Melena, characterized by black tarry stools, can occur with as little as 50 cc of blood in the stomach. How do we know this? We need to go back to clinical experiments involving oral administration of citrated blood in human subjects back in 1930’s and 40’s. 1-3 One study was performed on a group of “healthy medical students” who drank their own blood!3
Melena suggests an upper GI bleeding source where there is more time for enzymatic breakdown to transform blood to melena. Although gastric acid may also contribute to its formation, it does not appear to be a pre-requisite to melena as blood inserted into the small bowel or cecum can also produce melenic stools if it stays there long enough. Melena is dependent primarily on the length of transit time of blood in the GI tract, such that very rapid movement of 1 liter of blood from upper GI tract may lead to bright red blood per rectum, not melena, within 4 hours.2,4
Don’t get melena confused with other causes of dark stools such as oral iron supplementation and bismuth-containing medications (eg, Peptobismol®). In addition to its tarry texture, melena also has a characteristic pungent odor.
- Schiff L, Stevens R, Shaprio N, et al. Observations on the oral administration of citrated blood in man. Am J Med Sci 1942;203:409-12.
- Srygley FD, Gerardo CJ, Tran T, et al. Does this patient have a severe upper gastrointestinal bleed. JAMA 2012;307:1072-79. https://jamanetwork.com/journals/jama/article-abstract/1105075?redirect=true
- Daniel WA, Egan S. The quantity of blood required to produce a tarry stool. JAMA 1939;113:2232.
- Wilson ID. Hematemesis, melena, and hematochezia. In: Walker HK, Hall WD, Hurst JW, eds. Clinical Methods: The history, physical, and laboratory examinations. 3rd edition. Boston: Butterworths:1990. Chapter 85. Available from: https://www.ncbi.nlm.nih.gov/books/NBK411/
Contributed in part by Brad Lander, MD, Mass General Hospital, Boston, MA.
Yes, enteric pathogens such as Salmonella can predispose patients to inflammatory bowel disease (IBD) through several potential mechanisms: 1
- Causing permanent changes in the intestinal microbiota
- Altering the epithelial barrier in the gut
- Altering the interaction between the body’s immune system and the intestines
More specifically, Salmonella utilizes oxidized endogenous sulfur compounds released during acute intestinal inflammation to outgrow the fermentative microbiota of the colon.2 In addition, the neutrophil response to Salmonella infection can alter the constituent microbiome.3 Salmonella also modifies the tight junctions in the intestinal epithelium as it invades, thus activating the immune system (particularly toll-like-receptors), and creating a pro-inflammatory state with structural loss of the intestinal mucosa. 4 Lastly, Salmonella promotes cytokine release and neutrophil migration through pathogen recognition receptors, leaving the intestine in a pro-inflammatory state even following resolution of the infection. 1
Keep in mind that initial Salmonella infection may also mimic IBD, as it causes diffuse lesions in the colon similar to ulcerative colitis, and may cause ileitis in some patients. Stool cultures and biopsies of the colonic mucosa should help differentiate IBD from Salmonella infection. 5
- Schultz BM, Paduro CA, Salazar GA, et al. A potential role of Salmonella infection in the onset of inflammatory bowel diseases. Front Immunol 2017;8:191. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5329042/pdf/fimmu-08-00191.pdf
- Winter SE, Baumler AJ. A breathtaking feat: to compete with the gut microbiota, Salmonella drives its host to provide a respiratory electron acceptor. Gut Microbes 2011;2:58-60. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3225798/pdf/gmic0201_0058.pdf
- Gill N, Ferreira RB, Antunes LC, et al. Neutrophil elastase alters the murine gut microbiota resulting in enhanced Salmonella colonization. PLoS ONE 2012;7:e49646. http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0049646
- Bueno SM, Riquelme S, Riedel CA, et al. Mechanisms used by virulent Salmonella to impair dendritic cell function and evade adaptive immunity. Immunology 2012;137:28-36. https://www.ncbi.nlm.nih.gov/pubmed/22703384
- De Hertogh G, Geboes K. Crohn’s disease and infections: a complex relationship. MedGenMed 2004;6:14. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1435589
Contributed by Yasmin Islam MD, Mass General Hospital, Boston, MA.
