Diagnostic and therapeutic difficulties in retroperitoneal abscess.

Abstract: Abscesses developing within the retroperitoneal spaces are complicated and serious infections. These abscesses present insidiously, leading to considerable mortality and morbidity. A high clinical suspicion can help diagnose and treat this potentially fatal illness. Computed axial tomography is the best diagnostic modality for retroperitoneal abscess. Computed tomographic scan is useful, not only for diagnosing the retroperitoneal abscess, but can be used for therapeutic drainage of abscesses in high-surgical-risk patients. We present an illustrative case of retroperitoneal abscess and discuss the pathogenesis of retroperitoneal abscess, diagnosis, and treatment.

Key Words: computed axial tomography, retroperitoneal abscess

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Retroperitoneal abscess is a relatively rare condition and is often misdiagnosed or suspected late in its clinical course. It is a serious surgical infection associated with significant mortality rates. Early diagnosis and treatment decreases the morbidity and mortality rates significantly. An appreciation of the condition and its likely etiologic factors should improve awareness and possibly reduce mortality rates by early surgical drainage. We present an illustrative case and an overview of retroperitoneal abscess.

Case Report

An 84-year-old white male with a history of hypertension, oxygen-dependent, chronic obstructive lung disease, and long-standing peptic ulcer disease visited his primary physician, reporting a 3-month history of mild abdominal pain, lower extremity swelling, and increasing shortness of breath. He also had an occasional fever for 6 weeks before admission. He had no nausea, vomiting, constipation, hematochezia, or diarrhea. Physical examination at admission showed an elderly and chronically ill-appearing man with normal mental status. Vital signs confirmed a temperature of 98.8[degrees]F; heart rate was 84 bpm; respirations 18 per minute; and blood pressure 130/80 mm Hg. Heart and lung examinations were unremarkable. The abdomen was distended, bowel sounds were active, and he was tender to palpation over the upper abdomen, more pronounced in the left hypochondrium and epigastric region. No abdominal masses or organomegaly were palpated. Bilateral 3+ pitting leg edema was noted.

Admission laboratory data included a hemogram with mild leukocytosis with polymorphonuclear granulocytic predominance; serum transaminases were minimally elevated, and amylase and lipase were normal. Urine analysis was normal. On the day of admission, the patient had spiked a temperature. Ultrasound of the biliary tract was performed, showing a large calculus in the gallbladder with slightly dilated intrahepatic ducts, with a common bile duct measuring 7.9 mm. Subsequently, computed tomographic (CT) scan of the abdomen showed an extensive retroperitoneal cystic mass indicative of an inflammatory or neoplastic process. The mass was compressing the inferior vena cava (Fig. 1). A CT-guided biopsy was performed the next day through an anterior abdominal approach. On cyst puncture, pus was aspirated, and the Gram stain showed Gram-negative rods. Escherichia coli was grown on culture. Broad-spectrum antibiotic coverage with intravenous imipenem 500 mg every 8 hours was commenced. An esophagogastroduodenoscopy was unremarkable. An upper gastrointestinal series and small-bowel Gastrografin (Bristol-Myers Squibb, Princeton, NJ) study showed a large duodenal diverticulum in the third portion. No fistulous tract was noted. Pigtail catheters were placed under CT guidance into the abscess for surgical drainage, one catheter in the epigastric region and a second catheter in the right flank region cysts. Five hundred milliliters of fluid was collected from both catheters. The patient had significant relief after drainage of the abscess. A repeat CT scan after catheter drainage showed remarkable digression in the abscess bulk (Fig. 2). The patient had significant relief after drainage of the abscess. Despite aggressive catheter drainage and appropriate antibiotic coverage, the patient had cardiopulmonary failure and died. An autopsy request was declined.

Discussion

The retroperitoneum is a space between the peritoneum and transversalis fascia lining the posterior abdominal cavity. It extends laterally to the edges of the quadratus lumbar muscles, the diaphragm superiorly, and the pelvic brim inferiorly. The retroperitoneum is divided into an anterior space accommodating the colon, duodenum, and pancreas and a posterior space in which kidneys, aorta, and inferior vena cava are traversed. The area is closed superiorly but is open inferiorly, allowing retroperitoneal infections to be bilateral and to extend to the pelvis and thighs. (1,2)

The retrofascial space is located between the transverse fascia and the posterior parietal wall. It contains the vertebral column and paravertebral musculature. This area extends superiorly into the mediastinum and inferiorly into the pelvis and thighs. Infections of retrofascial area that are not strictly in the retroperitoneal space are included in the differential diagnosis of retroperitoneal abscess. Thus, infections and inflammatory processes of any of these structures can result in a retroperitoneal abscess.

