Residency · Residency · General Surgery
Lower GI Bleeding and Diverticular Hemorrhage
Overview
Lower gastrointestinal bleeding (LGIB) originates distal to the ligament of Treitz and accounts for approximately 20 to 30% of all GI hemorrhage. While most episodes of LGIB are self-limiting, with 80 to 85% ceasing spontaneously, the surgeon must be prepared to localize the bleeding source and intervene when conservative measures fail. Diverticular hemorrhage is the most common cause of acute LGIB in adults.
Etiology
Common Causes
Diverticular hemorrhage is the most common cause of acute LGIB in adults over 60, accounting for 30 to 40% of cases. Angiodysplasia (arteriovenous malformations) accounts for 10 to 20% and is the most common cause in patients over 65, typically involving the right colon and cecum. Colitis from inflammatory (ulcerative colitis, Crohn disease), ischemic, infectious, or radiation causes is another significant source. Hemorrhoids (5 to 10%) are the most common cause of rectal bleeding overall but usually produce only minor bleeding. Post-polypectomy bleeding occurs in approximately 5% of cases and can be immediate or delayed up to 14 days.
Less Common Causes
Less frequent etiologies include colorectal neoplasia, rectal ulcers (stercoral, NSAID-related, or solitary rectal ulcer syndrome), Meckel diverticulum in younger patients, colonic Dieulafoy lesions (rare), aortoenteric fistula (which must be excluded in patients with an aortic graft), endometriosis, rectal varices from portal hypertension, and small bowel sources in cases of obscure or overt bleeding.
Diverticular Hemorrhage
Pathophysiology
Diverticular hemorrhage is arterial in nature, originating from vasa recta at the dome or neck of the diverticulum. These arteries are exposed to injury at the thin-walled dome where they penetrate through the muscularis, making them susceptible to erosion and rupture. An important clinical point is that right-sided diverticula are responsible for the majority of diverticular hemorrhage, despite left-sided diverticulosis being far more common anatomically. The hallmark presentation is painless massive hematochezia, and a critical distinguishing feature is that hemorrhage and diverticulitis rarely coexist.
Risk Factors
NSAIDs are the strongest modifiable risk factor, conferring a three-fold increased risk. Other risk factors include aspirin and antiplatelet agents, anticoagulation, advanced age, hypertension, atherosclerosis, and obesity.
Natural History
Spontaneous cessation occurs in 80 to 85% of cases. However, the rebleeding rate is 25% after the first episode and 50% after the second episode. Surgery is generally recommended after a second significant episode or for ongoing hemorrhage that cannot be controlled.
Clinical Assessment
History
The evaluation of LGIB begins with characterizing the color and volume of rectal bleeding (bright red, maroon, or melena), hemodynamic symptoms (lightheadedness, syncope, palpitations), and the presence or absence of abdominal pain -- which is notably absent in diverticular hemorrhage but present in ischemic colitis and inflammatory bowel disease. Prior bleeding episodes, medication history (NSAIDs, aspirin, anticoagulants, antiplatelet agents), prior colonoscopy or polypectomy, radiation therapy, and surgical history (especially prior aortic grafting) must all be assessed.
Physical Examination and Initial Resuscitation
Hemodynamic assessment with vital signs and orthostatic changes is the first priority. The abdominal exam is usually benign in diverticular hemorrhage. Digital rectal exam evaluates for hemorrhoids, masses, and blood color. Anoscopy should be performed to evaluate for hemorrhoidal or anorectal sources.
Initial resuscitation includes two large-bore IV access lines and type and crossmatch. IV crystalloid is given first, with transfusion for hemoglobin below 7 g/dL (or below 8 to 9 g/dL with cardiovascular disease). Coagulopathy should be corrected and anticoagulation reversed when appropriate. NSAIDs and antiplatelet agents are held if possible. Critically, an NGT lavage or EGD should be performed to exclude an upper GI source when suspicion exists, as 10 to 15% of presumed LGIB is actually upper GI in origin.