Yes! Although a common cause of colitis, an increasing number of reports in the literature suggest C. difficile can cause enteritis as well.1 Antibiotic use is a major risk factor in most reports, with nearly one-half of the cases reported in patients with inflammatory bowel disease, many post-colectomy. 1-3
Mortality of C. difficile enteritis based on the first 83 cases in the literature appears to be 23%,1 but as high as 60%-83% depending on the report!2 Its diagnosis post-colectomy requires a high index of suspicion, as patients may not complain of “diarrhea” with chronically loose stools in the ileostomy bag. Be particularly on the lookout for C. difficile enteritis in these patients when there is increased stool output, fever, hypotension, and/or leukocytosis2, and when in doubt, send a stool specimen from the ileostomy bag for C. difficile testing.
Although the pathophysiology of C. difficile enteritis is not fully understood, few observations are particularly intriguing:
- Small bowel mucosa may be colonized by C. difficile in about 3% of the population, potentially serving as a reservoir.2
- Patients with ileostomy may develop a metaplasia of the terminal end mimicking colonic environment.4
- Exposure of rabbit ileum to C. difficile toxin A also causes significant epithelial necrosis with destruction of villi and neutrophil infiltration.5
- Dineen SP, Bailey SH, Pham TH, et al. Clostridium difficile enteritis: a report of two cases and systematic literature review. World J Gastrointest Surg 2013;5:37-42. https://www.wjgnet.com/1948-9366/full/v5/i3/37.htm
- Boland E, Thompson JS. Fulminant Clostridium difficile enteritis after proctocolectomy and ileal pouch-anal anastomosis. Gastroenterology Research and Practice 2008; 2008: Article ID 985658. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2633454/pdf/GRP2008-985658.pdf
- Freiler JF, Durning SJ, Ender PT. Clostridium difficile small bowel enteritis occurring after total colectomy. Clin Infect Dis 2001;33:1429-31. https://pdfs.semanticscholar.org/333b/d84978cfc4ac8fd21a15bc8fd26ff3160387.pdf
- Apel R, Cohen Z, Andrews CW, et al. Prospective evaluation of early morphological changes in pelvic ileal pouches. Gastroenterology 1994;107:435-43. http://www.gastrojournal.org/article/0016-5085(94)90169-4/pdf
- Triadafilopoulos G, Pothoulakis C, Obrien MJ, et al. Differential effects of Clostridium difficile toxins A and B on rabbit ileum. Gastroenterology 1987;93:273-279. https://www.ncbi.nlm.nih.gov/pubmed/3596162
Proton pump inhibitors (PPIs) have been associated with increased risk of Clostridium difficile infection, as well as acute gastroenteritis (AG) caused by Salmonella, Campylobacter, and most recently, norovirus. 1,2
A recent prospective study1 of over 38,000 patients (mean age ~ 70 y) found a significant association between PPI use and AG leading to hospitalization with a dose-response relationship. PPI use increased the risk of Salmonella, Campylobacter, and C. difficile infections. Of note, H2 receptor antagonists were not associated with AG-related hospitalization in this study.
A 2017 retrospective case-control study also showed an association between PPI use and norovirus infection in hospitalized patients (mean age ~80 y in both groups). Most cases occurred during epidemic years with a median hospital stay of 5 days before onset of symptoms. Given the usually short incubation period of norovirus AG (typically 12-48 h), many of these cases likely acquired the infection during their hospital stay.
Besides reducing the acidity of gastric juice, PPIs may increase the risk of AG by causing an overgrowth of bacteria in the GI tract, reduce its motility and adversely affect the immune response, including neutrophil chemotaxis. 3
Does your patient really need a PPI?
