Acute Abdomen and Peritonitis

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Chapter 49 Acute Abdomen and Peritonitis

William E. Charash, MD, PhD , Sarah Pesek, MD

1 What is an acute abdomen?

Any abdominal process that requires urgent (often surgical) intervention. Peritonitis (see question 7) is commonly but not necessarily present. Trauma is generally excluded from discussions of the acute abdomen.

2 What are some causes of acute abdomen that require invasive intervention?

image Perforated hollow viscus (e.g., perforated ulcer, appendicitis, diverticulitis). Perforations that are walled off by the host and not associated with diffuse peritonitis may in certain cases be managed noninvasively.

image Gangrenous hollow viscus, even in the absence of perforation (e.g., mesenteric ischemia, volvulus, complete large bowel obstruction, closed-loop small bowel obstruction, severe acalculous cholecystitis)

image Occlusive mesenteric ischemia, even in the absence of necrosis

image Intraabdominal abscess

image Uncontrolled hemorrhage

image Infected pancreatic necrosis

3 Name some causes of the acute abdomen that are initially treated medically but may ultimately require surgery

image Clostridium difficile colitis (see questions 11-13)

image Abdominal compartment syndrome (see questions 14-17)

image Ogilvie syndrome (see questions 19-20)

image Pancreatitis (see question 28)

image Diverticulitis, small bowel obstruction, inflammatory bowel disease, pelvic inflammatory disease

image Ischemic colitis

image Nonocclusive mesenteric ischemia

4 Which causes of acute abdomen should not require surgery?

Spontaneous bacterial peritonitis (see question 7), gastroenteritis.

5 List thoracic conditions that can cause abdominal pain

Lower lobe pneumonia, pulmonary embolism, pleuritis, empyema, ruptured esophagus, lower rib fractures, pericarditis, and myocardial infarction.

6 How does the initial evaluation of abdominal pain differ in critically ill patients?

The history and physical examination, the mainstay of abdominal evaluation, are often limited because of the patient’s depressed level of consciousness. Nonspecific findings such as unexplained sepsis, hypovolemia, and abdominal distention may suggest an acute abdomen.

7 What is peritonitis?

Inflammation of the peritoneum (visceral and/or parietal). Peritonitis is often accompanied by systemic sepsis. When it occurs spontaneously without any known source of contamination it is termed primary bacterial peritonitis. Secondary bacterial peritonitis originates from visceral pathology or from external sources, such as iatrogenic introduction or penetrating injury.

8 How does peritonitis manifest itself clinically?

As an acute abdomen. Abdominal findings include pain, tenderness, distention, involuntary guarding, or rigidity. Bowel sounds are not typically helpful in this diagnosis but are generally diminished. Other findings are those of systemic infection and may include fever, chills, tachycardia, diaphoresis, tachypnea, oliguria, disorientation, and circulatory collapse. The surface area of the peritoneum is large, roughly the same as the human body (approximately 1.7 m2 for a typical adult). Peritoneal inflammation will generate significant third-space fluid losses and resultant hypovolemia.

9 What laboratory tests are helpful in the setting of abdominal pain?

image A complete blood cell count. An elevated hemoglobin or hematocrit level may suggest third-space fluid losses with hemoconcentration. A low hematocrit may indicate preexisting anemia or active hemorrhage. Elevated white blood cell (WBC) count, especially with left shift, suggests an inflammatory process. A low WBC count may be present if a viral process or gastroenteritis exists, or in the case of overwhelming sepsis.

image Metabolic acidosis on an arterial blood gas level determination, or an elevated lactate level, may indicate an ischemic abdominal process.

image Elevated amylase and/or lipase level may suggest pancreatitis. Amylase may also be elevated with gastric or intestinal pathologic condition.

image Liver function tests may also be helpful.

10 What imaging studies can aid in the diagnosis?

image Oral and intravenous (IV), contrast-enhanced abdominal-pelvic computed tomography (CT) scanning provides the greatest yield. However, this requires a potentially high-risk patient transport. Further, IV contrast might result in contrast-induced nephropathy in a patient already at risk for acute kidney injury. Renal protection with sodium bicarbonate is recommended for high-risk patients.

image Upright (or semiupright) chest radiograph and two-position abdominal radiographs can demonstrate free air (hollow viscus perforation), bowel distention with air, and fluid levels (obstruction).

image Abdominal ultrasound can demonstrate peritoneal fluid collections and acute cholecystitis.

image Angiography or CT-angiography can reveal occlusive vascular disease or active hemorrhage.

