Mycobacterium Avium Complex Causing Intra-abdominal Abscess and Fibropurulent Peritonitis in an Aids Patient

May 25, 2007
Surgical Rounds, April 2006, Volume 0, Issue 0

Mark A. Mueller, Senior Resident; Michael Zdon, Professor and Vice Chairman, Department of Surgery, Chicago Medical School at Rosalind Franklin University of Medicine and Science, Mount Sinai Hospital Medical Center, Chicago, IL

Abdominal pain in patients with ac?quired immunodeficiency syndrome (AIDS) can present a diagnostic challenge for clinicians. A small but significant number of patients will require op?er?ative intervention. In addition to the more common surgical problems such as acute appendicitis, AIDS pa?tients may present with atypical conditions related to their infection. The authors report an unusual case of Mycobacterium avium complex causing intra-abdominal ab?scess and diffuse fibropurulent peritonitis in a 37-year-old man with AIDS.

Mark A. Mueller, MD

Senior Resident

Michael Zdon, MD

Professor and Vice Chairman

Department of Surgery

Chicago Medical School at

Rosalind Franklin University of Medicine and Science

Mount Sinai Hospital Medical Center

Chicago, IL

Mycobacterium avium

Abdominal pain requiring evaluation by a surgeon is common in patients with acquired immuno-deficiency syndrome (AIDS).1 Although most patients have relatively benign conditions such as gastroenteritis, a smaller subset of patients have severe intra-abdominal problems that may require surgical intervention. The most common of these are cytomegalovirus (CMV)-in?duced enterocolitis with perforation and acute appendicitis.2 complex (MAC) is common in patients with advanced AIDS and usually presents as disseminated disease.3,4 The gastrointestinal (GI) manifestation of MAC in patients with AIDS is generally limited to mesenteric lymphadenopathy or, less commonly, peritonitis in patients with ascites or those undergoing peritoneal dialysis.5 We describe an unusual case of MAC resulting in fibropurulent peritonitis and intra-abdominal abscess in an AIDS patient. Exploratory laparotomy was re?quired to rule out GI perforation.

Case report

A 37-year-old African American man came to the emergency department reporting abdominal pain, fever, and tachypnea of 24 hours' duration. He had tested positive for the human immunodeficiency virus (HIV) 5 years earlier, at which time he had already developed AIDS. The patient had been noncompliant in treating his infection for the first 4 years following the diagnosis. He also had been treated previously for MAC (diagnosed by blood culture), toxoplasmosis, and pneumocytis. Three months earlier, the patient was evaluated for abdominal pain and underwent a computed tomography (CT) scan of the abdomen, which was reported as normal. The patient's compliance with his antiviral regimen and MAC treatment was reported as excellent 6 months be?fore his current presentation to the hospital. His weight had increased from 93 lb to 132 lb and he was doing well, but he had discontinued his two-drug treatment for MAC on his own, after following the regimen for approximately 1 year.

During physical examination, the patient was in moderate distress and had a temperature of 101?F, blood pressure of 125/80 mm Hg, pulse of 102 beats per minute, and a respiratory rate of 25 breaths per minute. The abdomen had hypoactive bowel sounds, mild distention, and diffuse, moderate tenderness to palpation, but no peritoneal signs or masses.

His initial white blood cell count was 24,500/mm3 with 93% neutrophils. The patient's CD4 count was 33 cells/mm3. The patient's viral load was 5,200 copies/mL. A chest radiograph showed no acute changes.

The patient was admitted to the hospital and underwent an abdominal CT scan, which showed an 8 x 10-cm fluid collection abutting the left psoas muscle, with fat stranding around the mesentery consistent with an abscess (Figure 1). There was no evidence of free air or free fluid within the abdominal cavity.

Blood cultures were obtained, and the patient was started on broad-spectrum antibiotics. The patient underwent CT-guided drainage of the fluid collection. The aspirate was described as consistent with abscess; however, gram stain and initial cultures were negative for bacteria and acid-fast bacilli. On hospital day 4, the patient developed loose stools. An assay for Clostridium difficile was positive, and the patient was started on metronidazole. A flexible sigmoidoscopy was performed to 60 cm and was negative for inflammation or other signs consistent with colitis.

Over the next 5 days, the patient continued to have increasingly severe ab?dominal pain and fevers. Repeat CT scans showed persistence of the psoas fluid collection, additional intra-abdominal fluid collections, and inflammatory changes consistent with peritonitis (Figure 2). Since the patient's abdominal pain continued to worsen and the physical findings progressed to frank peritonitis, the decision was made to perform an ex?ploratory laparotomy to rule out GI perforation.

Upon entering the abdomen, several hundred cubic centimeters of free turbid fluid were encountered. This fluid was aspirated and sent to microbiology. Examination of the small bowel revealed numerous fi?bropurulent adhesions and exudate, which separated easily. At the base of the small bowel mesentery, a necrotic ab?scess cavity was seen, which measured approximately 6 x 6 cm. Numerous biopsies were taken of the fibropurulent exudates on the bowel serosa and of the tissue around the abscess cavity. Careful examination of the entire length of bowel re?vealed no evidence of perforation or ischemia. Drains were placed in the nec?ro?tic cavity at the base of the mesentery, and the abdomen was extensively irrigated.

