Year : 2009 | Volume
: 52 | Issue : 3 | Page : 370--373
Fulminant amebic colitis: A study of six cases
R Nisheena, Anuradha Ananthamurthy, YK Inchara
Department of Pathology, St. John's Medical College, Bangalore - 560 034, India
Department of Pathology, St.John«SQ»s Medical College, Bangalore - 560 034
Background: Amebic colitis although common, rarely presents as fulminant colitis which has a high morbidity and mortality unless treated promptly and appropriately. Aim: To study the clinical, morphological features and outcome of fulminant amebic colitis (FAC). Materials and m0 ethods: A retrospective study of six patients who underwent surgical resections from 2002-06 and were diagnosed with FAC, was carried out. The morphological features assessed included the average number of trophozoites per high-power field and the depth of invasion of trophozoites into the muscularis propria. Results: The study included five adults and one child who underwent surgery for fulminant colitis. Interestingly, a definite preoperative diagnosis of amebic colitis was made only in one patient and suspected in another. Intraoperatively, multiple perforations of the intestine with peritonitis were the most common findings. Gross examination typically revealed multiple ulcers with exudate and intervening normal mucosa. Microscopically, ulceration and myonecrosis with trophozoites within the exudate were seen in all cases. Trophozoites invading the muscularis propria were seen in five cases. Of the cases that showed myoinvasion by trophozoites, two patients expired within two weeks of surgery. One of the patients who expired also showed co-infection with Actinomyces. Conclusion: FAC is an uncommon outcome in amebic colitis with a high mortality requiring prompt surgical intervention.
|How to cite this article:|
Nisheena R, Ananthamurthy A, Inchara Y K. Fulminant amebic colitis: A study of six cases.Indian J Pathol Microbiol 2009;52:370-373
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Nisheena R, Ananthamurthy A, Inchara Y K. Fulminant amebic colitis: A study of six cases. Indian J Pathol Microbiol [serial online] 2009 [cited 2021 Jun 20 ];52:370-373
Available from: https://www.ijpmonline.org/text.asp?2009/52/3/370/54997
Amebic colitis, although a common clinical problem, seldom progresses or presents as a fulminant colitis. , Fulminant colitis due to amebic etiology is a rare disease with a high morbidity and mortality, the diagnosis of which requires a high index of clinical suspicion. ,, Demonstration of trophozoites in stool samples is insensitive and although serology is sensitive and specific, relying on serology may delay the diagnosis as seroconversion takes two to four weeks.  In fact, a diagnosis of fulminant colitis due to amebic etiology is seldom made preoperatively even in endemic areas leading to rapid deterioration of the patient.  Since the incidence of amebic colitis is increasing even in developed countries it is imperative to emphasize on the possible fulminant outcome of this disease.  We present in this study an analysis of six cases of fulminant amebic colitis (FAC) during a four year period from 2002 till 2006.
Materials and Methods
We retrospectively reviewed histopathology slides and medical records of six patients who presented as surgical emergencies and underwent colonic resections for fulminant colitis at our institution between 2002 and 2006. The clinical and preoperative findings, surgical management and follow-up data were reviewed retrospectively. All these patients had undergone colonic resections and the ulcer bases were extensively sampled from these specimens. The histopathological criteria for a diagnosis of FAC included demonstrable trophozoites of amoeba in the Hematoxylin and Eosin (H and E) sections which was then confirmed by the periodic acid Schiff (PAS) stain. The histological sections were reviewed in these cases with particular emphasis on the number of trophozoites per high-power field, depth of invasion of the trophozoites into the muscularis propria and the presence of muscle necrosis.  When the number of trophozoites were less than or equal to three per high-power field, we quantitated them as 'few' and when more than three per high-power field, as 'numerous'.
The demographic data, clinical diagnoses, histological findings and follow-up information of the six cases are summarized in [Table 1].
Demographics and clinical features
The study included five males and one female with the ages ranging from eight to 65 years. A definite preoperative diagnosis of amebic colitis was offered in only one case, with a suspicion of the same in another. In the other cases, clinical diagnoses included Crohn's disease, necrotizing enterocolitis and enteric fever. The commonest symptoms were loose stools (in all six patients), fever (in five patients) and abdominal pain (in five patients). Two of the patients also complained of passing blood in stools. Abdominal distension was seen in three patients, with guarding and rigidity in three patients. One of the cases in addition had a palpable liver of 4-5 cm size (Case 2).
Abdominal scans in all the cases showed features of peritonitis with enterocolitis. One patient also showed a hypoechoic area in the liver for which a differential diagnosis of an abscess and a metastatic neoplasm was given (Case 3). In one case, a complex bowel mass suggestive of an appendicular mass was seen in the right iliac fossa (Case 1). Leucocytosis was seen in three patients. One of the cases had pancytopenia (Case 2). None of the patients were either diabetic or alcoholic.
