Lymphatic drainage of the pelvis
Lymphatic drainage of the pelvic organs and the vulva
Lymph from the pelvic organs follows their arteries, so the ovary and the top of the uterus drain upwards with the ovarian vessels to the para-aortic nodes, while the cervix, body of the uterus, upper vagina and bladder drain to the iliac and obturator nodes on the side wall. Skin-derived parts (vulva, lower vagina, lower anal canal) drain to the inguinal nodes. This pattern decides how gynaecological cancers spread and which nodes are removed or sampled.
Two rules
- Viscera: lymph runs with the arteries. Organs supplied from the internal iliac drain to iliac and obturator nodes; organs supplied from the aorta (the gonad) drain to para-aortic nodes.
- Skin and ectoderm: the vulva, lower third of the vagina, perineum and anal canal below the pectinate line drain to the superficial inguinal nodes, as does the skin of the lower abdominal wall below the umbilicus.
- A useful comparison: the testis goes to para-aortic nodes but the scrotum to superficial inguinal nodes, for the same reasons.
Node groups
| Group | Position | Main territory |
|---|---|---|
| Superficial inguinal, horizontal group | Below the inguinal ligament | Vulva, lower vagina, perineum, anal canal below the line, lower abdominal wall, buttock; uterine cornu via the round ligament |
| Superficial inguinal, vertical group | Along the great saphenous vein | Lower limb (medial foot and leg) |
| Deep inguinal (femoral) | Medial to the femoral vein; highest node in the femoral canal | Superficial inguinal nodes; glans of the clitoris directly |
| External iliac | Along external iliac vessels | Deep inguinal nodes; bladder; cervix and upper vagina |
| Obturator | Below the external iliac vein, above the obturator nerve | First station for cervix and uterus |
| Internal iliac | Along internal iliac branches | Cervix, upper and middle vagina, bladder base, rectum, anal canal above the line |
| Sacral | In front of the sacrum | Cervix via the uterosacral ligaments, rectum |
| Common iliac | Along the common iliac vessels | All pelvic groups above |
| Para-aortic (lumbar) | Beside the aorta at L1–L2 | Ovary, tube, uterine fundus; common iliac nodes |
- At pelvic lymphadenectomy the obturator nodes are cleared from below the external iliac vein while the obturator nerve is preserved (thigh adduction).
- Bipedal lymphangiography fills inguinal, external iliac, common iliac and para-aortic nodes but not the internal iliac group, which drains the viscera, not the leg.
Drainage organ by organ
| Organ | First nodes |
|---|---|
| Ovary | Para-aortic at L1–L2, along the ovarian vessels; can involve pelvic nodes through the broad ligament |
| Tube | Para-aortic, with ovarian lymphatics |
| Uterine fundus | Para-aortic with the ovarian vessels |
| Cornu | Superficial inguinal along the round ligament |
| Body | External and internal iliac |
| Cervix | Parametrial, obturator, internal and external iliac; sacral via uterosacral ligaments |
| Upper third of vagina | Internal and external iliac (with the cervix) |
| Middle third of vagina | Internal iliac |
| Lower third of vagina | Superficial inguinal |
| Vulva | Superficial inguinal, then deep inguinal, then external iliac |
| Clitoris | Deep inguinal (and superficial) |
| Bladder | Mainly external iliac; internal iliac, obturator |
| Anal canal above / below pectinate line | Internal iliac / superficial inguinal |
Spread of gynaecological cancers
- Cervix: usually stepwise: parametrial and obturator, then internal and external iliac, then common iliac, then para-aortic. Para-aortic involvement without pelvic disease is unusual.
- Endometrium: body tumours reach pelvic nodes; fundal tumours can go straight to para-aortic nodes with the ovarian vessels, so isolated para-aortic disease occurs. Cornual tumours can reach the labia majora and inguinal nodes along the round ligament.
- Ovary: para-aortic nodes are the first lymphatic station, and they may be involved with clear pelvic nodes. Most spread, however, is transcoelomic across the peritoneum (omentum, right hemidiaphragm).
Vulva, vagina and infection
- Vulva: superficial inguinal, then deep inguinal (through the saphenous opening), then external iliac nodes. Lateral tumours drain to the same side; midline tumours (clitoris, perineal body) drain to both sides.