Diagnostic Workup
Colonoscopy
Colonoscopy is the diagnostic and therapeutic modality of choice for LGIB. It is performed after rapid bowel preparation (4 to 6 liters of PEG solution over 3 to 4 hours). Urgent colonoscopy within 24 hours is recommended for hemodynamically stable patients after resuscitation and bowel prep, identifying the source in 70 to 90% of cases and allowing therapeutic intervention with injection, electrocautery, hemoclips, or band ligation. Stigmata of recent hemorrhage -- active bleeding, a visible vessel, or an adherent clot in a diverticulum -- are amenable to endoscopic therapy. Limitations include poor visualization during massive active hemorrhage and the requirement for bowel preparation.
CT Angiography
CTA detects active bleeding at rates above 0.3 to 0.5 mL/min with a sensitivity of 85 to 95% and specificity of 92 to 95%. It is rapid, widely available, requires no bowel prep, and identifies the location of bleeding (right versus left colon) to guide further intervention. CTA is increasingly used as the first-line study in massive LGIB before colonoscopy or angiography. Its limitation is that it does not allow therapeutic intervention.
Conventional Angiography
Mesenteric angiography detects bleeding at rates above 0.5 to 1.0 mL/min and offers therapeutic capability through superselective embolization using coils, gelfoam, or microspheres. The success rate for embolization is 80 to 90%, with ischemic complications in 5 to 10% (higher in the right colon due to its single vascular supply). It is best used when CTA has confirmed active bleeding and localized the source.
Tagged Red Blood Cell Scan
The tagged RBC scan is the most sensitive test for detecting active bleeding (0.1 to 0.2 mL/min), and delayed images can detect intermittent bleeding over 24 hours. It localizes to a region (right versus left) but is not highly accurate for precise localization, and may guide subsequent angiography or surgical planning. Its limitations include poor anatomic precision, delayed results, and limited availability.
Meckel Scan
The technetium-99m pertechnetate scan is used for suspected Meckel diverticulum in younger patients and detects ectopic gastric mucosa with a sensitivity of 85% in children and 60% in adults.
Management Algorithm
For hemodynamically stable patients with minor bleeding, outpatient colonoscopy is appropriate, with exclusion of hemorrhoidal and anorectal sources. For hemodynamically stable patients with significant bleeding, the approach involves resuscitation, correction of coagulopathy, exclusion of an upper GI source, rapid bowel prep, and urgent colonoscopy within 24 hours with endoscopic therapy if a bleeding source with stigmata is identified.
For massive or ongoing hemorrhage, aggressive resuscitation with activation of a massive transfusion protocol if needed is followed by CTA to localize active bleeding. If CTA is positive, mesenteric angiography with embolization is performed. If CTA is negative and bleeding continues, a tagged RBC scan or repeat CTA is obtained. Surgery is indicated if interventional approaches fail or the patient is hemodynamically unstable.
When non-operative management fails and the bleeding source has been localized, segmental colectomy (right hemicolectomy, sigmoid colectomy, etc.) is performed. When the source is unlocalized, total abdominal colectomy with ileorectal anastomosis is the last resort, though subtotal colectomy should be avoided without first attempting localization given the significant morbidity. Mortality of emergent total colectomy is 10 to 25%.
Post-Polypectomy Bleeding
Post-polypectomy bleeding occurs in 1 to 6% of polypectomies, with higher rates for large polyps, right-sided locations, and thick stalks. Immediate bleeding occurs during or within 24 hours of the procedure, while delayed bleeding occurs up to 14 days post-procedure, most commonly at day 5 to 7. Management involves repeat colonoscopy with endoscopic hemostasis (injection, clips, cautery). Prevention includes prophylactic clip placement on large stalk polyps and injectable epinephrine.
Angiodysplasia
Angiodysplasia consists of degenerative, thin-walled, dilated mucosal and submucosal vessels, most commonly in the right colon and cecum. It is associated with aortic stenosis through Heyde syndrome, which involves acquired von Willebrand disease that may resolve after aortic valve replacement. Endoscopic treatment with argon plasma coagulation (APC) or electrocautery is first-line. Angiographic embolization is used for inaccessible or recurrent lesions. Hormonal therapy with estrogen-progesterone is no longer recommended, as RCTs have shown no benefit. Refractory cases may require segmental colectomy.
