29 LYMPHATIC DRAINAGE
Detailed notes
For MRCS Part A you are not tested on lymph physiology in detail — you are tested on which nodes drain which organ, because that determines where cancers metastasise and where surgeons must dissect. Two principles unlock most questions:
1. Lymphatics follow arteries — drainage of a gut segment mirrors its arterial supply.
2. Drainage follows embryology — organs that descend drag their lymphatics with them. The testis drains to L1/L2 para-aortic nodes, not to the inguinal nodes a few centimetres away.
The big picture: where does lymph ultimately go?
All lymph returns to the venous system at the root of the neck via two terminal ducts:
➡ Thoracic duct — begins as the cisterna chyli at L1/L2, ascends through the aortic hiatus (T12), crosses to the left at T5, and empties into the junction of the left subclavian and left internal jugular veins (left venous angle). Drains everything below the diaphragm plus the left upper body.
➡ Right lymphatic duct — drains the right side of the head, neck, thorax and right upper limb into the right venous angle.
👩⚕️ Thoracic duct injury during left-sided neck dissection or oesophagectomy causes a chylous leak — milky chylomicron-rich fluid. Treat with low-fat / MCT diet; ligate if persistent.
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Embryological rule — gonads and the para-aortic catch
The testes and ovaries develop on the posterior abdominal wall near the kidneys at L1/L2. They later descend (testes through the inguinal canal, ovaries into the pelvis) but keep their original lymphatic drainage to para-aortic nodes, travelling alongside the gonadal vessels.
This is the single most-tested fact in the chapter. The testis sits in the scrotum, but a testicular tumour spreads to the abdomen, not the groin. Scrotal skin drains where you would expect — to the superficial inguinal nodes.
| Structure | Drains to | Why |
|---|---|---|
| Testis | Para-aortic (L1/L2) | Embryological origin near kidney |
| Ovary | Para-aortic (L1/L2) | Same; travels with ovarian vessels in suspensory (infundibulopelvic) ligament |
| Scrotal skin | Superficial inguinal | Skin of perineum; not testis |
| Vulva | Superficial inguinal | External genitalia |
| Glans penis / clitoris | Deep inguinal (node of Cloquet) | Distal urethra and glans |
Gut rule — drainage follows the artery
Hindgut and pelvic structures drain along the inferior mesenteric and internal iliac systems; midgut along SMA branches; foregut along the coeliac trunk.
➡ Caecum and appendix → ileocolic nodes (midgut, SMA)
➡ Anal canal above the dentate (pectinate) line → internal iliac and inferior mesenteric nodes
➡ Anal canal below the dentate line → horizontal group of superficial inguinal nodes
The dentate line is the embryological junction between endoderm (hindgut) above and ectoderm (proctodeum) below. Everything changes here: epithelium, arterial supply, venous drainage, lymphatic drainage and innervation.
Pelvic organs — default is internal iliac
| Organ | Drainage |
|---|---|
| Cervix | Internal iliac, external iliac, obturator → common iliac → para-aortic |
| Body of uterus | Internal iliac |
| Fundus of uterus | Para-aortic (via ovarian vessels) and superficial inguinal (via round ligament through inguinal canal) |
| Prostate | Internal iliac, sacral, obturator |
| Bladder | Internal iliac (mostly), external iliac |
| Prostatic / membranous urethra | Internal iliac |
| Spongy urethra / glans | Deep inguinal |
The uterine fundus is a favourite SBA: fundal cancers can present with inguinal lymphadenopathy because the round ligament drags lymphatics through the inguinal canal to superficial inguinal nodes.
Breast lymphatics
About 75% of breast lymph drains to the axillary nodes; the remainder drains medially to the internal mammary (parasternal) nodes, with small contributions to supraclavicular and contralateral nodes.
Axillary nodes are divided into three levels by pectoralis minor:
➡ Level I — lateral to pec minor
➡ Level II — posterior to pec minor (includes Rotter's interpectoral nodes)
➡ Level III — medial to pec minor (apical, up to the clavicle)
Axillary clearance typically takes levels I and II. Sentinel lymph node biopsy identifies the first draining node; if negative, clearance is avoided and lymphoedema risk is reduced.