- Sentinel node biopsy in small vulval cancers: blue dye and a radioactive tracer injected round the tumour identify the first draining node; if it is clear, other nodes are unlikely to be involved, sparing a full groin dissection.
- Lower vagina: superficial inguinal nodes, like the vulva. Upper vagina: iliac nodes, like the cervix.
- Lymphogranuloma venereum (Chlamydia L1–L3): in women the cervix and upper vagina drain to perirectal and iliac nodes, so proctitis and rectal stricture are commoner than inguinal buboes.
Complications of lymph node dissection
- Lymphoedema: after inguinofemoral or pelvic dissection, protein-rich fluid accumulates, so swelling becomes firm and non-pitting with thickened skin and recurrent cellulitis.
- Lymphocele: a thin-walled cyst on the pelvic side wall weeks after pelvic lymphadenectomy; fluid rich in lymphocytes with creatinine equal to serum (urine would be far higher). It may compress the iliac vein (leg swelling, thrombosis) or the ureter.
Remember Follow the artery: gonad and fundus to the aorta, the rest of the pelvis to the iliac side wall, skin to the groin.
Exam trap Ovarian cancer spreads first to para-aortic, not inguinal or external iliac, nodes; the cornu drains along the round ligament to the superficial inguinal nodes.
Exam trap The lower third of the vagina and the vulva drain to superficial inguinal nodes; the upper vagina drains with the cervix to the iliac nodes.
Test yourself on this topic
5 of the 17 questions in our bank on this topic. Choose an answer to see why every option is right or wrong.
A 45-year-old woman with squamous carcinoma of the cervix has metastases in the para-aortic lymph nodes on staging CT and PET. Through which nodes has the tumour most likely spread to reach them?
Answer: Pelvic nodes, then common iliac nodes
Lymph from the cervix drains laterally through the parametrium to the paracervical, obturator, internal iliac and external iliac nodes (the pelvic nodes), and posteriorly along the uterosacral ligaments to sacral nodes. From these it passes up to the common iliac nodes and then to the para-aortic nodes. Cervical cancer usually spreads in this orderly stepwise way, so para-aortic disease without pelvic node involvement is unusual. The inguinal nodes are involved only if the tumour reaches the lower vagina.
Cervical lymph spread
- First: parametrial, obturator, iliac nodes
- Then: common iliac
- Then: para-aortic
- Usually stepwise
Remember Cervix spreads up the pelvic chain step by step.
Exam trap Skip metastasis to para-aortic nodes is uncommon in cervical cancer.
Why the other options are wrong
- Superficial then deep inguinal nodes Involved only if the tumour spreads to the lower third of the vagina.
- Inferior mesenteric nodes along the colon Drain the colon, not the cervix.
- Mediastinal nodes via the thoracic duct Reached only after the para-aortic nodes.
- Coeliac nodes along the stomach Drain the stomach and upper gut.
During a pelvic lymphadenectomy for endometrial cancer, the surgeon clears the obturator group of nodes. In which space do these nodes lie?
Answer: Below the external iliac vein, above the obturator nerve
The obturator nodes lie in the obturator fossa on the lateral pelvic wall, in the fatty tissue bounded above by the external iliac vein and below and laterally by the obturator nerve, with the obturator vessels deeper. They are first-station nodes for the cervix and uterus and are removed in pelvic lymphadenectomy. The obturator nerve must be identified and preserved as the nodes are lifted out, or the woman loses thigh adduction and sensation over the medial thigh. Para-aortic, presacral, femoral and mesorectal nodes are separate groups.
Obturator fossa nodes
- Above: external iliac vein
- Below: obturator nerve
- First station for cervix and uterus
- Preserve the nerve: thigh adduction
Remember Obturator nodes sit between the external iliac vein and the obturator nerve.
Exam trap The obturator nerve runs through the node field and is at risk during clearance.
Why the other options are wrong
- Between the aorta and the inferior vena cava These are para-aortic (interaortocaval) nodes.
- In front of the sacral promontory These are presacral or sacral nodes.
- Within the femoral canal below the inguinal ligament These are deep inguinal nodes.
- Beside the rectum in the mesorectum These are mesorectal nodes draining the rectum.
