Endometriosis — USMLE Step 2 CK Guide 2026

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This is a clinician-written, evidence-based summary aligned to the USMLE Step 2 CK Content Outline. It is intended for medical students preparing for USMLE Step 2 CK. Management reflects current ACC/AHA, USPSTF, and APA guidelines. Always cross-reference with UpToDate, institutional protocols, and clinical judgment.

Key points

Classic symptoms: cyclic pelvic pain, progressive dysmenorrhea, deep dyspareunia, dyschezia, and infertility
Diagnosis can be clinical; imaging helps identify endometriomas and deep infiltrating disease
First-line empiric treatment: NSAIDs plus hormonal suppression if not trying to conceive
Definitive diagnosis historically required laparoscopy with histology, but current guidance supports earlier clinical/imaging diagnosis and treatment
Endometriomas show ground-glass ultrasound appearance

Overview

Endometriosis is endometrial-like glands/stroma outside the uterus, commonly on ovaries, uterosacral ligaments, cul-de-sac, peritoneum, bladder, or bowel. Lesions cause inflammation, adhesions, fibrosis, pain, and infertility.

Epidemiology

It affects many reproductive-age patients and is especially common with chronic pelvic pain or infertility. Symptoms often begin in adolescence and diagnosis is frequently delayed. Risk factors include early menarche, short cycles, heavy/prolonged menses, nulliparity, family history, and outflow obstruction.

Clinical Features

Symptoms

Progressive dysmenorrhea beginning before menses and continuing through menses

Chronic pelvic pain

Deep dyspareunia

Dyschezia or cyclic bowel symptoms

Infertility

Acute severe unilateral pain suggests torsion/rupture

Signs

Uterosacral ligament tenderness or nodularity

Fixed retroverted uterus from adhesions

Adnexal mass from endometrioma

Pelvic exam may be normal

Fever/cervical motion tenderness suggests PID

Investigations

First-line

Pregnancy testExclude pregnancy-related emergencies

Pelvic ultrasoundFirst-line imaging; identifies endometriomas and alternative causes

STI testing/urinalysis when indicatedExclude PID, cervicitis, UTI, and mimics

Second-line

MRI pelvisDeep infiltrating disease, surgical planning, indeterminate ultrasound

Empiric treatment responseSupports diagnosis but does not exclude other pathology

Infertility evaluationSemen analysis, ovulation, tubal patency, ovarian reserve

Specialist

Diagnostic/therapeutic laparoscopyPersistent symptoms, uncertain diagnosis, endometrioma, fertility/surgical needs

HistologyBiopsy confirms diagnosis when surgery performed

Management

ACOG Clinical Practice Guideline: Diagnosis of Endometriosis and ACOG Endometriosis Guidance

Pain management when not seeking pregnancy

NSAIDs for dysmenorrhea/inflammatory pain
Continuous combined hormonal contraception or progestin therapy for suppression
Levonorgestrel IUD can reduce dysmenorrhea/pelvic pain
GnRH agonists/antagonists with add-back therapy for refractory pain

Surgical management

Laparoscopic excision/ablation can improve pain and fertility in selected patients
Endometrioma cystectomy for pain, suspicious features, or fertility planning but may reduce ovarian reserve
Hysterectomy +/- oophorectomy reserved for severe refractory disease when fertility not desired

Infertility

Hormonal suppression treats pain but does not improve fertility while suppressing ovulation
Surgery may improve fertility in selected cases
Assisted reproduction if infertility persists or disease advanced

Long-term care

Treat as chronic condition
Address pelvic floor, bowel/bladder symptoms, mental health, and pain sensitization
Reassess red flags, new mass, postmenopausal bleeding, or noncyclic severe symptoms

Complications

Infertility: Adhesions, inflammation, tubal dysfunction, endometriomas
Chronic pelvic pain: May persist due to sensitization/pelvic floor dysfunction
Endometrioma: Torsion/rupture risk and ovarian reserve implications
Adhesions: Fixed pelvic organs and bowel/bladder involvement
Malignant transformation: Rare association with clear cell/endometrioid ovarian cancer

USMLE Step 2 CK Exam Tips

1Cyclic pelvic pain + dysmenorrhea + dyspareunia + infertility = endometriosis
2Fixed retroverted uterus and uterosacral nodularity are classic
3Endometrioma ultrasound = ground-glass ovarian cyst
4First-line pain treatment = NSAIDs + hormonal suppression if pregnancy not desired
5Trying to conceive: do not give continuous hormonal suppression as fertility treatment
6Classic definitive diagnosis = laparoscopy with biopsy
7Acute severe unilateral pain in endometrioma = torsion or rupture evaluation

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