Intestinal Perforation

Etiology

There are ultimately four mechanisms that can lead to a perforation of the intestinal tract.[1]

1. Ischemia (bowel obstruction, necrosis)[2][3]
2. Infection (appendicitis, diverticulitis)[4][5]
3. Erosion (malignancy, ulcerative disease)[6][7]
4. Physical disruption (trauma, iatrogenic injury)[8][9]

Epidemiology

The common causes of a perforated viscus vary by patient age and geography. For instance, the most common cause in premature infants is necrotizing enterocolitis,[10] whereas in children and teenagers, appendicitis is a more common etiology. In adults, there are numerous causes without a particular gender predilection. This article reviews causes in adults in developed countries. 

Pathophysiology

As described above, four main mechanisms can lead to intestinal perforation. A thorough understanding of these mechanisms is critical to guide the appropriate workup and management.

Numerous etiologies can lead to ischemia and perforation. In the case of bowel obstruction (small or large), the physical distention of the bowel wall results in decreased perfusion.[3] This ultimately leads to full thickness wall necrosis and subsequent perforation. Bowel obstruction is more common in patients with a prior history of surgery (adhesions) but can also result from herniation and strangulation, inflammation, tumors, and foreign bodies. Decreased end-organ perfusion secondary to thrombotic or embolic disease can also result in full-thickness ischemia and perforation. As expected, this is more common in older patients, particularly those with a history of smoking, coronary artery disease, or clotting disorders.[11]

The most common infectious causes of perforation are appendicitis and diverticulitis. Appendicitis can be considered at any age, whereas diverticulitis is more common beyond middle age.[5] Both disease processes are usually presumed to be the result of entrapped fecal material in a blind ending structure, leading to increased intraluminal pressure, stasis, and infection leading to a localized abscess or frank perforation. Inflammatory diseases of the bowel, such as Crohn disease and ulcerative colitis can also lead to perforation, especially Crohn's, which is characterized by full thickness inflammation of the bowel wall.[12]

Erosive diseases, such as the local invasion of the wall of a viscus by a tumor or ulcerative disease, can also cause perforation. Stercoral perforation is a rare condition that is increasingly being recognized as a sequela of severe constipation. In peptic ulcer disease, there is direct erosion through the layers of the bowel wall by the ulcer itself, usually due to Helicobacter pylori infection, acid overproduction, or lack of acid protective mechanisms.[6] Tumors of the gastrointestinal (GI) tract are most commonly adenocarcinomas, which arise from the mucosa and, in advanced stages, can result in transmural invasion and perforation.[13]

Mechanical injury to the wall of a hollow viscus can be caused by penetrating or blunt trauma to the abdomen or iatrogenic injury from instrumentation, for example, endoscopy.[8][9][14]

In addition to the mechanism, the variation in bacterial flora between the upper and lower intestinal tract must also be considered. For instance, upper intestinal perforations proximal to the ligament of Trietz result in significantly less bacterial contamination than distal colonic perforations. In the treatment of distal perforations, antibiotics must include gram-negative and anaerobic coverage.[15]

History and Physical

The importance of a thorough history and physical cannot be overstated and is usually sufficient to ascertain the etiology of the perforation. Almost all patients experience some element of abdominal pain, and this is usually accompanied by nausea, vomiting, decreased bowel function, or fever. Details about the symptoms including the length of time, prior episodes, recent procedures such as ERCP and colonoscopy,[16][17] and exacerbating and relieving factors can be crucial in determining the cause of the perforation. A family history of cancer and a personal history of colonoscopy can be important to determine the likelihood of occult cancer or inflammatory bowel disease.

At the time of the initial evaluation, vital signs should be promptly assessed. These can show signs of SIRS or septic shock, and an urgent need for resuscitation and treatment may be warranted. On physical examination, it is important to visually inspect the abdomen for surgical scars, visible hernias or injuries, and distension. Palpation of the abdomen usually elicits discomfort and may yield peritoneal signs which are commonly present with perforation, peritonitis, or localized abscess.

Evaluation

There are multiple imaging modalities and laboratory tests that can be useful to identify the presence and etiology of a hollow viscus perforation. Abdominal and upright chest x-rays are quick and cheap and can identify even small amounts of pneumoperitoneum. Evidence of small and large bowel obstructions can also be visualized. CT of the abdomen and pelvis, however, is the most sensitive and specific test to diagnose a perforation and ascertain the most likely etiology.[18] Disease processes such as diverticulitis, appendicitis, and bowel obstructions can be readily identified on CT. The use of intravenous contrast is recommended to aid in visualizing potential areas of ischemia. Complications from a perforation such as an abscess and secondary bowel obstruction can also be identified with CT and guide management accordingly.