In a woman with a small, lateral vulval squamous carcinoma, blue dye and a radioactive tracer are injected around the tumour, and the first stained, radioactive groin node is removed. It shows no tumour. Why can full groin dissection be avoided?
Answer: It is the first node to receive tumour lymph
Lymph from a tumour drains in an orderly way to a first-echelon node, the sentinel node, before passing to other nodes in the basin. Dye or tracer injected around the tumour follows the same route and marks this node. If the sentinel node is free of tumour, the chance that other nodes in that groin contain metastases is very low, so the morbidity of full inguinofemoral lymphadenectomy, such as lymphoedema and wound breakdown, can be avoided in suitable small lateral tumours.
Sentinel node
- First node draining the tumour
- Found with blue dye and tracer
- Negative: others unlikely involved
- Avoids lymphoedema from full dissection
Remember Sentinel node negative: the rest of the basin is usually clear.
Exam trap Sentinel node biopsy suits small, unifocal tumours; it does not replace dissection when nodes are clinically involved.
Why the other options are wrong
- It is the node with the largest blood supply Blood supply is irrelevant to lymphatic spread.
- It is the only node in the inguinal region The groin has many nodes in superficial and deep groups.
- It filters lymph only from the lower limb The sentinel node is the first to drain the tumour, not the leg.
- It is the last node before the thoracic duct The thoracic duct is reached much later.
In a woman with carcinoma of the labium majus, the superficial inguinal nodes contain metastases. To which group of nodes does lymph from these nodes pass next?
Answer: Deep inguinal (femoral) nodes
Lymph from the vulva goes first to the superficial inguinal nodes in the subcutaneous tissue below the inguinal ligament. Efferents from these pass through the cribriform fascia of the saphenous opening to the deep inguinal nodes, which lie medial to the femoral vein in the femoral canal. From the deep nodes, the highest of which lies in the femoral ring, lymph passes to the external iliac nodes. The vulva does not normally drain directly to the internal iliac or para-aortic nodes.
Vulval lymph pathway
- First: superficial inguinal
- Through the saphenous opening
- Next: deep inguinal beside femoral vein
- Then: external iliac nodes
Remember Vulva: superficial inguinal, deep inguinal, external iliac.
Exam trap The vulva does not drain first to pelvic nodes; groins come first.
Why the other options are wrong
- Para-aortic nodes at the renal veins Receive ovarian and fundal lymph, not the vulva directly.
- Internal iliac nodes in the pelvis Receive the cervix, upper vagina and pelvic viscera.
- Popliteal nodes behind the knee Drain the lateral foot and calf.
- Sacral nodes on the sacrum Receive lymph from the posterior cervix and rectum.
A 30-year-old woman has rectal pain, mucopurulent rectal discharge and later a rectal stricture, with no groin swelling. Swabs are positive for Chlamydia trachomatis serovar L2. Why are inguinal buboes less common in women with this infection?
Answer: Cervix and upper vagina drain to deep pelvic nodes
Lymphogranuloma venereum is caused by the invasive L1–L3 serovars, which spread from the primary site to the draining lymph nodes. In men the primary lesion is usually on the penis, which drains to the inguinal nodes, producing buboes. In women the primary lesion is often on the cervix, posterior vagina or rectum, which drain to the iliac and perirectal nodes deep in the pelvis. Inflammation there causes proctocolitis, fistulae and rectal strictures rather than visible inguinal swelling.
LGV in women
- Serovars L1–L3
- Cervix, vagina, rectum drain to perirectal and iliac nodes
- Proctocolitis, rectal stricture
- Inguinal buboes less common
Remember Where the lesion drains decides where the bubo forms.
Exam trap Absence of groin nodes does not exclude LGV in a woman.
Why the other options are wrong
- Chlamydia cannot infect the inguinal nodes L serovars readily infect lymph nodes, including inguinal ones.
- Women lack a horizontal inguinal node group Women have the same inguinal node groups as men.
- Oestrogen prevents lymphatic invasion Oestrogen has no such protective role.
- The organism spreads only through blood LGV spreads by lymphatics, not mainly by blood.
Where this sits in the CPSP syllabus
- Obstetrics & Gynaecology, Paper 2: Pelvic organs, vessels and nerves, Lymphatic drainage of pelvic organs and the vulva