Antibiotic Therapy:

Antibiotic therapy for dogs and cats with septic peritonitis is empirical pending culture. However, cytologic characteristics, gram stain results, and the underlying cause (if known) may help direct initial antibiotic therapy. In one retrospective study of septic peritonitis, a high rate of bacterial resistance was found to ampicillin, cefazolin, and flouroquinolones. Lower rates of resistance were found to aminoglycosides and third generation cephalosporins.¹ Recently, the author has completed a microbiological survey of isolates from dogs with septic peritonitis. E. coli and Enterococcus sp. were the most common isolates. Combination therapy with Ampicillin / Aminoglycoside / Metronidazole or Ampicillin / Baytril / Metronidazole provide very appropriate empirical antibiotic choices in cases of community acquired septic peritonitis. Caution must be exercised when using aminoglycosides in animals with poor perfusion as they may potentiate acute renal failure; a condition already recognized as a complication of septic peritonitis in domestic animals. The addition of antibiotics with a strong anaerobic spectrum is appropriate (metronidazole).The author also identified that appropriate empirical antibiotic therapy (antibiotic therapy that was appropriate for all bacteria later isolated) resulted in improved survival compared to inappropriate antibiotic therapy (antibiotic therapy that did not adequately provide coverage against all isolated bacteria). In addition, the author also identified that among survivors of septic peritonitis, those that received appropriate empirical antibiotic therapy (as defined above) had a significantly shorter duration of hospitalization than those that did not receive appropriate empirical antibiotic therapy. It should be recognized that although antibiotic therapy is important, establishment of effective peritoneal drainage is also critical to maximize the likelihood of a positive outcome.

Surgical Goals:

Abdominal Drainage Techniques:

The decision of whether or not to provide postoperative abdominal drainage for animals with septic peritonitis is one that has been debated in the veterinary community for over 20 years without conclusive evidence to support primary closure (PC) over the various methods of peritoneal drainage or vice versa. Until a prospective, randomized clinical trial is performed in which patients are matched according to disease severity and cause, the answer to this question will go unanswered. However, it is the author's contention that providing appropriate abdominal drainage optimizes the likelihood of a positive outcome in dogs with septic peritonitis. Currently, providing appropriate peritoneal drainage in septic peritonitis is considered "standard-of-care".

At the present time, open peritoneal drainage (OPD) is recommended in dogs and cats with septic peritonitis and severe peritoneal contamination that cannot be adequately resolved during the operative period (ex. food within the peritoneum due to gastrostomy tube dislodgement). OPD is performed by placing a continuous monofilament suture pattern in the linea and not tightening it such that a 2-3cm gap remains to allow for drainage, while preventing evisceration. The abdomen is then bandaged with highly absorbent, sterile bandage material. Some surgeons prefer to lavage the peritoneum in the operating room daily when using this method and others merely perform bandage changes every 12-24 hours. Disadvantages of open peritoneal drainage include risk of evisceration, nosocomial infection, and labor intensity necessary to perform bandage changes.

A second method of abdominal drainage that has received recent attention involves utilization of closed suction drains placed within the abdominal cavity (one placed in the cranial abdomen and one placed caudally, both exiting paramedian.¹ These drains are then connected to reservoirs that generate gentle, continuous, negative pressure. The reservoirs are then emptied as necessary. A sterile bandage should be placed to cover the exit sites for the closed suction drains. This bandage should be changed daily. The author prefers to use closed suction drainage techniques when there is generalized peritonitis, but contamination has been well controlled and the source has been resolved. Closed suction drains are likely appropriate for all degrees of severity of septic peritonitis. Disadvantages of closed suction drainage include a low risk of ascending nosocomial infection. Obstruction of drain sites / tubes is rare.

When one of the methods of abdominal drainage is chosen for management of the septic peritonitis case, cytologic examination of the effusion will provide guidelines for when drainage techniques can safely cease. Closure should be considered or closed suction drains removed when cytologic evidence of bacterial contamination (phagocytosed bacteria and degenerate neutrophils) has resolved and volume of the effusion has decreased to <10mL/Kg/day.

Primary closure (PC) is ONLY recommended when contamination is completely controlled and there is only mild evidence of localized peritonitis. Eliminating bacterial infection from a body cavity is difficult without appropriate drainage techniques. The choice to attempt PC accepts this difficulty and the possibility that the patient will effuse further into the peritoneal space.