A 67-year-old man comes to the emergency department due to progressive fever and lethargy. The patient has also had severe right shoulder and abdominal pain, nausea, and vomiting for the past 2 days. He had an appendectomy during childhood and a pacemaker placed 10 years ago for symptomatic sinus bradycardia. He has no other medical problems and takes no medications. The patient does not use tobacco but drinks an occasional beer. Temperature is 38.4 C (101.1 F), blood pressure is 80/50 mm Hg, and pulse is 120/min and regular. Abdominal examination shows generalized tenderness with rebound tenderness. Right shoulder examination is normal. Upright chest x-ray is shown below. Which of the following is the most likely cause of this patient's condition?

Question

A 67-year-old man comes to the emergency department due to progressive fever and lethargy.  The patient has also had severe right shoulder and abdominal pain, nausea, and vomiting for the past 2 days.  He had an appendectomy during childhood and a pacemaker placed 10 years ago for symptomatic sinus bradycardia.  He has no other medical problems and takes no medications.  The patient does not use tobacco but drinks an occasional beer.  Temperature is 38.4 C (101.1 F), blood pressure is 80/50 mm Hg, and pulse is 120/min and regular.  Abdominal examination shows generalized tenderness with rebound tenderness.  Right shoulder examination is normal.  Upright chest x-ray is shown below.  Which of the following is the most likely cause of this patient's condition?

Quizplus · Accepted Answer

11ec160b_358b_0f8b_9249_2f85a276a1d0_MD0001_00 This patient's upright chest x-ray demonstrates free air under the diaphragm (pneumoperitoneum), likely due to perforation of a hollow abdominal viscus. The most common cause of pneumoperitoneum is a perforated duodenal ulcer, but perforation can occur anywhere along the gastrointestinal (or female reproductive) tract due to ulcers, tumors, trauma, or iatrogenic causes (eg, endoscopy, surgery). Contamination of the sterile peritoneal cavity with bowel contents leads to chemical (acid or chyme-related) or bacterial peritonitis, which, if left untreated, can progress to sepsis and death. Diffuse irritation of the parietal peritoneum results in severe abdominal pain with rigidity and rebound tenderness. Shoulder pain is another frequent finding and reflects referred pain from diaphragmatic irritation. Referred pain is due to convergence of multiple nociceptors (visceral and somatic) onto a single secondary neuron within the spinal cord, which causes the brain to misinterpret visceral pain as arising from a body surface. (Choice A) Other common causes of abdominal pain with associated diaphragmatic irritation and referred shoulder pain include acute cholecystitis/biliary colic and splenic lacerations. However, these would not be associated with intraabdominal free air. (Choice B) Acute pancreatitis causes epigastric abdominal pain that may be referred to the back. X-ray findings are often normal, although a localized ileus near the inflammed pancreas (sentinel loop sign) may be seen. (Choice C) Nephrolithiasis typically presents with colicky flank pain that is referred to the groin. Radiopaque stones (calcium, struvite, and cystine) may be visualized on plain radiography. (Choice E) Small bowel obstruction causes poorly localized, constant abdominal pain, which can be referred to the epigastrium. Plain radiography demonstrates dilation of the small bowel with air fluid levels; free air is not seen in the absence of perforation. Educational objective: Pneumoperitoneum is air or gas in the peritoneal cavity; it can be seen as free air under the diaphragm in an upright chest x-ray. The most common cause is a perforated duodenal ulcer, but perforation can occur anywhere along the gastrointestinal (or female reproductive) tract. Subsequent peritonitis can lead to diffuse abdominal pain with rebound and guarding, sometimes with referred shoulder pain due to diaphragmatic irritation.

A 67-Year-Old Man Comes to the Emergency Department Due to Progressive