Educational resource · Not a medical device · Infectious diseases review in progress · Does not replace clinical judgement

Diagram — Routes of dissemination — SeptiMap

name the routes by which an agent reaches an organ, with a sourced example for each, and find the atlas agents for each route. Educational resource, not a medical device.

Diagrams: mechanisms and principles

17 sourced diagrams · for medical students and practice

Each diagram reads step by step: an objective, the steps, three key points, a classic pitfall, its sources and the related atlas pages. Revision mode hides the labels to test yourself.

Preclinical · clinical years

Routes of dissemination

Objective: name the routes by which an agent reaches an organ, with a sourced example for each, and find the atlas agents for each route.

Step 6 / 6
Routes of dissemination1. Haematogenous — The agent travels in blood: fragments of an endocarditis vegetation embolise in arterial blood (septic emboli); Histoplasma reaches the reticuloendothelial system inside macrophages. 2. Contiguous — Brain abscess arises mostly from a contiguous focus of infection, or from a distant one. 3. Lymphatic — Cat-scratch disease: lymphadenopathy in the nodes draining the scratch site. 4. Ascending (ductal) — Urinary tract infection: a gut organism contaminates the periurethral area, then ascends the urethra to the bladder. 5. Direct — Inhalation: the extent of histoplasmosis depends on the amount of conidia inhaled and on cellular immunity. 6. Neural: a hypothesis — Listeria reaches the nervous system through blood, and by retrograde neural spread in animals; in humans, cranial nerve involvement may be secondary to rhombencephalitis.Haematogenousseptic embolifrom endocarditisContiguousbrain abscessfrom a nearby focusLymphaticcat scratch→ draining nodeAscending (ductal)urethra → bladder → kidneyDirectinhalation(histoplasmosis)Neural: hypothesisListeria: shownin animals only
  • Pathogen
  • Toxin, damage
  • Host (cells, tissues)
  • Immunity
  • Structure

Key points

  • Haematogenous: the agent travels in blood (septic emboli from endocarditis).
  • Contiguous and lymphatic: from a nearby focus, or to the draining nodes.
  • Ascending: urinary infection climbs from urethra to bladder, then kidney.

Classic pitfall

Presenting human Listeria rhombencephalitis as migration along cranial nerves: in humans, nerve involvement may be secondary.

Atlas agents by the route recorded in their page (atlas data: “direct” groups inoculation, inhalation and local spread).
RoutePages
Haematogenous
Contiguous
Lymphatic
Direct

Sources

Educational content · Illustrative mechanisms · Not applicable to individual clinical decisions · MDR 2017/745

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