•:• CASE 10

A 67-year-old man presented to the emergency department with a 6-hour history of bleeding per rectum. The patient’s symptoms began after he developed an urge to defecate that was followed by several voluminous bowel movements containing maroon-colored stool mixed with blood clots. The patient complains of feeling light-headed just prior to arriving at the hospital but denies any abdominal pain. His past medical history is significant for borderline hypertension managed with diet control. His surgical history is significant for a right inguinal hernia repair 2 years ago. His blood pressure is 100/80, pulse rate I 10/mm, and respiratory rate 20/mm. The results of an examination of his abdomen are unremarkable. The rectal examination revealed no masses and a large amount of maroon-colored stool in the rectal vault.

• What should be your next step?

• What is the most likely diagnosis?

• How would you confirm this diagnosis?

ANSWERS TO CASE 10: Lower Gastrointestinal Tract Hemorrhage

Swnmary: A 67-year-old man presents with acute lower gastrointestinal tract hemorrhage. The patient’s symptoms and vital signs indicate a significant acute hemorrhage.

• Next step: The patient’s presentation is highly suggestive of

hypovolemic shock: therefore, the initial treatment should consist of volume resuscitation with isotonic crystalloid solution and close

monitoring of his response to resuscitation.

• Most likely diagnosis: Acute lower GI tract hemorrhage.

• How to confirm the diagnosis: Place a nasogastric (NG) tube to

sample the upper Gl tract contents; the possibility of gastric bleeding can be eliminated if nonbloody, bilious material is recovered.

Esophagogastroduodenoscopy (EGD) is the definitive method of

evaluation to rule out a duodenal source of bleeding.

Analysis

Objectives

I. Be able to differentiate the clinical presentations of occult and acute anorectal, nonanorectal lower GI tract, and upper GI tract bleeding.

2. Learn a diagnostic and therapeutic approach to lower GI tract bleeding.

Considerations

The passage of maroon-colored stool and blood clots generally indicates acute bleeding from a lower GI tract source (distal to the ligament of Treitz). Maroon- colored stool represents a mixture of fecal material and blood, indicating that the bleeding source is located proximal to the lower rectal segment and anus. The passage of blood clots can occur with brisk bleeding from an upper GI tract source. Placenwnt of an NC tube is useful during the initial evaluation for possible upper CI tract bleeding, although up to 16% of patients may have nonbloody NG aspirate with upper GI tract bleeding originating from the duodenum. In patients older than 40 years. the most likely causes of acute lower GI tract bleeding are diverticulosis, angiodysplasia, and neoplasm, and these lesions are generally painless. When lower Gl tract bleeding occurs in the presence of abdominal pain, the possibility of an ischeniic bowel, inflammatory bowel disease. intussusception, and a ruptured abdominal aneurysm should be entertained. Following resuscitation, the primary goal in the treatment of a patient with acute and continued lower CI tract bleeding is localization of the bleeding site (colonoscopy. mesenteric angiography. and/or an isotope-labeled red blood cell I RBCI scan).

APPROACH TO LOWER GI TRACT BLEEDING

Definitions

Occult GI tract bleeding: Slow bleeding originating anywhere along the upper aerodigestive or lower GI tract, most commonly associated with neoplasm, gastritis. and esophagitis. Patients generally do not report bleeding and commonly present with iron-deficiency anemia, fatigue. and Hemoccult-positive stool.

Overt lower 61 tract bleeding: Hematochezia or melena. The most common causes in children and adolescents are Meckel’s diverticulum, inflammatory bowel disease, and polyps. In adults aged 20 to 60 years, the most common causes are diverticulosis, neoplasm, and inflammatory bowel disease. In older adults >60 years, the most common causes are diverticulosis, angiodysplasia, and neoplasm.

Tagged RBC scan: Nuclear medicine imaging using RBCs labeled with technetium-99m. This technique is highly sensitive in identifying active bleeding at a rate of 0.1 mL/min or greater; however, the images obtained may not localize the GI tract bleeding site accurately. Some recommend this imaging modality as an initial screening study before performing mesenteric angiography.

Mesenteric angiography: Selective angiography of the superior and infe nor mesentery arteries can help identify bleeding from the midgut and hindgut. This procedure has greater specificity in localizing the bleeding site than a tagged RBC scan. Selective injection of vasopressin or gel foam can be applied to treat active bleeding in patients who are not suitable surgical candidates. The bleeding generally has to be >0.5—1.0 mL/min to be visualized by angiography.

