EM guidemap - Lower GI bleed

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Introduction

Definitions and general principles

History of the present illness

Examination

Diagnostic testing

Medical decision making in the ED setting Medical decision-making in pediatric patients Appendix
Introduction

- this guidemap is focused on acute lower GI bleeds => see the "upper GI bleed" guidemap for a problem-solving  approach to an upper GI bleed

- the medical literature is not very clear or consistent about the etiology of acute lower GI bleeds, and there are a number of different recommended approaches in the medical literature => this guidemap offers a simple problem-solving approach to lower GI bleeding

- this guidemap is mainly focused on adult patients  => a seperate sub-section very briefly covers lower GI bleeding in children - because the etiology and problem-solving approach to lower GI bleeding in children is very different to that in adults

(* please note that the medical decision-making in pediatric patients section is only a very brief conceptual outline => use a pediatric EM textbook, or other definitive educational resource, for further information)

Definitions and general principles

- a lower GI bleed is defined as a GI bleed that originates from a source distal to the ligament of Treitz in the duodenum

- most major lower GI bleeds arise from the colon, and small intestinal bleeds represent < 10% of lower GI bleeds

- most major lower GI bleeds are intermittent and self-limiting, and 80% of lower GI bleeds stop spontaneously

- lower GI bleeds are rarely as massive and life-threatening as upper GI bleeds, and the need for critical fluid recuscitation is far less common

- lower GI bleeds are regarded as massive if 3 - 5 units of blood are required over 24 hours to maintain hemodynamic stability; other non-standardized criteria for a massive bleed include a hematocrit < 30, any hemodynamic instability, or a bleeding rate of > 30cc/hour

- it is much more difficult to definitively determine the source of isolated lower GI bleeds (compared to upper GI bleeds) because of the length of the intestine, the presence of stool within the colon + the difficulty of viewing the entire colon during emergency colonoscopy, the difficulty in accessing the entire small intestine via enteroscopy, the intermittent nature of lower GI bleeds, and the inability of alternative diagnostic procedures (such as bleeding scans and/or arteriography) to accuratedly localize the bleeding source

- colonoscopy is often performed after a delay of many hours-days (when the bleeding has ceased) and the colonoscopist often draws inferences from the presence of common colonic pathology (eg. diverticulosis and angiodysplasia in elderly patients) and presumes that they may represent the source of the bleeding  => the medical journal literature therefore has varying figures for the frequency of lower GI bleeding from these common disease entities

- there is also the conundrum that emergency surgery, with significant morbidity and mortality, may be required before a specific site of bleeding is even determined - because the rectal bleeding is massive and ongoing + the initial diagnostic tests are inconclusive or cannot be performed

- isolated lower GI bleeding usually presents as frank blood without any stool, and the blood can vary in color from bright red to dark maroon to maroon-black

- maroon-black stools are usually secondary to proximal bleeds, while bright red blood usually implies distal colonic, or rectal, or peri-anal bleeding

(* melena occurs when colonic bacteria interact with blood as it passes slowly through the colon and it takes ~ 14 hours for melena to develop - melena usually implies bleeding from the stomach or small intestine, or much more infrequently from the proximal colon)

- the source of bleeding can only be partly inferred from the color of the blood => blood continuously changes in color even when it arises from the same source - the color depends on the rate of bleeding + the duration of colonic transit time; different professional observers also describe the same bloody stools differently and frequently use different color descriptors when describing the same stool specimen eg. maroon-red or red-black

(* because of the length of the colon, there can be a delay in the clinical presentation => the sudden presentation of  rectal bleeding does not necessarily imply ongoing bleeding => the bleeding could have already stopped prior to the time of clinical presentation and the manifest rectal bleeding could be from a previous bleed)

- studies have shown that the patient's first description of the initial stool color has the highest informative value and the greatest correlation to the likely bleeding site (proximal vs distal)

- the sudden onset of bright red bleeding usually suggests a distal colonic or rectal bleed => however, a large proximal intestinal bleed can also appear bright red in color - if the intestinal transit time is very short

