Skin Ulcers (Non-Pressure, Non-Venous) — Clinical Documentation Guide (2026)

This Clinical Documentation Guide (CDG) covers non-pressure, non-venous chronic skin ulcers — primarily the FY2026 ICD-10-CM categories L97 (non-pressure chronic ulcer of lower limb, not elsewhere classified) and L98.4 (non-pressure chronic ulcer of skin, not elsewhere classified). Pressure ulcers (L89) and venous stasis ulcers (I87.2, I83.0–I83.2) are distinct conditions with their own CDGs — this guide links to both where appropriate. Content is intended for AAPC/AHIMA-credentialed coders, CDI specialists, and auditors working in wound care, vascular surgery, podiatry, and complex medical-surgical settings.

🔍 1. Definition

A non-pressure, non-venous chronic skin ulcer is a full-thickness skin defect of at least 4–6 weeks' duration that does not result primarily from sustained pressure over a bony prominence and is not caused primarily by venous hypertension or venous insufficiency. These ulcers arise instead from arterial insufficiency, neuropathy (especially diabetic), vasculitis, inflammatory dermatoses (pyoderma gangrenosum, calciphylaxis), trauma, malignancy, or a combination of etiologies, as classified by the CDC/NCHS ICD-10-CM classification.

The ICD-10-CM categories L97 and L98.4 are residual "not elsewhere classified" (NEC) categories, meaning they apply only when the ulcer cannot be more specifically assigned to a condition-specific code (e.g., diabetic foot ulcer combination code E11.621 + L97.5xx, or arterial ulcer from atherosclerosis I70.2xx–I70.7xx). Documentation of etiology is therefore critical to accurate code assignment, as detailed in the FY2026 ICD-10-CM Official Coding Guidelines.

Depth (severity) is the single most important documentation element for these codes — the 6th character determines whether HCC v28 RAF credit is generated, and the difference between a shallow ulcer (skin breakdown only) and one exposing fat, muscle, or bone can change risk-adjusted reimbursement by hundreds of dollars per member per year.

🗂️ 2. Alternative Terminology

🩺 3. Signs & Symptoms

Clinical presentation varies significantly by etiology but shared features include:

• Location: Lower extremity (thigh, calf, ankle, heel, dorsum of foot) for L97; trunk, back, buttock, and non-lower-extremity sites for L98.4
• Ulcer bed: May be pale/sloughy (arterial/ischemic), pink/granulating (healing), yellow/necrotic (infected or avascular), or black/eschar (dry necrosis)
• Wound edges: Punched-out (arterial), irregular/undermined (neuropathic), violaceous/irregular (pyoderma gangrenosum), or stellate (vasculitic)
• Pain: Often severe and worsening at night in arterial ulcers; notably absent in neuropathic ulcers; moderate in venous (distinguish from L97/L98.4 scope)
• Surrounding skin: Pallor, dependent rubor, hair loss, and shiny atrophic skin (arterial); hyperpigmentation (post-inflammatory); normal to indurated (neuropathic)
• Palpable pulses: Diminished or absent dorsalis pedis / posterior tibial pulses (arterial)
• Associated symptoms: Claudication, rest pain, sensory neuropathy, autonomic neuropathy signs (anhidrosis, warm foot in Charcot)
• Signs of infection: Erythema, warmth, purulent discharge, malodor, crepitus (gas-forming organisms), fever, leukocytosis
• Depth indicators documented by clinicians: "Skin breakdown only," "fat visible," "tendon/muscle exposed," "bone visible" or "probing to bone positive" — each maps to a different 6th-character depth code

🧭 4. Differential Diagnosis

📋 5. Clinical Indicators for Coders / CDI

🦴 6. Anatomy & Pathophysiology

Relevant Anatomy

The skin is a layered organ comprising the epidermis (outermost; keratinized stratified squamous epithelium), the dermis (collagen/elastin matrix, hair follicles, sweat glands, sensory nerves, blood vessels), and the hypodermis/subcutaneous fat layer (adipose connective tissue serving as insulation and vascular conduit). Below the skin lie fascia, muscle, tendon, and bone. The 6th-character depth codes in L97 and L98.4 directly map to these anatomic layers, as described in the NCBI anatomy reference (StatPearls — Integumentary System):

