Colon

Infectious colitis

Actinomycosis

Author: Elliot Weisenberg, M.D.

Topic Completed: 1 January 2017

Minor changes: 5 May 2021

Copyright: 2003-2021, PathologyOutlines.com, Inc.

PubMed Search: actinomycosis

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Table of Contents

Cite this page: Weisenberg E. Actinomycosis. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/colonactinomycosis.html. Accessed October 28th, 2021.

Definition / general

Infection of large intestine by actinomycotic microorganisms
Colonic actinomycosis is a subset of abdominal actinomycosis, but some sources do not discriminate between actinomycosis of abdomen and pelvis
Other common sites are oral cervicofacial actinomycosis ("lumpy jaw", see secondary chronic osteomyelitis), skin, thoracic and pelvic (cervix, kidney, ovary)

Epidemiology

Rare, but abdominal actinomycosis comprises 15 - 20% of actinomycosis in humans
Males are more commonly affected

Sites

Most common site is cecum, most often with concurrent ileal disease
Some cases are secondary to disease in appendix or female genital tract

Pathophysiology

Due to infection by anaerobic or microaerophilic, saprophytic bacteria of genus Actinomyces, a normal commensal of mouth, large intestine, vagina
Disruption of mucosa is necessary for disease - causes are trauma, surgery, diverticular disease, ingestion of foreign body, or less commonly other inflammatory processes
- In surgery related cases, disease may appear months after perforation leading to appendectomy or bowel resection, but without evidence of actinomycosis at the time
In some cases, no inciting event is identified; rare cases may originate through hematogenous spread
While actinomycotic colonies may dominate the histologic picture, it is likely that companion, or "co-pathogenic" bacteria may also be necessary for disease to occur, possibly by lowering oxygen tension

Etiology

Actinomyces israelii is the most common etiologic agent; however, at least five other species are implicated in human disease
Using comparative 16s ribosomal RNA, some bacteria traditionally associated with actinomycotic disease have been reclassified as Aracanobacterium, Actinobaculum or Cellulomonas

Clinical features

Usually indolent disease, but more severe in immunocompromised patients
Patients usually present with non-specific symptoms including abdominal pain, fever, change in bowel habits, sensation of a mass
Imaging studies reveal a mass-like lesion, cystic lesion or an abscess, often suggestive of malignancy
May coexist with other inflammatory lesions of colon with fistula or sinuses
Clumps of yellow bacteria known as sulfur granules are characteristically present
No cases of human to human transmission have been reported and Actinomyces has not been cultured from nature

Diagnosis

Usually by tissue biopsy or resection where the characteristic microorganisms are seen
Abdominal actinomycosis is rarely suspected clinically and most patients are diagnosed after major surgery
Diagnosis by microbiologic culture is uncommon as strict anaerobic conditions are necessary and antibiotics interfere with growth in culture

Prognostic factors

Most patients respond well to therapy

Case reports

17 year old boy with mass over sigmoid colon (APSP J Case Rep 2011;2:4)
38 year old woman with severe large bowel obstruction (Scand J Infect Dis 2006;38:231)
41 year old man with renal, colonic and retroperitoneal actinomycosis (West Afr J Med 2005;24:343)
50 year old woman with combined intra- and extraabdominal actinomycosis (Rom J Gastroenterol 2004;13:337)
53 year old man with abdominal actinomycosis containing a fish bone (Surg Today 2006;36:187)
57 year old liver transplant recipient with abdominal actinomycosis (Transpl Infect Dis 2012;14:86)
58 year old man with actinomycosis simulating malignant large bowel obstruction (Braz J Infect Dis 2004;8:186)
63 year old man with abdominal actinomycosis and multiple myeloma (Oncol Lett 2014;8:1876)
67 year old woman with actinomycosis of the sigmoid colon (World J Gastrointest Surg 2009;1:62)
72 year old woman with ascending colon actinomycosis mimicking cancer (BMC Gastroenterol 2005 Jan 4;5:1)
74 year old woman with abdominal actinomycosis (Acta Clin Belg 2014;69:152)
79 year old man with colonic actinomycosis invading abdominal wall (Int J Surg Case Rep 2010;1:9)

Treatment

Prolonged high dose antibiotics
Even with advanced clinical disease, most patients can be effectively treated with medical management alone; however, this is very uncommon with abdominal disease

Gross images

Images hosted on other servers:

Sigmoid colon mass

Microscopic (histologic) description

Characteristic clumps of basophilic filamentous bacteria in a vaguely rosette-like configuration surrounded by acute inflammatory cells are characteristic
Acute inflammation is accompanied by dense fibrosis described as "woody"
Eosinophilic clubs may be found at periphery (Splendore-Hoeppli phenomena)
Granulomatous inflammation may be present

Microscopic (histologic) images

Contributed by Asmaa Gaber Abdou, M.D.