Differential Diagnosis
The patient presents with bilateral lower extremity swelling, redness, and itching, which can be caused by a variety of conditions. Given the patient's complex medical history and laboratory results, the differential diagnosis can be categorized as follows:
- Single Most Likely Diagnosis
- Cellulitis: The patient's symptoms of bilateral lower extremity swelling, redness, and itching, along with a elevated WBC count (11.9) and CRP (9.081), are consistent with cellulitis. The absence of DVT on venous duplex also supports this diagnosis.
- Other Likely Diagnoses
- Chronic Venous Insufficiency: The patient's symptoms of lower extremity swelling and redness could be related to chronic venous insufficiency, especially given her history of ambulation with a walker and obesity.
- Stasis Dermatitis: The patient's itching and redness could be related to stasis dermatitis, which is a common condition in elderly patients with chronic venous insufficiency.
- Contact Dermatitis: The patient's itching and redness could be related to contact dermatitis, which could be caused by an allergic reaction to a substance in her environment.
- Do Not Miss Diagnoses
- Necrotizing Fasciitis: Although less likely, necrotizing fasciitis is a life-threatening condition that can present with similar symptoms, including severe pain, swelling, and redness. The patient's elevated WBC count and CRP increase the suspicion for this condition.
- Gas Gangrene: Gas gangrene is another life-threatening condition that can present with similar symptoms, including severe pain, swelling, and redness. The patient's elevated WBC count and CRP increase the suspicion for this condition.
- Rare Diagnoses
- Erythema Ab Igne: This is a rare condition caused by prolonged exposure to heat, which can cause redness and itching on the affected area.
- Lymphedema: Although less likely, lymphedema can cause swelling and redness in the affected limb, especially in patients with a history of obesity and chronic kidney disease.
Workup and Management
The patient's workup should include:
- Complete blood count (CBC) with differential to evaluate for signs of infection or inflammation
- Blood cultures to evaluate for bacteremia
- Wound culture to evaluate for bacterial infection
- Imaging studies, such as MRI or CT scan without contrast, to evaluate for signs of necrotizing fasciitis or gas gangrene
- Venous duplex to evaluate for DVT (already done)
Management should include:
- Antibiotics to treat cellulitis or other bacterial infections
- Pain management to control severe pain
- Wound care to promote healing and prevent further infection
- Elevation of the affected limb to reduce swelling
- Compression stockings to improve venous return
CT Scan with IV Contrast
Given the patient's chronic kidney disease stage 4, it is generally recommended to avoid CT scans with IV contrast due to the risk of contrast-induced nephropathy. However, if a CT scan is necessary to evaluate for a life-threatening condition, such as necrotizing fasciitis or gas gangrene, the benefits may outweigh the risks. In this case, alternative imaging modalities, such as MRI or CT scan without contrast, should be considered first. If a CT scan with IV contrast is necessary, the patient should be well-hydrated and the contrast dose should be minimized to reduce the risk of nephropathy.