hematogenous

Route of spread carries diagnostic weight. Haematogenous osteomyelitis is the usual mechanism in children, seeding the metaphysis of long bones where sluggish sinusoidal flow favours bacterial lodgement, most often with Staphylococcus aureus; in adults osteomyelitis is more often from contiguous spread or direct inoculation, as in diabetic foot ulcers or open fracture, and vertebral osteomyelitis is the usual haematogenous form. In sickle cell disease Salmonella osteomyelitis is characteristically haematogenous. For tumours, sarcomas typically metastasize haematogenously while carcinomas typically spread first by lymphatics, with important exceptions that favour blood-borne spread: renal cell carcinoma, hepatocellular carcinoma, follicular thyroid carcinoma, and choriocarcinoma. Venous drainage predicts destination, so gastrointestinal tumours seed the liver via the portal vein, while most other sites seed the lungs first. The Batson vertebral venous plexus, which is valveless, explains prostate cancer metastasizing to the vertebrae and pelvis, characteristically as osteoblastic lesions.