11 What causes C. difficile colitis?

Elaboration of toxin A and toxin B by living C. difficile organisms in the colon of the patient. Two conditions are necessary for this to happen. C. difficile, not a component of normal colonic flora, must be iatrogenically introduced into the host. Second, the host’s protective flora must be altered, most typically through the prior use of antibiotics. Both of these factors are within the control of the health care system. Risk factors for severe colitis include age greater than 60 years, residence in a long-term-care facility, gastric acid suppression, severe underlying disease, recent surgery, and immunosuppression.

12 How can C. difficile colitis be prevented?

The two primary approaches to preventing C. difficile infection are preventing exposure and decreasing risk of colitis once exposure has occurred. Clostridia species are spore-forming organisms. These spores are difficult to eradicate. Health care institutions must take great care to reduce the prevalence of these spores in their environment. Contact precautions should be used with patients with clinical symptoms consistent with C. difficile infection even before the results of diagnostic testing are known. Health care workers must wash their hands with soap and water after contact with patients and contaminated surfaces. Healthy gut flora decreases the risk of colitis if exposure occurs. Antibiotics alter this flora and should always be used judiciously.

13 How is C. difficile colitis treated?

The first step is discontinuation of the inciting antibiotic(s) as soon as possible. Antibiotic therapy directed at C. difficile consists of either metronidazole (oral preferred, or IV) or vancomycin (orally and/or rectally). Antimotility agents should not be used. Other therapies that might have benefit include probiotics, fecal transplantation, and IV immunoglobulin. Surgical treatment with colectomy (subtotal colectomy with ileostomy) is indicated for patients with fulminant colitis. Peritoneal signs, failure of improvement with antibiotic therapy, and signs of multiorgan failure all indicate the need for surgery.

14 What is intraabdominal hypertension (IAH)?

Sustained intraabdominal pressure of 12 mm Hg or higher.

15 How is intraabdominal pressure monitored?

Most commonly by transducing the pressure in the urinary bladder via a Foley catheter. Twenty to 50 mL saline solution is instilled into the urinary bladder to ensure a continuous column of fluid. A needle (connected to a pressure transducer) is aseptically placed into the sampling port of the drainage tubing, which is clamped downstream from the port. The pubic symphysis is used as a zero reference. Alternatively, the drainage tubing itself can be used as a manometer. Because urinary specific gravity is approximately 1, the height of the fluid column in centimeters needs to be multiplied by 0.74 to convert to millimeters of mercury. Respiratory variation should be observed in the measured pressure to confirm that pressure is being transduced in the abdomen.

16 What is abdominal compartment syndrome?

Intraabdominal hypertension (typically sustained above 20 mm Hg) with end-organ dysfunction (renal dysfunction, ventilator failure, or intestinal ischemia).

Risk factors include acute abdomen, peritonitis, abdominal surgery, trauma, burns, retroperitoneal bleeding, the systemic inflammatory response syndrome, and overresuscitation with fluids.

17 How is abdominal compartment syndrome managed?

Optimize sedation and analgesia. Avoid overresuscitation with fluids. Neuromuscular blockade may be used, if necessary. Prolonged requirement for neuromuscular blockade should prompt invasive intervention. Percutaneous catheter drainage of intraabdominal fluid may be effective. When a patient’s end-organ dysfunction is refractory to nonoperative management, surgical decompression is warranted. The open abdomen that is created is then typically managed with some form of negative pressure dressing.

18 What is Ogilvie syndrome?

Ogilvie syndrome, also known as acute colonic pseudoobstruction, is a massive dilation of the colon (cecum and right colon, potentially extending to the rectum) in the absence of mechanical obstruction. Although it can occur at any age, it is most prevalent in patients over 60 years of age. Ogilvie syndrome is seen in association with a wide spectrum of illnesses including abdominal or orthopedic surgery, trauma, severe infection, myocardial infarction, heart failure, neurologic disorders, metabolic derangements, and opiate administration.

