In most cases, considerable clinical improvement occurs within 48 hours of starting therapy
PERITONITIS IS a frequent complication of continuous ambulatory peritoneal dialysis (CAPD) and the most common cause of CAPD failure. About 60% of patients receiving CAPD will have at least one episode of peritonitis during the first year of this mode of dialysis, according to Ram Gokal, MD, Consultant Nephrologist and Honorary Lecturer at the University of Manchester in the United Kingdom. CAPD peritonitis is associated with catheter loss, adhesions, increased protein loss, return to hemodialysis, and considerable morbidity.1
Dr. Gokal spoke about CAPD peritonitis at the National Kidney Foundation's 2007 Clinical Meetings in Orlando.
Most episodes of CAPD peritoni-tis are caused by contamination of the dialysis tubing or extension of catheter exit site or tunnel infections. Peritonitis in patients receiving CAPD usually occurs within 48 hours of contamination. CAPD peritonitis risk is influenced by comorbidities, hypoalbuminemia, nutritional status, and patient race, income, and education level.2
An accurate diagnosis of CAPD peritonitis is based on both clinical and laboratory findings. The most common sign of CAPD peritonitis is cloudy effluent in the dialysate bag upon exchange. Characteristic features of CAPD peritonitis include abdominal pain or tenderness, fever, nausea, cloudy dialysate effluent containing more than 100 WBC/mm3, and the isolation of microorganisms from the dialysate.
All episodes of CAPD peritonitis are potentially serious. The severity of CAPD peritonitis may be influenced by etiology, causative organism, and duration of infection. Indications for catheter removal in patients with CAPD peritonitis include catheter or tunnel infection, fungal, tuberculous, persistent or re-lapsing peritonitis, bowel perforations, cuff erosion and protrusion, and post-transplant peritonitis.
Causative organisms
An episode of CAPD peritonitis is usually caused by a single pathogen, Dr. Gokal said. The causative organism is often a gram-positive coccus originating from the normal flora of the patient's skin. Coagulase-negative and coagulase posi-tive Staphylococcus species account for more than 50% of cases of CAPD peritonitis. Gram-negative organisms most frequently associated with CAPD peritonitis are Escherichia coli and Pseudomonas aeruginosa.
Severe CAPD peritonitis may be polymicrobial and involve a combination of anaerobic and gram-negative aerobic bacteria. CAPD peritonitis caused by anaerobic bacteria is often associated with intestinal perforation, whereas infection due to mycobacteria usually results
from previous exposure. Fungal peritoneal infections are rare, and the most common cause of these infections is Candida species.
Although the rate of CAPD peritonitis has declined in recent years, evidence suggests that the proportions of cases due to gram-negative organisms and methicillin-resistant coagulase-negative Staphylococcus (CoNS) have increased, according to Dr. Gokal. Among patients with CAPD peritonitis due to CoNS, resistance to methicillin increased significantly from 18.4% in 1992-1993 to 41.7% in 2000-2001. In contrast, the incidence of methicillin-resistant S. aureus did not change significantly during this same period. Catheter removal rates are significantly higher in patients with CAPD peritonitis due to a single gram-negative organism (16.6%) compared with gram-positive CAPD peritonitis (16.6% vs. 4.8%).3
Persistent infection
Most patients with CAPD peritonitis show considerable clinical improvement within 48 hours of initiating therapy. Occasionally, symptoms may persist beyond 48 to 96 hours. Reevaluation is essential in patients with persistent signs and symptoms of CAPD peritonitis at 96 hours after the start of treatment. Specifically, fluid cell counts, Gram stain, and cultures should be repeated and the antimicrobial regimen reassessed. Antibiotic removal techniques may be useful in an effort to maximize culture yield.
Among the principal clinical concerns in patients with CAPD peritonitis and persistent signs and
symptoms is the presence of intra-abdominal or gynecologic pathology requiring surgical intervention and the presence of mycobacteria, fungi, and other atypical organisms. In patients with persistent S. aureus CAPD peritonitis, the possibility of an underlying tunnel infection or intra-abdominal abscess should be considered. Ultrasonography and CT may reveal the presence of an occult abscess in such patients.
