A 64-year-old woman comes to the emergency department due to a 2-day history of worsening abdominal pain. She has a history of gallstones but has had no surgery due to high operative risk. Medical history includes chronic obstructive pulmonary disease, hypertension, and remote cervical cancer treated with surgery and chemotherapy. Abdominal CT scan shows multiple dilated small bowel loops with a decompressed distal ileum, and an abnormal bowel indicated by the arrow shown below: Which of the following is the most likely cause of this patient's current condition?

Question

A 64-year-old woman comes to the emergency department due to a 2-day history of worsening abdominal pain.  She has a history of gallstones but has had no surgery due to high operative risk.  Medical history includes chronic obstructive pulmonary disease, hypertension, and remote cervical cancer treated with surgery and chemotherapy.  Abdominal CT scan shows multiple dilated small bowel loops with a decompressed distal ileum, and an abnormal bowel indicated by the arrow shown below:  Which of the following is the most likely cause of this patient's current condition?

Quizplus · Accepted Answer

11ec160b_3ade_6f25_9249_fde2bedec375_MD0001_00 This patient with worsening abdominal pain has CT scan findings concerning for small bowel obstruction (SBO), a process in which a mechanical or functional obstruction disrupts the normal flow of intestinal intraluminal contents. SBO classically causes dilation of bowel proximal to the obstruction (eg, multiple dilated small bowel loops) and decompression of bowel distal to the obstruction (eg, decompressed distal ileum). Patients with SBO typically have abdominal pain, nausea, vomiting (usually bilious), and abdominal distension and tenderness. Common causes of mechanical SBO include peritoneal adhesions, hernias, and tumors. Computed tomography is the diagnostic test of choice because it usually can identify the specific site of obstruction (ie, transition point), assess obstruction severity (partial vs complete), and identify potential complications (eg, bowel necrosis, perforation). This patient's CT scan demonstrates a small bowel loop extending outside the peritoneal cavity into the left inguinal area, indicative of an inguinal hernia that has become trapped (ie, incarcerated) as the cause of SBO. Incarceration increases the risk of bowel strangulation (ie, ischemia leading to necrosis) and should prompt urgent surgical consultation. (Choice A) Gallstone ileus occurs when a large gallstone erodes into the intestinal lumen and becomes impacted (eg, at the ileocecal valve), causing mechanical obstruction. CT scan commonly shows obstructing gallstones or pneumobilia due to retrograde passage of intestinal gas into the biliary tract. (Choice C) Malrotation is characterized by incomplete physiologic rotation of the bowel in utero. Duodenal obstruction can occur due to abnormally positioned peritoneal bands; however, this occurs more commonly in infancy (vs adulthood). Imaging typically shows predominantly left-sided large bowel and right-sided small bowel. (Choice D) Volvulus occurs when an intestinal loop twists around itself and its mesentery. It can result in SBO, but CT scan classically reveals mesenteric twisting ("whirl sign") as the transition point (vs an incarcerated inguinal hernia). (Choice E) Peritoneal adhesions (fibrous bands) often form between intraabdominal organs and/or the abdominal wall following abdominal surgery and can cause mechanical SBO by trapping bowel loops during normal intestinal peristalsis. However, CT scan typically reveals an intraperitoneal transition point (vs an extraperitoneal hernia). Educational objective: Small bowel obstruction (SBO) occurs when a mechanical or functional obstruction disrupts the normal flow of intestinal intraluminal contents. A herniated bowel loop (eg, inguinal hernia) can cause SBO if it becomes trapped (ie, incarcerated) outside the peritoneal cavity. __________ References: Bowel obstruction: a narrative review for all physicians. (http://www.ncbi.nlm.nih.gov/pubmed/31168315)

A 64-Year-Old Woman Comes to the Emergency Department Due to a 2-Day