Streptococcus anginosus pyogenic liver abscess following a screening colonoscopy

A previously healthy 58-year-old man presented with a septic thrombosis of the right hepatic vein and a pyogenic liver abscess (PLA) one week after undergoing a screening colonoscopy. Blood cultures and a radiological drainage specimen were both positive for Streptococcus anginosus. Evolution was favourable after six weeks of antibiotherapy. To the authors’ knowledge, the present report is the first to describe a PLA following a screening colonoscopy with no intervention. The authors hypothesize that silent microperforations during colonoscopy contributed to the infection. Although 20% to 40% of reported PLA cases are cryptogenic in the literature, it may be because of failure to recognize and report a precipitating factor such as colonoscopy. As more cases similar to the present case are reported, the number of cryptogenic cases may decrease.


Streptococcus anginosus pyogenic liver abscess following a screening colonoscopy
Streptococcus anginosus, a species belonging to the Streptococcus milleri group, is frequently responsible for PLA (5).Intra-abdominal infections, such as diverticulitis, can occasionally cause PLA through drainage via the portal vein of an infected area (6).On the other hand, very few cases have been described following a colonoscopy (7)(8)(9).
We report a case involving a patient who presented with fever and right costal pain one week after undergoing a screening colonoscopy, who was ultimately diagnosed with S anginosus PLA and a septic thrombosis of the right hepatic vein.

Case PResentatIon
A previously healthy 58-year-old man presented with a four-day history of fever, chills and right subcostal pleuritic pain.One week before admission, the patient underwent a screening colonoscopy.It was performed without complications, although the patient complained of significant abdominal discomfort that was self-limiting after the procedure.The endoscopy revealed sigmoid diverticulosis and no further intervention has been performed.
On admission, the patient appeared ill, had a temperature of 40.4°C and normal blood pressure.No focus of infection was clearly identified on physical examination and initial workup was only remarkable for a white blood cell count of 17×10 9 /L.Blood cultures were drawn and an abdominal ultrasound revealed an hypodense lesion 6 cm × 5 cm × 4 cm in size in the right hepatic lobe without biliary pathology.Findings were further characterized with an abdominal computed tomography scan (Figure 1A), which confirmed a right hepatic lobe collection with thrombosis of the right hepatic vein (Figure 1B).There was no evidence of intestinal perforation.
The patient was treated with piperacillin-tazobactam and radiological drainage with placement of an indwelling catheter.Two sets of blood cultures were positive for S anginosus; the same germ grew from the radiological drainage specimen.Antibiotic therapy was subsequently changed to penicillin for a more focused antibiotic spectrum.
A transthoracic echocardiogram did not reveal any vegetation and a ventilation-perfusion scan was negative for septic emboli.Follow-up scan showed resolution of the abscess after six weeks of therapy.

DIsCUssIon
The incidence of PLA is stable, with 10 to 20 cases per 100 000 hospital admissions (1).S anginosus, a facultative anaerobic Gram-positive coccus found in the normal flora of the gastrointestinal tract, is one of the three species, with Streptococcus intermedius and Streptococcus constellatus, that forms the group S milleri.With Escherichia coli, this group is the most frequently isolated microorganism in contemporary PLA western series (2)(3)(4)(10)(11)(12)(13)(14)(15).
Early diagnosis of PLA is crucial because despite contemporary therapeutic advances, the mortality rate remains approximately 10% (2)(3)(4)(5)11,(16)(17)(18).The clinician must maintain a high level of suspicion because of its largely nonspecific clinical presentation.For example, in a recent retrospective study involving 63 patients with PLA (10), temperature, right upper quadrant pain and signs of peritonism were present in 59%, 39% and 14% of cases, respectively.The time between symptom onset and diagnosis was one week.
Biliary tract infections account for nearly one-half of cases; other seeding routes include portal and systemic bacteremia, direct intraperitoneal extension and liver trauma.However, 20% to 40% of cases remain cryptogenic.Proposed etiologies to explain this are: an undetected infection; a resolved infectious process in the portal region; and a transient bacteremia (19,20).
Very few infectious complications have been reported following colonoscopy, which could be due to the difficulty in deducing the causal relationship between these events (21).However, a case report case report

Bonenfant et al
Can J Infect Dis Med Microbiol Vol 24 No 2 Summer 2013 e46 describing a septic thrombophlebitis of the hepatic veins following a therapeutic colonoscopy has been published (7).In addition, colonoscopy has also been implicated in two cases of PLA (8,9): one case was after a malignant polypectomy (8); the other was after removal of an impacted fish bone (9).Transient bacteremia, which occurs in 4% of colonoscopies, does not appear to be associated with an increased risk of infection (21).We assume that the spread of infection is through microperforations.Unlike frank perforations, which complicate 0.1% of colonoscopies (22,23), little data on microperforations exist.Case reports describe patients with abdominal pain and elevated temperature several hours or days after endoscopy, and only serosa tear in laparoscopy (24)(25)(26).It is likely that the number of cases is underestimated because of the invasive nature of the examination needed to make a definitive diagnosis.
In our report, seeding of the liver was probably secondary to a septic thrombosis of a branch of the portal vein, which could have resulted from a microperforation during the colonoscopy.The present case is the first in which a screening colonoscopy without intervention was associated with PLA.It is possible that the percentage of cases reported to be cryptogenic in literature (20% to 40%) is overestimated because of failure to recognize and report a precipitating factor such as colonoscopy.As more cases similar to the present case are reported, the number of cryptogenic cases may decrease.

ConClUsIon
The present case reminds us of the importance of imaging the liver in cases of fever and nonspecific symptoms, seeking a PLA.It also raises questions as to the possible contribution of colonoscopy in the pathophysiology of PLA.Given the high number of endoscopies, it is important to clarify this relationship.

Figure 1 )
Figure 1) Abdominal computed tomography.a Hypodense collection in the right hepatic lobe, representing a pyogenic liver abscess (PLA).B Septic venous thrombosis (SVT) of the right hepatic vein Francis Bonenfant MD, Étienne Rousseau MD, Paul Farand MD MSc