From the Guidelines
A positive stool test in the rectal vault indicates the presence of a bacterial, viral, or parasitic infection, and the specific cause should be determined through stool testing for Salmonella, Shigella, Campylobacter, Yersinia, C. difficile, and STEC, as recommended by the 2017 Infectious Diseases Society of America clinical practice guidelines 1. The presence of a positive stool test in the rectal vault can have significant implications for patient management and public health. According to the guidelines, stool testing should be performed in people with diarrhea accompanied by fever, bloody or mucoid stools, severe abdominal cramping or tenderness, or signs of sepsis 1.
- The guidelines recommend testing for specific pathogens, including Salmonella, Shigella, Campylobacter, Yersinia, C. difficile, and STEC, in symptomatic hosts 1.
- The choice of testing should be based on clinical presentation, epidemiologic risk factors, and public health considerations 1.
- In immunocompromised patients, a broader range of potential causes should be considered, including bacterial, viral, parasitic, and fungal pathogens 1.
- The identification of the specific cause of the infection is important for guiding clinical management and public health control efforts 1.
- A positive stool test in the rectal vault can also indicate the presence of a rectovaginal fistula, which is an abnormal connection between the rectum and vagina, allowing stool to pass from the intestinal tract into the vagina 1.
- Management of a rectovaginal fistula typically involves surgical repair, and patients may require antibiotics and stool softeners to manage symptoms while awaiting definitive treatment 1.
From the Research
Positive Stool Test in the Rectal Vault
A positive stool test in the rectal vault can indicate the presence of a bacterial or viral pathogen.
- The yield of stool tests for bacterial pathogens in symptomatic patients is extremely low, as found in a study published in Gastroenterology report 2.
- Clinical predictors of positive stool culture include the month of presentation (summer season), fever, duration of abdominal pain, and requirement of IV fluid therapy, as identified in a study published in The Journal of emergency medicine 3.
- A Wright's stain of stool specimen can be used to detect fecal leukocytes and predict the presence of a bacterial pathogen on stool culture, with a sensitivity of 82% and specificity of 83%, as reported in The Journal of emergency medicine 4.
- Examination of a single stool specimen can be sufficient for most patients, especially when the prevalence of infection among the tested population is up to 20%, as found in a study published in Clinical infectious diseases 5.
- Rectal swabs can be used for diagnosis of viral gastroenteritis with a multiple real-time PCR assay, and are as reliable as stool samples for PCR-based diagnosis, as reported in Journal of clinical virology 6.
Implications of a Positive Stool Test
- A positive stool test can indicate the presence of a pathogen such as Campylobacter spp., Aeromonas spp., or norovirus, which can cause symptoms such as diarrhea, abdominal pain, and fever.
- Patients with positive stool cultures may have a higher risk of acute kidney injury, hospitalization, and mortality, as found in a study published in Gastroenterology report 2.
- The treatment of detected pathogens may have a minimum impact on the disease course of pouchitis, as reported in Gastroenterology report 2.