19 How is Ogilvie syndrome treated?

Treat the underlying medical conditions. Correct fluid and electrolyte imbalances. Minimize use of narcotics and anticholinergics. Administer nothing by mouth (NPO) with nasogastric tube decompression. A rectal tube may also be helpful. Patients should be ambulated, if possible. If no resolution occurs in 48 hours, or if cecal diameter exceeds 10 to 12 cm (see question 27), IV administration of 2.5 mg neostigmine over a 3-minute period may be therapeutic. Repeat once after 30 minutes if necessary. Profound bradycardia and heart block may result. Alternatively, colonoscopic decompression may be performed. Air insufflation must be avoided. Surgery is indicated in cases of actual or imminent perforation or in patients who are unresponsive to maximal nonsurgical measures.

20 How is acalculous cholecystitis managed?

Percutaneous cholecystostomy is appropriate for most critically ill patients. Cholecystectomy (open) should rarely be necessary in the critically ill patient.

21 When should an abdominal abscess be suspected?

When medical management for bacterial peritonitis fails. Also consider abdominal abscess in patients with fever, leukocytosis, and/or sepsis who have had blunt abdominal trauma, are recovering from abdominal surgery, or have unexplained abdominal findings.

22 Describe the management of nonocclusive mesenteric ischemia

The strategy is to increase mesenteric blood flow. This is done by ensuring adequate intravascular volume replacement. Vasopressin and α-adrenergic drugs should be avoided. β-Adrenergic agonism might be required. Surgery is reserved for patients with transmural necrosis or perforation.

23 How is occlusive mesenteric ischemia managed?

Time is of the essence. During the work-up of this diagnosis, the strategy described above for nonocclusive mesenteric ischemia should be employed. Once occlusive mesenteric ischemia is confirmed, emergent intervention is necessary. If bowel gangrene or perforation is suspected, emergent laparotomy with resection of necrotic bowel and restoration of blood flow via embolectomy or mesenteric revascularization should be performed. A second-look laparotomy is often planned at the conclusion of the initial surgery. Percutaneous catheter embolectomy or thrombolysis may be an option when perforation and necrosis are not suspected.

24 Which antibiotics should be used for intraabdominal infections?

Antibiotics with broad-spectrum activity against gram-negative organisms in combination with metronidazole should be used for patients with severe community-acquired intraabdominal infection. It is not generally necessary to cover methicillin-resistant Staphylococcus aureus (MRSA) in these patients. Enterococcus coverage should be reserved for high-risk patients. For infections that are hospital acquired, the regimen should be based on local microbiologic susceptibilities. MRSA and enterococcus coverage is often appropriate. Antifungal therapy might be appropriate. Broad-spectrum regimens should be tailored as culture and sensitivity results become known.

25 What should the duration of antibiotic treatment be?

Discontinue antibiotics once signs of abdominal infection have resolved (e.g., afebrile, benign abdominal examination results, normal WBC count, tolerating enteral feeding). Continued requirement beyond 7 days implies inadequate source control. Imaging to identify intraabdominal abscess should then be performed. Antibiotic treatment for uncomplicated acute appendicitis or gastric or small intestinal perforation should generally be limited to 24 hours.

26 How does the management of small bowel obstruction differ from that of large bowel obstruction?

Partial small bowel obstruction may be managed expectantly with a nasogastric (NG) tube, NPO, and IV fluids. Surgery is indicated if there is a failure to resolve or in the setting of complete or closed-loop obstruction. Large bowel obstruction usually requires more urgent intervention. A competent ileocecal valve will not allow for relief of colonic pressure. The increase in pressure may result in gangrene and/or perforation, particularly of the cecum.

27 What cecal diameter is worrisome for impending perforation?

Acute distention to 12 to 14 cm puts a patient at risk for ischemic necrosis and perforation. According to Laplace’s law, wall tension is proportional to diameter. If the diameter increases acutely, wall tension rises. The increase in wall tension results in a decrease in tissue perfusion. This can result in necrosis and perforation. Chronic distention does not generally result in increased wall tension and is not associated with ischemic necrosis.