Rigid proctosigmoidoscopy: A simple bedside procedure in which a non- flexible endoscope is used to visualize the most distal 25-cm segment of the lower GI tract.

Diagnostic colonoscopy: Flexible fiberoptic endoscopy that evaluates the entire colon and rectum and is reserved for hemodynamically stable patients. The reported success rate in identifying the bleeding source and site is as high as 75%, but this figure is highly variable depending on the operator and the timing. The advantages of this procedure are that it can rule out the possibility of a colorectal bleeding source and that identified bleeding angiodysplasia can be treated with epinephrine injection or coagulation.

Angiodysplasia: Also known as vascular ectasia. a common degenerative vascular lesion characterized by small, dilated, thin-walled veins in the mucosa of the GI tract. It occurs most commonly in the cecum and ascending colon of people older than 50 years. Approximately 50% of patients have associated cardiac disease. Up to 25% of patients with angiodysplasia have aortic stenosis. Most patients with angiodysplasia present with low-grade, self-limiting bleeding. although approximately 15% present with massive bleeding.

Clinical Approach

A patient presenting with overt lower GI tract bleeding should be quickly assessed for intravascular volume status and hemodynamic stability. A detailed history is important. The identification of coexisting medical problems may help identify patients whose bleeding is the result of coagulopathy or thrombocytopenia (medical causes of bleeding). If the patient has had a previous abdominal vascular reconstruction, the possibility of an aortoenteric fistula must be strongly considered and ruled out. The history elicited should include details regarding the quality and appearance of the bleeding. Melena (tarry stool) indicates the degradation of hemoglobin by bacteria and forms after blood has remained in the GI tract for >14 hours. Melena is usually associated with upper GI tract or small bowel bleeding hut can occur with bleeding from the ascending colon. The passage of maroon-colored stools generally excludes a possible bleeding source in the rectum and anus. Bleeding from the rectum is usually characterized by the passage of formed stools streaked with blood or the passage of fresh blood at the end of a normal bowel movement. Most episodes of overt lower Gl tract bleeding resolve spontaneously without specific therapy. It is important to rule out GI tract neoplasm as the source of bleeding in patients whose bleeding resolves. Patients whose bleeding creates adverse hernodynamic consequences or necessitates blood transfusion should undergo prompt evaluation to localize the source of bleeding so that operative excision can be accomplished. (See Figure 10—1 for management strategy.)

Comprehension Questions

[10.1] A 75-year-old man develops hematochezia and presents with hemodynamic instability. The patient’s vital signs improve slightly with crystalloid and packed red cells infusion. Which of the following is considered the most appropriate next step(s) in management?

A. EGD. proctosigmoidoscopy, and a barium enema

B. NG tube. proctosigmoidoscopy. and a tagged RBC scan with or without mesentery angiography.

C. NG tube. inesentery angiography, and colonoscopy

D. EGD and colonoscopy

10.21 Which of the following conditions is almost always associated with painless hematochezia?

A. Aortoenteric listula developing I year after an abdominal aortic aneurysm repair

B. Ischemic colitis involving the descending colon

C. Bleeding duodenal ulcer

D. Superior mesentery artery embolus

110.31 Which of the following diagnostic modalities has the greatest specificity in identifying the source of lower GI tract bleeding?

A. Tagged RBC scan

B. Barium enema

C. Colonoscopy

D. Surgical exploration

Answers

110.11 B. NG tube. proctosigmoidoscopy. and a tagged RBC scan are most appropriate for a patient who is unstable.

[10.2] A. Aortoenteric fistula following aortic reconstruction is nearly always associated with painless hematochezia.

110.31 C. Colonoscopy has the highest specificity in identifying the source of lower GI tract bleeding (ie, the lowest false-positive rate for bleeding source identification).

CLINICAL PEARLS

The primary goal in the treatment of a patient with acute and continued lower GI tract bleeding is localization of the bleeding site.

The ability to localize the bleeding during an abdominal exploration is greatly compromised. Exploratory laparotomy thus should be avoided prior to precise localization of the bleeding site.

Tagged RBC scan results should be interpreted with great caution because localization of bleeding to a region of the abdomen does not necessarily localize bleeding from a specific segment of the GI tract.

Colonoscopy should be reserved for stable patients with lower Gl tract bleeding.