History. Many aspects of either critical illness or the ICU environment make obtaining accurate data from the historical examination difficult. Comorbidities, such as dementia or delirium consequent to the admission diagnosis (e.g., traumatic brain injury or sepsis), are common. In fact, 70% or more of ICU patients experience delirium during their ICU course. Many interventions (e.g., mechanical ventilation, surgery) and pathology (e.g., orthopedic trauma, traumatic brain injury) necessitate sedation, narcotic analgesics, or paralysis in the course of treatment.

Acknowledging these limitations during an exhaustive attempt to acquire all historical data is essential. If feasible, temporarily discontinuing any sedating agent may enable an objective examination. For the alert patient, a pen and pad or electronic tablet may facilitate communication. Although tedious and conveying small volumes of data, any information may prove decisive for either continued observation or surgical exploration. The ICU nurse, present continuously at the patient bedside, is an invaluable source of information. All available family members, prior caregivers, or other close associates should be interviewed for any salient information that might facilitate a diagnosis (Table 45-1).

Questions to be posed are similar for all patients undergoing surgical evaluation of the acute abdomen. The aspects prompting a surgical evaluation are critically important: Right upper quadrant pain versus cardiovascular collapse. Is this the primary impetus for admission, or did it develop during the treatment of other pathology? A thorough understanding of past medical and surgical issues establishes the context in which to interpret the current signs and symptoms and generate a priority list of the risks of particular surgical diseases. It is here that the time invested in interviewing family members is rewarded. Determination of the duration of the

signs or symptoms that prompted the evaluation indicates the acuity of the process, as it relates to rapidity with which a diagnosis needs to be made and definitive treatment instituted. The details of the abdominal pain are important: Time of onset and aspects of duration, intensity, location, radiation, nature, exacerbating and mitigating circumstances if available. The gastrointestinal review of systems may generate useful data: Intolerance of tube feeds, nausea, emesis, hematemesis, melena, or hematochezia. Compromise of other subsystems, including the development of renal failure, acute lung injury, or hemodynamic instability, should raise concern of a catastrophic intra-abdominal process.

Finally, if time permits, identifying the medical decision-maker for this patient and advanced directives can simplify the decision process and ensure that the process of care achieves the patient’s wishes. These discussions should include aspects of quality and function of life in addition to those of life and death. However, emergency intervention should never be delayed awaiting informed consent.

Physical examination. Many of the conditions hindering a historical examination render the abdominal examination unreliable: Altered level of consciousness, either iatrogenic (e.g., narcotics) or because of concomitant pathology (e.g., stroke, trauma). Hence, there is a lack of sensitivity for subtle findings, and even signs of abdominal catastrophe may be obfuscated. Medications such as steroids and immunosuppressants may mask the signs of peritoneal irritation. In this context, alternate endpoints and surrogate markers of tenderness (facial grimacing and localization) are utilized, though this compromises specificity. Physiologic changes such as tachycardia or hypertension during the examination may also serve as surrogate markers of tenderness.

The physical evaluation commences with a review of vital signs: Heart rate, blood pressure, and urine output (Table 45-1). The frequency with which physiologic and biochemical data are recorded enables trends in these parameters to be tracked, which can elucidate the temporal sequence of events. For example, the detailed records can be reviewed to assess when oliguria ensured, when the ventilatory requirements increased, or when vasopressors were instituted. The combination of these data, lends insight into whether this process is acute, subacute, or has taken place over a period of hours or days.

A thorough abdominal examination should follow. The presence and location of abdominal scars should be noted and correlated with the details of the past surgical history. The presence, character, and location of tenderness should be elicited. Temporally related events (e.g., cardiac catheterization, ruptured abdominal aneurysms) and precipitating or alleviating factors (e.g., movement, meals, emesis) may narrow the differential (e.g., mesenteric ischemia, biliary colic). Peritonitis, in particular involuntary guarding, is suggestive of surgical pathology. Distension and tympany, although non-specific, suggest obstruction or ileus. A rectal examination should be performed to check for masses, distal passage of stool and presence of blood. Melena or hematochezia suggest mucosal injury (e.g., ischemia). The nature and volume of nasogastric aspirate (e.g., bloody vs. bilious) may provide insight. Hernias should be identified and characterized as reducible, incarcerated, or strangulated.

Extra-abdominal findings may provide additional corroboration of a particular diagnosis. Signs of peripheral vascular disease support a diagnosis of mesenteric ischemia/infarction. The lacelike livedo reticularis is an uncommon sign seen in cholesterol embolism, as might occur after cardiac catheterization. Similarly, atrial fibrillation may underlie distal embolization to the mesenteric circulation and bowel infarction. Alternatively, the absence of particular signs (e.g., scaphoid abdomen, absence of distension, and emesis) may reasonably exclude specific pathology.

Laboratory. Attempt to tailor labs specific to the differential diagnosis, although the paucity of historical and physical data usually translate into the acquisition of a broad amount of biochemical data: A complete blood count (CBC) with cell differential, electrolytes, liver function tests, amylase, lipase, urinalysis, arterial blood gas with lactate (Table 45-1).

Leukocytosis, a sign of inflammation, may be suggestive of an abdominal problem. However, its absence does not exclude surgical abdominal disease. Indeed, in a cohort of elderly patients (>80 years), fever and leukocytosis were absent in 33% of cases of acute surgical disease. In the absence of leukocytosis or leukopenia, a significant “left shift” (a large proportion of neutrophils or immature band forms) may be indicative of acute intra-abdominal pathology.