The foundation of penile and urethral reconstruction is the distinction between a graft (transferred to a new bed, where it develops a new blood supply) and a flap (transferred with its blood supply). This tab covers graft biology, graft types and their urologic uses, and general reconstructive technique.
Graft vs Flap
- A flap is excised and transferred with its blood supply preserved or surgically re-established at the recipient site (key considerations: the nature of the flap tissue, its vasculature, and the mechanics of transfer).
- A graft is transferred to a host bed where a new blood supply develops by a process called take, which requires ≈96 hours in two phases:
- Imbibition (≈48 h) — the graft "drinks" nutrients from the host bed; its temperature stays below core body temperature.
- Inosculation (≈48 h) — true microcirculation is re-established and the graft warms to core temperature.
Tissue Grafts
The skin layers, superficial to deep, are the epidermis (barrier), the superficial (papillary) dermis (bearing the superficial/intradermal plexus and some lymphatics), and the deep (reticular) dermis (bearing the deep/subdermal plexus, most of the lymphatics, and the greater collagen content that gives tissue its physical characteristics).
- Split-thickness graft — epidermis plus a variable amount of superficial dermis (no reticular dermis), exposing the superficial (intradermal) plexus. Advantage: favourable vascularity. Disadvantage: contracts and becomes brittle when mature. A mesh graft is a slit split-thickness graft (slits allow expansion or drainage of subgraft collections).
- Full-thickness graft — epidermis plus all the dermis, exposing the subdermal plexus and carrying most lymphatics and the tissue's physical characteristics. Advantage: contracts less, more durable. Disadvantage: more fastidious vascularity.
Grafts in Urology
- Primary urethral reconstruction uses (in order of usefulness): the oral mucosal graft (buccal, labial, or lingual — buccal mucosa has a panlaminar plexus), the bladder epithelial graft (limited distally by desiccation/hypertrophy), the rectal mucosa graft, skin grafts (FTSG/STSG — extragenital FTSGs take poorly except the posterior auricular/Wolfe graft), and dartos-based skin island flaps. Tunica vaginalis grafts give uniformly poor results in the urethra.
- Penile reconstruction favours an unmeshed thick (0.012–0.015 inch) STSG, which gives the best take and cosmesis (meshed/thinner grafts contract; FTSGs fail more often). Tunica vaginalis grafts are useful for small tunica albuginea defects of the corpora cavernosa.
Surgical Technique Generalities
Reconstruction aims to minimise tissue injury — bipolar cautery is often preferred (more confined field effects), and absorbable suture on a tapered needle is the rule in urethral surgery. Femoral neuropathy can follow lithotomy positioning (hip hyperabduction/hyperextension) or retractor injury. The femoral nerve (the largest branch of the lumbar plexus, from the anterior divisions of L2–L4) emerges between the psoas and iliacus and enters the thigh lateral to the external iliac artery; it provides sensation to the anterior thigh and medial leg and motor supply for knee extension.
Self-Test
1. What is the difference between a graft and a flap? A flap is transferred with its blood supply; a graft is transferred to a host bed where a new blood supply develops by "take."
2. How long does graft take require, and what are its two phases? About 96 hours, in two ~48-hour phases: imbibition (the graft "drinks" nutrients) then inosculation (microcirculation is re-established).
3. How do split- and full-thickness grafts differ — which has favourable vascularity, and which contracts/becomes brittle? A split-thickness graft carries epidermis plus variable superficial dermis (favourable vascularity, but it contracts and becomes brittle); a full-thickness graft carries all the dermis (more durable, but more fastidious vascularity). The split-thickness graft has the favourable vascularity and is the one that contracts.
4. Which grafts have been used successfully for primary urethral reconstruction? Oral mucosa (buccal/labial/lingual), bladder epithelium, rectal mucosa, skin grafts (FTSG/STSG), and dartos-based skin island flaps.