What do endometriosis stages 1–4 mean?

Endometriosis staging, most commonly the ASRM/rASRM system, scores findings seen at surgery, usually laparoscopy: lesion number, location, depth, and extent, ovarian endometriomas, and scar tissue called adhesions. Stage 1 or I is minimal, stage 2 or II mild, stage 3 or III moderate, often with ovarian involvement and more adhesions, and stage 4 or IV severe, with extensive disease or significant adhesions that can distort anatomy. There are four stages, not five, and this classification is useful shorthand for documentation and planning rather than a complete picture of the disease.

Stage does not reliably predict pain, impact on daily life, or case complexity: someone with stage 1 can have debilitating symptoms, while someone with stage 4 may have little pain, and a low stage does not make symptoms less real. Symptoms depend on disease behavior and subtype, including superficial disease, deep infiltrating endometriosis, and endometriomas, as well as exact locations such as the bowel, bladder, ureters, pelvic ligaments, and nerves, and coexisting conditions such as adenomyosis.

Because staging does not reliably capture nerve involvement, deep organ infiltration, or lesion inflammation, additional mapping systems such as ENZIAN and endometriosis-focused imaging, including ultrasound, can add important detail, although ultrasound alone does not establish a surgical stage. In our practice, we look beyond stage to the full symptom pattern and disease map, using operative findings, photos, and pathology when available to understand organ involvement and how completely disease could be safely excised, and to guide expectations for recovery, symptoms, and long-term goals involving pain relief, fertility, organ function, and recurrence risk.

If you’d like to explore evaluation or treatment options, you can schedule a consultation with our team to discuss how staging, disease subtypes, and your symptoms fit your goals.