- frank blood + no mucus + no stool in a middle-aged or elderly patient => suggests a bleeding vessel eg. diverticular bleed or angiodysplasia

- frank blood + no mucus + no stool in a young adolescent patient => suggests bleeding from a juvenile polyp or Meckel's diverticulum

- frank blood + mucus => suggests an inflammatory or ischemic colitis, or an intussusception, or a necrotizing enterocolitis, or a vasculitis (eg. Henoch-Schonlein, collagen disease)

- scanty blood + mucus + diarrhea => suggests an infectious enterocolitis (eg. Shigella), or an inflammatory colitis (eg. Crohn's disease or ulcerative colitis)

- bright red blood streaks on the surface of formed stool (or in the toilet bowl) => suggests rectal outlet bleeding (eg. hemorrhoids, anal fissure, anal ulcers, rectal polyp, rectal tumor, rectal proctitis)

- there is a definite association between NSIAD use and lower GI bleeds, especially diverticular bleeds

History of the present illness

- first inquire about the type of bleeding and duration of bleeding and whether the blood was mixed with stools, and whether the stools were watery or contained mucus

- inquire about the presence of symptoms of anemia and hypovolemia (weakness, lightheadedness, fatigue, effort dyspnea and syncope)

- painless streaks of bright red blood on the surface of formed stool suggests hemorrhoids (especially if the patient has a history of similar episodes related to hemorrhoids)

- streaks of bright red blood related to straining + hard stools + painful defecation suggests an anal fissure

- sudden bright red bleeding in a severely constipated patient suggests a stercoral ulcer (especially if it occurs during manual disimpaction)

- streaks of bright red blood + peri-anal discomfort suggests pinworm infection, or peri-anal strep cellulitis, or peri-anal fistulae, or external thrombosed hemorrhoids or ano-rectal trauma secondary to auto-erotic foreign body insertion or forced anal intercourse

- blood mixed with watery diarrheal stools suggests an infectious or inflammatory colitis

- the combination of fever + bloody diarrhea +/- abdominal cramps also suggests an inflammatory or infectious entero-colitis (eg. shigellae or hemorrhagic E coli, or malaria or amebiasis => check history of foreign travel)

- loose stools with varying amounts of blood + lower abdominal discomfort + elderly vasculopathic patient => think of ischemic colitis (especially if the patient has a previous history of hypotension +/- known vasculopathy)

- a recent change in bowel habits with weight loss and progressive constipation may suggest a colonic malignancy

- a previous history of severe lower GIT bleeding may suggest  recurrent diverticular bleeding or bleeding from angiodyplasia or other vascular anomalies

- a previous history of remote radiation therapy for prostate or pelvic cancer suggests radiation proctitis

- recent diagnostic colonoscopy suggests post-polypectomy bleeding

- finally, check for any history of a bleeding diathesis and obtain a complete drug history (NSIADs, aspirin or anticoagulants)

Examination

- first check the vital signs for evidence of hemodynamic instability and/or a fever

- examine the skin for petechiae and easy bruising (thrombocytopenia, Henoch-Schonlein purpura, other coagulopathy), and telangiectasia (hereditary hemorrhagic telangiectasia, Peutz-Jeghers syndrome)

- examine the abdomen for distension (intussusception, toxic megacolon), tenderness (inflammatory or infectious colitis or intussusception), or masses (intussusception, tumors, aneurysm)

- check the peri-anal area for anal fissures, scratch marks (pruritis ani), signs of trauma, pinworms, skin tags or fistula (Crohn's disease) or peri-anal cellulitis (Streptococcal)

- a digital rectal exam may confirm the presence of rectal bleeding and may pick up a rectal mass (40% of rectal tumors diagnosed by proctosigmoidoscopy are palpable)

Diagnostic testing

Anoscopy

- useful in diagnosing anal fissures or bleeding from internal hemorrhoids when a patient presents with rectal outlet bleeding

- the presence of non-bleeding hemorrhoids does not necessarily imply that they caused the rectal outlet bleeding

