PoCUS Diagnostic Accuracy for Fecal Impaction in the Emergency Department: A Prospective Study

Background Many medical specialties and paramedical fields are increasingly using point-of-care ultrasound (PoCUS). PoCUS is a pillar of clinical evaluation along with inspection, palpation, percussion, and auscultation, and it has become essential in daily clinical practice, as it enhances differential diagnosis. In a position statement published in 2015, the American Academy of Emergency Medicine followed by the European Federation of Societies for Ultrasound in Medicine and Biology in 2016 recommended the inclusion of PoCUS in the curricula of medical schools to improve the learning of core concepts and enhance students' understanding of physical examinations. The integration of PoCUS into clinical examination raises the issue of PoCUS diagnostic accuracy.

In everyday practice, fecal impaction is defined as the accumulation of hard fecal matter in the rectum and colon, with the absence of spontaneous evacuation. Its annual prevalence is estimated at 47.3% in nursing homes, affecting approximately 70% of nursing home patients. Furthermore, 42% of patients admitted to geriatric services suffer from fecal impaction.

In the United States, 21.9% of patients admitted to the emergency department (ED) with fecal impaction died in hospital, and severe morbidity was identified in 40.6% of patients. Over 90% of the patients with fecal impaction who visited the ED subsequently required hospitalization. In 2011, there were 42,000 ED visits in the US for fecal impaction, with patients aged over 65 being the most affected.

It is widely known that the incidence of fecal impaction increases with age and impairs quality of life in patients over 65 years of age. This common problem is often undiagnosed and thus frequently left untreated, whereas its prompt identification and treatment minimize the risk of complications. The most frequent symptoms are false diarrhea, fecal incontinence, behavioral disorders (agitation, delirium), loss of appetite, nausea, vomiting, abdominal pain, and electrolyte disorders. The site of impaction is most often rectal in 66.4% of cases. Fecal impaction is the most frequent cause of diarrhea in the elderly, with an incidence of 55%. Currently, in the ED, fecal impaction is diagnosed by plain abdominal X-rays or abdominal computed tomography (CT) scans if required as part of the ED investigations.

PoCUS is a valuable tool for investigating suspected fecal impaction, as it can guide the investigator to make a rapid diagnosis, thus leading to its rapid management. To analyze the presence of fecal impaction using PoCUS, the patient should be supine and comfortable. In the case of fecal retention in the rectal lumen, ultrasound waves are reflected from the surface of the contents at a depth deeper than the bladder (anechoic area), with a hyperechoic area with a half-moon shape being depicted in the transverse ultrasound image. In addition, with hard stool accumulation, an acoustic shadow appears in the transverse ultrasound image of the crescent-shaped hyperechoic area. By contrast, in the absence of fecal retention or gas in the rectal lumen, no obvious hyperechoic area is depicted. In the transverse ultrasound image, a circumferential hypoechoic area may be observed as an empty intestine.