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Appendix

Appendicitis

Granulomatous appendicitis

Authors: Maryam Kherad Pezhouh, M.D., M.Sc., Masoumeh Peykan Heyraty, M.D.

Editorial Board Member: Kimberley J. Evason, M.D., Ph.D.

Deputy Editor-in-Chief: Aaron R. Huber, D.O.

Last author update: 31 October 2023

Last staff update: 31 October 2023

Copyright: 2003-2024, PathologyOutlines.com, Inc.

PubMed Search: Granulomatous appendicitis

Table of Contents

Cite this page: Pezhouh MK, Heyraty MP. Granulomatous appendicitis. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/appendixidiopathicgran.html. Accessed December 22nd, 2024.

Definition / general

Granulomatous inflammation of appendix

Essential features

Granulomatous inflammation of appendix
Clinically resembles acute appendicitis
Does not recur after appendectomy

Terminology

Granulomatous appendicitis

ICD coding

ICD-10
- K36 - other appendicitis
- K37 - unspecified appendicitis
- K35.8 - other and unspecified acute appendicitis
- K35.80 - unspecified acute appendicitis
- K35.89 - other acute appendicitis
- K35.890 - other acute appendicitis without perforation or gangrene
- K35.891 - other acute appendicitis without perforation, with gangrene

Epidemiology

Identified in 0.1 - 2% of appendectomies; depends on geographical distribution of underlying disease (Clin Case Rep 2021;9:e05074)

Sites

Appendix

Pathophysiology

Granulomatous inflammation of the appendix, due to variety of etiologies, leads to an acute or subacute increase in intraluminal and intramural pressure and acute or subacute inflammatory processes

Etiology

Idiopathic granulomatous appendicitis is rare and is a diagnosis of exclusion
Secondary granulomatous appendicitis can be due to infectious etiologies such as Yersinia, tuberculosis, fungal and parasitic infection and noninfectious etiologies such as interval appendicitis, Crohn's disease, sarcoidosis or other granulomatous disease (Int J Surg Pathol 2010;18:14)

Clinical features

Main symptom is acute or subacute abdominal pain
Other symptoms include fever, anorexia, vomiting, diarrhea and malaise
On physical examination, tenderness and rebound tenderness can be seen
Similar to acute appendicitis (Surgeon 2003;1:286)

Diagnosis

Definite diagnosis is based on histological examination and special stains; serologic test, tissue microbial culture and PCR are sometimes necessary for diagnosis of underlying disease

Radiology description

Nonspecific, enlarged appendix, thickened appendicular wall, presence of right lower quadrant fat stranding surrounding the appendix and enlarged mesenteric lymph nodes (Abdom Imaging 2003;28:280, J Clin Imaging Sci 2012;2:73)

Case reports

17 year old boy with nausea and right lower quadrant abdominal pain (Clin Case Rep 2021;9:e05074)
20 year old diabetic man with a 3 day history of right lower quadrant abdominal pain associated with fever, vomiting and anorexia (Cureus 2022;14:e23247)
24 year man presented with acute abdominal pain localized in the right iliac fossa with rebound tenderness for 24 hours (BMJ Case Rep 2020;13:e238955)
26 year old woman presented with persistent right lower abdominal pain and mass on computed tomography (CT) scan suggesting an inflammatory tumor around appendix (Surg Today 2007;37:690)
28 year old man with Crohn's disease presenting as granulomatous appendicitis (Case Rep Gastroenterol 2019;13:398)

Treatment

Dependent on the etiology of granulomatous appendicitis

Gross description

Appendix can be normal appearing or show erythema, perforation, abscess formation or thick wall appearance

Microscopic (histologic) description

Presence of necrotizing or nonnecrotizing granulomas with or without focal acute inflammation, mucosal erosion, ulceration, fissures or lymphoid aggregates (Hum Pathol 1993;24:595)
Presence of numerous granulomas is a histopathologic feature distinguishing idiopathic granulomatous appendicitis from Crohn's disease (Hum Pathol 1993;24:595)

Microscopic (histologic) images

Contributed by Maryam Kherad Pezhouh, M.D., M.Sc. and Masoumeh Peykan Heyraty, M.D.

Multiple granulomas

Focal necrotizing granuloma

Necrotizing granuloma

Well formed granulomas

Negative stains

AFB, GMS

Sample pathology report

Appendix, appendectomy:
- Appendix with numerous granulomas, focally necrotizing (see comment)
- Comment: Sections show an appendix with granulomatous inflammation (focally necrotizing). There is no evidence of chronicity. Multiple levels were evaluated. Acid fast bacteria (AFB) stain is negative for mycobacteria, Grocott Gomori methenamine silver (GMS) stain is negative for fungal organisms. Possible etiologies include but are not limited to infectious etiologies, including Yersinia pseudotuberculosis, Mycobacterium tuberculosis, fungal or parasitic infection or sarcoidosis. Crohn's disease is less favored (due to lack of other features of inflammatory bowel disease [IBD]) but should be excluded clinically. Idiopathic granulomatous appendicitis may occur but is rare. Clinical correlation is recommended.

Differential diagnosis

Crohn's disease involving the appendix:
- Crohn's disease infrequently affects the appendix (Am J Surg Pathol 2021;45:1703)
- Distinction relies mainly on clinical history along with presence of active inflammation and crypt architectural distortion
Appendiceal diverticulosis:
- Congenital (true) or acquired (false) (incidence of 0.014% and 1.9%, respectively) (Hum Pathol 2008;39:1823)
- Occurs in relatively older age group (Surg Today 2012;42:363)
- Distinction relies on presence of diverticula
Interval appendicitis:
- Patients with complicated appendicitis (i.e., rupture) treated with antibiotics followed with delayed appendectomy
- Distinction relies on the clinical history

Board review style question #1

A 20 year old man presented to the emergency department with right lower quadrant abdominal pain and tenderness, vomiting, fever and anorexia. Appendectomy with clinical diagnosis of acute appendicitis was done and histologic examination is shown in the image above. What is the diagnosis?

Acute appendicitis
Appendix diverticula
Granulomatous appendicitis
Mucocele

Board review style answer #1

C. Granulomatous appendicitis. This section shows the formation of multiple granulomas. Answer A is incorrect because no significant acute inflammation supportive of acute appendicitis is present. Answer B is incorrect because no diverticula are identified. Answer D is incorrect because mucocele is a clinical diagnosis referring to a dilated appendix.

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Reference: Granulomatous appendicitis

Board review style question #2

A 17 year old boy presented with mild right lower quadrant abdominal pain, malaise and mild fever for 2 weeks. He was diagnosed with ruptured acute appendicitis and was treated with antibiotics. He presented 2 months after for an appendectomy. Histologic evaluation of the appendix revealed chronic inflammation and multiple granulomas. What is the most likely underlying cause of granulomatous appendicitis in this patient?

Crohn's disease
Interval appendectomy
Sarcoidosis
Tuberculosis

Board review style answer #2

B. Interval appendectomy. Interval appendectomy is an important cause of granulomatous inflammation in the appendix. Clinical history is the main clue in this scenario. Answer A is incorrect because Crohn's disease rarely involves the appendix. Answer D is incorrect because tuberculosis often presents with systemic symptoms and necrotizing granulomatous inflammation. Answer C is incorrect because sarcoidosis often shows well formed nonnecrotizing granulomas. Presence of a clinical history is helpful.

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Reference: Granulomatous appendicitis

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