Etiology of Pannus Ulcers in Morbidly Obese Patients
Ulcers developing on a large abdominal pannus in morbidly obese patients are primarily intertriginous ulcers caused by moisture, friction, and maceration, often complicated by secondary infection (panniculitis). 1
Primary Pathophysiologic Mechanisms
The ulcers arise from a combination of mechanical and environmental factors specific to the pannus:
- Moisture and maceration from trapped perspiration, inadequate air circulation, and poor hygiene access beneath the overhanging abdominal apron create a chronically moist environment that breaks down skin integrity 1
- Friction and shearing forces occur where skin surfaces rub against each other or against clothing, particularly at the inferior fold of the pannus where it contacts the suprapubic region or thighs 1, 2
- Pressure from the weight of the pannus itself can contribute to tissue ischemia, though this is secondary to the moisture and friction components in most cases 2
Secondary Complications
Once skin breakdown occurs, several complications frequently develop:
- Panniculitis (cellulitis of the pannus) develops when bacteria colonize the damaged skin, leading to inflammation of the subcutaneous fat and surrounding tissues 1
- Polymicrobial infection is common due to the warm, moist environment favoring bacterial overgrowth 3
- Chronic wound formation results from the inability to eliminate the causative factors (moisture, friction, pressure) while the pannus remains in place 1
Key Distinguishing Features from Other Ulcer Types
These are not primarily:
- Pressure ulcers in the classic sense—while pressure contributes, these ulcers lack the typical location over bony prominences (sacrum, heels, ischium) and instead occur in skin folds 4, 2
- Venous ulcers—though obesity can cause functional chronic venous insufficiency with ulcers on the lower limbs, pannus ulcers occur on the abdominal wall rather than the typical medial malleolar region 5
- Arterial ulcers—peripheral perfusion is typically adequate unless concurrent peripheral arterial disease exists 5
Clinical Implications for Management
The intertriginous/moisture-related etiology dictates specific management priorities:
- Moisture control is paramount: keep the area clean and dry, address any urinary or fecal incontinence that may contribute to moisture, and use barrier creams or powders to reduce maceration 1
- Friction reduction through proper positioning, supportive garments, or padding between skin surfaces 1
- Antimicrobial therapy when panniculitis develops, typically requiring coverage for skin flora including Staphylococcus and Streptococcus species 1
- Definitive treatment often requires panniculectomy to remove the causative tissue mass, as conservative wound care alone cannot eliminate the mechanical factors perpetuating ulceration 1, 6
Common Pitfall
Do not misclassify these as standard pressure ulcers and apply pressure ulcer protocols (repositioning every 2-4 hours, specialized mattresses) as the primary intervention—while these may help, they do not address the fundamental problem of moisture and friction within the pannus fold itself 4, 7, 1