Colon non tumor
Infectious colitis
Tuberculosis (TB) of colon

Author: Elliot Weisenberg, M.D. (see Authors page)

Revised: 2 December 2016, last major update November 2016

Copyright: (c) 2003-2016, PathologyOutlines.com, Inc.

PubMed Search: Tuberculosis[title] colon
Cite this page: Tuberculosis of colon. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/colonTB.html. Accessed December 10th, 2016.
Definition / General
  • Infection of the colon by Mycobacterium tuberculosis
  • See Mycobacteria infections other than TB for discussion of the less common Mycobacterium bovis, M. africanum, M. canetti, M. microti
Essential Features
  • Infection occurs by swallowing mycobacteria in sputum (or less commonly infected milk), miliary spread or direct extension from an involved lymph node or the Fallopian tube
  • Ileocolonic disease often occurs in the absence of active pulmonary disease
  • Common symptomatology includes weight loss, anorexia, fever, abdominal pain, diarrhea and palpable mass
  • Endoscopic findings include strictures, ulcers and mucosal hypertrophy
  • Biopsies show granulomatous inflammation with confluent granulomas, usually with caseous necrosis
  • Mycobacteria are detected by special stain, culture, nucleic acid amplification or PCR
  • Treatment is with multiple antibiotics and more aggressive treatment is necessary for multidrug resistant and extensively drug resistant TB
  • Surgery may be necessary in the setting of perforation or obstruction
  • Today colonic TB is uncommon but in the pre-antibiotic era, 70% of patients who died developed gastrointestinal TB
ICD-10 coding
  • A18.32
Epidemiology
  • Worldwide (2015): 10.4 million cases of TB and 1.8 million deaths (WHO 2015)
  • United States (2015): 9557 cases, rate 3.0 per 100,000 (CDC 2015)
  • Approximately 1/3 of world's population has evidence of TB infection
  • Disease of poverty, 95% of cases occur in developing world (61% Asia, 26% Africa)
  • Usually affects young to middle aged adults, but all at risk
  • Under 5% of cases of active TB represent intestinal TB
  • Extrapulmonary TB more common in AIDS patients
  • Risk factors: HIV / AIDS, substance abuse, silicosis, diabetes mellitus, chronic kidney disease, malnutrition, organ transplant, head and neck cancer, old age, infancy, immunosuppressive therapy, use of biologic treatments such as infliximab for immune mediated disease
Sites
  • Most common in cecum in conjunction with ileum (abundant lymphoid tissue), 70% of patients with gastrointestinal TB have ileocecal disease
  • Also other colorectal sites
  • Multiplicity in 28% - 44%
  • Ileocecum is most common site of abdominal and gastrointestinal TB
  • Isolated colorectal involvement is uncommon - only 10.8% of abdominal gastrointestinal TB
Pathophysiology
  • Non spore forming, aerobic, nonmotile bacillus with high lipid and mycolic acid content of cell wall
  • Slow growth, generation time 15 - 20 hours
  • Phagocytosed by macrophages, blocks formation of phagolysosome, replication occurs; bacteremia develops (primary TB)
  • Th1 response develops that allows macrophages to contain bacteria
  • Granulomatous inflammation with necrosis and tissue damage occurs
  • Contained infection usually becomes hyalinized and calcified
  • Reactivation may occur with diminished immune status
  • Usually infection is contained, 5% - 10% develop active disease, but 30% with HIV
  • Spread to GI tract via swallowed bacteria, hematogenous spread, direct extension from infected lymph nodes or Fallopian tube
  • Ileocecum a favored site in GI tract due to abundance of lymphoid tissue
Clinical Features
  • Usually chronic disease is present for months
  • Generally weight loss, fever, abdominal pain, diarrhea and often a palpable abdominal mass
  • May see night sweats, anorexia, GI bleeding, malabsorption
  • Perforation or intestinal obstruction may occur
Diagnosis
  • Diagnosis may be established by biopsy with demonstration of microorganisms with special stain, culture or molecular techniques
Laboratory
  • Nucleic acid amplification tests and PCR based assays, Xpert MTB / RIF test detects TB and rifampicin resistance, auramine-rhodamine or Ziehl-Neelsen smear of fresh tissue, Ziehl-Neelsen or Kinyoun stain of paraffin embedded tissue, culture (long turnaround time but recommended for confirmation)
  • Detection of antibiotic resistance is important (multidrug resistant or extensively drug resistant TB)
Radiology Description
  • Early nodular mucosal thickening with loss of symmetry in the fold pattern
  • May see fissures, sinus tracts, fistulae (rare), ulceration (perpendicular to long axis, cf. Crohn's disease), perforation
  • Obliteration of ileocecal angle with widely patent ileocecal valve
  • Rapid emptying of inflamed terminal ileum (Stierlin sign)
  • Often associated mesenteric lymphadenopathy with increased mesenteric thickness
Prognostic Factors
  • Worse prognosis in HIV with low CD4 counts, other immunodepressed states, elderly, debilitated
Case Reports
Treatment
  • Generally isoniazid (INH), rifampin, ethambutol (EMB) and pyrazinamide (PZA) for 6 to 9 months (with HIV an intensive phase of INH, a rifamycin, PZA and EMB for the first 2 months with continuous INH and a rifamycin for the last 4 months)
  • Drug resistant TB is resistant to at least one first line drug, extensively drug resistant is resistant to INH and rifampin, plus at least one of three injectable second line drugs (amikacin, kanamycin or capreomycin)
  • The CDC recommends expert consultation to treat drug resistant and extensively drug resistant TB
Gross Description
  • Ulcerative (most common), hypertrophic and mixed forms are described
  • Usually multiple superficial ulcers perpendicular to long axis of bowel; may see deep ulcers
  • May see thickened mucosal folds, strictures, ulcers, inflammatory nodules; fistulas are rare
Micro Description
  • Caseating granulomas, often confluent and numerous, often cuff of lymphocytes, lymphoid hyperplasia, aphthous to deep ulcers, often architectural distortion
  • AFB stains more likely to be positive in necrotic areas and histiocytes, bacteria may be rare to abundant
  • Hyalinization and calcification with chronicity / treatment
Micro Images

Images hosted on other server:
Missing Image

Caseating granuloma

Positive Stains
Videos


Endoscopy of tuberculosis of ascending colon
Differential Diagnosis