INTRODUCTION — Clostridium difficile causes antibiotic-associated colitis; it colonizes the human intestinal tract after the normal gut flora have been altered by antibiotic therapy. It is one of the most common healthcare-associated infections and a significant cause of morbidity and mortality among elderly hospitalized patients.
The clinical manifestations and diagnosis of C. difficile infection will be reviewed here. The treatment, pathophysiology, and epidemiology of this disorder are discussed separately. (See "Treatment of Clostridium difficile infection in adults" and "Epidemiology, microbiology, and pathophysiology of Clostridium difficile infection in adults".)
CLINICAL MANIFESTATIONS — Watery diarrhea is the cardinal clinical symptom of C. difficile infection, although it can cause a spectrum of manifestations ranging from the asymptomatic carrier state to severe fulminant disease with toxic megacolon (table 1) [1]. The basis for this range of symptomatic responses is not fully understood but may be related to various host and pathogen factors. (See "Epidemiology, microbiology, and pathophysiology of Clostridium difficile infection in adults".)
Carrier state — About 20 percent of hospitalized adults are C. difficile carriers who shed C. difficile in their stools but do not have diarrhea; in long term care facilities, carriage rate may approach 50 percent [2-4]. Although asymptomatic, these individuals serve as a reservoir for environmental contamination [3,4]. The host immune response to C. difficile may play a role in determining an individual's carrier status. Data on treatment of asymptomatic carriers are limited and routine treatment is not recommended. (See "Epidemiology, microbiology, and pathophysiology of Clostridium difficile infection in adults" and "Prevention and control of Clostridium difficile in hospital and institutional settings".)
Diarrhea with colitis — Manifestations of C. difficile-associated diarrhea with colitis include watery diarrhea up to 10 or 15 times daily with lower abdominal pain and cramping, low grade fever, and leukocytosis [5]. Fever (T>38.5) is a sign of severe C. difficile-associated diarrhea (CDAD); fever is associated with CDAD in about 15 percent of cases. Leukocytosis in the setting of CDAD is common; CDAD is reported to routinely be associated with a WBC on average of 15K. These symptoms generally occur in the setting of antibiotic administration; they may begin during antibiotic therapy or 5 to 10 days following antibiotic administration. Infrequently, symptoms present as late as 10 weeks after cessation of therapy [6].
The antibiotics most frequently implicated in predisposition to C. difficile infection are fluoroquinolones, clindamycin, cephalosporins, and penicillins, but virtually all antibiotics, including metronidazole and vancomycin, can predispose to C. difficile (table 2).
Physical examination generally demonstrates lower abdominal tenderness. Sigmoidoscopic or colonoscopic examination may demonstrate a spectrum of findings, from patchy mild erythema and friability to severe pseudomembranous colitis (see 'Pseudomembranous colitis' below).
Unexplained leukocytosis in hospitalized patients (even in the absence of diarrhea) may reflect underlying C. difficile infection [7,8]. In a prospective study of 60 patients with unexplained leukocytosis (white blood cell count >15,000/microL), for example, positive stool C. difficile toxin was observed in 58 percent of cases compared with 12 percent in controls [7]. When unexplained leukocytosis is due to CDAD, most often diarrhea develops in the next one to two days. (See "Causes of neutrophilia", section on 'Acute infection'.)
Pseudomembranous colitis — Patients with pseudomembranous colitis usually present with clinical manifestations of CDAD with colitis. In addition, sigmoidoscopic examination in these patients demonstrates the presence of pseudomembranes, which is sufficient to make a presumptive diagnosis of C. difficile infection.
Endoscopic findings — C. difficile toxin-induced cytoskeleton disruption manifests with gross findings of shallow ulcerations on the intestine mucosal surface [9]. Ulcer formation allows release of serum proteins, mucus, and inflammatory cells, which manifest grossly on the colorectal mucosal surface as pseudomembranes (virtually pathognomonic for C. difficile infection; there are rare reports of Klebsiella and other pathogens also capable of causing pseudomembranous colitis).
Pseudomembranes manifest as raised yellow or off-white plaques up to 2 cm in diameter, scattered over the colorectal mucosa (picture 1 and picture 2). Some patients with pseudomembranous colitis have scattered lesions with relatively normal appearing intervening mucosa, whereas others have a confluent pseudomembrane covering the entire mucosa. Other gross findings include may include bowel wall edema, erythema, friability, and inflammation; these may be observed with or without presence of pseudomembranes.
In some cases, pseudomembranes may be absent in the rectosigmoid area but may be visualized more proximally with colonoscopy, although colonoscopy is not indicated for diagnosis of C. difficile [8]. Colonoscopy may demonstrate pseudomembranes even if sigmoidoscopy does not [8,10].
Histopathology — The pathologic features of pseudomembranous colitis (PMC) have been classified into three distinct types [11]:
Imaging — Abdominal computed tomography (CT) scan in patients with pseudomembranous colitis demonstrates pronounced thickening of the colonic wall (picture 3) [12].
