Should I consider acute acalculous cholecystitis in my elderly ambulatory patient admitted with right upper quadrant pain?

Short answer: Yes! Although we usually associate acute acalculous cholecystitis (AAC) with critically ill patients (eg, with sepsis, trauma, shock, major burns) in ICUs, AAC is not as rare as we might think in ambulatory patients. In fact, a 7 year study of AAC involving multiple centers reported that AAC among outpatients was increasing in prevalence and accounted for 77% of all cases (1)!

Although the pathophysiology of ACC is not fully understood, bile stasis and ischemia of the gallbladder either due to microvascular or macrovascular pathology have been implicated as potential causes (2). One study found that 72% of outpatients who developed ACC had atherosclerotic disease associated with hypertension, coronary, peripheral or cerebral vascular disease, diabetes or congestive heart failure (1). Interestingly, in contrast to calculous cholecystitis, “multiple arterial occlusions” have been observed on pathological examination of the gallbladder in at least some patients with ACC and accordingly a name change to “acute ischemic cholecystitis” has been proposed (3).

AAC can also complicate acute mesenteric ischemia and may herald critical ischemia and mesenteric infarction (3). The fact that cystic artery is a terminal branch artery probably doesn’t help and leaves the gallbladder more vulnerable to ischemia when arterial blood flow is compromised irrespective of the cause (4).

Of course, besides vascular ischemia there are numerous other causes of ACC, including infectious (eg, viral hepatitis, cytomegalovirus, Epstein-Barr virus, Salmonella, brucellosis, malaria, Rickettsia and enteroviruses), as well as many non-infectious causes such as vasculitides and, more recently, check-point inhibitor toxicity (1,5-8).

Bonus Pearl: Did you know that in contrast to cholecystitis associated with gallstones (where females and 4th and 5th decade age groups predominate), ACC in ambulatory patients is generally more common among males and older age groups (mean age 65 y) (1)?


If you liked this post, download the app and sign up under MENU to catch future pearls straight into your inbox, all for free! 


1. Savoca PE, Longo WE, Zucker KA, et al. The increasing prevalence of acalculous cholecystitis in outpatients: Result of a 7-year study. Ann Surg 1990;211: 433-37.
2. Huffman JL, Schenker S. Acute acalculous cholecystitis: A review. Clin Gastroenterol Hepatol 2010;8:15-22.
3. Hakala T, Nuutinene PJO, Ruokonen ET, et al. Microangiopathy in acute acalculous cholecystitis Br J Surg 1997;84:1249-52.
4. Melo R, Pedro LM, Silvestre L, et al. Acute acalculous cholecystitis as a rare manifestation of chronic mesenteric ischemia. A case report. Int J Surg Case Rep 2016;25:207-11.
5. Aguilera-Alonso D, Median EVL, Del Rosal T, et al. Acalculous cholecystitis in a pediatric patient with Plasmodium falciparum infection: A case report and literature review. Ped Infect Dis J 2018;37: e43-e45.  
6. Kaya S, Eskazan AE, Ay N, et al. Acute acalculous cholecystitis due to viral hepatitis A. Case Rep Infect Dis 2013;Article ID 407182.
7. Simoes AS, Marinhas A, Coelho P, et al. Acalculous acute cholecystitis during the course of an enteroviral infection. BMJ Case Rep 2013;12.
8. Abu-Sbeih H, Tran CN, Ge PS, et al. Case series of cancer patients who developed cholecystitis related to immune checkpoint inhibitor treatment. J ImmunoTherapy of Cancer 2019;7:118.



Should I consider acute acalculous cholecystitis in my elderly ambulatory patient admitted with right upper quadrant pain?

My patient with erythema multiforme has tested positive for Mycoplasma pneumoniae IgM antibody. Does this mean she has an acute M. pneumonia infection as the cause of her acute illness?

Not necessarily! Although detection of IgM in the serum of patients has proven valuable in diagnosing many infections during their early phase, particularly before IgG is detected, less well known is that false-positive IgM results are not uncommon. 1

More specific to M. pneumoniae IgM, false-positive results have been reported in 10-80% of patients without a clinical diagnosis of acute M. pneumoniae infection 2-4 and 3-15% of blood donors. 4

False-positive IgM results may also occur when testing for other infectious agents, such as the agent of Lyme disease (Borrelia burgdorferi), arboviruses (eg, Zika virus), and herpes simplex, Epstein-Barr, cytomegalovirus, hepatitis A and measles viruses. 1,5  

Reports of false positive IgM results include a patient with congestive heart failure and mildly elevated liver enzymes who had a false-positive hepatitis IgM which led to unnecessary public health investigation and exclusion from an adult day care center. 1 Another patient with sulfa rash had a false-positive measles IgM antibody resulting in callback of >100 patients and healthcare providers for testing!5

There are many potential mechanisms for false-positive IgM results, including polyclonal B cell activation, “vigorous immune response”, cross-reactive antibodies, autoimmune disease, subclinical reactivation of latent viruses, influenza vaccination, overreading weakly reactive results, and persistence of antibodies long after the resolution of the acute disease. 1,2

In our patient, a significant rise in M. pneumoniae IgG between acute and convalescent samples several weeks apart may be more helpful in diagnosing an acute infection accounting for her erythema multiforme.



  1. Landry ML. Immunoglobulin M for acute infection: true or false? Clin Vac Immunol 2016;23:540-5.
  2. Csango PA, Pedersen JE, Hess RD. Comparison of four Mycoplasma pneumoniae IgM-, IgG- and IgA-specific enzyme immunoassays in blood donors and patients. Clin Micro Infect 2004;10:1089-1104.
  3. Thacker WL, Talkington DF. Analysis of complement fixation and commercial enzyme immunoassays for detection of antibodies to Mycoplasma pneumoniae in human serum. Clin Diag Lab Immunol 2000;7:778-80.
  4. Ryuta U, Juri O, Inoue Y, et al. Rapid detection of Mycoplasma pneumoniae IgM antibodies using immunoCard Mycoplasma kit compared with complement fixation (CF) tests and clinical application. European Respiratory Journal 2012; 40: P 2466 (Abstract). 
  5. Woods CR. False-positive results for immunoglobulin M serologic results: explanations and examples. J Ped Infect Dis Soc 2013;2:87-90.

If you liked this post, sign up under MENU and get future pearls straight into your mailbox!

My patient with erythema multiforme has tested positive for Mycoplasma pneumoniae IgM antibody. Does this mean she has an acute M. pneumonia infection as the cause of her acute illness?