Postoperatively, the patient was continued on broad-spectrum antibiotics and remained on total parenteral nutrition, taking nothing by mouth, until bowel function resumed on postoperative day 5. Because of the negative bacterial cultures, the patient was empirically placed on ethambutol, pyrazinamide, and isoniazid for broad coverage of atypical pathogens. The patient's pain markedly decreased by postoperative day 2, and drainage was minimal. The drains were removed on postoperative day 3. All oper?ative specimens were negative for bacterial growth. Sub?sequently, the fi?brous biopsies and intra-abdominal fluid were positive for MAC. The patient was discharged to home on postoperative day 7, tolerating a regular diet with minimal discomfort. At subsequent follow-up, he reported no further abdominal symptoms.

Discussion

Although the incidence of opportunistic infections in patients with HIV has decreased with current antiviral regimens, the incidence of HIV infection is increasing, resulting in a growing number of patients requiring evaluation by general surgeons for AIDS-related problems.1,2,5 While most AIDS patients with abdominal pain do not require operative intervention, there are a significant number of patients with abdominal symptoms requiring more extensive investigation.6-8 The most commonly reported intra-ab??dominal conditions that require lapa-rotomy to alleviate abdominal symptoms are CMV enterocolitis with or without perforation, acute appendicitis, complications from non-Hodgkin's lymphoma, and mesenteric adenopathy from MAC infections.2,7,9

While CMV can be detected in more than 80% of individuals over the age of 35, it is generally of no consequence un?less significant immunosuppression is present.10 In AIDS patients, CMV most commonly affects the colon but can cause significant infection in any portion of the GI tract. In those with CMV colitis, sigmoidoscopy frequently reveals geographic ulcers, friability, mucosal edema, and erythema.11 Biopsy usually demonstrates the typical intranuclear inclusion bodies characteristic of CMV and can be confirmed by polymerase chain reaction. Al?though generally treated medically when diagnosed, suspicion of perforation with peritonitis warrants laparotomy with resection of the involved segment. Pri?mary anastomosis is rarely recommended because the risk of anastomotic disruption is high.12

Disseminated infections with MAC are fairly common in patients with advanced AIDS.3 MAC is acquired from the environment and enters the body through the GI tract. In immunodeficient patients, the organism's adherence to the mucosal surface is rapidly followed by invasion of the gut wall. Organisms multiply within the macrophages and are released with cell rupture.3 Infection spreads through local lymphatics to the mesenteric lymph nodes, where multiplication again occurs in macrophages, and eventually the organism breaks out, resulting in hem?atogenous dissemination. When the disease progresses to include the entire gut, patients generally experience nausea, diarrhea, and weight loss.13 Hemato?gen?ous dissemination is thought to be re?sponsible for the fever and night sweats observed in some patients.

With regard to conditions requiring sur?gical evaluation, MAC has been associated with a variety of conditions, in?cluding abdominal pain with enlarged mesenteric or retroperitoneal lympha?denopathy and peritonitis in patients with ascites or on continuous peritoneal dialysis.14,15 Al?though abscess formation is rare, there have been individual reports of isolated abscesses involving the psoas muscles, kidneys, spinal epidural space, and liver.16-19

Our patient's initial presentation ap?peared to be an isolated abscess in the ret-r?operitoneum. Initial percutaneous drain-age was significant for the absence of any bacterial pathogens, suggesting an atypical infection. Given MAC's pre?dilection for affecting lymph nodes in the bowel mesentery and retroperitoneum, it is possible that the etiology of this collection resulted from a MAC infection and necrosis of lymph nodes in the small bowel mesentery. This finding would be consistent with the findings at laparotomy. In addition, Dworkin has described a MAC-induced abscess in the axillary lymph node of an AIDS patient on an?tiretroviral therapy.20

After percutaneous drainage, our pa?tient's condition deteriorated. There was increasing evidence of peritonitis, and he eventually required laparotomy to ex?clude GI perforation. Findings at laparotomy included diffuse fibropurulent exudates on the bowel surface and a necrotic ab?scess cavity within the small bowel mesentery. No perforation was identified within the GI tract. It is possible that intra-abdominal con?tamination occurred at the time of attempted percutaneous drainage, resulting in a more diffuse in?fection. The combination of lavage, drain?age, and broad antimicrobial coverage for atypical path?ogens in addition to antiretroviral therapy resulted in an uneventful recovery.

Conclusion

Abdominal pain in an AIDS patient can present a diagnostic challenge. While most serious conditions requiring operative intervention (such as CMV enterocolitis with perforation or appendicitis) can be relatively straightforward, the susceptibility of AIDS patients to a variety of unusual pathogens can result in clinical presentations that necessitate laparot?omy to rule out conditions requiring bowel resection.

References

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