Recurrent disease: relapse vs reinfection — Recurrence of symptoms after successful initial therapy for C. difficile, due to relapse of the initial infecting strain or due to reinfection with a new strain, develops in 10 to 25 percent of cases; patients may experience several episodes of recurrence. Recurrence may present within days or weeks of completing treatment; the clinical presentation may be similar to or more severe than the initial presentation [13]. Recurrence may be related to variability in the host immune response to C. difficile infection. (See "Treatment of Clostridium difficile infection in adults", section on 'Management of initial recurrence' and "Epidemiology, microbiology, and pathophysiology of Clostridium difficile infection in adults".)
Recurrent C. difficile infection often represents relapse rather than reinfection, regardless of the interval between episodes. Among 134 paired stool isolates from 102 patients with recurrent C. difficile infections, isolates obtained two to eight weeks apart were identical in 88 percent of cases; isolates obtained 8 weeks to 11 months apart were identical in 65 percent of cases [14].
Some patients with recurrent diarrhea, cramping, and bloating after treatment of C. difficile may have postinfectious irritable bowel syndrome or other inflammatory colitides including collagenous or microscopic colitis, concomitant ulcerative colitis or Crohn’s disease, or celiac disease (See "Pathophysiology of irritable bowel syndrome".)
Fulminant colitis — The manifestations of fulminant colitis typically include severe lower quadrant or diffuse abdominal pain, diarrhea, abdominal distention, fever, hypovolemia, lactic acidosis, and marked leukocytosis (up to 40,000 white blood cells/microL or higher) [15,16]. Diarrhea may be less prominent in patients with prolonged ileus due to pooling of secretions in the dilated, atonic colon. Other potential complications of fulminant colitis include toxic megacolon and bowel perforation [17].
Toxic megacolon is a clinical diagnosis based upon the finding of colonic dilatation (>7 cm in its greatest diameter) accompanied by severe systemic toxicity. Abdominal plain films may also demonstrate small bowel dilatation, air-fluid levels (mimicking an intestinal obstruction or ischemia), and "thumb printing" (scalloping of the bowel wall) due to submucosal edema (picture 4 and picture 5). (See "Toxic megacolon".)
Bowel perforation presents with abdominal rigidity, involuntary guarding, diminished bowel sounds, rebound tenderness, and severe localized tenderness in the left or right lower quadrants. Abdominal radiographs may demonstrate free abdominal air.
Aggressive diagnostic and therapeutic interventions are warranted in the setting of fulminant C. difficile infection. Bedside sigmoidoscopy or colonoscopy may be performed to make a presumptive diagnosis of C. difficile infection by evaluating for presence of pseudomembranes. Given the risk of perforation, care should be taken to introduce minimal amounts of air to avoid exacerbating ileus or distention. Prompt surgical consultation is warranted to assess the requirement for colectomy [18]. (See "Treatment of Clostridium difficile infection in adults", section on 'Treatment'.)
UNUSUAL PRESENTATIONS — Other manifestations of C. difficile include protein-losing enteropathy with ascites, C. difficile infection in the setting of chronic inflammatory bowel disease, and extracolonic involvement.
Protein-losing enteropathy with ascites — Many patients with C. difficile infection develop protein-losing enteropathy with hypoalbuminemia, and a few may exhibit ascites and peripheral edema [19,20]. Inflammation of the bowel wall allows leakage of albumin into the lumen, causing colonic loss of albumin with inadequate compensatory hepatic synthesis. As a result, serum albumin levels may drop below 2.0 g/dL (20 g/L). The protein-losing enteropathy responds to appropriate medical therapy of the infection. (See "Protein-losing gastroenteropathy" and "Treatment of Clostridium difficile infection in adults".)
Clostridium difficile and inflammatory bowel disease — Infection with C. difficile (as well as other enteric pathogens) may complicate the course of inflammatory bowel disease (IBD) [21,22]. Enteric infections account for about 10 percent of symptomatic relapses in patients with IBD; C. difficile accounts for about one-half of these infections [23]. Rates of C. difficile among IBD patients appear to be increasing in some institutions [24,25]. The association between IBD and C. difficile may be due to a variety of factors, including antibiotic use for treatment of other gastrointestinal pathogens and frequent hospitalization for management of IBD flares. Rarely, C. difficile can trigger an initial bout of IBD [23].
C. difficile infection in IBD patients requires prompt diagnosis and management, since failure to diagnose the infection can lead to inappropriate treatment with glucocorticoids or immunosuppressive therapy. Furthermore, C. difficile may be difficult to distinguish from an IBD relapse given the similar symptoms of diarrhea, abdominal pain, and low grade fever. Thus, a high index of suspicion is required when evaluating IBD patients with apparent flares, especially those who have recently received antibiotics and/or been hospitalized.
The diagnosis requires the use of laboratory tools; endoscopy is usually not helpful because IBD patients generally do not develop pseudomembranes. Given the preexisting colonic pathology, patients with IBD who develop C. difficile colitis more frequently may require colectomy (20 percent in one series) [25]. Specific antibiotic and surgical management is discussed in detail separately. (See "Treatment of Clostridium difficile infection in adults".)