- young patients (< 40 years) with self-limited rectal outlet bleeding of uncertain cause may only require outpatient referral for elective proctosigmoidoscopy, while middle aged or elderly patients often require colonoscopy to exclude more proximal malignant pathology

Sigmoidoscopy

- useful for determining the etiology in rectal outlet bleeding, evaluating traumatic anorectal tears, and for obtaining rectal biopsies in patients with suspected inflammatory colitis or rectosigmoid malignancy

- may demonstrate stigmata of recent bleeding and localize the bleeding source to the rectum or lower left colon

- however, most patients with frank bleeding require a complete colonoscopy to rule-out more proximal colonic pathology; sigmoidoscopy alone only identifies the cause of lower GI bleeding in < 10% of cases

- also useful for ensuring that the rectal mucosa is free of overt pathology in the massively bleeding patient, who requires immediate surgery and a total colectomy => a normal rectum having no signs of pathology may allow the surgeon to perform a rectal anastamosis with a low risk of post-operative recurrent lower GI bleeding

Nasogastric aspiration

- recommended by some experts for all patients who present with hematochezia - because 10% of hematochezia cases can be due to an upper GI bleed

- however, other experts believe that an upper GI bleeding source is only likely if the hematochezia is massive and/or ongoing, or if the patient is hemodynamically unstable => those experts suggest that routine insertion of a NGT to exclude an upper GI bleed is not required in stable patients with self-limited hematochezia

Bleeding scan

- used to determine the probable site of lower GI bleeding if the bleeding is thought to be ongoing => bleeding has to occur at a rate of > 0.1 - 0.5ml/min for the test to be positive

- only 50% of bleeding scans are positive and there is some evidence to suggest that active bleeding, as defined by the passage of bright red blood or dark red blood at the time of the TRBC scan, increases the likelihood of a positive scan

(* the presence of hemodynamic instability at the time of clinical presentation and the total number of blood units transfused does not correlate with the likelihood of a positive TRBC scan)

- a TRBC scan is a non-invasive study that can be rapidly performed; however, it can only be performed in the stable patient

- of limited localizing value because it may only detect a pool of blood that has already moved distally down the colon away from the bleeding site; however, it can often semi-localize the bleeding to a certain area of the abdomen (right-sided vs left-sided, or gastro-duodenal vs distal small bowel)

- a TRBC scan cannot make a specific diagnosis; it also has no therapeutic value

- may be most useful prior to mesenteric arteriography => a strongly positive scan showing an immediate blush can allow the arteriographer to perform selective mesenteric vessel catheterization depending on the apparent site of bleeding

(* planned selective sub-total colectomy surgery should not be based solely on the results of a TRBC scan without obtaining more accurate information from other diagnostic procedures; the role of a TRBC scan prior to angiography is still not well-defined)

- a weakly positive scan (only a delayed blush is visible) suggests a slow bleed => arteriography is probably not warranted because it is unlikely to be positive => colonoscopy is probably the preferable diagnostic procedure

Arteriography

- used if the bleeding is vigorous and ongoing and emergency colonoscopy is not feasible, or if the results of emergency colonoscopy are inconclusive

- also used if lower GI bleeding persists or recurs + repeat colonoscopy has not revealed a source

- has the potential advantage of providing more accurate localization of the bleeding site than a TRBC scan, it may also provide a specific diagnosis if a particular angiographic pattern can be seen (AV malformation), and it offers an opportunity for simultaneous non-surgical therapy (vasopressin or embolization)

- requires a bleeding rate of > 2 ml/min to be positive

- a dye, such as methylene blue, can be injected into the relevant artery if very active bleeding is identified => the bleeding site may be then be easier to localize if immediate surgery is performed

- a vasopressin infusion (0.2 - 0.4 units/min) can be used if an anatomical bleeding site is found => generally helpful in stopping, or slowing, the bleeding in 80% of patients; however, recurrent bleeding occurs in 50% of patients during the same hospitalization period

