Bacteroides peritonitis associated with colon cancer in a continuous ambulatory peritoneal dialysis patient. (CASE HISTORIES).

ABSTRACT: Peritonitis is not an uncommon complication of continuous ambulatory peritoneal dialysis (CAPD). We report a case of Bacteroides fragilis-induced bacterial peritonitis, probably due to clinically occult malignancy, in a 76-year-old woman on CAPD.

PERITONITIS is not an unusual complication of CAPD. (12) An average of two thirds of patients on CAPD have peritonitis during the first year of dialysis, (3) and recurrent peritonitis complicates the course of many of these patients. (4) Occasionally, an unusual bacterium will be encountered, signifying an underlying process not directly associated with CAPD. We report the case of a 76-year-old woman in whom Bacteroides fragilis induced bacterial peritonitis probably originated from clinically occult malignancy.

CASE REPORT

A 76-year-old white woman with end-stage renal disease, who had had multiple episodes of peritonitis since beginning CAPD 2 years earlier, was admitted to the hospital with abdominal pain, chills, and fever of 1 day's duration. Before this admission, she had completed several courses of antibiotic therapy for Enterobacter peritonitis.

The patient had a history of similar complaints of intermittent abdominal pain but not as severe as this episode. One day before admission, she had one episode of vomiting and diarrhea. She noticed a cloudy effluent with a good deal of sediment. She denied any chest pain or shortness of breath. Her medical history consisted of end-stage renal disease, sub-acute cutaneous lupus erythematosus, chronic hypertension, and hypoalbuminemia. Surgical history consisted of a cholecystectomy and percutaneous renal biopsy. Recent medications included sertraline (50 mg/day), epoetin alfa (Epogen) (5,000 U three times a week), and multivitamins.

On admission, the patient was alert, awake, and oriented, with a temperature of 100.1[degrees]F. The abdomen was soft but diffusely tender. There was no rebound tenderness or guarding. Bowel sounds were present and the skin surrounding the peritoneal catheter was clean without any signs of inflammation. Pertinent laboratory values were white blood cell count (WBC) 6,500/[mm.sup.3], hemoglobin 9.3 g/dL, platelet count 145/[mm.sup.3], sodium 135 mEq/L, potassium 4 mEq/L, serum urea nitrogen 29 mg/dL, creatinine 3.8 mg/dL, serum amylase 40 mg/dL, albumin 1.9 mg/dL, and normal liver enzyme levels. Peritoneal fluid was cloudy with a WBC of 2,730/[mm.sup.3] (80% neutrophils, 5% lymphocytes). Amylase was absent in the peritoneal fluid. Chest radiography showed free air under the right side of the diaphragm, which is a common finding in a peritoneal dialysis patient.

Intravenous (IV) amikacin and ceftazidime were started empirically after blood, urine, and peritoneal samples were taken for culture. Initially, there was no growth in either blood or urine cultures; however, after 96 hours the anaerobic bottle of peritoneal fluid grew B fragilis. Consequently, IV metronidazole was added to the treatment regimen. The patient became afebrile, and abdominal pain disappeared. Because of the recurrent nature of the patient's peritonitis and the growth of B fragilis, computed tomography of the abdominal and pelvic region was done. It revealed a mass in the ascending colon. There were also multiple nodules in the right lower lung that were missed by the chest radiographs.

A colonoscopy was subsequently done. A fungating mass in the right colon and cecum was identified and biopsied.

The remainder of the colon was normal without any diverticula or ulcers. The biopsy revealed a moderately differentiated adenocarcinoma. The patient refused surgical intervention.

DISCUSSION

Peritonitis is not an unusual complication of CAPD, with an overall incidence close to 0.6 to 0.7 episodes per patient per year. (1,2) On average, two thirds of patients will have peritonitis within 8 to 9 months after initiation of CAPD treatment. (3) Recurrent peritonitis will complicate the course of 20 to 30 of such patients. (4)

A single pathogen originating from the normal flora of the skin or upper respiratory tract is the usual cause of CAPD peritonitis. The most common etiologic agents of peritonitis are gram-positive cocci (coagulase-negative staphylococci), which account for at least 50% of the infections. Gram-negative bacteria account for the most of the remaining cases of bacterial peritonitis. (3)

Anaerobic infection of the peritoneum is rare and accounts for only about 3% of the total cases of peritoneal infection in CAPD patients. (5) Presence of anaerobic organisms or two or more gram-negative enteric organisms in the peritoneal fluid should alert the physician of possible underlying intra-abdominal disease. (6) Failure to respond to standard measures should alert the physician to the possibility of an intra-abdominal emergency. (7)