[FIGURE 1 OMITTED]

[FIGURE 2 OMITTED]

The incidence of retroperitoneal abscess is reported to be highest in the third to sixth decades of life, with a slightly higher predominance in males. (3) Patients present with an insidious onset of a chronic debilitating illness and generalized symptoms of a serious infection including flank, abdominal, and groin pain, weakness, fever, chills, anorexia. Rarely, the patient may be asymptomatic. Physical examination usually reveals a chronically ill patient with fever, intermittent and spiking, and associated tachycardia. (4,5) A mass, when palpable, is tender and is present in the abdomen, flank, and, rarely, in the thigh, groin, or scrotum. Laboratory results usually reveal leukocytosis, with a polymorphonuclear predominance. Routine laboratory findings (complete blood count, bone morphogenic protein, urinalysis) may not be revealing. (1)

Plain abdominal films may reveal an abnormality in 38 to 90% of patients. They may reveal an abnormal psoas shadow, scoliosis, loss of renal outline, or a soft tissue mass. Intravenous pyelography may demonstrate fixation of the kidney or deviation of ureters. Chest radiography may show elevation of the ipsilateral diaphragm, pleural effusion, or basilar atelectasis caused by the intra-abdominal process. Barium contrast studies disclose displacement of the viscera or extravasation of the contrast and occasionally a fistulous tract. (1,2,4) Ultrasound, gallium 67 citrate, and indium 111 chloride scanning are noninvasive and accurate methods of discovering and localizing retroperitoneal abscesses. (6,7) Clearly, considering the numerous imaging options available, obtaining an abdominal CT offers the definitive standard for diagnosing retroperitoneal abscesses and their anatomic extent. (8)

Retroperitoneal abscesses usually complicate perforation of adjacent bowels arising from neoplastic disease, (9) diverticulitis, retroperitoneal appendicitis, pancreatitis, pancreatic cancer, biliary tract disease, peptic ulcer disease, inflammatory bowel disease, (10) genitourinary extravasation secondary to obstruction, osteomyelitis of vertebral bodies, or 12th rib. (1) Less common causes include trauma, hematogenous or lymphatic seeding from a distant infection, and postoperative complication. (3) Iliac lymphadenitis has been reported as a rare cause of retroperitoneal abscess. (11) In the case here reported, the source of the patient's abscess remained obscure.

The microbiology of retroperitoneal abscess shows a monomorphic predominance of coliform organisms and Staphylococcus aureus. Some reviews stress a polymorphic pathology with a mixture of S aureus, Streptococcus pneumonia, coliforms, and anaerobic organisms. Mycobacteriae chelonae, (12) actinomycosis, (2) Entamoeba histolytica, (13) and Clostridium perfringens (14) have been sporadically reported.

Conclusion

Diagnostic delay and consequent postponed treatment of retroperitoneal abscesses commonly occur. Expeditious diagnosis with the use of abdominal CT scans for anatomic definition of the abscess, combined with adequate surgical drainage and antibiotic support improve survival chances. CT-guided percutaneous drainage, at least as a temporizing measure, is suitable for those patients with a high surgical risk, as was the case for our patient. It is generally accepted, as noted in this case, that treatment with antibiotics alone is associated with a 100% mortality rate, which is decreased to 31 and 16% for treatment consisting of surgical drainage and surgical drainage with broad-spectrum antibiotic coverage, respectively. Appropriate antimicrobial coverage should include a combination of aminoglycosides and metronidazole or clindamycin. For pancreatic (peripancreatic) abscess, imipenem achieves bactericidal levels in pancreatic tissue for most causative organisms. Review of the literature emphasizes the difficulty in diagnosing retroperitoneal abscess because its prodromal phase, without an acutely obvious associated event, may be long and symptoms intermittent until late in the disease process. The result is a high mortality rate, even when aggressive therapy is given. Achieving the best outcome requires inclusion of retroperitoneal abscess in the differential diagnosis in an appropriate clinical setting.

I'll sleep when I'm dead.
--Warren Zevon

Accepted April 7, 2004.

References

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13. Rhode CM, Jennings WD. Retroperitoneal retrofascial space infections. Am Surg 1964;30:799-810.

14. Nortan KI, Cohen BA, Reiner MA, et al. Retroperitoneal abscess from perforated sigmoid diverticulitis. Am Coll Gastroenterol 1985;80:986-988.

RELATED ARTICLE: Key Points

* Retroperitoneal abscess is a serious surgical infection and is often misdiagnosed or suspected late in its clinical course.

* The early use of abdominal computed tomography avoids other less productive studies, rendering it cost-effective and most definitive for diagnosing retroperitoneal abscess.

* Treatment consists of surgical drainage with broad-spectrum antibiotic coverage.

Anuradha Tunuguntla, MD, Rafi Raza, MD, and Larry Hudgins, MD

From the Department of Internal Medicine, Quillen College of Medicine, East Tennessee State University, Quillen Veterans Administrative Medical Center, Johnson City, TN.

Reprint requests to Larry Hudgins, MD, Medical Service, VA Medical Center, Mountain Home, TN 37684. Email: [e-mail]