This case describes a previously healthy patient who underwent a routine colonoscopy with polypectomy followed by a septic shock state secondary to likely Clostridium infection, resulting in abdominal gas gangrene. With aggressive medical management with IV antibiotics, fluids and inotropic support, the patient survived with full recovery at 4 months follow up. Iatrogenic Clostridium infection is a rare but documented complication after colonoscopy. In the limited literature surrounding this condition, it has been almost universally fatal, even with aggressive surgical management [7,8,9].
Colonic gas gangrene is a highly fatal infection, with Clostridium toxin production leading to rapid haemodynamic collapse and a rapidly expanding margin of bowel necrosis that can move up to 2 cm per hour [4]. It is caused by infection with Gram positive Clostridium species, either through traumatic or spontaneous routes. Traumatic Clostridium infections are typically caused by C. perfringens, whilst spontaneous infection is typically caused by C. septicum and usually occurs in association with gastrointestinal malignancy or immunosuppression [4,5,6, 10]. C. perfringens is a Gram positive, anaerobic, spore forming bacilli, found in soil and normal gastrointestinal flora in 70% of healthy individuals [7]. Systemic signs of gas gangrene infection include shock, septic myocardial depression and haemolytic anaemia [11, 12]. Septic shock in C. perfringens infection is mediated by alpha and theta toxins. The exact mechanisms of theta toxin are poorly understood, but it appears to cause a reduction in peripheral vascular resistance, leading to systemic hypotension [13]. Alpha toxin exerts its main effect on the heart, resulting in bradycardia and myocardial depression, while also increasing vascular permeability and inducing haemolysis [11, 12]. This reduction in cardiac output occurs prior to the onset of hypotension, and renders the body unable to compensate for the effect of theta toxin of peripheral vascular resistance, leading to profound shock [12].
One of the hallmarks of necrotizing clostridial infections is the production of gas in tissues. This was evidenced in this case by the presence of pneumatosis intestinalis, the radiographic sign of intramural gas in the gastrointestinal tract. Whilst there are several causes for this appearance (including ischemia, necrotising enterocolitis or gas gangrene infection) this patient’s history, presentation with septic shock and septic myocardial depression and new intravascular haemolysis suggest gas gangrene to be the most likely cause in this case [14, 15].
Three cases of gas gangrene post-colonoscopy have been reported in the literature to date [7,8,9]. All three of these cases were also associated with polypectomy, as was seen in our case report, however these cases reported retroperitoneal rather than intramural infection [7,8,9]. These patients were also typically older, ranging from 58 to 61 years of age. The presence of risk factors for gas gangrene was variable. Similar to our patient, 2 of these cases reported no prior medical history and no risk factors for spontaneous gas gangrene [5, 7, 9]. One patient suffered Crohn’s disease although the use of immunosuppressive therapy was not reported [8]. Although not classical, the combination of identification of C. perfringens in the reported cases and a lack of risk factors for spontaneous infection seem to imply that this clinical scenario of gas gangrene infection post-polypectomy could be considered a traumatic rather than a spontaneous gas gangrene infection.
The most striking difference between the case reported here and those in the literature is that all 3 cases reported prior were fatal within 48 h of the initial colonoscopy. Misdiagnosis likely plays a role in these poor outcomes with all cases initially being diagnosed as iatrogenic colonic perforation, as opposed to infection, thus delaying initiation of antibiotic therapy [7,8,9]. The case reported by Shaw et al. received imipenem only after exploratory laparotomy. Similarly, the patient reported by Boenicke et al. was started on cefotaxime and metronidazole after a first exploratory laparotomy, with penicillin and meropenem being only added after a second operation. The case by Gioia et al. received no antibiotic treatment prior to death, which occurred in the operating theatre. An autopsy case series of 8 patients with colonic gas gangrene not in association with colonoscopy revealed a similarly poor outcomes, with only 1 case correctly diagnosed prior to patient death [16]. This case series was limited in the reporting what medical or surgical treatment was provided. This dearth of available literature means clinicians are without high quality evidence in managing this condition.
The choice of antibiotic is controversial and limited by available literature. Penicillins have historically been used as the treatment of choice for clostridial infections although more recent evidence has shown better outcomes using clindamycin or tetracycline antibiotics [10]. This is theorised to be due to the inhibition of toxin synthesis resulting in reduced vasodilation, myocardial depression and thus less severe shock [10]. Alongside antibiotic therapy, surgical debridement is also thought to be important in the management of gas gangrene infection, however evidence exists to suggest a non-operative approach may be a viable option in colonic gas gangrene. Morris et al. reported 97 cases of pneumatosis intestinalis (of which gas gangrene is a cause) and found 50% of cases could be managed non-operatively with no increase in mortality compared to surgical management [14]. However, the number of patients with pneumatosis intestinalis due to infection was not reported in this study, making extrapolation to cases of gas gangrene limited [14]. Another potential treatment option is hyperbaric oxygen, however this is not yet considered standard of care and was unavailable at our institution [10].
In this case there were a number of factors that differentiated this case from existing reports and may have contributed to this patient surviving what has previously been reported as a universally fatal complication. Early recognition, early and appropriate antibiotic therapy and good supportive medical management likely contributed to this patient’s favourable outcome. Gas gangrene is often misdiagnosed initially as perforation, a more common cause of rapid deterioration post-procedure, feared by most gastroenterologists. In previously reported studies, the diagnosis of gas gangrene was made posthumously. Because of the rapid progression of this condition, it is important for gastroenterologists to maintain a wide differential in the unwell patient post-colonoscopy and entertain both medical and surgical causes. In reported studies, antibiotic choice was highly variable, in terms of both timing and agent chosen, as reported above. In our case the patient was initiated on a penicillin at the time of admission and was on full appropriate antibiotics within 24 h of colonoscopy. This, plus his ICU support, was likely a determining factor in his good outcome, even without surgical management.
A limitation of this case is that positive cultures for clostridia where unable to be obtained, making this a presumed gas gangrene infection, however clostridium species are notoriously difficult to culture, and thus negative blood cultures does not rule out infection [17]. Culture diagnosis was only achieved on post-mortem specimens in the three previously described cases, and seven of the eight patients from the autopsy case series [7,8,9]. It is possible the physiological response observed in this cause could result from other causes of bacterial sepsis or that the observed gas could be a mechanical consequence of polypectomy, however the combination of features described make clostridial myonecrosis highly likely. The strength of this case is that it is, to the authors knowledge, the first report of a patient surviving this rare colonoscopy complication, which may have contributed to the difficulty in obtaining samples for culture.
In conclusion, we present a case of post-colonoscopy gas gangrene successfully treated with medical and antibiotic therapy alone, with resolution of symptoms at 4 months follow-up. This case is to our knowledge the first successful treatment of post-colonoscopy gas gangrene. The patient’s satisfactory clinical course was likely due to early diagnosis and initiation of appropriate antibiotic therapy. We show that gas gangrene can be successfully managed without surgical intervention, but high-quality evidence to support this practice is lacking. Endoscopists should be aware of this rare but potentially lethal condition and consider it in the differential of a rapidly deteriorating patient post-colonoscopy.