Catheter removal and surgical exploration should be considered in patients with CAPD peritonitis, Dr. Gokal said. Patients who have not improved clinically by 96 hours should be cultured for anaerobic bacteria. The optimal duration of anti-microbial therapy following catheter removal in patients with resistant CAPD peritonitis has not been established. Intraperitoneal urokinase is a simple and effective treatment that may help avoid the need for catheter removal and interim hemodialysis in patients with resis-tant CAPD peritonitis.4
Relapsing infection
Relapsing CAPD peritonitis is defined arbitrarily as a second episode of peritonitis caused by the same organism that caused the immediately preceding episode and occurring within four weeks of completion of antibiotic treatment for the previous infection. The clinical signs and symptoms of relapsing CAPD peritonitis are similar to those of sporadic CAPD peritonitis. The release of planktonic bacteria from biofilm on the walls of catheters may be a contributing factor in patients with multiple episodes of CAPD peritonitis.
The reappearance of organisms causing infection was documented in 90 patients with more than four episodes of culture-positive peritonitis, of whom 59 (65%) had at least half of their episodes caused by the same organism.5 Sequential analyses for independence revealed that for S. epidermidis and for S. aureus, there was a significantly increased likelihood for these organisms to follow themselves as causative organisms of peritonitis. When the data were analyzed using the Spearman correlation test, the results indicated that the likelihood of repeat infections occurring was significantly greater than by chance alone. Of 67 patients with catheter changes and subsequent peritonitis, only 10 (15%) developed repeat infections with the same or-ganism after the catheter change.
The application of mupirocin ointment to the catheter exit site may be useful for the prevention of recurrent CAPD infections caused by S. aureus. In addition to reducing S. aureus exit-site infections, mupirocin ointment may help decrease the rates of staphylococcal CAPD peritonitis and catheter loss. Whether the ointment should be applied in the nares, and whether it should be used only in staphylococcal nasal carriers, has not been conclusively determined.6
Intracatheter streptokinase (SK) has been advocated as an effective treatment with minimal adverse effects in patients with recurrent CAPD peritonitis. A review of 35 instillations of intracatheter SK in 20 patients with recurrent CAPD peritonitis revealed a high (86%) adverse effect profile consisting of fever, on-set of turbid dialysis effluent and/or abdominal pain.7
References
1. Saklayen MG. CAPD peritonitis. Incidence, pathogens, diagnosis, and management. Med Clin North Am. 1990;74:997-1010.
2. Chow KM, Szeto CC, Leung CB, et al. A risk analysis of continuous ambulatory peritoneal dialysis-related peritonitis. Perit Dial Int. 2005;25:374-379.
3. Kim DK, Yoo TH, Ryu DR, et al. Changes in causative organisms and their antimicrobial susceptibilities in CAPD peritonitis: a single center's experience over one decade. Perit Dial Int. 2004;24:424-432.
4. Innes A, Burden RP, Finch RG, Morgan AG. Treatment of resistant peritonitis in continuous ambulatory peritoneal dialysis with intraperitoneal urokinase: a double-blind clinical trial. Nephrol Dial Transplant. 1994;9:797-799.
5. Finkelstein ES, Jekel J, Troidle L, et al. Patterns of infection in patients maintained on long-term peritoneal dialysis therapy with multiple episodes of peritonitis. Am J Kidney Dis. 2002;39:1278-1286.
6. Thodis E, Passadakis P, Vargemezis V, Oreopoulos DG. Prevention of catheter related infections in patients on CAPD. Int J Artif Organs. 2001;24:671-682.
7. Nankivell BJ, LakeN, Gillies A. Intracatheter streptokinase for recurrent peritonitis in CAPD. Clin Nephrol. 1991;35:20-23.