Fecal impaction: Clinical sciences

Fecal impaction occurs when a hard mass of compacted stool in the colon cannot be voluntarily evacuated. It usually results from chronic constipation and is highly associated with elderly, immobile, and institutionalized patients because of their reduced ability to sense and respond to the increasing burden of stool. If left untreated, fecal impaction can lead to complications like bowel ulceration and perforation.

When assessing a patient with signs and symptoms suggestive of fecal impaction, first perform an ABCDE assessment to determine if the patient is unstable or stable. If the patient is unstable, start acute management immediately to stabilize their airway, breathing, and circulation. This means that you might need to intubate the patient, obtain IV access, administer fluids, and monitor their vitals before continuing with your assessment.

Next, obtain a focused history and physical exam, as well as labs such as CBC, CMP, and lactate. History might reveal chronic constipation, bloating, abdominal pain, and possibly opioid usage. Physical exam typically shows abdominal distension and signs of peritonitis, such as diffuse tenderness to palpation, guarding, and rebound pain.

On digital rectal examination, you’ll usually notice a large, hardened mass of stool in the rectum and possibly rectal bleeding. Finally, labs may show leukocytosis, lactic acidosis, or anemia. In some patients, you might also notice electrolyte abnormalities like hypercalcemia, hyperkalemia, or hypermagnesemia which might actually be the cause of their constipation; or hypernatremia due to dehydration from excessive vomiting. Alright, if you see these signs and symptoms, suspect fecal impaction.

Okay, your next step is to start supportive care. Initiate IV fluid resuscitation, electrolyte replacement, broad-spectrum antibiotics, and bowel rest. Additionally, if the patient has nausea and vomiting, place a nasogastric tube to decompress the bowel. However, if the patient has severe anemia, be sure to provide a blood transfusion.

Alright, once the supportive care is initiated, you should order an abdominal x-ray and CT, which will help you make a diagnosis. On x-ray, you will typically see a large stool burden overlying the rectum, with or without proximal colonic distention. CT findings may include evidence of bowel ischemia, such as pneumatosis or portal venous gas. Now, if you see pneumoperitoneum in the setting of a patient who has stercoral colitis, then you should suspect secondary stercoral perforation. This is when an unresolved impacted fecal mass, or fecaloma, causes pressure necrosis, and ultimately, the necrotic bowel perforates. If you notice any of these signs, go ahead and call a surgical consultation for an emergent laparotomy.

Now, let’s go back to abdominal x-ray and CT. If you see a large colonic stool burden without any signs of ischemia or perforation, and especially if the patient is having active rectal bleeding, proceed with lower endoscopy, which can be both diagnostic and therapeutic. After the impacted stool is removed, endoscopy will show an irregular, bleeding mucosal ulceration, whose contour correlates to nearby impacted feces. If this is the case, you can diagnose a stercoral ulcer leading to acute lower GI bleed. Initial treatment includes injectant, thermal, or mechanical endoscopic hemostasis. Then, continue supportive care, transfuse blood products as needed, and make sure to treat underlying causes.

Okay, now that unstable patients are taken care of, let’s return to the ABCDE assessment and talk about stable patients. Your first step here is to obtain a focused history and physical exam, as well as labs like CBC, CMP, and lactate. Stable patients also report chronic constipation, bloating and abdominal pain, as well as possible nausea and vomiting. Don’t forget to ask about common risk factors such as opioid or anticholinergic medication usage, hypothyroidism, history of functional immobility or institutional care, and any prior neuropsychiatric diagnoses.

Here’s a high-yield fact! Although fecal impaction is related to constipation, patients may present with other forms of bowel and bladder dysfunction. It is not uncommon for patients to have urinary tract infections, urinary incontinence, or even paradoxical diarrhea when watery stools leak past the solid impaction.

On the flip side, a physical exam often reveals abdominal distention, and sometimes abdominal tenderness to palpation. If the patient is thin, and the impaction is bulky enough, you may even be able to palpate a left lower quadrant mass! The key finding of fecal impaction is a large rectal stool burden during the digital rectal examination. But remember, in some cases the impaction may be too proximal to feel, so don’t rule it out based solely on the rectal exam! Finally, labs might show electrolyte abnormalities like hypercalcemia, hyperkalemia, hypermagnesemia, or hypernatremia.

At this point, go ahead and obtain an abdominal x-ray. This typically shows a large burden of stool in the colon and rectum. The intraluminal stool has a soft tissue mixed-density appearance, due to its mixture of solid and gas components. Sometimes, you might see radiopaque fecaliths, which are hard calcified fecal masses. At this point, diagnose fecal impaction and initiate supportive care.