Misidentified Metastases: Diagnosing and Managing Pyogenic Liver Abscesses in a Breast Cancer Survivor

Introduction

Pyogenic liver abscesses are pockets of pus of variable sizes within the liver. Although it is more prevalent in Asia, where its incidence was as high as 15.45 per 100 000 person-years in 2011, it is relatively rare in the United States, with an annual incidence of 3.6 per 100 000 people and a mortality risk estimated at 10% [1,2].

Due to their rarity, they are seldom considered in differential diagnoses in developed countries. If untreated, they are can be life-threatening; thus, early diagnosis and treatment are critical to achieving good outcomes [3]. A high index of suspicion is needed as the patient may not present with the classic symptoms of fever, as was the case with our patient. This can delay diagnosis and increase the risk of mortality.

This case report reviews the clinical presentation, risk factors, diagnosis, and management of multiple pyogenic liver abscesses.

Case Report

A 76-year-old woman with a past medical history of breast cancer status after lumpectomy in remission for 3 years and recent multiple rib fractures following a ground-level fall presented to the Emergency Department (ED) for evaluation of a 5-day history of diarrhea associated with vague abdominal pain.

On presentation, the patient appeared clinically stable, with a temperature of 36.5°C, blood pressure of 113/64 mmHg, and a heart rate of 110 beats per minute. The respiratory rate was 22 breaths per minute with an oxygen saturation of 93% on 3 liters/minute of oxygen. The physical examination was significant for reproducible right chest wall tenderness, mild right upper abdominal quadrant and epigastric tenderness, and bilateral pitting pretibial edema. The laboratory evaluation was pertinent for a white blood cell count of 7.5×103µ/L with 27% bands, C-reactive protein greater than 16 mg/dl, lactate of 2 mmol/L, and elevated liver transaminases [alanine aminotransferase 181 U/L, aspartate aminotransferase 186 U/L, and alkaline phosphatase 124 U/L. A stool examination was not done as the diarrhea resolved within 1 day of admission.

Due to the history of recent falls and concern for abdominal trauma, a trauma series of imaging was obtained in the ED, including computed tomography (CT) scans of the chest, abdomen, and pelvis, which showed nondisplaced or minimally displaced right rib (ribs 3–8) fractures and mild subcutaneous edema, with interval development of extensive hepatic metastatic disease, presumably from breast cancer, although not confirmed, and possible but less likely extensive small abscesses. CT scans also showed a minimally hydropic gallbladder with trace pericholecystic fluid and a common duct 9 mm in diameter (Figures 1, 2).

A diagnosis of sepsis with a presumed intra-abdominal source was made, and the patient received fluid resuscitation and was started on piperacillin/tazobactam and vancomycin after blood cultures were obtained. She remained febrile despite the antibiotic therapy, so GI was consulted due to concern for choledocholithiasis in the setting of a dilated common bile duct. A follow-up MRI of the abdomen with and magnetic resonance cholangiopancreatography (MRCP) without contrast was performed to characterize the biliary system further. The MRI showed innumerable non-enhancing T2 hyperintense lesions throughout the liver, which were less than 2 cm, and a normal biliary system. These lesions were considered unusual for metastatic disease, and abscesses were considered (Figure 3).

Aspiration/biopsy was recommended for further evaluation. CT-guided aspiration of the hepatic lesions done by Interventional Radiology noted serosanguineous purulent-appearing material. Both blood and hepatic aspirate cultures grew Streptococcus intermedius. In consultation with infectious disease specialists, antibiotics were de-escalated to ceftriaxone and metronidazole.

Due to the multiple sites of the hepatic abscess, therapeutic abscess drainage was not done, and the patient was continued on antibiotics. She was hospitalized for 9 days and was subsequently transitioned to cefadroxil at hospital discharge for a total duration of 4 weeks of antibiotics. She improved remarkably on this treatment and did well after discharge.

Discussion

A pyogenic liver abscess (PLA) can develop from a liver injury, a biliary tract infection, or an intra-abdominal infection that spreads from the portal circulation. PLA not related to trauma is more common in males aged 40–60 years [4–7].

The most common clinical signs include fever, abdominal pain, nausea/vomiting, loss of appetite, localized guarding, hepatomegaly, and toxic appearance [8,9]. Our patient had no fever but presented with bandemia, diarrhea, and vague abdominal pain. This emphasizes the need for high suspicion, as patients do not always present with classic clinical features.

Given the patient’s history of breast cancer, the initial suspicion was breast metastasis; however, an alternate diagnosis was sought due to the development of sepsis, which is a documented complication of PLA [10]. It is important to differentiate between abscesses and metastases in a patient with preexisting malignancy like our patient, as their management and prognosis are very different. A diagnostic dilemma exists in this setting, and early conclusion could lead to an incorrect diagnosis. An adequate history-taking, physical exam, and imaging are required to help solve the diagnostic dilemma. However, the imaging features of hepatic abscesses and metastases are often difficult to distinguish due to nonspecific imaging features of hepatic abscesses related to their maturity. Furthermore, there are overlapping imaging features between the 2 diseases, such as peripheral rim enhancement and diffusion restriction, and small hepatic abscesses often do not show typical imaging features of cluster double target signs [11]. Thus, the imaging method of choice is MRI [12]. Confirmation is done with needle aspiration to aid antibiotic choice and ensure clear and accurate communication with patients and their families.

PLA can be cryptogenic with an unknown cause, but when organisms are identified, they are usually polymicrobial. Common organisms include Escherichia coli, Klebsiella, Streptococcus, Staphylococcus, and anaerobic organisms [7,12].

Streptococcus intermedius is an anaerobic beta-hemolytic gram-positive member of the Streptococcus anginosus group (SAG). It is part of the normal flora of the mouth, gastrointestinal tract, and genitourinary tract but has also been associated with significant morbidity and mortality in patients when it causes invasive infections [13–16]. Without treatment, mortality has been reported to be as high as 100% and can be decreased to 2.5–4% with treatment [8,14].

Most patients with S. intermedius abscesses have been reported to be immunocompromised [8,17]. Immunocompromise in patients with liver abscesses caused by Streptococcus intermedius is defined as any patient with chronic conditions such as diabetes mellitus, hypertension, human immunodeficiency virus/acquired immunodeficiency syndrome, cancer, or coronary artery disease. Other risk factors listed include colon disorders, lifestyle choices such as alcohol use, tobacco use, raw beef intake, IV drug use, and surgical interventions such as dental work or laparoscopic hysterectomy [8,16,18].

The most commonly used antibiotics were fluoroquinolones, third-generation cephalosporins with metronidazole for 4–6 weeks, and it is usually curative for abscesses less than 5 cm in size. Combining antibiotics with aspiration, especially for abscesses greater than 5 cm, is preferable. Large abscesses (≥5 cm) can be drained percutaneously or surgically if there is abscess rupture, loculated abscess, or if the patient also has biliary and/or intra-abdominal pathology [8,17]. Our patient’s multiple abscesses were all <2 cm and were managed only with antibiotics.

Conclusions

This patient’s case represents multiple metastatic liver abscesses secondary to Streptococcus intermedius bacteremia. Early diagnosis is crucial considering the high mortality of invasive Streptococcus liver abscesses. We also highlight the importance of good clinical reasoning and the diagnostic challenges of diagnosing liver abscesses in developed countries like the United States.