- vasopressin therapy is only useful in slowing or stopping the bleeding if it is arterial, and venous bleeding from an AV malformation is unlikely to respond to vasopressin therapy

- selective vessel embolization is very risky in colonic bleeding because of the general inadequacy of the collateral circulation in the colon and the high risk of iatrogenic bowel infarction => it should probably only be used if surgery is inadvisable because of certain co-morbidities

- arteriography is associated with major morbidity (hematoma formation, femoral artery thrombosis, contrast reactions, renal failure and TIAs), it requires skilled personnel and it suffers from the disadvantage that it removes the patient from the ED/ICU for a prolonged period of time

Colonoscopy

- offers the colonoscopist an opportunity to make a specific diagnosis + undertake non-surgical endoscopic therapy

- it is probably the optimum initial diagnostic procedure if the bleeding is self-limited and stops => thereby allowing for a thorough bowel cleansing prior to diagnostic colonoscopy

- the major conundrum is that it technically difficult to perform a diagnostic and therapeutic colonoscopy if bleeding continues and adequate bowel preparation is not possible => however, too great a delay may result in the colonoscopist not seeing a bleeding site because the active bleeding has already ceased

- urgent colonoscopy (arbitrarily defined as performance of the procedure within 12 hours of clinical presentation following an oral purge using 4 - 6L of a balanced polyethylene-glycol electrolyte solution) usually results in a definite diagnosis in ~ 75% of cases - using semi-specific diagnostic criteria like active bleeding, non-bleeding visible vessel, adherent clot, fresh blood localized to a colonic segment, ulceration of a diverticulum with fresh blood in the immediate area, and fresh blood in the proximal colon with no blood in the terminal ileum

(* adequate hemodynamic recuscitation should always precede colonoscopy, and patient safety concerns should always override the diagnostic desires of the admitting physician)

- comparison studies have not been performed comparing the diagnostic value of emergency colonoscopy to a combination strategy, which utilizes bleeding scans + arteriography => however, prompt emergency colonoscopy is steadily gaining favor (within 1 - 3 hours of oral lavage or continuous nasogastric infusion of Golytely electrolyte solution at 25ml/kg/hour) because it may even identify the source of colonic bleeds that have recently stopped bleeding and because endoscopic therapy may be possible if an anatomic colonic bleeding source is found

- the downside of emergency colonoscopy is that it is difficult, requires "experience" and is associated with an increased risk of colonic injury and perforation

- one setting in which early colonoscopy is particularly helpful is the post-polypectomy patient who presents with early bleeding (within a few days of the polypectomy) that is most likely from the site of the polypectomy => resnaring of the stalk or cauterization may be totally curative

(* post-polypectomy bleeding that occurs 2 weeks after the polypectomy procedure may be due to disruption of the adherent clot => conservative observation is recommended => colonoscopy is only warranted if bleeding is ongoing)

- enteroscopy is an endoscopic procedure that requires special expertise, and it is used to investigate possible bleeding from the small intestine if colonoscopy is negative and recurrent bleeding occurs

Medical decision-making in the ED

- first determine whether the patient is hemodynamically stable and concentrate your initial efforts on ensuring hemodynamic stability

(* standard laboratory testing includes - CBC, PT/PTT, type-and-screen, liver function tests, glucose and electrolytes; hemodynamically unstable patients, or hemodynamically stable patients with massive bleeding, or hemodynamically stable patients with anemia + active bleeding require cross-matching for 2 - 6 units of blood)

- consult a gastro-enterologist and a surgeon if the rectal bleeding is massive and/or the patient is hemodynamically unstable

Fluid recuscitation

- first ensure hemodynamic stability by normal saline fluid administration

- fluid administration is tailored to the patient's needs; caution is advisable in elderly patients at risk of CHF, or in renal failure or cirrhotic patients; vasopressors are contra-indicated in hypovolemic patients

- packed cells should be administered if > 20 - 30cc/kg of normal saline is required to acutely recuscitate a hypovolemic patient; the threshold should be lower if the patient is obviously anemic

