Deep Endometriosis Affecting the Urogenital Tract: Long-term Outcomes and Impact on Renal Function (RENDO)

Endometriosis is a chronic estrogen-dependent disease characterized by the presence and growth of endometrium-like tissue outside the uterine cavity.

This ectopic endometrial tissue induces a chronic local and systemic inflammatory response, resulting in the most common manifestations of the disease: chronic pelvic pain, infertility, and pelvic adhesions. In deep endometriosis (DE), adhesions and infiltrative growth may damage adjacent organs.

Overall, endometriosis affects approximately 10% of women of reproductive age. Its prevalence is higher among women with infertility (20-50%) and among patients with chronic pelvic pain (up to 90%).

The disease is usually categorized as superficial peritoneal, ovarian, or deep endometriosis (DE). Deep endometriosis is a progressive form of the disease that may affect organs beyond the pelvic cavity, including the urinary tract, alter their anatomy, and cause functional impairment.

Urogenital involvement occurs in approximately 1-5.5% of all women with endometriosis; the prevalence is substantially higher among patients with DE, reaching 16-53% according to the available literature.

Within the urinary tract, the bladder is most commonly affected (70-85%), followed by the ureters (9-23%), kidneys (approximately 4%), and urethra (approximately 2%).

Ureteral endometriosis is therefore a relatively rare but clinically significant entity. It may be unilateral or bilateral, with a predominance of left-sided involvement.

Two basic forms are distinguished:

• "Extrinsic" - ureteral stenosis caused by periureteral fibrosis and the presence of DE lesions without infiltration of the ureteral wall.
• "Intrinsic" - ureteral stenosis caused by direct infiltration of the ureteral wall by endometriotic tissue.

Ureteral stenosis causes secondary hydronephrosis and, unless treated in a timely manner, may lead to a progressive loss of renal function.

The disease frequently remains asymptomatic for a prolonged period. Up to half of cases are diagnosed incidentally or only at an advanced stage, when renal damage is already irreversible.

Early detection and timely planning of surgical management are therefore essential for preserving renal function.

The main surgical procedures are:

• ureterolysis - release of the ureter from fibrotic adhesions, preferred for the extrinsic form;
• ureteroneocystostomy (UCNA) - indicated for the intrinsic form when the affected segment must be resected and the ureter reimplanted into the bladder;
• ureteroureterostomy (ureteral anastomosis) - appropriate for the intrinsic form when, following resection, the distal ureteral segment is sufficiently long to allow anastomosis of healthy margins.

Despite the clinical significance of the condition, prospective studies objectively evaluating the evolution of renal function after the individual types of surgical management of ureteral endometriosis are still lacking.

A modern diagnostic strategy combining specialized ultrasound, dynamic renal scintigraphy (MAG3), and analysis of urinary biomarkers of tubular injury (KIM-1, CCL-2, L-FABP) enables earlier detection of renal dysfunction and more accurate monitoring of postoperative recovery. Identification of sensitive biomarkers of early renal injury and validation of an algorithm for their use could substantially improve decisions regarding the timing of surgery and subsequent postoperative follow-up.

Based on our experience, some patients surgically treated for hydronephrosis caused by DE-related ureteral stenosis show persistent morphological changes on renal ultrasound and the manifestation of systemic conditions such as arterial hypertension during long-term follow-up. To date, no study has focused on the long-term follow-up of patients with ureteral DE and its potential consequences. The expected benefit of this study is to establish clear criteria for the indication of surgical treatment of ureteral endometriosis and to develop an evidence-based protocol for long-term follow-up.