Lymphatic Drainage by Region

The two lymphatic ducts

Thoracic duct. The body's main lymph channel starts at the cisterna chyli, a sac at L1–L2 that collects the intestinal and lumbar trunks. It passes through the aortic hiatus (T12) with the aorta, ascends in the posterior mediastinum between the aorta and azygos vein behind the esophagus, crosses to the left at about T4–T5, and arches in the root of the neck to empty at the left venous angle — the junction of the left subclavian and left internal jugular veins.

Chylothorax. Injury to the duct — esophagectomy or other thoracic surgery, trauma, or malignancy (lymphoma is the leading nontraumatic cause) — leaks chyle into the pleural space. The fluid is milky and lymphocyte-rich, with triglycerides >110 mg/dL and chylomicrons. Because the duct lies right of midline low in the chest and left of midline above T5, injury below about T5 tends to give a right-sided effusion and injury above it a left-sided one.

Pseudochylothorax also looks milky, but it is a long-standing effusion rich in cholesterol (cholesterol crystals, cholesterol >200 mg/dL) with low triglycerides and no chylomicrons.

Management logic. Drain the effusion and switch to a low-fat diet built on medium-chain triglycerides, which are absorbed directly into portal blood rather than packaged into chylomicrons, so duct flow falls. Persistent leaks may need duct ligation or embolization.

Skin and limb drainage

Umbilical watershed. Trunk skin above the umbilicus drains to the axillary nodes; skin below it (lower abdominal wall, flank, buttock) drains to the superficial inguinal nodes.

Superficial inguinal nodes. A horizontal group below the inguinal ligament collects the lower abdominal wall, buttock, perineum, scrotum, vulva, lower vagina, and anal canal below the pectinate line; a vertical group along the end of the great saphenous vein collects most superficial lymph of the leg. Both pass lymph to the deep inguinal nodes (medial to the femoral vein, which also receive the glans penis and clitoris) and then to the external iliac nodes.

Popliteal nodes. Superficial lymphatics travel with the superficial veins. Those with the small saphenous vein — dorsolateral foot, heel, posterior calf — reach the popliteal nodes first; those with the great saphenous vein (medial foot, leg, thigh) run straight to the groin.

Upper limb. Nearly all arm lymph reaches the axillary nodes; lymph from the ulnar side of the hand and forearm may first pass through the epitrochlear nodes above the medial epicondyle.

Visceral and pelvic drainage

Gut. Lymph follows the arteries: foregut to celiac, midgut to superior mesenteric, hindgut to inferior mesenteric nodes, all converging on the cisterna chyli. The stomach therefore drains to celiac nodes.

Gonads. Testes and ovaries develop high on the posterior abdominal wall near L1–L2 and keep their vessels and lymphatics as they descend, so lymph returns along the gonadal vessels to the para-aortic (lumbar) nodes near the renal veins. Testicular cancer thus spreads to retroperitoneal nodes and skips the groin, whereas scrotal skin cancer spreads to superficial inguinal nodes.

A testicular mass is removed through the groin by radical inguinal orchiectomy; cutting through the scrotum could open a new route to the inguinal nodes.

Breast drainage and the sentinel node

Routes. Most lymph, particularly from the lateral quadrants, flows to the axilla. The medial quadrants also drain to the internal mammary (parasternal) nodes along the internal thoracic vessels, some inferior lymph reaches abdominal nodes, and lymph can cross to the opposite breast.

Axillary levels. Defined by pectoralis minor: level I lateral (inferior) to it, level II behind it (including the interpectoral nodes), level III medial (superior) to it at the apex. Lymph moves I → II → III → subclavian trunk, so level III involvement means more advanced spread.

Full axillary dissection risks arm lymphedema and injury to the intercostobrachial (numb medial arm), long thoracic (winged scapula), and thoracodorsal (weak latissimus dorsi) nerves.

Blocked dermal lymphatics. Tumor emboli plugging skin lymphatics cause edema dimpled by hair follicles — peau d'orange, the hallmark of inflammatory breast cancer.

Named nodes as clinical clues

A left supraclavicular node in a young man warrants a testicular exam: germ cell tumors can climb from the para-aortic nodes up the thoracic duct.

Parinaud oculoglandular syndrome. Granulomatous conjunctivitis with an ipsilateral tender preauricular node, classically after cat contact (cat-scratch disease).