- the requirement for packed cells depends on the initial hemoglobin level + rate of bleeding + presence of underlying ischemic heart disease => the "target" hemoglobin level should be flexible and ~ 10 g/dl in elderly patients with ischemic heart disease and poor cardiovascular reserve, and 6 - 8 g/dl in young, previously healthy patients

(* rigid guidelines for the administration of blood products should be avoided => use your clinical judgement => the transfusion requirment should be based on the:- i) patient's age, ii) presence of co-morbidities, iii) patient's cardiovascular reserve, iv) baseline hematocrit, v) rate of bleeding and vi) clinical efficacy of therapy

- serial vital signs + serial hemoglobin levels are the best indicators of the balance between ongoing bleeding and ongoing fluid recuscitation

Correct any coagulopathy

- correct any coagulopathy prn with 10 - 15 ml/kg of FFP (if PT > 1.5) and/or platelet transfusions (if platelet count < 50,000/cu.mm)

(* avoid giving FFP and platelets based on an empirical formula relating to the number of units of transfused packed cells; transfusion decisions should also be affected by the presence of other coagulopathies eg. DIC, or the presence of qualitative platelet defects induced by renal failure or aspirin/NSIADs)

- do not empirically give large doses of vitamin K (10mg) to patients taking warfarin for critically important reasons (eg. mechanical heart valve) because the patient will become resistant to coumadin for an extended period of time => use FFP to temporarily correct the anticoagulant-induced coagulopathy during the acute bleeding period => prothromin complexes are only necessary if FFP is not effective in correcting the coagulopathy

(* small doses of sc vitamin K - 1mg - may be acceptable)

Emergency surgery

- it is occasionally necessary to perform emergency surgery without a clear idea of the specific bleeding site if the bleeding is massive and ongoing + the patient is too hemodynamically unstable to permit arteriography or emergency colonoscopy

- surgery is optimally performed in concert with intra-operative colonoscopy + proximal enteroscopy to help localize the bleeding site and limit the amount of required bowel resection

- a total colectomy (with ileosigmoidostomy or ileoproctostomy) is often required for non-localized colonic bleeding; preservation of the rectosigmoid is always preferable if flexible intra-operative sigmoidoscopy has excluded disease of that area of the bowel

Admission for further diagnostic workup and therapy

- consult a gastro-enterologist emergently if the patient is hemodynamically stable, but the rectal bleeding is either massive and/or actively ongoing

- further diagnostic workup is dependent on the practice-pattern of the gastro-enterologist => he will either arrange an emergency arteriography or proceed directly to colonoscopy

- emergency surgery may still be required if the bleeding is massive and ongoing + colonoscopic therapy or arteriographic therapy (vasopressin infusion or selective embolisation) is not possible or successful

- self-limited frank rectal bleeding or hematochezia usually warrants admission to hospital for further diagnostic testing and specialist consultation => the gastro-enterologist will probably first perform an urgent colonoscopy or a bleeding scan depending on his practice style + his threshold for actively pursuing a diagnosis

(* some gastro-enterologists only perform diagnostic testing if the patient requires multiple blood transfusions and they do not investigate minor self-limited rectal bleeds)

- if the rectal bleeding is self-limited + suggestive of rectal outlet bleeding (but a definitive source cannot be identified and treated) => arrange outpatient follow-up with the patient's family doctor or a proctologist

Medical decision-making in pediatric patients

- the approach to rectal bleeding is different in pediatric patients because the etiology of the bleeding is so very different

Common causes of rectal bleeding in children

Infant

Older child Less common causes of rectal bleeding in children

Infant

Older child Problem-solving approach to rectal bleeding in children

The following problem-solving approach is very brief and over-simplified, and should only be regarded as a very basic guide:

- for an otherwise healthy formula-fed, or breast-fed, infant who presents with blood-streaked mucus in the stool + has no anal fissure => obtain a stool culture for common infectious pathogens => presume that the infant has milk protein-induced colitis => change the formula to a casein hydrolysate formula => arrange follow-up telephonic consultation with a pediatrician within 24 hours

