Special Considerations

THE ELDERLY ABDOMEN In a large combined series of >40,000 patients presenting with acute abdominal pain (<1 week duration), about one patient in four was >50 years old. Diagnostic accuracy in this group fell below 50 percent, reaching a low of about 30 percent in octogenarians, whose corresponding mortality was about 70 times that of patients <30 years old.16

Reasons for Increased Diagnostic Error in the Evaluation of the Elderly Abdomen DIFFERENT PREVALENCE OF DISEASE The causes of abdominal pain in elderly patients occur with a substantially different frequency than in younger persons, requiring that the emergency physician approach older patients with a different weighting of prior probabilities than those in younger adults. For example, as shown in IabJ.e.68-2, the most common cause of abdominal pain in virtually all consecutive series of adults presenting to the ED is NSAP.16 When ED patients are dichotomized by age at 50 years, NSAP remains at the top of the list of diagnoses among the younger cohort; however, among the older patients, prevalence is markedly diminished to <20 percent, as shown in IabJ.e.68-3.34

DIFFERENT KINDS OF DISEASE Another explanation for the increased error and mortality in elderly abdominal pain is that, in addition to an age-related shift in the frequency of certain diseases, there are a number of serious causes of abdominal pain that only rarely arise among younger patients. Specifically, older patients are at risk for vascular causes of abdominal pain—e.g., mesenteric ischemia, AAA, and myocardial infarction. 1 34

DIFFERENT EVOLUTION OF DISEASE Among common causes of abdominal pain in both young and old, the nature of the presentation and evolution of the same illness is often very different. Using appendicitis as the most common example, those >50 years of age are much more likely to have generalized pain and tenderness (about 14 percent) than are younger patients (about 2 percent).12 This failure to localize to an area of maximum pain/tenderness may help to account for the nearly 10-fold difference in perforation rate (4 versus 37 percent) in those >60 years of age as compared with their younger counterparts. Later presentation in the course of illness may also contribute to the increased perforation rate (75 percent of the elderly with appendicitis have >24 h of symptoms before seeking care), as may the higher frequency of distention in older patients, making the physical examination more difficult.

DIFFERENT THRESHOLD FOR INTERVENTION An additional contributor to the high incidence of perforation in all causes of elderly abdominal pain is the understandable reluctance to operate upon frail elderly patients without clear-cut signs of peritoneal irritation. This is reflected in the well-established inverse association between negative laparotomies and perforated appendices. At about the age of 45 years, the negative laparotomy rate begins to decrease in parallel with the increase in perforations until each plateaus at about 80 years. 16 Thus, the negative laparotomy rate for appendicitis is lowest in the oldest, who are the group most likely to perforate and therefore most in need of early, expedient surgery.

General Strategies for Evaluation of the Elderly Abdomen ANTICIPATE THE NEED FOR SURGICAL INTERVENTION Assume that the elderly patient with abdominal pain has surgical disease. About 40 percent of all patients >65 years of age presenting to the ED with this complaint ultimately require surgery.

ABDOMINAL AORTIC ANEURYSM Apparent renal colic is an abdominal aortic aneurysm (AAA) until proven otherwise. Do not be misled by the presence of hematuria.

MESENTERIC ISCHEMIA Consider the diagnosis of mesenteric ischemia in all elderly patients with abdominal pain, especially if the pain appears out of proportion to tenderness. The presence of atrial fibrillation, cardiovascular or peripheral vascular disease, especially recent MI, increases the likelihood of mesenteric ischemia. Bloody diarrhea will not be seen until mucosa begins to slough and is far more common in ischemic colitis, which is a relatively benign disease in comparison with mesenteric ischemia.

IMAGING Be liberal with imaging in the elderly who have abdominal pain of unclear etiology. If there is a serious question about important underlying abdominal disease in the setting of a relatively "well-looking" elderly patient, one should have a low threshold for performing an abdominal CT.

GASTROENTERITIS Attributing vomiting or diarrhea in the elderly to gastroenteritis is inadvisable, particularly in association with abdominal pain.

CONSTIPATION Because the prevalence of constipation is so high in the elderly, it is a risky explanation for abdominal pain of sufficient severity to bring an older person to an ED. As a corollary to this, apparent resolution of abdominal pain in the elderly with an enema (which is itself a questionable intervention) should not be taken as evidence of a causal relationship between constipation and abdominal pain.

HIV/AIDS There are several features of patients with HIV and/or acquired immunodeficiency syndrome (AIDS) presenting to the ED with abdominal pain that merit special attention.35 Abdominal pain is rarely the index event that identifies a patient with HIV disease. Rather, most patients presenting with HIV-associated acute abdominal pain will have previously met criteria for AIDS.

Enterocolitis is the most common cause of abdominal pain in AIDS patients. It is typically accompanied by profuse diarrhea and dehydration. If associated with fecal leukocytes, it is more often accompanied by bacteremia than in immunocompetent patients. Perforation, when it occurs, tends to be large bowel perforation, often caused by Cytomegalovirus (CMV).35 Obstruction presents typically but may be due to an atypical cause such as Kaposi's sarcoma, lymphoma, or atypical mycobacteria.

Biliary tract disease is very common in AIDS patients, presenting in one of two unique forms: (1) AIDS-related cholangiopathy, caused principally by CMV or Cryptosporidium sp., which can be treated with sphincterotomy, and (2) AIDS-associated cholecystitis, which is usually acalculous and has a propensity for early perforation.

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