There is also a high prevalence of C. difficile carriage in patients with IBD. This was illustrated in a study of 122 patients with longstanding IBD in which the frequency of C. difficile carriage was higher in IBD patients than in healthy volunteers (8 versus 1 percent, respectively), in the absence of recent antibiotics or hospitalization [26]. Despite this observation, none developed symptomatic disease in the subsequent six months. The reason for this observation is not certain; possibilities include altered colonic microbial flora, mucosal inflammation, and impaired mucosal innate immunity.
Extracolonic involvement — Rare cases of C. difficile appendicitis, small bowel enteritis, and extraintestinal involvement have been described.
DIFFERENTIAL DIAGNOSIS — Although C. difficile is the major infectious cause of antibiotic-associated diarrhea, it must be distinguished from other infectious and noninfectious causes of diarrhea. Staphylococcus aureus was previously implicated as an important cause of antibiotic-associated pseudomembranous colitis [32,33]. Other potential pathogens include Klebsiella oxytoca, Clostridium perfringens, Candida spp, and Salmonella [34-39].
Among noninfectious causes, antibiotic-associated diarrhea may be attributable to osmotic mechanisms rather than C. difficile infection. Differentiation of this noninfectious form of antibiotic-associated diarrhea may be difficult, especially in patients who also may be asymptomatic C. difficile carriers. Cessation of symptoms with discontinuation of oral intake is a distinguishing feature of osmotic diarrhea (figure 1). The presence of fever and leukocytosis favor C. difficile or other infectious etiology. (See "Approach to the adult with chronic diarrhea in developed countries".)
Postinfectious irritable bowel syndrome occurs in about 10 percent of patients who have been successfully treated for an initial bout of C. difficile. These patients may have up to 10 watery stools per day and are often convinced that they are suffering from a relapse of their original C. difficile infection. (See "Pathophysiology of irritable bowel syndrome".)
DIAGNOSIS — Diagnostic evaluation should be pursued in the setting of clinically significant diarrhea (usually defined as three or more loose stools per day for at least two days); suspicion is warranted if many stools (10 to 15) occur with fever or nocturnal diarrhea even if only one day in duration. However, some patients with C. difficile have ileus [40,41]. There is no clinical role for testing stool from asymptomatic patients or in patients on therapy for acute disease who may still have positive stool assays during or after clinical recovery.
The diagnosis should be based on results from a laboratory diagnostic test or an endoscopic evaluation that demonstrates pseudomembranes in the colon.
Laboratory diagnosis — There are two categories of laboratory tests for C. difficile: toxin assays (which evaluate for evidence of toxin), and organism detection assays (which evaluate for the presence of the organism).
The optimal approach for laboratory diagnosis of C. difficile is uncertain. Anaerobic stool culture is the most sensitive test but is not practical due to its slow turnaround time; the need to detect toxin production by the recovered isolate further slows down this approach. Cytotoxicity assay also takes too long for routine clinical use, but it is the standard against which other clinical tests should be compared.
Many laboratories use enzyme immunoassay (EIA) testing for C. difficile toxins A and B, which is rapid but less sensitive than the cytotoxicity assay. One strategy to overcome this problem is to test for glutamate dehydrogenase (GDH), an essential enzyme produced by all C. difficile isolates (in the presence or absence of toxin production). This may be used as initial screening followed by cytotoxicity testing for positive samples.
Polymerase chain reaction (PCR) of stool appears to be rapid, sensitive and specific. Major clinical laboratories are beginning to adopt this tool as their primary diagnostic approach; more data would be helpful to support routine use of this modality. Repeat PCR within seven days of a negative result is rarely useful, except for patients with evidence of a new infection [42].
Toxin assays — Toxin assays include cytotoxicity assay, EIA and PCR. Most strains produce both toxins A and B though some clinically relevant strains produce toxin A or B only [43-47].
Organism detection — Organism detection assays include common antigen testing and anaerobic culture. An inherent problem with detection of the organism rather than the toxin is that not all C. difficile strains are toxigenic and up to 30 percent of hospitalized patients are colonized without disease [3]. In one study of hospitalized patients colonized with C. difficile, 92 percent of patients with diarrhea were colonized with toxigenic strains, compared with 81 percent of asymptomatic carriers [60]. Some laboratories use one of these methods to screen stool samples, with subsequent cytotoxin testing for positive samples [61].
Anaerobic culture is not a routinely used diagnostic tool in most clinical laboratories since it is relatively slow and labor intensive. However, it remains an important tool for epidemiologic surveillance [53].
Endoscopy — Colonoscopy or sigmoidoscopy can be a useful adjunctive tool for diagnosis of C. difficile in the following settings:
Endoscopy is not warranted in patients with classic clinical findings and a positive stool toxin assay. In the setting of fulminant colitis, care should be taken to introduce minimal amounts of air given the risk of perforation. Gross and histologic findings obtained by endoscopic evaluation are discussed in detail above. (See 'Endoscopic findings' above and 'Pseudomembranous colitis' above.)
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