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Cervical lymph nodes — Levels I–VI
Head and neck cancers are staged by cervical level, and these are highly examinable:
| Level | Location | Typical content |
|---|---|---|
| I | Submental (Ia) and submandibular (Ib) | Floor of mouth, anterior tongue, lip |
| II | Upper deep cervical (skull base to hyoid), along IJV | Oropharynx, larynx, parotid |
| III | Middle deep cervical (hyoid to cricoid) | Oropharynx, hypopharynx, larynx |
| IV | Lower deep cervical (cricoid to clavicle) | Hypopharynx, larynx, thyroid, oesophagus |
| V | Posterior triangle | Nasopharynx, scalp |
| VI | Central / anterior (paratracheal, prelaryngeal — Delphian node) | Thyroid, subglottic larynx |
👩⚕️ Virchow's node (left supraclavicular) signals thoraco-abdominal malignancy — classically gastric cancer, also pancreatic, oesophageal, testicular and ovarian. Tumour cells track up the thoracic duct to its termination at the left venous angle.
Lower limb
➡ Superficial lymphatics → superficial inguinal nodes at the saphenous opening. Also drain perineum, lower abdominal wall below umbilicus, gluteal region and anal canal below the dentate line.
➡ Deep lymphatics → deep inguinal nodes along the femoral vein. The most superior is the node of Cloquet in the femoral canal. Onward drainage is to external iliac nodes.
Sentinel node biopsy
The sentinel node is the first node a tumour drains to. If histologically negative, the basin is assumed clear and block dissection is avoided. Used routinely in breast cancer and melanoma. Identified with blue dye (patent blue), radio-labelled colloid (Tc-99m), or both ("dual technique").
Lymphoedema
Accumulation of protein-rich interstitial fluid due to impaired lymphatic drainage.
| Type | Cause |
|---|---|
| Primary | Congenital lymphatic malformation. Subtypes: congenital (Milroy disease), praecox (puberty), tarda (>35y) |
| Secondary | Acquired obstruction: filariasis (Wuchereria bancrofti — commonest worldwide), malignancy, post-surgery (axillary clearance), post-radiotherapy, infection |
Non-pitting (chronic), positive Stemmer's sign (cannot pinch skinfold at base of second toe), recurrent cellulitis. Treatment is conservative — compression, manual lymphatic drainage, skin care.
Test yourself
[Image: MCQs banner]
What is the lymphatic drainage of the testis?
- ((Para-aortic (L1/L2)::☑️ Testis develops on posterior abdominal wall near kidney; lymphatics travel with gonadal vessels.))
- ((Superficial inguinal::This is where scrotal skin drains — not the testis itself.))
- ((Internal iliac::Drains pelvic organs (prostate, bladder, cervix), not the gonads.))
- ((Deep inguinal::Drains glans penis (node of Cloquet) and deep lower limb.))
👩⚕️ Classic exam trap: scrotal skin → inguinal; testis inside → para-aortic.
A woman with ovarian cancer is most likely to have metastasis to which nodes?
- ((Inguinal::External genitalia and lower limb drain here.))
- ((Internal iliac::Cervix, body of uterus, prostate and bladder drain here.))
- ((External iliac::Receives drainage from lower limb deep nodes and some pelvic structures.))
- ((Para-aortic::☑️ Ovary descends from L1/L2; drains alongside ovarian vessels in the infundibulopelvic ligament.))
The lymphatic drainage of the body of the uterus is primarily to:
- ((External iliac::Receives some cervical drainage, not body.))
- ((Para-aortic::Drains the fundus (via ovarian vessels), not the body.))
- ((Internal iliac::☑️ Body of uterus drains to internal iliac nodes — the default for pelvic organs.))
- ((Obturator::A secondary station for cervical drainage.))
A carcinoma of the uterine cervix first spreads to which nodes?
- ((Deep inguinal::Drains glans/clitoris and deep lower limb.))
- ((Internal iliac::☑️ First-station drainage for the cervix; also external iliac and obturator.))
- ((Para-aortic::Late-station spread via common iliac.))
- ((Superficial inguinal::Drains vulva, not cervix.))
What is the lymphatic drainage of the prostate?
- ((Internal iliac::☑️ Prostate drains to internal iliac, with sacral and obturator nodes also involved.))
- ((Para-aortic::Reserved for gonads, not accessory sex organs.))
- ((Superficial inguinal::Drains external genitalia skin.))
- ((External iliac::Bladder partially drains here, not prostate.))
A 56-year-old woman has a squamous carcinoma below the dentate line. Most likely nodal spread?
- ((Internal iliac::Drains the anal canal ABOVE the dentate line.))
- ((External iliac::Not the primary route for the anal canal.))
- ((Mesorectal::First station for rectal tumours.))
- ((Horizontal superficial inguinal::☑️ Below the dentate line is ectodermal — drains like perineal skin.))
👩⚕️ The dentate line is an embryological watershed: above = hindgut (endoderm), below = proctodeum (ectoderm). Everything changes at this line.
What is the lymphatic drainage of the glans penis?
