Mr. T is a 66-year-old man who arrives at the emergency department with bloody stools and dizziness. His symptoms started 2 hours ago.
|What is the differential diagnosis of GI bleeding. How would you frame the differential?|
The approach to GI bleeding is similar to the approach to other potentially life-threatening illnesses. Patient stabilization, specifically, hemodynamic stabilization is the first step in management. In a patient with GI bleeding, management precedes diagnosis, usually made by colonoscopy or esophagogastroduodenoscopy (EGD).
Initial management takes a very regimented course. The patient must be hemodynamically stabilized, preparation must be made in case of further bleeding, and initial diagnostic tests must be completed.
Clinically assess volume status.
Signs of shock may be seen with 30–40% volume depletion.
Orthostasis can be seen with 20–25% volume depletion.
Tachycardia may be present with 15% volume depletion.
Calculate necessary replacement (weight in kg × 0.6 (lean body weight made up of water) × % volume depletion).
Replace fluid losses initially with normal saline or Ringers solution.
Administer typed (or O−) blood if there has been a large degree of blood loss.
Preparation for further bleeding
All patients should have their blood typed and be cross-matched for at least 2 units.
Patients may initially have normal Hcts that drop only with fluid replacement.
It is common for a patient with a significant GI bleed to have a normal Hct at presentation.
Remember that the physical exam is insensitive for anemia (see Chapter 6, Anemia).
Two large bore IVs
IVs should be 16 gauge or greater.
Flow = ΔP (πr4/8μ) where ΔP is the pressure differential, r is the radius of the IV, μ is the viscosity of the fluid, and L is the length of the IV.
Flow can therefore be maximized by
Increasing the pressure behind the fluid being infused (squeezing the bag).
Decreasing the length of the IV.
Increasing the gauge of the IV (the most effective as the flow goes up by the fourth power of any increase).
Large gauge IVs (16 and larger) are much more effective than central lines for volume resuscitation.
Always make sure your patient has 2 usable large bore IVs, so you do not have to worry about IV access should life-threatening bleeding develop.
In large bleeds, a Foley catheter can help monitor fluid status.
Initial diagnostic tests
CBC and platelet count
Basic metabolic panel (chem-7)
Liver function tests (LFTs) (Abnormal LFTs raise the risk of underlying severe liver disease and thus coagulopathy and varices.)
Prothrombin time and partial thromboplastin time
Upright chest radiograph
Can diagnose perforated viscus
May provide clues to other diagnoses
Possibly nasogastric (NG) tube placement, which may help localize the source and acuity of blood loss
The differential diagnosis of GI bleeding is based on an anatomic framework. Upper GI bleeds originate proximal to the ligament of Treitz, while lower GI bleeds are distal and primarily colonic. The causes of upper and lower GI bleeding are arranged in the approximate order of frequency. Bleeding from a small bowel source is less common. The last category is anorectal bleeding. These are generally smaller bleeds with limited potential to cause hemodynamic instability.
Upper GI bleeds
Peptic ulcer disease
Lower GI bleeds
Malignancy or polyp
Less common small bowel sources
Mr. T was well until this morning. Abdominal cramping developed while he was eating breakfast. He did not have nausea. He went to the bathroom and passed a large bowel movement of stool mixed with blood. Afterward, he felt better and went to lie down. About 30 minutes later, he had the same sensation and this time passed what he described as “about a pint” of bright red blood. While getting up from the toilet, he became dizzy and had to sit on the bathroom floor for 15 minutes before he could crawl to the phone to dial 911.
|At this point, what is the leading hypothesis, what are the active alternatives, and is there a must not miss diagnosis? Given this differential diagnosis, what tests should be ordered?|
The lack of nausea, vomiting, or abdominal pain, and the presence of bright red blood per rectum are pivotal points in this case and make a lower GI source most likely. Cramping is often seen with GI bleeds, caused by blood passing through the bowel. The volume of blood makes hemorrhoids or fissures unlikely, so bleeding from diverticuli, colitis, malignancy, or angiodysplasia have to be considered most likely. Whether he has had recent change in bowel habits, weight loss, or previous bloody stools is unknown; all these factors would heighten suspicion for colitis or malignancy. Upper sources of bleeding must also be considered. A brisk bleed from an upper source can present with bright red blood per rectum. Assuming there is no history of liver disease, peptic ulcer disease would be the most likely cause. Table 17–1 lists the differential diagnosis.
|Blood is a cathartic. A brisk bleed from an upper source can present with bright red blood per rectum.|
Table 17–1. Diagnostic Hypotheses for Mr. T.
| Save Table
Table 17–1. Diagnostic Hypotheses for Mr. T.
|Diagnostic Hypotheses||Clinical Clues||Important Tests|
Brisk self-limited bleeds
History of diverticuli
Brisk lower GI bleeds
More common with end-stage renal disease
|Colonoscopy or small bowel endoscopy|
|Peptic ulcer disease|
May present with epigastric pain or weight loss
|Active Alternative—Must Not Miss|
|Colon cancer||History of anemia or changing ...|
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