28 When should surgery be considered for acute pancreatitis?

Surgical intervention may be required for certain complications of acute pancreatitis such as hemorrhage (from erosion into a blood vessel, or splenic vein thrombosis with spontaneous rupture of the spleen) or necrosis of an adjacent viscus (such as the transverse colon). Open debridement is indicated in the setting of infected pancreatic necrosis. Debridement for necrotizing pancreatitis in the absence of infection is rarely undertaken because of the high morbidity and mortality of operative intervention without compelling evidence of benefit. Abdominal decompression through midline laparotomy or catheter drainage of significant fluid collections may be required if abdominal compartment syndrome develops.

29 How does diagnosis of the acute abdomen differ in immunocompromised patients?

Immunocompromised patients may have the same diseases as immunocompetent patients. However, they may be seen initially only with nonspecific symptoms such as altered mental status and tachycardia. They may lack the classic signs of an acute abdomen because of their blunted immune response. In addition, the differential diagnosis in this patient population should be expanded to include cytomegalovirus infection, opportunistic infections, neutropenic enterocolitis (typhlitis), and drug toxicity.

30 What is the significance of bloody diarrhea after abdominal aortic aneurysm (AAA) repair?

Evacuation of the colon (with or without bloody mucus) in the immediate postoperative period is highly concerning for ischemic colitis. Bedside proctosigmoidoscopy should be immediately performed. Ideally, the surgeon who would intervene operatively should be present. Melena or hematochezia in a patient with a more distant history of AAA repair could signify aortoenteric fistula.

31 When is early surgical consultation warranted?

If reasonable suspicion exists that a patient’s condition will ultimately require surgical management, the surgical service should be consulted, even if surgical intervention is not yet required. A worsening abdominal examination result may signal the need for surgical involvement. An open collaborative relationship between consulting services should be fostered.

Key Points Acute abdomen and peritonitisimage

1. Peritonitis is associated with hypovolemia. This is due to (third space) fluid losses into the inflamed peritoneal membranes, visceral walls, and the free peritoneal space. Circulatory shock may ensue.

2. Prevention of C. difficile infection. Every one of us must take ownership of this nosocomial epidemic! Wash your hands with soap and water!

3. Abdominal compartment syndrome. Consider this diagnosis in all patients with organ failure and abdominal distention.

4. Be sure no mechanical obstruction exists before administering neostigmine in Ogilvie syndrome. Obtain a water-soluble contrast enema first.

5. Cecal diameter in large bowel obstruction or pseudoobstruction. Monitor cecal diameter with serial abdominal radiographs. Acute cecal distention to 12 cm or greater may demand immediate intervention.

Bibliography

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2 Cheatham M.L. Abdominal compartment syndrome. Curr Opin Crit Care. 2009;15:154–162.

3 Chen E.H., Mills A.M. Abdominal pain in special populations. Emerg Med Clin North Am. 2011;29:449–458.

4 De Giorgio R., Knowles C.H. Acute colonic pseudo-obstruction. Br J Surg. 2009;96:229–239.

5 Frossard J.L., Steer M.L., Pastor C.M. Acute pancreatitis. Lancet. 2008;371:143–152.

6 Heinlen L., Ballard J.D. Clostridium difficile infection. Am J Med Sci. 2010;340:247–252.

7 Kolkman J.J., Mensink P.B. Non-occlusive mesenteric ischaemia: a common disorder in gastroenterology and intensive care. Best Pract Res Clin Gastroenterol. 2003;17:457–473.

8 Renner P., Kienle K., Dahlke M.H., et al. Intestinal ischemia: current treatment concepts. Langenbecks Arch Surg. 2011;396:3–11.

9 Solomkin J.S., Mazuski J.E., Bradley J.S., et al. Diagnosis and management of complicated intra-abdominal infection in adults and children: guidelines by the Surgical Infection Society and the Infectious Diseases Society of America. Surg Infect (Larchmt). 2010;11:79–109.

10 Stoker J., van Randen A., Laméris W., et al. Imaging patients with acute abdominal pain. Radiology. 2009;253:31–46.

11 Trevisani G.T., Hyman N.H., Church J.M. Neostigmine: safe and effective treatment for acute colonic pseudo-obstruction. Dis Colon Rectum. 2000;43:599–603.

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