- ((Superficial inguinal::Drains penile and scrotal skin, not the glans.))
- ((External iliac::Receives onward drainage from deep inguinal, but not primary.))
- ((Internal iliac::Drains prostatic and membranous urethra.))
- ((Deep inguinal (node of Cloquet)::☑️ Glans, clitoris and spongy urethra drain to deep inguinal nodes.))
What is the lymphatic drainage of the scrotal skin?
- ((Horizontal superficial inguinal::☑️ Scrotal SKIN drains as perineal skin — superficial inguinal.))
- ((Vertical superficial inguinal::Receives superficial lower limb drainage.))
- ((Deep inguinal::Drains the glans penis.))
- ((Para-aortic::Drains the testis itself — not the scrotal skin overlying it.))
A woman has bilateral inguinofemoral lymphadenopathy and bleeding onto her underwear. Most likely primary?
- ((Cervix::Cervical cancer spreads to internal iliac, not inguinal.))
- ((Vulva::☑️ Vulval cancer bleeds onto underwear and drains to superficial inguinal/femoral nodes.))
- ((Body of uterus::Drains to internal iliac.))
- ((Ovary::Drains to para-aortic; would not produce groin nodes.))
Lymphatic drainage of the caecum?
- ((Ileocolic::☑️ Caecum is midgut; lymphatics follow the ileocolic artery (SMA branch).))
- ((Inferior mesenteric::Drains hindgut — descending colon, sigmoid, upper rectum.))
- ((Internal iliac::Drains pelvic organs.))
- ((Inguinal::Not relevant to bowel.))
The thoracic duct drains into:
- ((Right brachiocephalic vein::This is roughly where the right lymphatic duct empties.))
- ((Junction of left subclavian and left internal jugular veins::☑️ Thoracic duct ends at the left venous angle.))
- ((Azygos vein::Systemic venous tributary draining the posterior thorax — not lymph.))
- ((Superior vena cava directly::Lymph never enters the SVC directly; always via the venous angles.))
A left supraclavicular lymph node is enlarged in a patient with weight loss. What is the most likely diagnosis?
- ((Hodgkin lymphoma of the neck::Possible but less specific than the classic sign described.))
- ((Tuberculous lymphadenitis::Causes cervical adenopathy but rarely isolated to left supraclavicular.))
- ((Gastric carcinoma (Virchow's node)::☑️ Abdominal malignancy spreads up the thoracic duct to its termination on the left.))
- ((Right-sided lung cancer::Would more likely drain to right supraclavicular via the right lymphatic duct.))
Which axillary level lies medial to pectoralis minor?
- ((Level I::Lateral to pec minor.))
- ((Level II::Posterior to (deep to) pec minor.))
- ((Level III::☑️ Apical group, medial to pec minor, extending to the clavicle.))
- ((Rotter's nodes::Lie between pec major and pec minor — interpectoral.))
Approximately what proportion of breast lymph drains to the axilla?
- ((25%::Roughly the proportion that drains medially (internal mammary).))
- ((50%::Underestimate.))
- ((75%::☑️ Around 75% of breast lymph drains to axillary nodes; remainder to internal mammary and others.))
- ((100%::Ignores the medial (internal mammary) drainage.))
Revision summary
➡ Thoracic duct: cisterna chyli at L1/L2 → left venous angle. Drains everything below diaphragm + left upper body.
➡ Right lymphatic duct: right upper quadrant only.
➡ Testis and ovary → para-aortic L1/L2 (embryology — follows gonadal vessels).
➡ Scrotal skin / vulva → superficial inguinal.
➡ Glans penis / clitoris / spongy urethra → deep inguinal (node of Cloquet).
➡ Cervix, body of uterus, prostate, bladder → internal iliac (default pelvic node).
➡ Uterine fundus → para-aortic (via ovarian vessels) and superficial inguinal (via round ligament).
➡ Anal canal above dentate → internal iliac / IMA nodes. Below dentate → superficial inguinal.
➡ Caecum → ileocolic (midgut, SMA).
➡ Breast: 75% axilla, rest internal mammary. Axillary levels I (lateral), II (deep), III (medial to pec minor).
➡ Cervical levels I–VI: I submental/submandibular, II–IV deep cervical chain, V posterior triangle, VI central/paratracheal.
➡ Virchow's node (left supraclavicular) — classically gastric cancer via thoracic duct.
➡ Sentinel node biopsy: blue dye + Tc-99m; routine in breast and melanoma.
➡ Lymphoedema: primary (Milroy, praecox, tarda) vs secondary (filariasis worldwide, axillary clearance in UK). Stemmer's sign positive.