causes extrinsic obstruction, compressing the ureter externally. Less commonly, the tissue invades the ureter wall, causing intrinsic obstruction. Both result in a narrowing, or stricture, of the passageway.
Consequences of Ureteral Obstruction
When the ureter is narrowed or blocked by endometriotic tissue and scar formation, urine flow is impeded. The blockage causes urine to back up, leading to hydroureter (dilation of the tube). As urine accumulates, the kidney’s collecting system swells, a condition known as hydronephrosis.
Chronic hydronephrosis progressively damages kidney tissue, potentially resulting in the loss of renal function. Furthermore, static, backed-up urine (stasis) allows salts and minerals to crystallize. This crystallization forms secondary kidney stones and increases the risk of recurrent urinary tract infections. This obstructive process links endometriosis to kidney stone development.
Recognizing Symptoms and Diagnostic Methods
Ureteral obstruction caused by endometriosis often mimics a typical kidney stone, causing severe flank pain that may radiate to the groin. This pain can be cyclical, worsening during menstruation as the tissue swells. Despite this, many cases are initially asymptomatic, referred to as “silent obstruction,” with up to 50% of patients lacking genitourinary symptoms at diagnosis.
Diagnosis requires clinical suspicion combined with specialized imaging. A transabdominal ultrasound is often used first to detect hydronephrosis, indicating a blockage. Computed Tomography (CT) scans and Magnetic Resonance Imaging (MRI) identify the obstruction’s location and visualize the deep infiltrating lesion causing compression. Sometimes, an Intravenous Pyelogram (IVP) or ureteroscopy confirms the stricture and the extent of ureteral damage.
Treatment for Endometriosis-Related Kidney Issues
Management focuses on two primary goals: relieving the urinary tract obstruction and removing the underlying disease. For acute obstruction, a temporary measure like placing a ureteral stent may be necessary. The stent bypasses the blockage, restores urine flow, and helps decompress the kidney while definitive treatment is planned.
Long-term resolution often requires surgical excision of the endometriotic lesion, especially when significant fibrosis or scarring is present. This complex surgery, often involving gynecologic and urologic surgeons, includes a procedure called ureterolysis to carefully free the ureter from scar tissue. Depending on the extent of the damage, a segment of the ureter may need to be removed and the remaining ends reconnected or reimplanted into the bladder. Hormonal suppression therapy can manage mild cases or symptoms but is generally insufficient to reverse established ureteral strictures.