Ischemic Colitis
Ischemic colitis is the most common form of intestinal ischemia, affecting watershed areas: the splenic flexure (Griffiths point) and the rectosigmoid junction (Sudeck point). Patients present with sudden crampy left-sided abdominal pain, urgency, and bloody diarrhea. CT findings include bowel wall thickening, thumbprinting, and pericolonic stranding. Colonoscopy reveals mucosal edema, hemorrhagic mucosa, and the single-stripe sign (longitudinal ulceration along the antimesenteric border). Management is usually conservative (IV fluids, bowel rest, antibiotics if severe), with surgery reserved for perforation, peritonitis, or stricture formation.
<image>Anatomical diagram of a colonic diverticulum showing the relationship of the vasa recta to the diverticular wall. Illustrate how the artery penetrates through the muscularis at the neck of the diverticulum, is exposed at the thin dome composed only of mucosa and serosa, and is susceptible to erosion and rupture causing arterial hemorrhage. Include a cross-section view showing the diverticulum protruding through the muscle layer at the point of vasa recta penetration.</image>
<image>Diagnostic algorithm flowchart for acute lower GI bleeding showing initial assessment and resuscitation, exclusion of upper GI source, then branching pathways based on hemodynamic stability and bleeding severity: minor bleeding (outpatient colonoscopy), significant stable bleeding (urgent colonoscopy after bowel prep), and massive hemorrhage (CTA followed by angioembolization or surgery). Include decision points for failed interventions leading to segmental vs. total colectomy.</image>
<image>Colonoscopic and CT angiographic images of common LGIB etiologies: (1) diverticular hemorrhage showing active bleeding from a diverticulum with visible vessel, (2) angiodysplasia showing a cherry-red vascular lesion in the cecum, (3) CT angiography with active contrast extravasation into the colonic lumen indicating active hemorrhage, and (4) ischemic colitis showing segmental mucosal edema and hemorrhage with thumbprinting pattern on CT.</image>
Clinical Pearls
Up to 15% of presumed lower GI bleeding is actually from an upper GI source, so an NGT aspirate or EGD should always be considered, especially with hemodynamic instability. Diverticular hemorrhage is painless; if significant abdominal pain accompanies colonic bleeding, ischemic colitis, IBD, or other diagnoses should be considered. Right-sided diverticula cause the majority of diverticular hemorrhage despite left-sided diverticulosis being more prevalent. NSAIDs are the strongest modifiable risk factor for diverticular hemorrhage. CT angiography has largely replaced tagged RBC scanning as the initial study for massive LGIB because it is faster, more widely available, and more anatomically precise. A bleeding source must be localized before performing segmental colectomy, as blind segmental resection has unacceptable rebleeding rates. Total abdominal colectomy with ileorectal anastomosis is the last resort for unlocalized massive LGIB but carries significant morbidity and mortality. Heyde syndrome (angiodysplasia plus aortic stenosis) involves acquired von Willebrand disease that may resolve after aortic valve replacement. After two significant episodes of diverticular hemorrhage, elective segmental colectomy should be considered to prevent further recurrence.
References
- Strate LL, Gralnek IM. ACG clinical guideline: Management of patients with acute lower gastrointestinal bleeding. Am J Gastroenterol. 2016;111(4):459-474.
- Oakland K, Chadwick G, East JE, et al. Diagnosis and management of acute lower gastrointestinal bleeding: guidelines from the British Society of Gastroenterology. Gut. 2019;68(5):776-789.
- Sengupta N, Tapper EB, Feuerstein JD. Early versus delayed colonoscopy in hospitalized patients with lower gastrointestinal bleeding. J Clin Gastroenterol. 2017;51(4):352-359.
- Defined SR. ACR Appropriateness Criteria: Radiologic management of lower gastrointestinal tract bleeding. J Am Coll Radiol. 2014;11(4):345-351.