- Chen Y, Liu B, Glass K, et al. Use of proton pump inhibitor and the risk of hospitalization for infectious gastroenteritis. PLoS One 2016;11:e0168618. Doi:10.1371/journal.pone. 0168618. http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0168618
- Prag C, Prag M, Fredlund H. Proton pump inhibitors as a risk factor for norovirus infection. Epidemiol Infect 2017;145:1617-23. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5426289/pdf/S0950268817000528a.pdf
- Wandall JH. Effects of omeprazole on neutrophil chemotaxis, super oxide production, degranulation, and translocation of cytochrome b-245. Gut 1992;33:617-21. https://www.ncbi.nlm.nih.gov/pubmed/1319381
Octreotide is routinely used in the treatment of variceal bleeding due to its vasoconstrictive effects on the splanchnic vasculature.1 In non-variceal upper GI bleed (NVUGB), however, the evidence for routine use of octreotide is hard to come by with an international consensus panel recommending its use only on a case-by-case basis in patients with very active bleeding while awaiting endoscopy or surgery.2,3
These recommendations are based on the failure of several randomized controlled trials in demonstrating the superiority of octreotide in NVUGB over placebo, either alone or with ranitidine, except in a small subset of patients with actively oozing ulcers.4-6 Although a meta-analysis has suggested that octreotide may reduce the risk of continued bleeding in NVUGB,7 the validity of some of the included studies has been questioned.8
On the other hand, octreotide decreases gastric mucosal blood flow and inhibits acid and pepsin secretion, which may potentially benefit patients who are actively bleeding.9
Final fun fact: Did you know that octreotide may be effective in the treatment of chylothorax?
- Avgerinos A, Armonis A, Raptis S. Somatostatin and octreotide in the management of acute variceal hemorrhage. Hepatogastroenterology 1995;42:145-50. http://europepmc.org/abstract/med/7672763
- Barkun AN, Barrdou M, Kulpers EJ, et al. International concensus recommendations on the management of patients with nonvariceal upper gastrointestinal bleeding. Ann Intern Med 2010;152:101-113. http://annals.org/aim/article/745521/international-consensus-recommendations-management-patients-nonvariceal-upper-gastrointestinal-bleeding
- Barkun A, Bardou M, Marshall JK, Nonvariceal Upper GIBCCG Consensus Conference Group. Consensus recommendations for managing patients with nonvariceal upper gastrointestinal bleeding. Ann Intern Med 2003;139:843–857. https://www.ncbi.nlm.nih.gov/pubmed/14623622
- Nikolopoulou VN, Thomopoulos KC, Katsakoulis EC, et al. The effect of octreotide as an adjunct treatment in active nonvariceal upper gastrointestinal bleeding. J Clin Gastroenterol 2004;38:243-7. http://journals.lww.com/jcge/Abstract/2004/03000/The_Effect_of_Octreotide_as_an_Adjunct_Treatment.9.aspx
- Archimandritis A, Tsirantonaki M, Tryphonos M, et al. Ranitidine versus ranitidine plus octreotide in the treatment of acute non-variceal upper gastrointestinal bleeding: a prospective randomized study. Curr Med Res Opin. 2000;16(3):178-83. http://www.tandfonline.com/doi/abs/10.1185/0300799009117023
- Okan A, Simsek I, Akpinar H, et al. Somatostatin and ranitidine in the treatment of non-variceal upper gastrointestinal bleeding: a prospective, randomized, double-blind, controlled study. Hepatogastroenterology 2000;47:1325-7. http://europepmc.org/abstract/med/11100343
- Imperiale TF, Birgisson S. Somatostatin or octreotide compared with H2 antagonists and placebo in the management of acute nonvariceal upper gastrointestinal hemorrhage: a meta-analysis. Ann Intern Med 1997;127:1062–1071. http://annals.org/aim/article/711021/somatostatin-octreotide-compared-h-2-antagonists-placebo-management-acute-nonvariceal
- Palmer KR. Non-variceal upper gastrointestinal haemorrhage: guidelines. Gut. 2002;51 (Suppl 4): iv1–iv6. http://gut.bmj.com/content/51/suppl_4/iv1.short
- Sgouros SN, Bergele C, Viazis N, et al. Somatostatin and its analogues in peptic ulcer bleeding: facts and pathophysiological aspects. Dig Liver Dis. 2006;38:143-8. http://www.sciencedirect.com/science/article/pii/S1590865805002434
Contributed byAlice Choi, Medical Student, Harvard Medical School
Depends on how high the serum levels are! Although the clearance of both amylase and lipase appears to be impaired in patients with significant renal insufficiency (eg, creatinine clearance <50ml/min), serum levels greater than 2-4 times the upper limits of normal for these enzymes are still considered suggestive of pancreatitis in these patients1-3.