• 6th char 1 — Skin breakdown only: Ulcer limited to epidermis ± superficial dermis
• 6th char 2 — Fat layer exposed: Full-thickness dermis destroyed; subcutaneous fat visible
• 6th char 3 — Necrosis of muscle: Full-thickness wound with muscle necrosis (myonecrosis)
• 6th char 4 — Necrosis of bone: Bone exposed and/or necrotic (osteonecrosis); consider M86 osteomyelitis
• 6th char 5 — Muscle involvement without necrosis: Muscle exposed but viable; tendon visible
• 6th char 6 — Bone involvement without necrosis: Bone visible/probed but not necrotic; high infection risk
• 6th char 8 — Other specified severity
• 6th char 9 — Severity unspecified (documentation inadequate)

Pathophysiology by Etiology

Arterial/Ischemic: Peripheral arterial occlusive disease (PAOD) reduces tissue oxygen delivery. ABI <0.4 indicates critical limb ischemia. Tissue hypoxia causes coagulative necrosis; wounds fail to granulate. Per AHA/ACC 2024 Peripheral Artery Disease Guidelines, critical limb-threatening ischemia (CLTI) is defined by rest pain, gangrene, or ischemic wounds.

Diabetic Neuropathic: Sensory neuropathy eliminates protective pain sensation; motor neuropathy causes foot deformity (claw toes, Charcot); autonomic neuropathy produces dry skin and fissures. Repetitive mechanical trauma on insensate skin creates plantar ulcers at pressure points. Hyperglycemia impairs neutrophil chemotaxis, collagen synthesis, and angiogenesis. The ADA Standards of Care 2024 classify diabetic foot ulcers using the Wagner or PEDIS systems and emphasize the combination E11.621 + L97.5xx as the mandatory coding pair.

Inflammatory/Vasculitic: Immune-complex deposition or neutrophilic infiltration (pyoderma gangrenosum — L88) causes tissue destruction. Calciphylaxis involves medial calcification and thrombosis of dermal arterioles in CKD stage 4–5/dialysis patients, producing ischemic necrosis. Per StatPearls — Calciphylaxis, mortality is 45–80% at 1 year.

Wound Healing Biology: Normal healing progresses through hemostasis (0–2 days) → inflammation (1–4 days) → proliferation (4–21 days) → remodeling (21 days–2 years). Chronic non-healing wounds are arrested in a persistent pro-inflammatory state with elevated matrix metalloproteinases (MMPs), reduced growth factors, and senescent cells, as reviewed in PMC Wound Repair Review (2022).

💊 7. Medication Impact / Treatment

Pharmacologic management is etiology-dependent and directly affects code assignment and clinical indicators:

Antiplatelet / Anticoagulant Agents

Aspirin, clopidogrel (Plavix), ticagrelor, rivaroxaban, and warfarin are used in arterial ulcer patients. Presence of anticoagulation may be relevant to bleeding risk documentation for wound procedures. Use Z79.01 (anticoagulant) or Z79.02 (antiplatelet) as secondary codes per FY2026 Guidelines Section I.C.21.c.3.

Insulin / Antidiabetic Agents

In diabetic foot ulcer patients, insulin use (Z79.4) or oral antidiabetic agents (Z79.84) must be coded when applicable. Long-term insulin use is a secondary code only — it does not change E11 to E10 (Type 1 DM).

Wound-Directed Pharmacology

• Topical antimicrobials: Silver sulfadiazine, cadexomer iodine, PHMB — used for infected/critically colonized wounds
• Becaplermin gel (Regranex, PDGF-BB): FDA-approved for diabetic neuropathic lower-extremity ulcers; limited to one tube/course; requires REMS acknowledgment
• Collagenase (Santyl): Enzymatic debridement agent coded under 97602 (non-selective debridement) when applied by a clinician
• Pentoxifylline: Used off-label for arterial insufficiency and venous ulcers; improves RBC deformability
• Cilostazol: PDE-3 inhibitor approved for claudication in PAD; may improve peripheral perfusion around arterial ulcers
• Systemic antibiotics: For confirmed wound infection; organism-specific; document causative organism for ICD-10-CM B95–B97 codes
• Immunosuppressants (PG, vasculitis): Prednisone, cyclosporine, infliximab; relevant for pathergy-based ulcer management; document underlying condition for accurate L88 vs. L97 assignment

Preview ends here. The full guide continues with FY2026 ICD-10-CM code sets, CPT surgical coding, MS-DRG mapping, reimbursement guidance, CDI query templates, and an audit checklist — all available to CCO Members.

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