Many case reports illustrate the value of obtaining anaerobic culture of the peritoneal fluid when treatment-resistant peritonitis exists. (7-10) Bowel gangrene, cholecystitis, diverticulitis with bowel perforation, intra-abdominal abscess, pancreatitis, and infectious colitis are some of the underlying conditions that have been associated with intra-abdominal peritonitis. (6) Few reports have indicated the relationship of intra-abdominal malignancy to peritonitis. (11,12)

Localizing signs indicative of the underlying condition are usually absent in intra-abdominal peritonitis. (13) As in our case, radiologic signs are sometimes helpful in detecting the underlying cause. Because of the diagnostic difficulties and deteriorating clinical picture caused by prolongation of severe infection, Tzamaloukas et al (6) suggested an early laparotomy, when a reasonable diagnostic probability of peritonitis with intra-abdominal disease is present.

Mortality depends on the type of intra-abdominal peritonitis disease and comorbid factors, including delays in surgery, development of severe malnutrition, and thrombocytopenia. Bowel gangrene, severe hypoalbuminemia, and thrombocytopenia are associated with greater mortality. (6) A good index of suspicion, early diagnosis, and appropriate treatment will reduce mortality significantly in CAPD patients with intra-abdominal peritonitis.

In our patient, the B fragilis peritonitis was presumably caused by secondary bowel perforation due to the underlying malignancy. Colonoscopy did not reveal any diverticula, inflammatory bowel disease, or other colonic conditions that might lead to perforation. Physicians should remain open to unusual presentations of bacteroides infection; in our patient's case, the infection was an indicator of bowel perforation caused by underlying malignancy.

References

(1.) Diaz-Buxo JA: Management of peritonitis in automated peritoneal dialysis patients Adv Perit Dial 1998; 14:131-136

(2.) Fried L, Piraino B: Peritonitis Textbook of Peritoneal Dialysis. Gokal R, Khanna R, Krediet RT, (eds). Boston, Kluwer Academic Publishers, 2nd Ed, 2000, p 545-564

(3.) Saldayen MG: CAPD peritonitis, incidence, pathogens, diagnosis, and management. Med Clin North Am 1990; 74:997-1010

(4.) Peterson PK, Matzke G, Keane WF: current concepts in the management of peritonitis in patients undergoing continuous ambulatory peritoneal dialysis. Rev InfectDis 1987; 9:604-612

(5.) Vas 5: Infections of continuous ambulatory peritoneal dialysis catheters. Infect Dis Clin North Am 1989; 3:301-328

(6.) Tzamaloukas AH, Obermiller LE, Gibel LJ, et al: Peritonitis associated with intra-abdominal pathology in continuous ambulatory peritoneal dialysis patients. Perit Dial Int 1993; 13:335-337

(7.) Miller GV, Bhandari 8, Brownjohn AM, et al: Surgical peritonitis in the GAPD patient. Ann R Coll Surg Engl 1998; 80:36-39

(8.) Kaplan RA, Alon V, Hellerstein 5, et al: Unusual causes of peritonitis in three children receiving peritoneal dialysis. Pent Dial Int 1993; 13:60-63

(9.) Hess VK, Baumgartner D, Maass D, et al: Appendicitis perforata in CAPD patients report of two cases. Perit Dial Bull 1985, pp 237-240

(10.) Fanelli C, Peterson CJ, Schoolwerth AC: Poodle peritonitis. Pent Dial Int 1990; 10:247-248

(11.) Brook I, Frazier EH: Aerobic and anaerobic infection associated with malignancy. Support Care Cancer 1998; 6:125-131

(12.) Wilson SE, Hopkins JA: Clinical correlates of anaerobic bacteriology in peritonitis. Clin Infect Dis 1995; 20(suppl 2):S251-S256

(13.) Spence PA, Mathews RE, Khanna R, et al: Indications for operation when peritonitis occurs in patients on chronic ambulatory peritoneal dialysis. Surg Gynecol Obstet 1985; 161:450-452

KEY POINTS

* Peritonitis is not an uncommon complication of CAPD.

* A single pathogen originating from the normal flora of the skin or upper respiratory tract is the usual cause of CAPO peritonitis.

* Many case reports show the value of obtaining anaerobic culture of the peritoneal fluid when treatment-resistant peritonitis exists.

* Mortality depends on the type of intra-abdominal peritonitis disease and comorbid factors.

* A good index of suspicion, early diagnosis, and appropriate treatment will reduce mortality significantly in CARD patients with intra-abdominal peritonitis.