Chest Pain and Intermittent Diarrhea andHematochezia in an Older Man

A 68-year-old man with severe emphysema complains ofchest pain that began that morning. He has also had intermittentdiarrhea and occasional blood in his stool for thepast 2 weeks.Three years earlier, he underwent coronary arterybypass surgery for 3-vessel disease; a small infarct in the anteriorleft ventricular wall was detected during the operation.He has smoked 2 packs of cigarettes a day for the last 25years, and he drinks alcohol frequently--especially duringdifficult times, such as the recent death of his wife.The patient is pale and thin. Temperature is 37.2^oC(99^oF); heart rate, 112 beats per minute with normalrhythm; respiration rate, 19 breaths per minute; and bloodpressure, 105/65 mm Hg. Head and neck are normal.Chest is barrel-shaped and air exchange is poor; however, nocrackles or rales are audible. Abdomen is soft, with normalbowel sounds; the upper abdomen is mildly and diffuselytender. There is no evidence of organomegaly. Extremitiesare normal.Hematocrit is 28%. An ECG reveals Q waves in theanterior leads but is otherwise normal. An abdominal radiographshows no abnormalities.Fluid resuscitation is started, and the patient is placedon bowel rest with nothing to eat. That evening he has diarrheain which small amounts of blood are visible. A nasogastrictube is placed with the tip in the stomach; aspirationreveals no blood.To determine the source of the patient's GI bleeding,which diagnostic test would you order--and why?WHICH TEST--AND WHY: Nuclear medicine procedurescan be of great benefit in the evaluation of active bleeding.When used before endoscopy or other more invasivetests, they can increase the sensitivity of such tests for theidentification of a bleeding source byhelping to localize the site of the hemorrhage.They also confirm activebleeding.The most frequently used nuclearmedicine study in this setting isa technetium-labeled red blood cell(RBC) scan. Its advantages are:

• Extreme sensitivity for hemorrhage(bleeding rates as low as 0.1 mL/mincan be detected).
• Well-labeled RBCs can be used forup to 24 hours after injection (whichis helpful in cases of intermittenthemorrhage).

Among the disadvantages of thisscan:

• It can take several hours to labelthe patient's RBCs (the exact time requireddepends on the expertise ofthe nuclear medicine department).
• Imaging times can be quite prolonged(they often last several hoursfollowing injection, and images may beobtained intermittently for 24 hours).

A technetium sulfur colloid scancan also be used to evaluate occultbleeding. An important advantage ofthis scan is that the tracer used requires minimal preparation before it can be injected.Thus, this study can be extremely useful in an acutely illpatient who is actively hemorrhaging and in whom immediatelocalization of a bleeding site is required before anemergent procedure, such as angiography or endoscopy.Disadvantages of this technique are:

• Obscuration of the hepatic and splenic flexure of thecolon secondary to uptake in the liver and the spleen,respectively.
• Clearance of activity from the blood pool within 15 minutesof injection, which limits the time during which hemorrhagecan be observed.

Here, the intermittent nature of the patient's GIsymptoms makes the

technetium-labeled RBC scan

themore appropriate of these 2 studies.On the RBC scan, a focal area of increased activitythat appears within the bowel and becomes larger overtime constitutes a positive result. In addition, the area ofincreased activity should move with peristalsis (both antegradeand retrograde). Such movement is typically moreeasily appreciated in a cine format, in which the study isviewed as a "movie." Subtle, smaller areas of hemorrhageare also more easily appreciated in this format.

What this scan shows.

A planar image obtainedimmediately after the labeled RBCs were administereddemonstrates the patient's blood pool and serves as a baselineimage (

Figure 1

). Another planar image, obtained 14minutes later (

Figure 2

), reveals a "blush" of activity withinthe upper abdomen in the midline that was not visibleon the baseline image. A subsequent planar image showsactivity in the upper abdomen in the distribution of thecolon (

Figure 3

). Additional images show this activitymoving along the course of the colon and on to therectum.The midtransverse colon was identified as the locationof hemorrhage. Angiography failed to show the bleedingsite. Vasopressin therapy was administered, followed byendoscopy, which revealed a dilated vessel that extendedto the bowel lumen in the midtransverse colon and wasconsistent with an arteriovenous malformation. The patientunderwent electrocautery of the vessel.For 2 days following the procedure, no bleedingepisodes were noted and tests for occult blood were negative.The patient was subsequently discharged.