Treatment and Outcome
All six patients underwent surgical resections of the colon. Peroperative findings were cecal mass (one patient) and peritonitis (three patients). Four patients showed necrotic and edematous bowel loops with multiple perforations. While two patients died in the postoperative period, the rest recovered completely. One of the patients who died postoperatively had pancytopenia and an enlarged liver (Case 2). Pathology revealed a dual infection with actinomycosis in this patient (see below).
All the colectomy specimens when opened showed multiple ulcers in the mucosa. Frank necrosis of the bowel loops was also seen with exudates on the external aspect. The ulcers were typically discrete with intervening areas of normal-appearing mucosa [Figure 1].
Histopathology showed extensive ulceration of the mucosa with necrosis of the colonic wall. Trophozoites of amoeba were seen in all the cases, predominantly in the exudate of the ulcer base. The trophozoites appeared to be round to oval structures about the size of macrophages with ingested red blood cells [Figure 2]. These trophozoites were highlighted by the PAS stain [Figure 3]. While two of the cases showed only a few trophozoites (three or less per high-power field) the other four showed numerous (more than three per high-power field) trophozoites which were easily found. In one case the trophozoites were few in number and were seen invading only up to the submucosa with no myoinvasion while in the rest trophozoites of amoebae were seen invading the muscle wall. Two of the cases (Cases 2 and 3) showing transmural invasion by trophozoites expired during the postoperative period. One of these cases (Case 2) interestingly also showed filamentous colonies of actinomyces which stained positively with the PAS stain and the silver stain, Gomori's methanamine silver (GMS) stain [Figure 4]. As mentioned earlier this patient exhibited pancytopenia and an enlarged liver. The other patient who died (Case 3) had multiple hypoechoic lesions in the liver and peroperatively showed evidence of fecal peritonitis. The single case that did not show myoinvasion by trophozoites had a localized cecal mass with superficial ulcers and no evidence of peritonitis (Case 1).
Fulminant colitis due to amebic etiology is often not suspected clinically even in endemic areas.  Our study reflects this problem wherein a colitis of amebic etiology was suspected only in two cases (Cases 1 and 6). The commonest clinical symptoms were loose stools, fever and abdominal pain, which are concurrent with previous studies. 
In our series one of the cases had a hypoechoic lesion in the liver and a probable diagnosis of liver abscess or metastasis was rendered radiologically. Despite this, the possibility of an amebic etiology was not entertained clinically.
Although amebic infection is common in endemic areas such as ours, why in certain individuals an aggressive course is encountered, is difficult to explain. The reasons attributed to this are a more virulent strain of the organism and higher susceptibility of the host either due to associated chronic diseases, coexistent malignancies or chronic alcoholism. 
The presence of amebic trophozoites as ratified by special stains such as the PAS stain, along with myonecrosis and ulceration of the colon justifies the morphologic diagnosis of FAC.  Although two of the four cases who died postoperatively showed trophozoite invasion through the muscularis propria, it is unclear whether the presence of this feature portrays an unfavorable outcome in patients with FAC, as three of the patients with myoinvasion indeed survived. In addition, in this study the number of trophozoites seen did not seem to correlate with the severity of the disease, supporting the findings of previous studies.  One of our cases also showed colonies of actinomycosis. To the best of our knowledge, there have been no reports in the English literature of FAC with associated actinomycosis.
A high index of clinical suspicion and early treatment is crucial for recovery from FAC. The presence of a liver abscess, especially if associated with colonic symptoms should prompt one to suspect FAC.  Early surgical intervention is warranted when an acute abdominal syndrome is present. , Four of the six patients in our series recovered completely after surgery indicating that early surgical intervention can be lifesaving in these cases. Some of the clinical factors associated with a bad prognosis in FAC have been hypokalemia and age above 60 years.  There have not been any major studies looking into the morphological features associated with a poor outcome in FAC. As the number of cases in this study is small, it is difficult to state categorically the morphological features associated with an unfavorable prognosis. The presence of an associated infection with actinomycosis probably contributed to the poor prognosis in one of our patients. Further documentation of morphological features on more number of cases is necessary to assess the prognostic indicators in FAC.
The clinical and morphological features of six cases of FAC are documented here. The most common presenting complaints were those of an acute abdomen with abdominal pain, loose stools and fever. All the cases underwent colonic resections for fulminant colitis. While four of the patients survived, two died in the postoperative period. Multiple ulcers and necrosis of the bowel wall were characteristic gross features. Trophozoites were demonstrated in all the cases and the PAS stain helped in highlighting these organisms. In the presence of an acute abdomen with associated liver abscess a high index of clinical suspicion is necessary to establish a diagnosis of FAC.
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