Diagnosis

As with every patient admitted to the ICU, early diagnosis is of vital importance. The history and clinical picture can provide important clues. Recent diagnostic and therapeutic interventions such as colonoscopy, endoscopic retrograde cholangiopancreatography, or abdominal surgery will clearly direct the search for the cause of the illness.

Signs on physical examination depend largely on the site of the perforation. Subcutaneous emphysema in the neck region can be the result of an esophageal perforation, but has also been reported after duodenal, gastric, or large bowel perforation. Absent liver dullness on abdominal percussion is a classical sign of intra-abdominal air. Absence of bowel sounds is indicative of peritonitis accompanying bowel perforation, but can also be the result of a general severe illness (multiple organ failure) or the use of sedatives and analgesic medication. Further signs of peritonitis are usually difficult to interpret in the typical ICU patient, who is usually too sick or sedated to be able to respond to percussion and palpation of the abdomen or is on artificial ventilation. Moreover, these patients are often on medications (corticosteroids, non-steroidal anti-inflammatory drugs, chemotherapy) that will suppress many of the important clinical symptoms.

Blood chemistry and hematology are of limited value in the diagnosis of a perforated viscus. However, a markedly elevated serum alkaline phosphatase may be the only discriminating finding indicating gallbladder perforation ( Madl„§.L§L 1992).

Valuable information can be gained from the use of radiological diagnostic tools. Simple radiography of the thorax can reveal a pneumomediastinum in the case of esophageal perforation with or without mediastinitis. Free abdominal air on a plain abdominal radiograph is often proof of a perforation of a peptic ulcer in either stomach or duodenum or of a perforated small or large bowel. However, free air cannot be visualized in 30 to 50 per cent of patients with a perforated peptic ulcer, in

70 per cent with a perforated small bowel, and in 63 per cent with a perforated large bowel (Winek. ..eta/ 1988). Conversely, in patients with blunt abdominal trauma, intra-abdominal air can be present without a perforated viscus ( Hamilton..etal 1995). CT scanning is of value in detecting the cause of an intra-abdominal catastrophe, particularly when abscesses that can be treated by percutaneous drainage are suspected. However, the patient must be relatively stable to be able to withstand transportation to the radiology department. Suboptimal monitoring during CT scanning should also be taken into account. In postsurgical patients, oral (water-soluble) contrast or a rectal contrast enema may enhance the possibility of detecting an anastomotic leakage. A fluid collection surrounding a thick-walled gallbladder suggests perforation of this organ. The value of CT scanning in the detection of a perforated viscus in trauma patients is still under debate ( .H.§.mjltg.n.„..§Lal... 1995), but intraperitoneal fluid of unknown origin, retroperitoneal, mesenteric, or intramural air, or a pneumoperitoneum may provide important information.

Ultrasound is another valuable tool in the diagnosis of intra-abdominal pathology. Its advantage is the possibility of examining the patient in the ICU. Drawbacks are the investigator-dependent reliability and technical limitations (e.g. air interposition). Ultrasound is still the first choice for detection of intra-abdominal fluid collections or gallbladder abnormalities.

In certain circumstances more invasive techniques may be appropriate. Peritoneal lavage can be used to exclude bowel perforation in patients with blunt abdominal trauma (Wisner —■■.§.[ 1990). Laparoscopy in experienced hands may detect a perforated viscus, with the advantage of potential laparoscopic repair (e.g. perforated peptic ulcer).

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