ESSENTIALS OF DIAGNOSIS
Red streak from wound or 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, cellulitis, or an abscess. 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.
Throbbing pain is usually present at the site of bacterial invasion from a wound, cellulitis, or abscess. Malaise, anorexia, sweating, chills, and fever of 38–40°C develop quickly, often with a rapid pulse. The red streak, when present, may be definite or may be faint and easily missed (eFigure 12–20), especially in dark-skinned patients. The involved regional lymph nodes may be significantly enlarged and are usually quite tender. The infection may progress rapidly, often in a matter of hours, and may lead to septicemia and death.
Ascending lymphangitis characterized by lymphatic streaking up the leg in a 55-year-old man with cellulitis. (Used, with permission, from Richard P. Usatine, MD, in Usatine RP, Smith MA, Mayeaux EJ Jr, Chumley HS. The Color Atlas of Family Medicine, 3rd ed. McGraw-Hill, 2019.)
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.
The erythema and induration of superficial thrombophlebitis are 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) is a cause of lymphadenitis; 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, a late finding, may be palpated or auscultated; and subcutaneous air may be present on radiography or CT scan. Immediate surgical consultation ...