In children, the preferred primary test is ultrasound given its ease and lack of radiation exposure. If necessary, secondary testing such as x-ray, MRI, and CT are reasonable options.[19]

Treatment / Management

Once the initial assessment is complete and an intestinal perforation is suspected, management can ensue. Many, but not all causes of perforated viscus, require surgery. However, all cases should be evaluated by a surgeon.[1] For both operative and nonoperative patients, initial treatment includes bowel rest, intravenous fluids, intravenous broad-spectrum antibiotics, and frequent abdominal examinations. Instances that are accompanied by sepsis and peritonitis are more likely to require surgery, whereas those that do not may amenable to conservative management.[20][21] Contained or controlled perforations can be managed conservatively with interventional radiology guided drainage of fluid collections.[22] However, the failure of conservative management with persistence of symptoms and/or development of sepsis necessitate surgical intervention. Historically, laparotomy has been the intervention of choice for acute abdomen; recently, however, laparoscopic exploration has emerged as a viable option to identify and treat the source of perforation.[23] Resection or repair of the perforated site with or without drainage and diversion is usually undertaken. Duodenal perforations, on the other hand, are generally treated with omental patch repair without resection. Risks and benefits of surgery, particularly amongst elderly patient and those with medical comorbidities, should be thoroughly discussed before offering surgical intervention.[24]

Differential Diagnosis

The differential diagnosis for the location of intestinal perforation can be narrowed down based on several factors. A thorough history and physical taking can help to diagnosis acute and chronic onsets of disease and likely location of the perforation. Importantly, being able to narrow down the likely location of the perforation along the intestinal tract helps to narrow down the intervention.

Upper GI perforation (stomach and duodenum) is most commonly caused by peptic ulcer disease with severe epigastric or back pain, with acute onset. Sometimes there are chronic symptoms leading up to the perforation event, such as dyspepsia, bloating, nausea, and early satiety.[6] Less commonly, malignancy or traumatic perforation are possibilities. Imaging usually shows upper abdominal free air and possible leakage of contents into the peritoneal cavity. Usage of oral contrast can be seen extravasating soon after ingestion. Acute onset of periumbilical pain, nausea, vomiting, and decreased bowel function are symptoms of bowel obstruction. Imaging suggesting free intraperitoneal air with dilated small or large bowel can signify this as a source of perforation. Presence of an incarcerated hernia, history of abdominal surgery, or findings of intussusception on imaging sometimes is present in these cases.[25]

Colonic perforation should be considered with a history of left lower quadrant or history of diverticulitis also usually with decreased stool output. Malignancy is a consideration also, especially with lack of endoscopy screening history. Imaging typically shows free air located near the area of perforation with possible abscess formation present due to the leakage of stool into the peritoneal cavity.[5] Rarely, free intraperitoneal air can be caused by benign pneumatosis intestinalis unrelated to ischemia and can be managed without surgical intervention.[26]

Prognosis

Short- and long-term prognoses of a patient with bowel perforation depend on multiple factors. For instance, age, medical comorbidities, benign or malignant cause, and tolerance to treatment are important considerations when discussing prognosis. Since surgery is commonly necessary, patients who are unable to tolerate or choose not to undergo surgery when it is required may have a worse prognosis.[27] Morbidity can also be quite high, including delayed intraabdominal infection risk and hernia formation from surgical healing. Thromboembolism and cardiopulmonary complications are higher in older patient populations, as well as a worsened quality of life. These factors must be discussed candidly with patients and families before surgery, in the elderly especially, to determine their expectations and desires.[28]

Complications

Complications caused by an intestinal perforation can be related to the disease process that caused it or the treatments that are enlisted. Perforation and subsequent leakage of intestinal contents can lead to peritonitis and eventually sepsis if left untreated. Adequate resuscitation and antibiotic initiation early on are important to decrease the physiologic detriment of the infection.

If necessary for control of leakage, surgery can be undertaken, and it is important to discuss potential complications of surgery with patients and their families. Risks of infection, bleeding, potential anastomotic leakage, hernia formation exist. Other risks of pulmonary complications, thromboembolic events, cardiovascular events, and possible prolonged need for ventilator support must also be discussed as well as expected recovery and possible level of function.