A 72-year-old man presents to the emergency department with a two-day history of a painful, red, swollen left leg. 

His past medical history includes type 2 diabetes, hypercholesterolaemia and hypertension.

On examination, his respiratory rate is 18/min, heart rate is 136/min, blood pressure is 108/72 and temperature 38.6ºC. The left lower leg is erythematous and hot to touch. There are no discernible areas of necrosis. The left leg is 3.1cm larger than the right. The right leg is normal in appearance and temperature.

What is the most likely diagnosis?

Options:
explanation: This patient does have cellulitis. They have a red, swollen leg after a history of penetrating trauma (that introduced infection to the leg). However, this is not the whole picture. Cellulitis is unlikely to cause such a high heart rate without being accompanied by sepsis. A heart rate above 130/min is a red flag symptom of sepsis. According to NICE guidelines, any patient with one red flag feature of sepsis should have an urgent senior review and be managed as sepsis until proven otherwise
name: Cellulitis
label: b
answer: no
explanation: Deep vein thrombosis (DVT) also presents with a red, hot, swollen leg. However, this patient has no risk factors for DVT – no surgery, long haul travel, malignancy, personal history of thrombosis or family history of thrombosis (which could suggest hereditary thrombophilia). A diagnosis of DVT would not explain why this patient developed these symptoms after a penetrating leg injury (unless this history clearly stated prolonged immobility after this injury). Pulmonary embolism (associated with deep vein thrombosis) can present with tachycardia; however, this patient has pyrexia of 38.6ºC, whereas DVT and PE typically present with a no fever or a low-grade fever
name: Deep vein thrombosis
label: c
answer: no
explanation: A ruptured Baker's cyst can present similarly to a DVT and cellulitis, with redness, swelling and pain. However, a ruptured Baker's cyst does not explain the presence of a fever and tachycardia. Symptoms of a ruptured Baker's cyst are usually only confined to the leg, without any systemic symptoms
name: Ruptured Baker's cyst
label: e
answer: no
explanation: Necrotising fasciitis is a life-threatening infection of the skin. It can present after a penetrating injury, typically as an area of erythema with a necrotic centre. This necrosis can spread, leading to sepsis and death. What differentiates this case from necrotising fasciitis is the time course. Necrotising fasciitis is rapidly progressive, so it is unlikely this patient will have a slow progression over a couple of days. There is also likely to be signs of necrosis on limb examination
name: Necrotising fasciitis
label: d
answer: no
explanation: Sepsis is a dysregulated immune response to infection, most often associated with a bacterial infection. In this case, this patient likely has cellulitis of their leg, which has progressed to sepsis. The examination findings suggest sepsis is the most likely diagnosis. He has a heart rate of 136/min, a red flag feature of sepsis (>130/min). They are also presenting with a high fever, which supports the diagnosis of cellulitis and sepsis. Heart rate can be raised for other reasons, including pain and anxiety. However, in the case of someone presenting with red flag features of sepsis in the clinical context of infection, they should be treated as sepsis until proven otherwise. If they have a high heart rate from anxiety or pain, they would probably also have high blood pressure as well. According to NICE guidelines, any patient with one red flag feature of sepsis should have an urgent senior review and be managed as sepsis until proven otherwise. In addition to a senior review, they should have the "sepsis 6" within 1 hour (including blood culture, blood lactate, urine output measurements, IV antibiotics, IV fluids and oxygen). This patient is quite well considering the likely diagnosis of sepsis. However, as they are a 27-year-old man, they probably have an excellent physiological reserve and compensate well. This patient should still be treated promptly to prevent rapid deterioration
name: Sepsis
label: a
answer: yes

Correct answer: a