Chapter 37: Venous Infections

INTRODUCTION

Suppurative phlebitis, or venous infection, is a clinical condition that is often associated with thrombosis of the involved section of the vein, bacteremia, and metastatic abscesses. The infection is intravascular, so the associated bacteremia is often continuous, as is also seen in endocarditis, infections of arterial prostheses, and catheter sepsis. Naturally occurring suppurative phlebitis is an uncommon disease. Cases typically arise from an antecedent infection in close anatomic proximity to the primarily affected vessel. Nosocomial cases caused by instrumentation of the venous system also occur. Suppurative phlebitis can cause significant systemic complications and mortality if not recognized and treated promptly and appropriately.

CLASSIFICATION

Naturally occurring suppurative thrombophlebitis occurs when an infection spreads to involve an adjacent venous structure or when a venous thrombosis becomes secondarily infected. Although any vein may potentially be involved, several clinical syndromes involving deep veins are well described. Perhaps the most well-known syndrome involving thrombophlebitis is Lemierre's syndrome, defined as postanginal sepsis with thrombophlebitis of the internal jugular vein. Lemierre first described the syndrome in 1936, and it remains a significant clinical entity today.¹ Pylephlebitis, first described in 1926 by Kramer and Robinson, is suppurative thrombophlebitis of the portal vein.² It is most commonly caused by complicated intraabdominal infections. The mesenteric vessels may also be involved. The most frequently associated infections leading to pylephlebitis include diverticulitis³ and appendicitis,^4,5 although it has also been described as a complication of choledocholithiasis,⁶ pyelonephritis,² and Crohn's disease.^7,8 Other peritoneal sites of suppurative phlebitis include the pelvic veins after pelvic infection, which often occurs in the postpartum period.^9,10 Suppurative thrombophlebitis of the veins of the head and neck is well described with cases having been reported to involve the ophthalmic vein,¹¹ lateral venous sinuses^12,13 and cavernous sinus^14,15 after episodes of sinusitis or otitis media.^16,17

PATHOGENESIS

Suppurative phlebitis occurs through two main mechanisms. In some cases, established venous thromboses become infected by circulating bacteria in the blood, with ensuing infection of the venous wall. In most cases, infection is caused by spread of bacteria from adjacent infected tissue to the affected vein. In Lemierre's syndrome, for example, the precipitating infection is often in the oropharynx. Mucosal damage from bacterial or viral pharyngitis or odontogenic infection results in invasion of bacteria into the lateral pharyngeal space with subsequent development of phlebitis of the internal jugular vein.¹⁸ Invasion of the retropharyngeal soft tissue may lead to phlebitis and thrombosis of the tonsillar veins with propagation to the internal jugular vein.¹⁹ Thrombophlebitis of the portal, mesenteric, or pelvic veins occurs in much the same manner. Inflammation of infected tissue adjacent to a deep blood vessel allows progression of infection to the vessel wall with subsequent propagation of infection and metastatic infection from that site.