The causes of melaena are potentially any cause of a haematemesis:
- oesophagitis
- Mallory-Weiss tear
- oesophageal varices
- peptic ulcer disease
- gastric neoplasms
Occasionally, a distal small-intestinal bleed, such as that from a Meckel’s diverticulum or a lesion of the right colon, can cause melaena. While causing dark stools, the stools in those taking iron supplementation have a different appearance to that of melaena and without the typical smell and, the FOBT will usually be negative.
Factors predictive of upper GI source of bleed:
- patient-reported history of melena (LR 5.1-5.9)
- melenic stool on examination (LR 25)
- blood or coffee grounds in nasogastric lavage (LR 9.6)
- ratio of blood urea nitrogen to serum creatinine greater than 30 (LR 7.5)
- blood clots in stool (LR 0.05) – i.e. upper GI source less likely
- bright blood detected in nasogastric lavage (LR 3.1 for severe bleed)¹
Start prior to endoscopy:
- proton pump inhibitor
- erythromycin
- antibiotics (cirrhosis)
- somatostatin (suspected variceal bleeding).
While aggressive management is important in any resuscitative effort, one issue of resuscitative efforts of acute physiological insults is overcorrection (or too rapid a correction), including that of blood transfusion. Roughly, aim then, for the following threshold Hb levels to guide resuscitative efforts for various patient groups while nonetheless ensuring always, of course, that haemodynamics are stabilised:
- Hb ≥ 10 g/dL (100 g/L): active ischemia
- Hb ≥ 9 g/dL (90 g/L): risk of ischaemia
- Hb ≥ 8 g/dL (80 g/L): no significant comorbidities
- Hb ≥7 g/dL (70 g/L): suspected variceal bleeding – avoid over-transfusion (Hb > 10) in patients with suspected variceal bleeding as it can exacerbate bleeding.¹
If haemodynamic stability has been achieved, do no be perturbed then—perhaps be quite comfortable, in fact—by a Hb that is not above 10.
Apart from a dilutional anticoagulation in a patient presumably with premorbid coagulopathy (cirrhosis), the paradoxical results for zealous blood transfusion likely reflect an over-aggressive replacement of circulating blood volume in the setting of a reflex venoconstriction (large capacitance vessels and post-capillary venules) in response to the initial insult; in short, a subsequent tissue congestion. It seems difficult to conceive how Hb levels above those quoted can be, in and of themselves, deleterious.
References
- Saltzman, John R. “Approach to acute upper gastrointestinal bleeding in adults.” UpToDate. Mar 09, 2021.
- Sereda S, Lamont I, Hunt P. “The experience of a haematemesis and melaena unit: a review of the first 513 consecutive admissions.” Med J Aust. 1977 Mar 12;1(11):362-6. PMID: 300834.
- Ramesh, Jayapal et al. “Gastroscopy Negative Melaena: Is Further Investigation Justified? A Retrospective Review.” Gastrointestinal Endoscopy, Volume 63, Issue 5, AB219
- Augustin S, González A, Genescà J. “Acute esophageal variceal bleeding: Current strategies and new perspectives.” World J Hepatol. 2010;2(7):261-274. doi:10.4254/wjh.v2.i7.261.