(* a Wright stain of the stool showing many eosinophils supports a diagnosis of allergic colitis; however, always first think of necrotizing enterocolitis in neonates - especially if the neonate is > 2 weeks premature, has feeding intolerance and appears "sick"; also think of Hirschprung's enterocolitis if the neonate has a history of impaired defecation + abdominal distension)

- for an otherwise healthy child who presents with a mild self-limited bright red rectal bleed without anemia => first consider and exclude an anal fissure, local anorectal trauma, pinworms, rectal prolapse, peri-anal streptococcal infection and infectious diarrhea (or antibiotic-induced colitis) => then consider flexible sigmoidoscopy to detect a juvenile polyp or inflammatory colitis if no apparent pathology is detected during the clinical examination

- if no source is found by sigmoidoscopy + the bleeding is painless and sudden and significant  => consider a Tc99 Meckels scan

(* Meckel's diverticulum is the most common source of small bowel hemorrhage in children ~ 2 years of age => intestinal duplication is the second most common cause)

- colonoscopy may be warranted for severe bleeding (or recurrent bleeding) to identify a more proximal juvenile polyp (most common cause of painless rectal bleeding in children), or a vascular malformation, or intestinal duplication ulceration

(* colonoscopy should be preceded by bowel preperation using a continuous nasogastric infusion of polyethylene-glycol electrolyte solution at 25ml/kg/hour until the fecal contents have been adequately evacuated)

- angiography and scintigraphy are used prn to investigate obscure bleeding if colonoscopy is negative

- consider more serious pathology in infants (or children) if they are hemodynamically unstable, anemic, febrile, irritable, lethargic, appear to have abdominal pain or tenderness, have palpable abdominal masses or abdominal distension or vomiting, or have a significant history of constipation or diarrhea => they may require an extensive diagnostic workup

- red currant jelly stools (blood mixed with mucus) suggests an intussusception or inflammatory colitis; lethargy, vomiting, episodic abdominal pain, abdominal distension, and a palpable sausage-shaped abdominal mass supports a tentative diagnosis of intussusception; diarrhea + abdominal cramping + fever +/- vomiting suggests an inflammatory enterocolitis

- consider rare entities in immuno-compromised children with AIDS eg. mycobacterium avium, disseminated aspergillosis, cytomegalovirus ileitis, typhilitis

- consider hemolytic-uremic syndrome (due to E coli 0157:H7) if thrombocytopenia + microangiopathic anemia +/- impaired renal function is present

- consider Henoch-Schonlein purpura if there is a petechial rash +/- arthalgia +/- diarrhea +/- unexplanied abdominal pain

- consider infectious diarrhea or amebiasis if there is a history of foreign travel

- unexplained recurrent rectal bleeding, despite an extensive previous workup, should suggest Munchausen's syndrome by proxy

Appendix

Causes of lower GI bleeding in adults

Inflammatory

Vasculitis Anatomic sources Neoplasms Drugs Vascular disese Infectious - bacterial Infectious - parasitic Infectious - viral Others Conditions Mistaken for Blood in the Stool

Hematemesis

 Melena  Hematochezia Substances That Interfere with Guaiac Tests for Fecal Occult Blood

 False-positive results

 False-negative results Apt-Downey test

- used to differentiate infant blood from maternal blood

- mix equal parts of stool and water => centrifuge => mix supernatant with 1% sodium hydroxide in a ratio of 5:1 => mixture turns yellow if blood is of maternal origin; remains pink if blood of infant origin

Disclaimer: My EM guidemaps reflect my personal approach to problem-solving/managing clinical cases in an ED setting and they should not be regarded as the standard of care. They merely represent the personal opinions of the author and they should only be used in clinical practice if the reader-user has substantial reason to believe that the clinical advice contained in the guidemaps is valid and accurate. The guidemaps are not meant to be "authoritative" and the reader-user should consult standard medical textbooks and expert opinion articles/guidelines for more authoritative advice. The reader-user should particularly confirm all drug doses, their indications and contra-indications, prior to their use.