Interestingly, in hemodialysis patients, elevation of lipase may also be due to the lipolytic effect of heparin during this procedure. That’s why obtaining serum lipase levels before, not after, hemodialysis has been recommended4
Also fascinating is that most of the elevation of serum amylase in patients with significant renal insufficiency appears to be related to the elevation of salivary, not pancreatic, isoenzyme of amylase4.
Final fun fact: Did you know that at one time the diagnosis of pancreatitis was based on the activity of serum on starch (for amylase) and olive oil (for lipase)? 5
- Levitt MD, Rapoport M, Cooperband SR. The renal clearance of amylase in renal insufficiency, acute pancreatitis, and macroamylasemia. Ann Intern Med 1969;71:920-25. http://annals.org/aim/article/683643/renal-clearance-amylase-renal-insufficiency-acute-pancreatitis-macroamylasemia
- Collen MJ, Ansher AF, Chapman AB, et al. Serum amylase in patients with renal insufficiency and renal failure. Am J Gastroenterol 1990;85:1377-80. https://www.ncbi.nlm.nih.gov/pubmed/1699413
- Royce VL, Jensen DM, Corwin HL. Pancreatic enzymes in chronic renal failure. Arch Intern Med 1987;147:537-39. https://www.ncbi.nlm.nih.gov/pubmed/2435254
- Vaziri ND, Change D, Malekpour A, et al. Pancreatic enzymes in patients with end-stage renal disease maintained on hemodialysis. Am J Gastroenterol 1988;83:410-12. https://www.ncbi.nlm.nih.gov/pubmed/2450453
- Editorial. Pancreatic enzymes. N Engl J Med 1963;268:901-2. http://www.nejm.org/doi/pdf/10.1056/NEJM196304182681613
The general agreement in the literature is that oral iron supplementation does not cause a false-positive guaiac-based fecal occult blood test (GFOBT).
GFOBT is based on rapid oxidization of α-guaiaconic acid to “guaiacum blue”, with hemoglobin serving as a catalyst through a non-enzymatic or “pseudoperoxidase” action. Although in vitro Fe3+ may serve as an oxidizing agent, this reaction is possible only under acidic conditions not found in the stool (pH ≥ 6-7)1. Also, in the absence of a catalyst, Fe3+ alone would not be expected to cause rapid (within 30 seconds) conversion of α-guaiaconic acid to guaiacum blue1.
Although a number of earlier clinical studies reported false-positive GBFOBT because of oral iron supplementation, subsequent investigations have uniformly failed to confirm these findings2. Potential reasons for earlier false-positive GBFOBT results include false interpretation of the color change—eg, green instead of blue— particularly when the discoloration is weakly positive, and non-standardized method of stool collection with the possibility of stool sample contamination by toilet water.
Other fascinating facts: Did you know that guaiac plant extract was used for centuries for treatment of syphilis and that the earliest application of guaiac testing was in forensic medicine in 1800s?
- McDonnell WM, Ryan JA, Seeger DM, Elta GH. Effect of iron on the guaiac reaction. Gastroenterology. 1989 Jan;96(1):74-8. https://www.ncbi.nlm.nih.gov/pubmed/2909440
- Anderson GD, Yellig TR, Krone RE. An investigation into the effects of oral iron supplementation on in vivo hemoccult stool testing. Am J Gastroenterol 1990;85:558-561. https://www.ncbi.nlm.nih.gov/pubmed/218661
Contributed by Brian Li, Medical Student, Harvard Medical School