ESSENTIALS OF DIAGNOSIS
Red streak from wound or area of cellulitis toward regional lymph nodes, which are usually enlarged and tender.
Chills, fever, and malaise may be present.
Lymphangitis and lymphadenitis are common manifestations of a bacterial infection that is usually caused by hemolytic streptococci or S aureus (or by both organisms) and becomes invasive, generally from an infected wound. The wound may be very small or superficial, or an established abscess may be present, feeding bacteria into the lymphatics. The involvement of the lymphatics is often manifested by a red streak in the skin extending in the direction of the regional lymph nodes, which are, in turn, generally tender and engorged. Systemic manifestations include fever, chills, and malaise. The infection may progress rapidly, often in a matter of hours, and may lead to septicemia and even death.
Throbbing pain is usually present in the area of cellulitis at the site of bacterial invasion. Malaise, anorexia, sweating, chills, and fever of 38–40°C develop rapidly. The red streak, when present, may be definite or may be very faint and easily missed, especially in dark-skinned patients. It is usually tender or indurated in the area of cellulitis. The involved regional lymph nodes may be significantly enlarged and are usually quite tender. The pulse is often rapid.
Leukocytosis with a left shift is usually present. Blood cultures may be positive, most often for staphylococcal or streptococcal species. Culture and sensitivity studies of the wound exudate or pus may be helpful in treatment of the more severe or refractory infections but are often difficult to interpret because of skin contaminants.
Lymphangitis may be confused with superficial thrombophlebitis, but the erythema and induration of thrombophlebitis is localized in and around the thrombosed vein. Venous thrombosis is not associated with lymphadenitis, and a wound of entrance with secondary cellulitis is generally absent.
Cat-scratch fever (Bartonella henselae) should be considered when lymphadenitis is present; the nodes, though often very large, are relatively nontender. Exposure to cats is common, but the patient may have forgotten about the scratch.
It is extremely important to differentiate cellulitis from acute streptococcal hemolytic gangrene or a necrotizing soft tissue infection. These are deeper infections that may be extensive and are potentially lethal. Patients are more seriously ill; there may be redness due to leakage of red cells, creating a non-blanching erythema; subcutaneous crepitus may be palpated or auscultated; and subcutaneous air may be present on radiography or CT scan. Immediate surgical consultation for wide debridement of all involved deep tissues should be pursued if a necrotizing infection is suspected.